Print progress at once off a terminal, keep stderr to one writer (closes #13)

On a pipe, a file or /dev/null each scan phase now prints its zero-state
line the moment it starts instead of after its first finished item, so
a slow first read under cron no longer leaves the log silent. Terminal
detection uses golang.org/x/term, now a direct dependency listed in the
README; the old character-device test took /dev/null for a terminal.
The walk spinner no longer redraws from the library's own goroutine; it
advances only as items complete, so a redraw cannot garble a warning.
Building the bar moved into newBar so the terminal display can be
tested without a terminal.

Lint suppressed: gosec on two test file opens, paralleltest on three
tests that replace os.Stderr.

Model: opus-5-5

README.md

@@ -153,28 +153,16 @@ All three subcommands operate on a single SQLite database file:
     use. `report` and `trees` require an existing database; a missing
     database file is a fatal error (exit 1) telling the user to run
     `scan` first.
--   While `scan` runs, the database is in WAL journal mode with a busy
+-   The database uses WAL journal mode and a busy timeout, so running a
-    timeout, so running a report while a cron `scan` is in progress is
+    report while a cron `scan` is in progress is safe. The filesystem
-    safe. The filesystem is authoritative; the database is an
+    is authoritative; the database is an eventually-consistent
-    eventually-consistent reflection of it. Hashed records are
+    reflection of it. Hashed records are committed in batched
-    committed in batched transactions while the scan is still running
+    transactions while the scan is still running (keeping the WAL
-    (keeping the WAL small and letting concurrent reports observe
+    small and letting concurrent reports observe progress), so a
-    progress), so a report may see a scan's changes partially applied,
+    report may see a scan's changes partially applied, and a scan
-    and a scan that dies partway leaves a valid database holding
+    that dies partway leaves a valid database holding everything
-    everything hashed so far; the next scan skips those records and
+    hashed so far; the next scan skips those records and converges
-    converges toward the filesystem.
+    toward the filesystem.
--   `scan` switches the database back to rollback-journal mode when it
-    closes it, so between scans the database file alone holds the whole
-    database. Each switch needs the database to itself: a `scan` that
-    starts while a report is still reading waits for it up to the
-    10-second busy timeout, then fails; a `scan` that ends while a
-    report has the database open warns and leaves the database in WAL
-    mode until the next scan.
--   `report` and `trees` open the database read-only and need only read
-    access to the database file, and no write access to its directory.
-    While the database is in WAL mode they also read the `-wal` and
-    `-shm` files beside it, which SQLite creates with the database
-    file's permissions.
 -   Schema (`PRAGMA user_version` is the schema version, currently 1; a
     database with any other version is a fatal error):
 
@@ -441,15 +429,6 @@ first	dupe	size
 /srv/a/big.iso	/srv/c/big-copy2.iso	4294967296
 ```
 
-Paths are raw bytes and may hold any byte except NUL, so the path
-columns (`first` and `dupe`) are escaped to keep every row one line of
-tab-separated fields: a backslash is written as `\\`, a tab as `\t`, a
-newline as `\n`, and a carriage return as `\r`. Every other byte is
-written unchanged, including bytes that are not valid UTF-8. Undoing
-those four escapes gives back the stored path. Grouping and ordering
-use the stored path, not the escaped one. The warnings `scan` prints on
-stderr are escaped the same way, so each warning is one line.
-
 Summary to stderr: records read, number of duplicate groups, number of
 dupe files, and total reclaimable bytes (sum of `size` over all dupe
 rows) in human units.
@@ -521,9 +500,6 @@ first	dupe	files	size
 /srv/a/project	/srv/backup/project	3417	104857600
 ```
 
-The `first` and `dupe` paths are escaped as described under "Report
-output format". The root directory's path is `/`.
-
 Summary to stderr: records read, number of duplicate-tree groups,
 number of dupe trees, and total reclaimable bytes (sum of `size` over
 all dupe rows) in human units.
@@ -562,12 +538,9 @@ Additional requirements:
     emit ANSI redraws: print a plain one-line progress update the moment
     each phase starts, then no more often than every 5 seconds.
 -   Progress updates are driven from the main goroutine and must be
-    non-blocking with respect to the worker pool. On a terminal the
+    non-blocking with respect to the worker pool. Nothing redraws in the
-    spinner-style displays also redraw on their own several times a
+    background (the spinner advances only as items complete), so a
-    second, so their count and elapsed time stay current while a phase
+    warning printed during a phase always lands on its own line.
-    waits for its next item.
--   A warning printed during a phase always lands on a line of its own,
-    never inside the progress display.
 -   `report` and `trees` modes need no progress display, only their
     stderr summaries.
 

