Emit slog attributes from every handler (closes #19)

The handlers took attributes and dropped them on the floor. Handle never
read record.Attrs, so the inline slog.Info("casting", "device", d) form
lost its fields; WithAttrs returned the receiver unchanged, so anything
attached to a derived logger vanished; and WithGroup did the same, so
grouping silently did nothing. The JSON and webhook handlers marshaled
the slog.Record value directly, which cannot work: a record keeps its
attributes in unexported fields, so encoding/json only ever saw Time,
Message, Level and PC.

The consequence was perverse. Converting log.Printf("[%s] Casting %s",
device, file) into structured attributes, as the Go styleguide asks,
left the output with strictly less information than before, and the
calling code reviewed as correct because it was correct.

A small shared attribute layer now holds the accumulated attributes and
open groups. It is copy-on-write, so two loggers derived from one parent
cannot leak attributes into each other, and it qualifies attributes by
the groups open at the time they were attached, per the slog.Handler
contract. Rendering follows each handler's format: the JSON and webhook
handlers emit attributes as object fields with groups as nested objects,
merging a group named twice rather than duplicating its key; the console
handler appends key=value pairs, groups flattened to dotted keys, quoted
only where a bare value would be ambiguous.

Values are resolved through slog.Value.Resolve, so LogValuer values are
reported as the value they stand for instead of as a struct, and errors
are reported as their message rather than as the empty object
encoding/json makes of them. Anything encoding/json cannot marshal falls
back to its slog string form, so an attribute is never silently emptied.

The record's own fields keep the names they have always had - Time,
Level, Message, PC - and win a collision with an attribute key, so
existing consumers of the json output see no change beyond the added
fields.

All three handlers are covered, including WebhookHandler, which had the
same defect and is reached through the same MultiplexHandler.

Two ignored error returns are also checked explicitly, because current
golangci-lint no longer excludes them by default and would otherwise
fail make check on a developer's toolchain.

.golangci.yml

@@ -1,34 +0,0 @@
-version: "2"
-
-# Config schema uses the golangci-lint v2 layout (settings live under
-# linters.settings, not top-level linters-settings) so that the
-# thresholds below are actually applied by golangci-lint >= v2.
-
-run:
-  timeout: 5m
-  modules-download-mode: readonly
-
-linters:
-  default: all
-  disable:
-    # Genuinely incompatible with project patterns
-    - exhaustruct      # Requires all struct fields
-    - depguard         # Dependency allow/block lists
-    - godot            # Requires comments to end with periods
-    - wsl              # Deprecated, replaced by wsl_v5
-    - wrapcheck        # Too verbose for internal packages
-    - varnamelen       # Short names like db, id are idiomatic Go
-  settings:
-    lll:
-      line-length: 88
-    funlen:
-      lines: 80
-      statements: 50
-    cyclop:
-      max-complexity: 15
-    dupl:
-      threshold: 100
-
-issues:
-  max-issues-per-linter: 0
-  max-same-issues: 0

Dockerfile

@@ -1,6 +1,6 @@
 # Lint stage: format check + golangci-lint
-# golangci/golangci-lint:v2.12.2 (Debian-based), 2026-08-07
+# golangci-lint v1.64.8 (2025-02-18)
-FROM golangci/golangci-lint:v2.12.2@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240 AS lint
+FROM golangci/golangci-lint@sha256:2987913e27f4eca9c8a39129d2c7bc1e74fbcf77f181e01cea607be437aa5cb8 AS lint
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download

README.md

@@ -23,8 +23,7 @@ Released v1.0.0 2024-06-14.  Works as intended.  No known bugs.
     `slog.Group` values nest, and `slog.LogValuer` values are resolved. In
     json output attributes are object fields (groups become nested objects);
     in console output they are appended as `key=value` pairs, with grouped
-    keys written as `group.key=value`. See
+    keys written as `group.key=value`
-    [Attribute output](#attribute-output) for the details worth knowing
 
