Record the gomodguard_v2 migration in TODO.md (closes #57)

Adds the Completed Steps entry for re-vendoring the canonical
.golangci.yml, which switches off the deprecated gomodguard and runs
gomodguard_v2 and depguard in its place.

Model: opus-5-5

.gitattributes

@@ -0,0 +1,4 @@
+# Every PR adds an entry at the top of TODO.md's Completed Steps; union keeps
+# both sides instead of conflicting. Git never reports a conflict here: read
+# the merged entries after every merge or rebase.
+TODO.md merge=union

README.md

@@ -413,10 +413,10 @@ pixa finds: `/etc/pixa/config.yml`, `/etc/pixa/config.yaml`,
 `~/.config/pixa/config.yml`, `~/.config/pixa/config.yaml`, then `config.yml`
 and `config.yaml` in the working directory. A named file that does not exist,
 cannot be read or does not parse aborts startup. Of the files pixa looks for on
-its own, one it finds but cannot read or parse aborts startup; one it cannot
+its own, only one that does not exist is passed over, without a message. One
-find, for any reason, is passed over without a message, even when the file is
+that pixa cannot read or parse aborts startup, naming the file. So does one in a
-there in a directory pixa may not enter. With no file, pixa uses the environment
+directory pixa may not enter, whether or not it is there, since pixa cannot
-and the defaults.
+tell. With no file, pixa uses the environment and the defaults.
 
 | Variable                             | Config key                      | Meaning                                                                      |
 | ------------------------------------ | ------------------------------- | ---------------------------------------------------------------------------- |

TODO.md

@@ -3,6 +3,8 @@
 * branch per issue from `next`
 * do the work in Next Step
 * move Next Step to the top of Completed Steps
+* `TODO.md` merges with git's union merge (`.gitattributes`), which never
+  reports a conflict: read the merged entries after every merge or rebase
 * move the top item of Future Steps into Next Step
 * commit (`TODO.md` changes in the same commit as the work)
 * open a PR based on `next`
@@ -29,6 +31,28 @@ P2: security: referer blacklist
 
 # Completed Steps
 
+- 2026-10-04 `TODO.md` merges with git's union merge (closes #190): a root
+  `.gitattributes`, copied from `sneak/prompts`, marks it `merge=union`, so two
+  branches that each add an entry at the top of Completed Steps merge without a
+  conflict and keep both entries. Git now never reports a conflict in
+  `TODO.md`: a real one keeps both versions of the lines, and two entries that
+  share an identical line can end up one inside the other, which a rebase can
+  do to an entry already on `next`. The Workflow above says to read the merged
+  entries after every merge or rebase.
+- 2026-10-04 `TestEvictionRunsOnPeriodicSchedule` no longer races the evictor
+  (closes #183): it wrote each variant file and then inserted its accounting row
+  by hand, and a reconciliation pass between the two adopted the file first, so
+  the insert failed. It now writes the files only, while holding the test
+  database's only connection so the evictor's startup pass waits after walking
+  the empty variant directory; a periodic reconciliation pass then adopts the
+  files and the eviction pass after it evicts them. No other test in
+  `internal/imgcache` inserts a row by hand after starting the evictor. Test
+  only.
+- 2026-10-04 a config file pixa cannot read aborts startup (closes #176): of the
+  places pixa looks for its config file on its own, only one where the file does
+  not exist is passed over; any other error, such as a directory on the path
+  that pixa may not enter, aborts startup naming the file, as a file that does
+  not parse already did.
 - 2026-10-04 `.golangci.yml` re-vendored from the canonical copy (closes #57):
   the deprecated `gomodguard` is switched off, so lint runs print no
   deprecation warning; its successor `gomodguard_v2` runs with the shared

internal/config/config.go

@@ -4,6 +4,7 @@ package config
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"log/slog"
 	"math"
 	"net/netip"
@@ -14,6 +15,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
 	"git.eeqj.de/sneak/smartconfig"
@@ -778,19 +780,27 @@ func loadConfigFile(log *slog.Logger, appName string) (*smartconfig.Config, erro
 	for _, path := range configPaths {
 		cleanPath := filepath.Clean(path)
 