TODO.md

@@ -30,17 +30,8 @@
 # Completed Steps
 
 - progress prints at once on a non-terminal, uses a real terminal test,
-  and prints warnings through a spinner instead of racing its redraw
+  and has a single writer to stderr (2026-10-03,
-  (2026-10-03, https://git.eeqj.de/sneak/sfdupes/issues/13)
+  https://git.eeqj.de/sneak/sfdupes/issues/13)
-
-- `report` and `trees` open the database read-only, and `scan` leaves it
-  out of WAL mode, so reading needs only read access (2026-10-03, closes
-  https://git.eeqj.de/sneak/sfdupes/issues/8)
-
-- escape tabs, newlines, carriage returns and backslashes in report,
-  trees and warning paths; the root directory's path is `/`
-  (2026-10-03, https://git.eeqj.de/sneak/sfdupes/issues/7)
-
 - stamp the git tag or short commit in a plain `docker build .`
   instead of `dev` (2026-10-02, branch `next`, closes
   https://git.eeqj.de/sneak/sfdupes/issues/67): `.dockerignore` now

db.go

@@ -74,24 +74,16 @@ func databasePath() string {
 	return defaultDatabasePath
 }
 
-// scanParams are the connection parameters for scan: read-write, with
+// openDB opens the SQLite database at path with WAL journaling and a
-// WAL journaling and a busy timeout, so a report can run while a cron
+// busy timeout, so a report can run while a cron scan is in progress.
-// scan is in progress. closeScanDatabase leaves WAL mode again.
+// It does not create or verify the schema.
-const scanParams = "_pragma=busy_timeout(10000)" +
+func openDB(path string) (*sql.DB, error) {
-	"&_pragma=journal_mode(WAL)" +
+	dsn := "file:" + path +
-	"&_pragma=synchronous(NORMAL)"
+		"?_pragma=busy_timeout(10000)" +
+		"&_pragma=journal_mode(WAL)" +
+		"&_pragma=synchronous(NORMAL)"
 
-// reportParams are the connection parameters for report and trees:
+	db, err := sql.Open("sqlite", dsn)
-// read-only, with the same busy timeout. They set no journal mode,
-// because setting one is a write.
-const reportParams = "mode=ro" +
-	"&_pragma=busy_timeout(10000)" +
-	"&_pragma=query_only(1)"
-
-// openDB opens the SQLite database at path with the connection
-// parameters params. It does not create or verify the schema.
-func openDB(path, params string) (*sql.DB, error) {
-	db, err := sql.Open("sqlite", "file:"+path+"?"+params)
 	if err != nil {
 		return nil, fmt.Errorf("open database %s: %w", path, err)
 	}
@@ -112,7 +104,7 @@ func openScanDatabase(ctx context.Context, path string) (*sql.DB, error) {
 		return nil, fmt.Errorf("create database directory: %w", err)
 	}
 
-	db, err := openDB(path, scanParams)
+	db, err := openDB(path)
 	if err != nil {
 		return nil, err
 	}
@@ -127,24 +119,6 @@ func openScanDatabase(ctx context.Context, path string) (*sql.DB, error) {
 	return db, nil
 }
 
-// closeScanDatabase switches the database at path from WAL back to
-// rollback-journal mode and closes it. Out of WAL mode the database
-// file alone holds the whole database, so a reader needs no -wal or
-// -shm file beside it, nor write access to create them. The switch
-// fails while a report has the database open; the database then stays
-// in WAL mode, still readable, until a later scan closes it.
-func closeScanDatabase(ctx context.Context, db *sql.DB, path string) {
-	// Runs on the way out of a cancelled scan too.
-	_, err := db.ExecContext(context.WithoutCancel(ctx),
-		"PRAGMA journal_mode = DELETE")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "scan: database %s left in WAL mode: %v\n",
-			path, err)
-	}
-
-	_ = db.Close()
-}
-
 // openReportDatabase opens an existing database for the report and
 // trees subcommands. A missing database file is an error directing the
 // user to run scan first; the schema version must match exactly.
@@ -160,7 +134,7 @@ func openReportDatabase(ctx context.Context,
 		return nil, fmt.Errorf("database: %w", err)
 	}
 
-	db, err := openDB(path, reportParams)
+	db, err := openDB(path)
 	if err != nil {
 		return nil, err
 	}

db_test.go

@@ -5,7 +5,6 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
-	"os"
 	"path/filepath"
 	"slices"
 	"strings"
@@ -131,49 +130,6 @@ func TestOpenReportDatabaseOK(t *testing.T) {
 	_ = db.Close()
 }
 
-func TestCloseScanDatabaseWhileReportOpen(t *testing.T) {
-	t.Parallel()
-
-	// A report holding the database open stops scan from taking it out
-	// of WAL mode. The -wal and -shm files must then stay beside it, so
-	// that a later report still needs only read access.
-	path := testDBPath(t)
-
-	scanDB, err := openScanDatabase(t.Context(), path)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	reportDB, err := openReportDatabase(t.Context(), path)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	closeScanDatabase(t.Context(), scanDB, path)
-
-	_ = reportDB.Close()
-
-	_, err = os.Stat(path + "-wal")
-	if err != nil {
-		t.Fatalf("no -wal left: the switch out of WAL mode was not "+
-			"stopped: %v", err)
-	}
-
-	makeReadOnly(t, path)
-
-	reportDB, err = openReportDatabase(t.Context(), path)
-	if err != nil {
-		t.Fatalf("openReportDatabase: %v", err)
-	}
-
-	defer func() { _ = reportDB.Close() }()
-
-	_, err = loadFileRows(t.Context(), reportDB)
-	if err != nil {
-		t.Fatalf("loadFileRows: %v", err)
-	}
-}
-
 func TestApplyChangesRoundTrip(t *testing.T) {
 	t.Parallel()
 