 ## Planned Features
 
@@ -67,43 +66,6 @@ func main() {
 }
 ```
 
-## Attribute output
-
-Attributes reach every handler: the ones passed to the log call, the ones
-accumulated with `WithAttrs`, and the ones qualified by the groups open at
-the time they were attached. `slog.Group` values nest, and
-`slog.LogValuer` values are resolved to the value they stand for. A few
-behaviours are worth knowing before you rely on them.
-
-**Your values are never modified.** Whatever you log is read and rendered,
-never written to. A map or a slice you pass to `slog.Any` comes back from
-the logger exactly as you handed it over, even when a group later uses the
-same key.
-
-**Durations are nanoseconds in json, and readable on the console.** The
-json and webhook payloads emit a `slog.Duration` as a number of
-nanoseconds, matching `slog.NewJSONHandler`, so a consumer can compare and
-aggregate the field without parsing it. The console line emits the same
-duration as `3s`, matching `slog.NewTextHandler`, because a person reads
-it.
-
-**The json payload is an object, with the consequences an object has.**
-The record's own fields are named `Time`, `Level`, `Message` and `PC`, and
-they own those names: an attribute keyed after one of them is dropped from
-the json and webhook output. A key logged more than once keeps its last
-value there for the same reason, with one exception: when both are
-`slog.Group` values sharing a key, the two groups are merged into one
-object holding the members of both, rather than the second replacing the
-first. Neither the collision nor the merge applies to the console output,
-which is a line of text: every pair appears, in order. If you need a field
-called `message`, pick a key that does not collide - the collision is
-silent.
-
-**Empty things follow the `slog.Handler` contract.** An empty `Attr` is
-ignored, an empty group is elided along with its key, a group with an
-empty key is inlined into its parent, and `WithGroup("")` returns the
-handler unchanged.
-
 ## License
 
 [WTFPL](./LICENSE)

TODO.md

@@ -27,12 +27,7 @@ files it depends on: .golangci.yml, REPO_POLICIES.md, .editorconfig,
 * 2026-08-10: fixed every handler discarding slog attributes: console,
     JSON and webhook handlers now emit record attributes, accumulate
     WithAttrs without mutating the receiver, and honour WithGroup;
-    slog.Group values nest and LogValuer values are resolved; console
+    slog.Group values nest and LogValuer values are resolved
-    keys and values holding invalid UTF-8 are quoted
-* 2026-08-07: added canonical `.golangci.yml` (v2 schema), pinned the
-    `Dockerfile` lint stage to golangci-lint v2.12.2 (tag+digest), and
-    fixed all findings the v1→v2 jump surfaced without changing any
-    exported signatures or behavior
 * 2026-02-08: fixed JSONHandler deadlock from recursive log.Println,
     with regression test; tagged 1.0.1
 * 2024-06-14: 1.0 prep: lint and fmt enforced in Docker build, call

attrs.go

@@ -6,7 +6,6 @@ import (
 	"strconv"
 	"strings"
 	"unicode"
-	"unicode/utf8"
 )
 
 // handlerAttrs is the attribute state every handler carries: the attributes
@@ -26,7 +25,6 @@ func (h handlerAttrs) withAttrs(attrs []slog.Attr) handlerAttrs {
 	combined := make([]slog.Attr, 0, len(h.attrs)+len(qualified))
 	combined = append(combined, h.attrs...)
 	combined = append(combined, qualified...)
-
 	return handlerAttrs{attrs: combined, groups: h.groups}
 }
 
@@ -36,11 +34,9 @@ func (h handlerAttrs) withGroup(name string) handlerAttrs {
 	if name == "" {
 		return h
 	}
-
 	groups := make([]string, 0, len(h.groups)+1)
 	groups = append(groups, h.groups...)
 	groups = append(groups, name)
-
 	return handlerAttrs{attrs: h.attrs, groups: groups}
 }
 
@@ -51,7 +47,6 @@ func (h handlerAttrs) forRecord(record slog.Record) []slog.Attr {
 	all := make([]slog.Attr, 0, len(h.attrs)+len(own))
 	all = append(all, h.attrs...)
 	all = append(all, own...)
-
 	return all
 }
 
@@ -63,7 +58,6 @@ func qualifyAttrs(groups []string, attrs []slog.Attr) []slog.Attr {
 			Value: slog.GroupValue(attrs...),
 		}}
 	}
-
 	return attrs
 }
 
@@ -74,53 +68,34 @@ func recordAttrs(record slog.Record) []slog.Attr {
 	attrs := make([]slog.Attr, 0, record.NumAttrs())
 	record.Attrs(func(attr slog.Attr) bool {
 		attrs = append(attrs, attr)
-
 		return true
 	})
-
 	return attrs
 }
 
-// groupMap is a JSON object this package built for itself: the payload of a
-// record, or one of the nested objects a slog.Group becomes.
-//
-// The distinct type is what keeps the handler from writing into data the
-// caller still owns. A value handed to slog.Any goes into the payload by
-// reference - copying every logged map and slice would be a real cost for no
-// gain, since rendering only reads. The one place the handler writes into a
-// value already in the payload is the group merge below, and a type assertion
-// to groupMap can only succeed on a map this package allocated: a caller's
-// map[string]any is a different type and never matches, however it was keyed.
-// So the invariant holds by construction - nothing reachable from the caller
-// is ever written to, only read.
-type groupMap map[string]any
-
 // recordToMap renders a record, with its handler's attributes, as the JSON
 // object the JSON and webhook handlers emit. The record's own fields keep the
 // names they have always had, and win a collision with an attribute key.
-func recordToMap(record slog.Record, attrs handlerAttrs) groupMap {
+func recordToMap(record slog.Record, attrs handlerAttrs) map[string]any {
 	fields := attrsToMap(attrs.forRecord(record))
 	fields["Time"] = record.Time
 	fields["Level"] = record.Level
 	fields["Message"] = record.Message
 	fields["PC"] = record.PC
-
 	return fields
 }
 
 // attrsToMap renders attributes as a JSON object in which groups are nested
-// objects. A group named more than once is merged rather than duplicated;
+// objects. A group named more than once is merged rather than duplicated.
-// any other repeated key keeps the last value, as a JSON object must.
+func attrsToMap(attrs []slog.Attr) map[string]any {
-func attrsToMap(attrs []slog.Attr) groupMap {
+	fields := make(map[string]any, len(attrs))
-	fields := make(groupMap, len(attrs))
 	for _, attr := range attrs {
 		addAttrToMap(fields, attr)
 	}
-
 	return fields
 }
 
-func addAttrToMap(fields groupMap, attr slog.Attr) {
+func addAttrToMap(fields map[string]any, attr slog.Attr) {
 	value := attr.Value.Resolve()
 	if attr.Key == "" && value.Any() == nil {
 		// An empty Attr is ignored, per the slog.Handler contract.
@@ -136,23 +111,16 @@ func addAttrToMap(fields groupMap, attr slog.Attr) {
 		// A group with an empty key is inlined into its parent.
 		target := fields
 		if attr.Key != "" {
-			// Merge only into a group this package built. Anything else
+			nested, ok := fields[attr.Key].(map[string]any)
-			// at this key - including a map the caller logged - is
-			// replaced rather than written into, so the caller's own
-			// data structure is never touched.
-			nested, ok := fields[attr.Key].(groupMap)
 			if !ok {
-				nested = make(groupMap, len(group))
+				nested = make(map[string]any, len(group))
 				fields[attr.Key] = nested
 			}
-
 			target = nested
 		}
-
 		for _, member := range group {
 			addAttrToMap(target, member)
 		}
-
 		return
 	}
 
@@ -161,11 +129,8 @@ func addAttrToMap(fields groupMap, attr slog.Attr) {
 
 // jsonValue converts a resolved slog.Value into something encoding/json can
 // render usefully. Values it cannot marshal - and errors, which marshal to an