+		// Only a config file that does not exist is skipped, including
+		// one whose path runs through a file, such as under a HOME of
+		// /dev/null. One that cannot be read or does not parse is a
+		// fatal startup error.
 		_, statErr := os.Stat(cleanPath)
-		if statErr == nil {
+		if errors.Is(statErr, fs.ErrNotExist) || errors.Is(statErr, syscall.ENOTDIR) {
-			// A config file that exists but does not parse is a fatal
+			continue
-			// startup error, never something to skip over.
-			sc, err := smartconfig.NewFromConfigPath(path)
-			if err != nil {
-				return nil, fmt.Errorf("failed to parse config file %s: %w", path, err)
-			}
-
-			log.Info("loaded config file", "path", path)
-
-			return sc, nil
 		}
+
+		if statErr != nil {
+			return nil, fmt.Errorf("failed to read config file %s: %w", path, statErr)
+		}
+
+		sc, err := smartconfig.NewFromConfigPath(path)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse config file %s: %w", path, err)
+		}
+
+		log.Info("loaded config file", "path", path)
+
+		return sc, nil
 	}
 
 	return nil, nil //nolint:nilnil // nil config is valid (use defaults)

internal/config/config_validation_internal_test.go

@@ -564,6 +564,116 @@ func TestMalformedConfigFileAbortsStartup(t *testing.T) {
 	t.Logf("got expected error: %v", err)
 }
 
+// TestConfigFileInDirectoryPixaMayNotEnterAbortsStartup checks that a
+// config file pixa cannot read because it may not enter its directory
+// aborts startup instead of being passed over.
+func TestConfigFileInDirectoryPixaMayNotEnterAbortsStartup(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root may enter any directory")
+	}
+
+	home := t.TempDir()
+	configDir := filepath.Join(home, ".config", "pixa-test-nonexistent-app")
+	configPath := filepath.Join(configDir, "config.yml")
+
+	err := os.MkdirAll(configDir, 0o700)
+	if err != nil {
+		t.Fatalf("failed to create config directory: %v", err)
+	}
+
+	err = os.WriteFile(configPath, []byte(signingKeyLine), 0o600)
+	if err != nil {
+		t.Fatalf("failed to write config: %v", err)
+	}
+
+	err = os.Chmod(configDir, 0)
+	if err != nil {
+		t.Fatalf("failed to remove the config directory's permissions: %v", err)
+	}
+
+	// Give the directory back its permissions so t.TempDir can remove it.
+	t.Cleanup(func() {
+		//nolint:gosec // G302: a directory needs its execute bit to be removed
+		_ = os.Chmod(configDir, 0o700)
+	})
+
+	// The ~/.config candidate is the only one that exists: the appname
+	// rules out /etc, and the working directory is empty.
+	t.Setenv("PIXA_CONFIG_PATH", "")
+	t.Setenv("HOME", home)
+	t.Chdir(t.TempDir())
+
+	log := slog.New(slog.DiscardHandler)
+
+	sc, err := loadConfigFile(log, "pixa-test-nonexistent-app")
+	if err == nil {
+		t.Fatalf("config file pixa cannot read must abort startup, got config: %v",
+			sc)
+	}
+
+	t.Logf("got expected error: %v", err)
+
+	if !strings.Contains(err.Error(), configPath) {
+		t.Errorf("error %q does not name the config file %s", err.Error(), configPath)
+	}
+}
+
+// TestConfigFileLinkingToItselfAbortsStartup checks that a config file
+// pixa cannot read for a reason other than not existing aborts startup,
+// as root too: a symbolic link to itself fails with "too many levels of
+// symbolic links".
+func TestConfigFileLinkingToItselfAbortsStartup(t *testing.T) {
+	workDir := t.TempDir()
+
+	err := os.Symlink("config.yml", filepath.Join(workDir, "config.yml"))
+	if err != nil {
+		t.Fatalf("failed to create symbolic link: %v", err)
+	}
+
+	// Only the working directory's config.yml is there: the appname rules
+	// out /etc, and HOME is empty.
+	t.Setenv("PIXA_CONFIG_PATH", "")
+	t.Setenv("HOME", t.TempDir())
+	t.Chdir(workDir)
+
+	log := slog.New(slog.DiscardHandler)
+
+	sc, err := loadConfigFile(log, "pixa-test-nonexistent-app")
+	if err == nil {
+		t.Fatalf("config file pixa cannot read must abort startup, got config: %v",
+			sc)
+	}
+
+	t.Logf("got expected error: %v", err)
+
+	if !strings.Contains(err.Error(), "config.yml") {
+		t.Errorf("error %q does not name the config file config.yml", err.Error())
+	}
+}
+
+// TestConfigPathThroughFileIsPassedOver checks that a config file path
+// that runs through a file, such as one under a HOME of /dev/null, is
+// passed over like one that does not exist, since no file can be there.
+func TestConfigPathThroughFileIsPassedOver(t *testing.T) {
+	// No config file is there: the appname rules out /etc, HOME is
+	// /dev/null, and the working directory is empty.
+	t.Setenv("PIXA_CONFIG_PATH", "")
+	t.Setenv("HOME", os.DevNull)
+	t.Chdir(t.TempDir())
+
+	log := slog.New(slog.DiscardHandler)
+
+	sc, err := loadConfigFile(log, "pixa-test-nonexistent-app")
+	if err != nil {
+		t.Fatalf("a config path through a file must be passed over, got error: %v",
+			err)
+	}
+
+	if sc != nil {
+		t.Errorf("expected no config file, got config: %v", sc)
+	}
+}
+
 func TestEnsureStateDirCreatesDirectory(t *testing.T) {
 	t.Parallel()
 