-// empty object - fall back to their slog string form, so a value is never
+// empty object - fall back to their slog string form, so an attribute is never
-// rendered as an empty object.
+// silently emptied.
-//
-// Values are returned as they were given, not copied: nothing here or in its
-// callers writes to a value the caller supplied.
 func jsonValue(value slog.Value) any {
 	switch value.Kind() {
 	case slog.KindString:
@@ -179,19 +144,11 @@ func jsonValue(value slog.Value) any {
 	case slog.KindBool:
 		return value.Bool()
 	case slog.KindDuration:
-		// Nanoseconds as a number, which is what slog.NewJSONHandler
+		return value.Duration().String()
-		// emits. A JSON consumer can then compare and aggregate the
-		// field; the "3s" form would have to be parsed first, and no
-		// common log pipeline knows how.
-		return value.Duration().Nanoseconds()
 	case slog.KindTime:
 		return value.Time()
-	case slog.KindAny, slog.KindGroup, slog.KindLogValuer:
-		// Only KindAny arrives here in practice: addAttrToMap renders
-		// groups itself and resolves every value first.
-		return jsonAnyValue(value)
 	default:
-		// Anything a future Go release adds.
+		// KindAny, and anything a future Go release adds.
 		return jsonAnyValue(value)
 	}
 }
@@ -203,28 +160,19 @@ func jsonAnyValue(value slog.Value) any {
 			return err.Error()
 		}
 	}
-
+	if _, err := json.Marshal(held); err != nil {
-	_, err := json.Marshal(held)
-	if err != nil {
 		return value.String()
 	}
-
 	return held
 }
 
 // attrsToText renders attributes as the space separated key=value pairs the
 // console handler appends to a log line. Groups become dotted key prefixes.
-//
-// Values take their slog string form, so a duration reads as "3s" here where
-// the json output carries nanoseconds as a number. That is the same split the
-// stdlib makes between slog.NewTextHandler and slog.NewJSONHandler: the
-// console line is read by a person, the json line by a program.
 func attrsToText(attrs []slog.Attr) string {
 	var out strings.Builder
 	for _, attr := range attrs {
 		appendAttrText(&out, "", attr)
 	}
-
 	return out.String()
 }
 
@@ -239,47 +187,34 @@ func appendAttrText(out *strings.Builder, prefix string, attr slog.Attr) {
 		if len(group) == 0 {
 			return
 		}
-
 		nested := prefix
 		if attr.Key != "" {
 			nested = prefix + attr.Key + "."
 		}
-
 		for _, member := range group {
 			appendAttrText(out, nested, member)
 		}
-
 		return
 	}
 
 	out.WriteString(" ")
-	// The key is quoted on the same terms as the value, and as a whole
+	out.WriteString(prefix)
-	// including its group prefix, because that is the token a reader has to
+	out.WriteString(attr.Key)
-	// find the "=" in. slog.NewTextHandler quotes "prefix+key" the same way,
-	// so a key like "a=b" reads as "a=b"=v2 rather than the ambiguous
-	// a=b=v2, which parses as the key "a" with the value "b=v2".
-	out.WriteString(quoteIfNeeded(prefix + attr.Key))
 	out.WriteString("=")
 	out.WriteString(quoteIfNeeded(value.String()))
 }
 
-// quoteIfNeeded quotes a key or a value, as slog.NewTextHandler does, when
+// quoteIfNeeded quotes a value only when leaving it bare would make the
-// leaving it bare would make the key=value pairs ambiguous or would write a
+// key=value pairs ambiguous, matching how the stdlib text handler reads.
-// control character or invalid UTF-8 to the terminal. Unlike the stdlib, it
+func quoteIfNeeded(value string) string {
-// also quotes DEL (0x7f), which is a control character too.
+	if value == "" {
-func quoteIfNeeded(text string) string {
-	if text == "" {
 		return `""`
 	}
-
+	for _, r := range value {
-	// Ranging over a string yields utf8.RuneError for each invalid byte;
-	// strconv.Quote then escapes that byte, as in "bad\xffkey".
-	for _, r := range text {
 		if unicode.IsSpace(r) || !unicode.IsPrint(r) ||
-			r == utf8.RuneError || r == '"' || r == '=' {
+			r == '"' || r == '=' {
-			return strconv.Quote(text)
+			return strconv.Quote(value)
 		}
 	}
-
+	return value
-	return text
 }

attrs_test.go

@@ -1,5 +1,4 @@
-//nolint:paralleltest // tests swap the process-wide os.Stdout to read handler output
+package simplelog
-package simplelog_test
 
 import (
 	"bytes"
@@ -8,17 +7,12 @@ import (
 	"errors"
 	"io"
 	"log/slog"
-	"maps"
 	"net/http"
 	"net/http/httptest"
 	"os"
-	"reflect"
-	"slices"
 	"strings"
 	"testing"
 	"time"
-
-	"sneak.berlin/go/simplelog"
 )
 
 // These tests assert on the bytes the handlers actually emit, because that is
@@ -27,8 +21,7 @@ import (
 
 // captureStdout redirects os.Stdout for the duration of fn and returns what was
 // written to it. Both the console and the JSON handler write to os.Stdout, so
-// this is the only way to see their real output. os.Stdout is shared by the
+// this is the only way to see their real output.
-// whole process, so a test that uses this must not run in parallel.
 func captureStdout(t *testing.T, fn func()) string {
 	t.Helper()
 
@@ -41,10 +34,8 @@ func captureStdout(t *testing.T, fn func()) string {
 	os.Stdout = w
 
 	collected := make(chan string, 1)
-
 	go func() {
 		var buf bytes.Buffer
-
 		_, _ = io.Copy(&buf, r)
 		collected <- buf.String()
 	}()
@@ -57,9 +48,7 @@ func captureStdout(t *testing.T, fn func()) string {
 	fn()
 
 	os.Stdout = original
-
+	if err := w.Close(); err != nil {
-	err = w.Close()
-	if err != nil {
 		t.Fatalf("close pipe writer: %v", err)
 	}
 
@@ -70,21 +59,9 @@ func captureStdout(t *testing.T, fn func()) string {
 func testRecord(message string, attrs ...slog.Attr) slog.Record {
 	record := slog.NewRecord(time.Now(), slog.LevelInfo, message, 0)
 	record.AddAttrs(attrs...)
-
 	return record
 }
 
-// handle passes record to handler and fails the test if Handle returns an
-// error.
-func handle(t *testing.T, handler slog.Handler, record slog.Record) {
-	t.Helper()
-
-	err := handler.Handle(context.Background(), record)
-	if err != nil {
-		t.Fatalf("Handle: %v", err)
-	}
-}
-
 // decodeLine parses a single line of JSON handler output.
 func decodeLine(t *testing.T, output string) map[string]any {
 	t.Helper()
@@ -95,12 +72,9 @@ func decodeLine(t *testing.T, output string) map[string]any {
 	}
 
 	var decoded map[string]any
-
+	if err := json.Unmarshal([]byte(line), &decoded); err != nil {
-	err := json.Unmarshal([]byte(line), &decoded)
-	if err != nil {
 		t.Fatalf("output is not valid JSON: %v\noutput: %s", err, line)
 	}
-
 	return decoded
 }
 
@@ -112,7 +86,6 @@ func wantField(t *testing.T, decoded map[string]any, key string, want any) {
 	if !ok {
 		t.Fatalf("field %q missing from output: %v", key, decoded)
 	}
-
 	if got != want {
 		t.Fatalf("field %q = %v, want %v", key, got, want)
 	}
@@ -126,34 +99,13 @@ func wantGroup(t *testing.T, decoded map[string]any, key string) map[string]any
 	if !ok {
 		t.Fatalf("group %q missing from output: %v", key, decoded)
 	}
-
 	group, ok := got.(map[string]any)
 	if !ok {
 		t.Fatalf("field %q = %v, want a nested object", key, got)
 	}
-
 	return group
 }
 
-// wantNoField asserts that a decoded JSON object does not carry key.
-func wantNoField(t *testing.T, decoded map[string]any, key string) {
-	t.Helper()
-
-	if got, present := decoded[key]; present {
-		t.Fatalf("field %q unexpectedly present as %v: %v", key, got, decoded)
-	}
-}
-
-// wantUnchanged asserts that a value the caller still owns was not written to
-// by the handler. Logging must read what it is handed, never modify it.
-func wantUnchanged(t *testing.T, what string, got, want any) {
-	t.Helper()
-
-	if !reflect.DeepEqual(got, want) {
-		t.Fatalf("handler mutated the caller's %s: got %v, want %v", what, got, want)
-	}
-}
-
 // wantContains asserts that console output contains a fragment.
 func wantContains(t *testing.T, output, fragment string) {
 	t.Helper()
@@ -184,19 +136,18 @@ func (c castTarget) LogValue() slog.Value {
 
 var _ slog.LogValuer = castTarget{}
 
-// errConnectionRefused is the error the ResolvesValues tests log.
-var errConnectionRefused = errors.New("connection refused")
-
 func TestJSONHandlerEmitsRecordAttrs(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
+		handler := NewJSONHandler()
 		record := testRecord(
 			"casting",
 			slog.String("device", "livingroom"),
 			slog.String("file", "movie.mp4"),
 			slog.Int("attempt", 3),
 		)
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	decoded := decodeLine(t, output)
@@ -208,11 +159,13 @@ func TestJSONHandlerEmitsRecordAttrs(t *testing.T) {
 
 func TestJSONHandlerWithAttrsAccumulates(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler().
+		handler := NewJSONHandler().
 			WithAttrs([]slog.Attr{slog.String("service", "cattbox")}).
 			WithAttrs([]slog.Attr{slog.String("component", "caster")})
 		record := testRecord("casting", slog.String("device", "livingroom"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	decoded := decodeLine(t, output)
@@ -222,38 +175,43 @@ func TestJSONHandlerWithAttrsAccumulates(t *testing.T) {
 }
 
 func TestJSONHandlerWithAttrsDoesNotMutateReceiver(t *testing.T) {
-	parent := simplelog.NewJSONHandler()
+	parent := NewJSONHandler()
 	first := parent.WithAttrs([]slog.Attr{slog.String("worker", "first")})
 	second := parent.WithAttrs([]slog.Attr{slog.String("worker", "second")})
 
 	firstOutput := captureStdout(t, func() {
-		handle(t, first, testRecord("work"))
+		if err := first.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 	secondOutput := captureStdout(t, func() {
-		handle(t, second, testRecord("work"))
+		if err := second.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 	parentOutput := captureStdout(t, func() {
-		handle(t, parent, testRecord("work"))
+		if err := parent.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantField(t, decodeLine(t, firstOutput), "worker", "first")
 	wantField(t, decodeLine(t, secondOutput), "worker", "second")
 
 	if _, present := decodeLine(t, parentOutput)["worker"]; present {
-		t.Fatalf(
+		t.Fatalf("parent handler leaked an attribute from a derived handler: %s", parentOutput)
-			"parent handler leaked an attribute from a derived handler: %s",
-			parentOutput,
-		)
 	}
 }
 
 func TestJSONHandlerWithGroupNestsAttrs(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler().
+		handler := NewJSONHandler().
 			WithGroup("cast").
 			WithAttrs([]slog.Attr{slog.String("device", "livingroom")})
 		record := testRecord("casting", slog.String("file", "movie.mp4"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	decoded := decodeLine(t, output)
@@ -266,14 +224,16 @@ func TestJSONHandlerWithGroupNestsAttrs(t *testing.T) {
 
 func TestJSONHandlerResolvesValues(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
+		handler := NewJSONHandler()
 		record := testRecord(
 			"cast failed",
 			slog.Group("request", slog.Int("status", 502), slog.String("method", "POST")),
 			slog.Any("target", castTarget{id: "chromecast-7"}),
-			slog.Any("error", errConnectionRefused),
+			slog.Any("error", errors.New("connection refused")),
 		)
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	decoded := decodeLine(t, output)
@@ -287,14 +247,16 @@ func TestJSONHandlerResolvesValues(t *testing.T) {
 
 func TestConsoleHandlerEmitsRecordAttrs(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
+		handler := NewConsoleHandler()
 		record := testRecord(
 			"casting",
 			slog.String("device", "livingroom"),
 			slog.String("file", "movie.mp4"),
 			slog.Int("attempt", 3),
 		)
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, output, "casting")
@@ -305,129 +267,25 @@ func TestConsoleHandlerEmitsRecordAttrs(t *testing.T) {
 
 func TestConsoleHandlerQuotesValuesNeedingIt(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
+		handler := NewConsoleHandler()
 		record := testRecord("casting", slog.String("file", "The Movie.mp4"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, output, `file="The Movie.mp4"`)
 }
 
-// TestConsoleHandlerQuotesKeysNeedingIt pins the key side of the same rule.
-// A key is quoted on the same terms as a value, and as one token including
-// its group prefix, so that the "=" separating the pair is always the first
-// one outside quotes. Every case here was compared against
-// slog.NewTextHandler, which renders each of them identically.
-func TestConsoleHandlerQuotesKeysNeedingIt(t *testing.T) {
-	tests := []struct {
-		name    string
-		build   func() slog.Handler
-		attrs   []slog.Attr
-		want    string
-		notWant string
-	}{
-		{
-			name:    "an ordinary key is left bare",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String("device", "livingroom")},
-			want:    " device=livingroom",
-			notWant: `"device"`,
-		},
-		{
-			name:    "a key containing an equals sign is quoted",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String("a=b", "v2")},
-			want:    ` "a=b"=v2`,
-			notWant: " a=b=v2",
-		},
-		{
-			name:    "a key containing a space is quoted",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String("my key", "v")},
-			want:    ` "my key"=v`,
-			notWant: " my key=v",
-		},
-		{
-			name:    "a key containing a quote is escaped",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String(`he"llo`, "v")},
-			want:    ` "he\"llo"=v`,
-			notWant: ` he"llo=v`,
-		},
-		{
-			name:    "a printable non-ascii key is left bare",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String("キー", "v")},
-			want:    " キー=v",
-			notWant: `"キー"`,
-		},
-		{
-			name:  "a group prefix is quoted together with its key",
-			build: func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs: []slog.Attr{
-				slog.Group("grp", slog.String("a=b", "v")),
-			},
-			want:    ` "grp.a=b"=v`,
-			notWant: " grp.a=b=v",
-		},
-		{
-			name: "a WithGroup prefix needing quotes is quoted with its key",
-			build: func() slog.Handler {
-				return simplelog.NewConsoleHandler().WithGroup("my grp")
-			},
-			attrs:   []slog.Attr{slog.String("k", "v")},
-			want:    ` "my grp.k"=v`,
-			notWant: " my grp.k=v",
-		},
-		{
-			name:    "an empty key is quoted rather than left as a gap",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{slog.String("", "v")},
-			want:    ` ""=v`,
-			notWant: " =v",
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			output := captureStdout(t, func() {
-				handle(t, test.build(), testRecord("casting", test.attrs...))
-			})
-
-			wantContains(t, output, test.want)
-			wantNotContains(t, output, test.notWant)
-		})
-	}
-}
-
-// TestConsoleHandlerQuotesInvalidUTF8 checks that a key or a value holding
-// invalid UTF-8 is quoted with the bad byte escaped, as slog.NewTextHandler
-// does, so the raw byte never reaches the terminal. Valid non-ASCII stays bare.
-func TestConsoleHandlerQuotesInvalidUTF8(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
-		record := testRecord(
-			"casting",
-			slog.String("bad\xffkey", "v"),
-			slog.String("raw", "bad\xffvalue"),
-			slog.String("title", "Amélie"),
-		)
-		handle(t, handler, record)
-	})
-
-	wantContains(t, output, ` "bad\xffkey"=v`)
-	wantContains(t, output, ` raw="bad\xffvalue"`)
-	wantContains(t, output, " title=Amélie")
-	wantNotContains(t, output, "\xff")
-}
-