internal/imgcache/eviction_internal_test.go

@@ -681,6 +681,11 @@ func TestEvictionRunsUnderWritePressure(t *testing.T) {
 	assertNoDanglingReferences(t, cache)
 }
 
+// TestEvictionRunsOnPeriodicSchedule writes three variant files straight
+// to disk, bypassing StoreVariant, so they have no accounting rows and no
+// write-pressure notification fires. Only a periodic reconciliation pass
+// can then adopt them, and only the eviction pass that follows it can
+// evict them.
 func TestEvictionRunsOnPeriodicSchedule(t *testing.T) {
 	t.Parallel()
 
@@ -688,13 +693,29 @@ func TestEvictionRunsOnPeriodicSchedule(t *testing.T) {
 
 	cache, _ := newEvictionTestCache(t, limit)
 
-	// Start the evictor while the cache is empty, then create tracked
+	// Hold the test database's only connection, so the startup pass
-	// over-limit state WITHOUT going through the store methods, so no
+	// waits for it after walking the still empty variant directory: the
-	// write-pressure notification fires and only the periodic ticker
+	// files written while it waits are first seen by a periodic pass.
-	// can trigger eviction.
+	conn, err := cache.db.Conn(t.Context())
+	if err != nil {
+		t.Fatalf("failed to take the database connection: %v", err)
+	}
+
+	defer func() { _ = conn.Close() }()
+
 	cache.StartEviction(100 * time.Millisecond)
 	defer func() { _ = cache.StopEviction(t.Context()) }()
 
+	deadline := time.Now().Add(5 * time.Second)
+
+	for cache.db.Stats().WaitCount == 0 {
+		if time.Now().After(deadline) {
+			t.Fatal("the startup pass never waited for the database")
+		}
+
+		time.Sleep(10 * time.Millisecond)
+	}
+
 	keys := []VariantKey{
 		testVariantKeyOne, testVariantKeyTwo, testVariantKeyThree,
 	}
@@ -703,25 +724,43 @@ func TestEvictionRunsOnPeriodicSchedule(t *testing.T) {
 	for i, key := range keys {
 		content := bytes.Repeat([]byte{fills[i]}, 1000)
 
-		_, err := cache.variants.Store(key, bytes.NewReader(content), "image/webp")
+		_, err = cache.variants.Store(key, bytes.NewReader(content), "image/webp")
 		if err != nil {
 			t.Fatalf("failed to store variant file: %v", err)
 		}
+	}
 
-		_, err = cache.db.ExecContext(t.Context(),
+	_ = conn.Close()
-			`INSERT INTO variant_content (cache_key, size_bytes, content_type)
+
-			 VALUES (?, ?, ?)`,
+	// Only one of the 1000-byte files fits under the limit: wait until
-			string(key), len(content), "image/webp",
+	// the evictor has removed the other two.
-		)
+	stored := len(keys)
-		if err != nil {
+	deadline = time.Now().Add(5 * time.Second)
-			t.Fatalf("failed to insert variant accounting row: %v", err)
+
+	for stored > 1 && time.Now().Before(deadline) {
+		time.Sleep(25 * time.Millisecond)
+
+		stored = 0
+
+		for _, key := range keys {
+			if cache.variants.Exists(key) {
+				stored++
+			}
 		}
 	}
 
-	usage := waitForUsageAtOrBelow(t, cache, limit, 5*time.Second)
+	if stored > 1 {
+		t.Fatalf("periodic schedule did not trigger eviction: %d of %d "+
+			"variant files still on disk, want at most 1", stored, len(keys))
+	}
+
+	usage, err := cache.UsageBytes(t.Context())
+	if err != nil {
+		t.Fatalf("UsageBytes failed: %v", err)
+	}
+
 	if usage > limit {
-		t.Errorf("periodic schedule did not trigger eviction: usage = %d, want <= %d",
+		t.Errorf("usage after eviction = %d, want <= %d", usage, limit)
-			usage, limit)
 	}
 
 	assertNoDanglingReferences(t, cache)