 func TestConsoleHandlerWithAttrsAccumulates(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler().
+		handler := NewConsoleHandler().
 			WithAttrs([]slog.Attr{slog.String("service", "cattbox")}).
 			WithAttrs([]slog.Attr{slog.String("component", "caster")})
 		record := testRecord("casting", slog.String("device", "livingroom"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, output, "service=cattbox")
@@ -436,18 +294,24 @@ func TestConsoleHandlerWithAttrsAccumulates(t *testing.T) {
 }
 
 func TestConsoleHandlerWithAttrsDoesNotMutateReceiver(t *testing.T) {
-	parent := simplelog.NewConsoleHandler()
+	parent := NewConsoleHandler()
 	first := parent.WithAttrs([]slog.Attr{slog.String("worker", "first")})
 	second := parent.WithAttrs([]slog.Attr{slog.String("worker", "second")})
 
 	firstOutput := captureStdout(t, func() {
-		handle(t, first, testRecord("work"))
+		if err := first.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 	secondOutput := captureStdout(t, func() {
-		handle(t, second, testRecord("work"))
+		if err := second.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 	parentOutput := captureStdout(t, func() {
-		handle(t, parent, testRecord("work"))
+		if err := parent.Handle(context.Background(), testRecord("work")); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, firstOutput, "worker=first")
@@ -459,11 +323,13 @@ func TestConsoleHandlerWithAttrsDoesNotMutateReceiver(t *testing.T) {
 
 func TestConsoleHandlerWithGroupQualifiesAttrs(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler().
+		handler := NewConsoleHandler().
 			WithGroup("cast").
 			WithAttrs([]slog.Attr{slog.String("device", "livingroom")})
 		record := testRecord("casting", slog.String("file", "movie.mp4"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, output, "cast.device=livingroom")
@@ -472,14 +338,16 @@ func TestConsoleHandlerWithGroupQualifiesAttrs(t *testing.T) {
 
 func TestConsoleHandlerResolvesValues(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
+		handler := NewConsoleHandler()
 		record := testRecord(
 			"cast failed",
 			slog.Group("request", slog.Int("status", 502)),
 			slog.Any("target", castTarget{id: "chromecast-7"}),
-			slog.Any("error", errConnectionRefused),
+			slog.Any("error", errors.New("connection refused")),
 		)
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	wantContains(t, output, "request.status=502")
@@ -488,32 +356,29 @@ func TestConsoleHandlerResolvesValues(t *testing.T) {
 }
 
 func TestWebhookHandlerEmitsAttrs(t *testing.T) {
-	t.Parallel()
-
 	bodies := make(chan []byte, 1)
-
 	server := httptest.NewServer(http.HandlerFunc(
 		func(w http.ResponseWriter, r *http.Request) {
 			body, err := io.ReadAll(r.Body)
 			if err != nil {
 				t.Errorf("read webhook body: %v", err)
 			}
-
 			bodies <- body
-
 			w.WriteHeader(http.StatusOK)
 		},
 	))
 	defer server.Close()
 
-	handler, err := simplelog.NewWebhookHandler(server.URL)
+	handler, err := NewWebhookHandler(server.URL)
 	if err != nil {
 		t.Fatalf("NewWebhookHandler: %v", err)
 	}
 
 	withAttrs := handler.WithAttrs([]slog.Attr{slog.String("service", "cattbox")})
 	record := testRecord("casting", slog.String("device", "livingroom"))
-	handle(t, withAttrs, record)
+	if err := withAttrs.Handle(context.Background(), record); err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
 
 	var body []byte
 	select {
@@ -528,385 +393,18 @@ func TestWebhookHandlerEmitsAttrs(t *testing.T) {
 }
 
 // TestMultiplexHandlerPassesAttrsThrough guards the composite handler that
-// package init installs: attributes must survive the multiplex too. It is
+// package init installs: attributes must survive the multiplex too.
-// built while stdout is the capture pipe, which is not a terminal, so it
-// writes through the JSON handler.
 func TestMultiplexHandlerPassesAttrsThrough(t *testing.T) {
 	output := captureStdout(t, func() {
-		handler := simplelog.NewMultiplexHandler().
+		handler := (&MultiplexHandler{handlers: []ExtendedHandler{NewJSONHandler()}}).
 			WithAttrs([]slog.Attr{slog.String("service", "cattbox")})
 		record := testRecord("casting", slog.String("device", "livingroom"))
-		handle(t, handler, record)
+		if err := handler.Handle(context.Background(), record); err != nil {
+			t.Fatalf("Handle: %v", err)
+		}
 	})
 
 	decoded := decodeLine(t, output)
 	wantField(t, decoded, "service", "cattbox")
 	wantField(t, decoded, "device", "livingroom")
 }
-
-// A logging library must read the values it is handed and never write to them.
-// The dangerous shape is a group that shares a key with something the caller
-// logged by reference: merging the group's members into whatever already sits
-// at that key would reach straight back into the caller's own data structure.
-// The next four tests hold every handler to that, through both the record path
-// and the derived-logger path.
-
-func TestJSONHandlerDoesNotMutateCallerMap(t *testing.T) {
-	caller := map[string]any{"mine": "untouched"}
-	want := maps.Clone(caller)
-
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
-		record := testRecord(
-			"casting",
-			slog.Any("g", caller),
-			slog.Group("g", slog.Int("injected", 1)),
-		)
-		handle(t, handler, record)
-	})
-
-	wantUnchanged(t, "map", caller, want)
-
-	// The later attribute wins the key outright, as any repeated key does.
-	group := wantGroup(t, decodeLine(t, output), "g")
-	wantField(t, group, "injected", float64(1))
-	wantNoField(t, group, "mine")
-}
-
-func TestJSONHandlerDoesNotMutateCallerMapThroughWithAttrs(t *testing.T) {
-	caller := map[string]any{"id": "req-1"}
-	want := maps.Clone(caller)
-
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler().
-			WithAttrs([]slog.Attr{slog.Any("req", caller)}).
-			WithGroup("req")
-		record := testRecord("cast failed", slog.Int("status", 502))
-		handle(t, handler, record)
-	})
-
-	wantUnchanged(t, "map", caller, want)
-
-	group := wantGroup(t, decodeLine(t, output), "req")
-	wantField(t, group, "status", float64(502))
-	wantNoField(t, group, "id")
-}
-
-// TestJSONHandlerDoesNotMutateCallerSlice is the slice form of the same
-// hazard: a caller's slice is also handed over by reference, and appending
-// into its spare capacity would be just as visible to the caller as writing
-// into its map. The slice is built with room to spare so that an append within
-// capacity cannot hide behind an unchanged length.
-func TestJSONHandlerDoesNotMutateCallerSlice(t *testing.T) {
-	caller := make([]any, 2, 4)
-	caller[0] = "first"
-	caller[1] = "second"
-	backing := slices.Clone(caller[:cap(caller)])
-
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
-		record := testRecord(
-			"casting",
-			slog.Any("s", caller),
-			slog.Group("s", slog.Int("injected", 1)),
-		)
-		handle(t, handler, record)
-	})
-
-	wantUnchanged(t, "slice", caller, backing[:2])
-	wantUnchanged(t, "slice backing array", caller[:cap(caller)], backing)
-
-	group := wantGroup(t, decodeLine(t, output), "s")
-	wantField(t, group, "injected", float64(1))
-}
-
-func TestConsoleHandlerDoesNotMutateCallerMap(t *testing.T) {
-	caller := map[string]any{"mine": "untouched"}
-	want := maps.Clone(caller)
-
-	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
-		record := testRecord(
-			"casting",
-			slog.Any("g", caller),
-			slog.Group("g", slog.Int("injected", 1)),
-		)
-		handle(t, handler, record)
-	})
-
-	wantUnchanged(t, "map", caller, want)
-	wantContains(t, output, "g.injected=1")
-}
-
-func TestWebhookHandlerDoesNotMutateCallerMap(t *testing.T) {
-	t.Parallel()
-
-	caller := map[string]any{"id": "req-1"}
-	want := maps.Clone(caller)
-
-	bodies := make(chan []byte, 1)
-
-	server := httptest.NewServer(http.HandlerFunc(
-		func(w http.ResponseWriter, r *http.Request) {
-			body, err := io.ReadAll(r.Body)
-			if err != nil {
-				t.Errorf("read webhook body: %v", err)
-			}
-
-			bodies <- body
-
-			w.WriteHeader(http.StatusOK)
-		},
-	))
-	defer server.Close()
-
-	handler, err := simplelog.NewWebhookHandler(server.URL)
-	if err != nil {
-		t.Fatalf("NewWebhookHandler: %v", err)
-	}
-
-	derived := handler.
-		WithAttrs([]slog.Attr{slog.Any("req", caller)}).
-		WithGroup("req")
-	record := testRecord("cast failed", slog.Int("status", 502))
-	handle(t, derived, record)
-
-	var body []byte
-	select {
-	case body = <-bodies:
-	case <-time.After(5 * time.Second):
-		t.Fatal("webhook handler posted nothing")
-	}
-
-	wantUnchanged(t, "map", caller, want)
-
-	group := wantGroup(t, decodeLine(t, string(body)), "req")
-	wantField(t, group, "status", float64(502))
-}
-
-// TestJSONHandlerRendersDurationAsNanoseconds pins the json rendering of a
-// duration to a number of nanoseconds, which is what slog.NewJSONHandler
-// emits. A consumer that sums or compares the field needs a number; the "3s"
-// form would silently arrive as a string.
-func TestJSONHandlerRendersDurationAsNanoseconds(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
-		record := testRecord("casting", slog.Duration("elapsed", 3*time.Second))
-		handle(t, handler, record)
-	})
-
-	decoded := decodeLine(t, output)
-	if _, isNumber := decoded["elapsed"].(float64); !isNumber {
-		t.Fatalf("field \"elapsed\" = %#v, want a json number", decoded["elapsed"])
-	}
-
-	wantField(t, decoded, "elapsed", float64((3 * time.Second).Nanoseconds()))
-}
-
-// TestConsoleHandlerRendersDurationReadably is the other half of that choice:
-// the console line is read by a person, so it carries the same human-readable
-// form slog.NewTextHandler uses.
-func TestConsoleHandlerRendersDurationReadably(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
-		record := testRecord("casting", slog.Duration("elapsed", 3*time.Second))
-		handle(t, handler, record)
-	})
-
-	wantContains(t, output, "elapsed=3s")
-}
-
-// TestJSONHandlerContractEdgeCases pins the slog.Handler contract's four
-// edge cases. Every case carries a control attribute as well, so a handler
-// that emitted no attributes at all would fail rather than pass by omission.
-//
-// The empty group is attached through WithAttrs rather than to the record,
-// because slog.Record.AddAttrs elides empty groups itself: routed through the
-// record, the case would never reach the handler at all.
-func TestJSONHandlerContractEdgeCases(t *testing.T) {
-	tests := []struct {
-		name   string
-		build  func() slog.Handler
-		attrs  []slog.Attr
-		verify func(t *testing.T, decoded map[string]any)
-	}{
-		{
-			name:  "empty attr is ignored",
-			build: func() slog.Handler { return simplelog.NewJSONHandler() },
-			attrs: []slog.Attr{{}, slog.String("kept", "yes")},
-			verify: func(t *testing.T, decoded map[string]any) {
-				t.Helper()
-				wantField(t, decoded, "kept", "yes")
-				wantNoField(t, decoded, "")
-			},
-		},
-		{
-			name: "empty group is elided along with its key",
-			build: func() slog.Handler {
-				return simplelog.NewJSONHandler().
-					WithAttrs([]slog.Attr{slog.Group("empty")})
-			},
-			attrs: []slog.Attr{slog.String("kept", "yes")},
-			verify: func(t *testing.T, decoded map[string]any) {
-				t.Helper()
-				wantField(t, decoded, "kept", "yes")
-				wantNoField(t, decoded, "empty")
-			},
-		},
-		{
-			name:  "group with an empty key is inlined",
-			build: func() slog.Handler { return simplelog.NewJSONHandler() },
-			attrs: []slog.Attr{
-				slog.Group("", slog.String("inner", "yes")),
-			},
-			verify: func(t *testing.T, decoded map[string]any) {
-				t.Helper()
-				wantField(t, decoded, "inner", "yes")
-				wantNoField(t, decoded, "")
-			},
-		},
-		{
-			name: "WithGroup with an empty name is a no-op",
-			build: func() slog.Handler {
-				return simplelog.NewJSONHandler().WithGroup("")
-			},
-			attrs: []slog.Attr{slog.String("kept", "yes")},
-			verify: func(t *testing.T, decoded map[string]any) {
-				t.Helper()
-				wantField(t, decoded, "kept", "yes")
-				wantNoField(t, decoded, "")
-			},
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			output := captureStdout(t, func() {
-				handle(t, test.build(), testRecord("casting", test.attrs...))
-			})
-
-			test.verify(t, decodeLine(t, output))
-		})
-	}
-}
-
-// TestConsoleHandlerContractEdgeCases holds the console handler to the same
-// four rules, since it renders attributes through its own code path.
-func TestConsoleHandlerContractEdgeCases(t *testing.T) {
-	tests := []struct {
-		name    string
-		build   func() slog.Handler
-		attrs   []slog.Attr
-		want    string
-		notWant string
-	}{
-		{
-			name:    "empty attr is ignored",
-			build:   func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs:   []slog.Attr{{}, slog.String("kept", "yes")},
-			want:    "kept=yes",
-			notWant: " =",
-		},
-		{
-			name: "empty group is elided along with its key",
-			build: func() slog.Handler {
-				return simplelog.NewConsoleHandler().
-					WithAttrs([]slog.Attr{slog.Group("empty")})
-			},
-			attrs:   []slog.Attr{slog.String("kept", "yes")},
-			want:    "kept=yes",
-			notWant: "empty=",
-		},
-		{
-			name:  "group with an empty key is inlined",
-			build: func() slog.Handler { return simplelog.NewConsoleHandler() },
-			attrs: []slog.Attr{
-				slog.Group("", slog.String("inner", "yes")),
-			},
-			want:    " inner=yes",
-			notWant: ".inner=",
-		},
-		{
-			name: "WithGroup with an empty name is a no-op",
-			build: func() slog.Handler {
-				return simplelog.NewConsoleHandler().WithGroup("")
-			},
-			attrs:   []slog.Attr{slog.String("kept", "yes")},
-			want:    " kept=yes",
-			notWant: ".kept=",
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			output := captureStdout(t, func() {
-				handle(t, test.build(), testRecord("casting", test.attrs...))
-			})
-
-			wantContains(t, output, test.want)
-			wantNotContains(t, output, test.notWant)
-		})
-	}
-}
-
-// TestJSONHandlerRecordFieldsWinKeyCollision pins a caller-visible surprise:
-// the json payload is an object, so the record's own fields own their names
-// and an attribute keyed after one of them is dropped rather than emitted.
-func TestJSONHandlerRecordFieldsWinKeyCollision(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
-		record := testRecord(
-			"the real message",
-			slog.String("Time", "hijacked"),
-			slog.String("Level", "hijacked"),
-			slog.String("Message", "hijacked"),
-			slog.String("PC", "hijacked"),
-			slog.String("kept", "yes"),
-		)
-		handle(t, handler, record)
-	})
-
-	decoded := decodeLine(t, output)
-	wantField(t, decoded, "kept", "yes")
-	wantField(t, decoded, "Message", "the real message")
-	wantField(t, decoded, "Level", "INFO")
-
-	for _, reserved := range []string{"Time", "PC"} {
-		if decoded[reserved] == "hijacked" {
-			t.Fatalf("attribute overwrote the record's own %q field: %v", reserved, decoded)
-		}
-	}
-}
-
-// TestJSONHandlerDuplicateKeysKeepLast pins the other consequence of the
-// payload being an object: a key logged twice collapses to its last value.
-func TestJSONHandlerDuplicateKeysKeepLast(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewJSONHandler()
-		record := testRecord(
-			"casting",
-			slog.String("device", "kitchen"),
-			slog.String("device", "livingroom"),
-		)
-		handle(t, handler, record)
-	})
-
-	wantField(t, decodeLine(t, output), "device", "livingroom")
-}
-
-// TestConsoleHandlerKeepsDuplicateKeys is the console counterpart: a line of
-// text is not an object, so both pairs survive there.
-func TestConsoleHandlerKeepsDuplicateKeys(t *testing.T) {
-	output := captureStdout(t, func() {
-		handler := simplelog.NewConsoleHandler()
-		record := testRecord(
-			"casting",
-			slog.String("device", "kitchen"),
-			slog.String("device", "livingroom"),
-		)
-		handle(t, handler, record)
-	})
-
-	wantContains(t, output, "device=kitchen")
-	wantContains(t, output, "device=livingroom")
-}

cmd/example/main.go

@@ -1,5 +1,3 @@
-// Command example demonstrates logging through simplelog's default
-// slog handler.
 package main
 
 import (
@@ -8,15 +6,13 @@ import (
 	_ "sneak.berlin/go/simplelog"
 )
 
-// attemptNumber is the example login attempt count logged below.
-const attemptNumber = 3
-
 func main() {
+
 	// log structured data with slog as usual:
 	slog.Info(
 		"User login attempt",
 		slog.String("user", "JohnDoe"),
-		slog.Int("attempt", attemptNumber),
+		slog.Int("attempt", 3),
 	)
 	slog.Warn(
 		"Configuration mismatch",

console_handler.go

@@ -4,41 +4,28 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
-	"os"
 	"runtime"
 	"time"
 
 	"github.com/fatih/color"
 )
 
-// callerSkipFrames is the number of stack frames between runtime.Caller
-// and the slog call site that produced the record.
-const callerSkipFrames = 4
-
-// ConsoleHandler writes human-readable, colored log lines to stdout.
 type ConsoleHandler struct {
 	attrs handlerAttrs
 }
 
-// NewConsoleHandler returns a new ConsoleHandler.
 func NewConsoleHandler() *ConsoleHandler {
 	return &ConsoleHandler{}
 }
 
-// Handle writes the record to stdout as a colored, timestamped line
-// including the caller file and line, followed by the attributes as
-// key=value pairs.
 func (c *ConsoleHandler) Handle(
-	_ context.Context,
+	ctx context.Context,
 	record slog.Record,
 ) error {
 	timestamp := time.Now().UTC().Format("2006-01-02T15:04:05.000Z07:00")
-
+	var colorFunc func(format string, a ...interface{}) string
-	var colorFunc func(format string, a ...any) string
 
 	switch record.Level {
-	case slog.LevelDebug:
-		colorFunc = color.New(color.FgWhite).SprintfFunc()
 	case slog.LevelInfo:
 		colorFunc = color.New(color.FgBlue).SprintfFunc()
 	case slog.LevelWarn:
@@ -50,14 +37,12 @@ func (c *ConsoleHandler) Handle(
 	}
 
 	// Get the caller information
-	_, file, line, ok := runtime.Caller(callerSkipFrames)
+	_, file, line, ok := runtime.Caller(4)
 	if !ok {
 		file = "???"
 		line = 0
 	}
-
+	fmt.Println(
-	_, _ = fmt.Fprintln(
-		os.Stdout,
 		colorFunc(
 			"%s [%s] %s:%d: %s%s",
 			timestamp,
@@ -68,35 +53,26 @@ func (c *ConsoleHandler) Handle(
 			attrsToText(c.attrs.forRecord(record)),
 		),
 	)
-
 	return nil
 }
 
-// Enabled reports whether the handler processes records at the given
-// level; it always returns true.
 func (c *ConsoleHandler) Enabled(
-	_ context.Context,
+	ctx context.Context,
-	_ slog.Level,
+	level slog.Level,
 ) bool {
 	return true
 }
 
-// WithAttrs returns a new handler that also emits attrs, qualified by the
-// groups open now. The receiver is not modified.
 func (c *ConsoleHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	if len(attrs) == 0 {
 		return c
 	}
-
 	return &ConsoleHandler{attrs: c.attrs.withAttrs(attrs)}
 }
 
-// WithGroup returns a new handler that qualifies later attributes with
-// the group name. An empty name returns the receiver.
 func (c *ConsoleHandler) WithGroup(name string) slog.Handler {
 	if name == "" {
 		return c
 	}
-
 	return &ConsoleHandler{attrs: c.attrs.withGroup(name)}
 }

event.go

@@ -7,8 +7,6 @@ import (
 	"github.com/google/uuid"
 )
 
-// Event is a single structured log entry with a unique ID and
-// timestamp.
 type Event struct {
 	ID        uuid.UUID       `json:"id"`
 	Timestamp time.Time       `json:"timestamp"`
@@ -17,8 +15,6 @@ type Event struct {
 	Data      json.RawMessage `json:"data"`
 }
 
-// NewEvent returns an Event with a fresh ID and the current UTC
-// timestamp.
 func NewEvent(level, message string, data json.RawMessage) Event {
 	return Event{
 		ID:        uuid.New(),

handler.go

@@ -2,7 +2,7 @@ package simplelog
 
 import "log/slog"
 
-// ExtendedHandler defines the interface for different log outputs.
+// Handler defines the interface for different log outputs.
 type ExtendedHandler interface {
 	slog.Handler
 }

json_handler.go

@@ -8,51 +8,37 @@ import (
 	"os"
 )
 
-// JSONHandler writes each log record to stdout as a JSON document.
 type JSONHandler struct {
 	attrs handlerAttrs
 }
 
-// NewJSONHandler returns a new JSONHandler.
 func NewJSONHandler() *JSONHandler {
 	return &JSONHandler{}
 }
 
-// Handle marshals the record, with its attributes, to one JSON object and
+func (j *JSONHandler) Handle(ctx context.Context, record slog.Record) error {
-// writes it to stdout.
-func (j *JSONHandler) Handle(_ context.Context, record slog.Record) error {
 	jsonData, err := json.Marshal(recordToMap(record, j.attrs))
 	if err != nil {
-		return err
+		return fmt.Errorf("error marshaling log record: %w", err)
 	}
-
 	_, _ = fmt.Fprintln(os.Stdout, string(jsonData))
-
 	return nil
 }
 
-// Enabled reports whether the handler processes records at the given
+func (j *JSONHandler) Enabled(ctx context.Context, level slog.Level) bool {
-// level; it always returns true.
-func (j *JSONHandler) Enabled(_ context.Context, _ slog.Level) bool {
 	return true
 }
 
-// WithAttrs returns a new handler that also emits attrs, qualified by the
-// groups open now. The receiver is not modified.
 func (j *JSONHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	if len(attrs) == 0 {
 		return j
 	}
-
 	return &JSONHandler{attrs: j.attrs.withAttrs(attrs)}
 }
 
-// WithGroup returns a new handler that nests later attributes in an
-// object named after the group. An empty name returns the receiver.
 func (j *JSONHandler) WithGroup(name string) slog.Handler {
 	if name == "" {
 		return j
 	}
-
 	return &JSONHandler{attrs: j.attrs.withGroup(name)}
 }

json_handler_test.go

@@ -1,27 +1,22 @@
-package simplelog_test
+package simplelog
 
 import (
 	"log/slog"
 	"testing"
 	"time"
-
-	"sneak.berlin/go/simplelog"
 )
 
 // TestJSONHandlerDeadlock verifies that JSONHandler.Handle does not deadlock
 // when the default slog handler routes log.Println back through slog.
 // On the unfixed code this test will hang (deadlock); with the fix it completes.
 func TestJSONHandlerDeadlock(t *testing.T) {
-	t.Parallel()
+	handler := NewJSONHandler()
-
-	handler := simplelog.NewJSONHandler()
 
 	// Set our handler as the default so log.Println routes through slog
 	logger := slog.New(handler)
 	slog.SetDefault(logger)
 
 	done := make(chan struct{})
-
 	go func() {
 		// This call deadlocks on unfixed code because Handle() calls
 		// log.Println() which re-enters slog → Handle() → log.Println() …

simplelog.go

@@ -1,7 +1,3 @@
-// Package simplelog installs a multiplexing slog handler as the process
-// default on import. It logs human-readable colored output when stdout is
-// a terminal, JSON otherwise, and can additionally POST each record to a
-// webhook configured via the LOGGER_WEBHOOK_URL environment variable.
 package simplelog
 
 import (
@@ -17,31 +13,23 @@ import (
 	"github.com/mattn/go-isatty"
 )
 
-//nolint:gochecknoglobals // webhook destination is read once from the environment
-var webhookURL = os.Getenv("LOGGER_WEBHOOK_URL")
-
-//nolint:gochecknoglobals // package-level default logger state is the package's design
 var (
-	ourCustomLogger  *slog.Logger
+	webhookURL = os.Getenv("LOGGER_WEBHOOK_URL")
-	ourCustomHandler slog.Handler
 )
 
-//nolint:gochecknoinits // installs itself as slog default on import by design
+var ourCustomLogger *slog.Logger
+var ourCustomHandler slog.Handler
+
 func init() {
 	ourCustomHandler = NewMultiplexHandler()
 	ourCustomLogger = slog.New(ourCustomHandler)
 	slog.SetDefault(ourCustomLogger)
 }
 
-// MultiplexHandler fans each log record out to a set of underlying
-// handlers.
 type MultiplexHandler struct {
 	handlers []ExtendedHandler
 }
 
-// NewMultiplexHandler returns a handler that writes colored console
-// output when stdout is a terminal and JSON otherwise, plus an optional
-// webhook handler when LOGGER_WEBHOOK_URL is set.
 func NewMultiplexHandler() slog.Handler {
 	cl := &MultiplexHandler{}
 	if isatty.IsTerminal(os.Stdout.Fd()) {
@@ -49,69 +37,52 @@ func NewMultiplexHandler() slog.Handler {
 	} else {
 		cl.handlers = append(cl.handlers, NewJSONHandler())
 	}
-
 	if webhookURL != "" {
 		handler, err := NewWebhookHandler(webhookURL)
 		if err != nil {
 			log.Fatalf("Failed to initialize Webhook handler: %v", err)
 		}
-
 		cl.handlers = append(cl.handlers, handler)
 	}
-
 	return cl
 }
 
-// Handle forwards the record to every underlying handler, stopping at
-// the first error.
 func (cl *MultiplexHandler) Handle(
 	ctx context.Context,
 	record slog.Record,
 ) error {
 	for _, handler := range cl.handlers {
-		err := handler.Handle(ctx, record)
+		if err := handler.Handle(ctx, record); err != nil {
-		if err != nil {
 			return err
 		}
 	}
-
 	return nil
 }
 
-// Enabled reports whether the handler processes records at the given
-// level; it always returns true.
 func (cl *MultiplexHandler) Enabled(
-	_ context.Context,
+	ctx context.Context,
-	_ slog.Level,
+	level slog.Level,
 ) bool {
 	// send us all events
 	return true
 }
 
-// WithAttrs returns a new MultiplexHandler whose underlying handlers
-// each carry the given attributes.
 func (cl *MultiplexHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	newHandlers := make([]ExtendedHandler, len(cl.handlers))
 	for i, handler := range cl.handlers {
 		newHandlers[i] = handler.WithAttrs(attrs)
 	}
-
 	return &MultiplexHandler{handlers: newHandlers}
 }
 
-// WithGroup returns a new MultiplexHandler whose underlying handlers
-// each use the given group name.
 func (cl *MultiplexHandler) WithGroup(name string) slog.Handler {
 	newHandlers := make([]ExtendedHandler, len(cl.handlers))
 	for i, handler := range cl.handlers {
 		newHandlers[i] = handler.WithGroup(name)
 	}
-
 	return &MultiplexHandler{handlers: newHandlers}
 }
 
-// ExtendedEvent describes an Event augmented with caller file and line
-// information.
 type ExtendedEvent interface {
 	GetID() uuid.UUID
 	GetTimestamp() time.Time
@@ -124,7 +95,6 @@ type ExtendedEvent interface {
 
 type extendedEvent struct {
 	Event
-
 	File string `json:"file"`
 	Line int    `json:"line"`
 }
@@ -157,10 +127,6 @@ func (e extendedEvent) GetLine() int {
 	return e.Line
 }
 
-// NewExtendedEvent wraps baseEvent with the caller file and line it was
-// logged from.
-//
-//nolint:ireturn // returning the interface is this constructor's public API
 func NewExtendedEvent(baseEvent Event, file string, line int) ExtendedEvent {
 	return extendedEvent{
 		Event: baseEvent,

simplelog_test.go

@@ -1,9 +1,8 @@
-package simplelog_test
+package simplelog
 
 import "testing"
 
 // TestCompile checks if the package compiles successfully.
 func TestCompile(t *testing.T) {
-	t.Parallel()
 	// This test ensures that the simplelog package compiles without error.
 }

tools/relp_log_trial.go

@@ -1,5 +1,3 @@
-// Command relp_log_trial emits sample log messages through simplelog's
-// default slog handler for manual testing.
 package main
 
 import (
@@ -8,22 +6,11 @@ import (
 	_ "sneak.berlin/go/simplelog" // Using underscore to only invoke init()
 )
 
-// examplePort is the sample database port logged below.
-const examplePort = 5432
-
 func main() {
 	// Send some test messages with structured data
 	slog.Info("Starting the application", slog.String("status", "initialized"))
-	slog.Info(
+	slog.Info("Attempting to connect to database", slog.String("host", "localhost"), slog.Int("port", 5432))
-		"Attempting to connect to database",
-		slog.String("host", "localhost"),
-		slog.Int("port", examplePort),
-	)
 	slog.Warn("Using default configuration", slog.String("configuration", "default"))
-	slog.Error(
+	slog.Error("Failed to load module", slog.String("module", "finance"), slog.String("error", "module not found"))
-		"Failed to load module",
-		slog.String("module", "finance"),
-		slog.String("error", "module not found"),
-	)
 	slog.Info("Shutting down the application", slog.String("status", "stopped"))
 }

webhook_handler.go

@@ -10,82 +10,51 @@ import (
 	"net/url"
 )
 
-// WebhookHandler POSTs each log record as JSON to a configured webhook
-// URL.
 type WebhookHandler struct {
 	webhookURL string
 	attrs      handlerAttrs
 }
 
-// NewWebhookHandler returns a WebhookHandler that delivers records to
+func (w *WebhookHandler) Enabled(ctx context.Context, level slog.Level) bool {
-// the given URL, validating the URL first.
-func NewWebhookHandler(webhookURL string) (*WebhookHandler, error) {
-	_, err := url.ParseRequestURI(webhookURL)
-	if err != nil {
-		return nil, fmt.Errorf("invalid webhook URL: %w", err)
-	}
-
-	return &WebhookHandler{webhookURL: webhookURL}, nil
-}
-
-// Enabled reports whether the handler processes records at the given
-// level; it always returns true.
-func (w *WebhookHandler) Enabled(_ context.Context, _ slog.Level) bool {
 	return true
 }
 
-// WithAttrs returns a new handler that also emits attrs, qualified by the
-// groups open now. The receiver is not modified.
 func (w *WebhookHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	if len(attrs) == 0 {
 		return w
 	}
-
 	return &WebhookHandler{
 		webhookURL: w.webhookURL,
 		attrs:      w.attrs.withAttrs(attrs),
 	}
 }
 
-// WithGroup returns a new handler that nests later attributes in an
-// object named after the group. An empty name returns the receiver.
 func (w *WebhookHandler) WithGroup(name string) slog.Handler {
 	if name == "" {
 		return w
 	}
-
 	return &WebhookHandler{
 		webhookURL: w.webhookURL,
 		attrs:      w.attrs.withGroup(name),
 	}
 }
 
-// Handle marshals the record, with its attributes, to one JSON object and
+func NewWebhookHandler(webhookURL string) (*WebhookHandler, error) {
-// POSTs it to the webhook URL.
+	if _, err := url.ParseRequestURI(webhookURL); err != nil {
+		return nil, fmt.Errorf("invalid webhook URL: %v", err)
+	}
+	return &WebhookHandler{webhookURL: webhookURL}, nil
+}
+
 func (w *WebhookHandler) Handle(ctx context.Context, record slog.Record) error {
 	jsonData, err := json.Marshal(recordToMap(record, w.attrs))
 	if err != nil {
-		return fmt.Errorf("error marshaling event: %w", err)
+		return fmt.Errorf("error marshaling event: %v", err)
 	}
-
+	response, err := http.Post(w.webhookURL, "application/json", bytes.NewBuffer(jsonData))
-	request, err := http.NewRequestWithContext(
-		ctx,
-		http.MethodPost,
-		w.webhookURL,
-		bytes.NewReader(jsonData),
-	)
-	if err != nil {
-		return fmt.Errorf("error creating webhook request: %w", err)
-	}
-
-	request.Header.Set("Content-Type", "application/json")
-
-	response, err := http.DefaultClient.Do(request)
 	if err != nil {
 		return err
 	}
-
 	defer func() { _ = response.Body.Close() }()
-
 	return nil
 }