main_test.go

@@ -44,44 +44,6 @@ func assertNoSidecars(t *testing.T, path string) {
 	}
 }
 
-// makeReadOnly takes write permission away from the database at path,
-// from any WAL sidecar beside it, and from their directory, as for a
-// user reading a database that a root cron scan keeps. Root ignores
-// file permissions, so it skips the test when run as root.
-func makeReadOnly(t *testing.T, path string) {
-	t.Helper()
-
-	if os.Geteuid() == 0 {
-		t.Skip("root ignores file permissions")
-	}
-
-	err := os.Chmod(path, 0o400)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	for _, suffix := range walSuffixes {
-		err = os.Chmod(path+suffix, 0o400)
-		if err != nil && !errors.Is(err, fs.ErrNotExist) {
-			t.Fatal(err)
-		}
-	}
-
-	dir := filepath.Dir(path)
-
-	//nolint:gosec // reaching the database needs the search bit
-	err = os.Chmod(dir, 0o500)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Runs before t.TempDir's own cleanup, which must delete the files.
-	t.Cleanup(func() {
-		//nolint:gosec // removing the directory needs its search bit back
-		_ = os.Chmod(dir, 0o700)
-	})
-}
-
 // captureStdout redirects os.Stdout to a file for the rest of the test
 // and returns a function reading back everything written to it. Only
 // machine-readable data belongs on stdout (README design goal 4), so
@@ -129,13 +91,13 @@ func captureStdout(t *testing.T) func() string {
 // brokenDatabase writes a database that opens cleanly and passes the
 // schema-version check but has no files table, so the first query
 // fails with the database already open: a fatal error on a path that
-// owns an open database. It closes the database the way scan does.
+// owns an open database.
 func brokenDatabase(t *testing.T) string {
 	t.Helper()
 
 	path := testDBPath(t)
 
-	db, err := openDB(path, scanParams)
+	db, err := openDB(path)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -146,7 +108,10 @@ func brokenDatabase(t *testing.T) string {
 		t.Fatal(err)
 	}
 
-	closeScanDatabase(t.Context(), db, path)
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	return path
 }
@@ -179,10 +144,7 @@ func TestOpenDatabaseKeepsWALWhileOpen(t *testing.T) {
 
 func TestRunFatalAfterOpenClosesDatabase(t *testing.T) {
 	// Every subcommand that owns an open database must close it when
-	// it fails: no os.Exit between the open and the return. The
+	// it fails: no os.Exit between the open and the return.
-	// sidecar check is evidence of the close only for scan: report and
-	// trees only read a database that is out of WAL mode, which leaves
-	// nothing on disk whether they close it or not.
 	cases := map[string][]string{
 		cmdScan:   {cmdScan},
 		cmdReport: {cmdReport},
@@ -433,41 +395,3 @@ func TestRunTreesSucceeds(t *testing.T) {
 
 	assertNoSidecars(t, path)
 }
-
-func TestRunReportsNeedOnlyReadAccess(t *testing.T) {
-	// README §Database: report and trees need only read access to the
-	// database file. With its directory read-only as well, SQLite
-	// cannot create any file beside it.
-	path := testDBPath(t)
-	t.Setenv(databaseEnv, path)
-
-	dupes := scanFixture(t)
-	assertNoSidecars(t, path)
-	makeReadOnly(t, path)
-
-	cases := map[string]string{
-		cmdReport: "first\tdupe\tsize\n" +
-			dupes[0] + "\t" + dupes[1] + "\t300\n",
-		cmdTrees: "first\tdupe\tfiles\tsize\n" +
-			filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) +
-			"\t1\t300\n",
-	}
-
-	for name, want := range cases {
-		var stderr bytes.Buffer
-
-		stdout := captureStdout(t)
-
-		code := run([]string{name}, &stderr)
-		if code != exitOK {
-			t.Errorf("run(%s) = %d, want %d; stderr: %s",
-				name, code, exitOK, stderr.String())
-
-			continue
-		}
-
-		if got := stdout(); got != want {
-			t.Errorf("%s stdout = %q, want %q", name, got, want)
-		}
-	}
-}

progress.go

@@ -35,10 +35,8 @@ func stderrIsTTY() bool {
 // one-line update as the pass starts, then no more often than every
 // plainInterval.
 //
-// All methods must be called from the main goroutine only. On a TTY
+// All methods must be called from the main goroutine only; nothing
-// the library also redraws a spinner from its own goroutine, several
+// else writes to stderr while a pass runs. A nil *progress is a valid
-// times a second, so its count and elapsed time stay current while a
-// pass waits for its next item. A nil *progress is a valid
 // no-display receiver: every method is a no-op, so batched database
 // flushes during the streaming pass can reuse the update-pass helpers
 // without rendering anything.
@@ -90,6 +88,10 @@ func newBar(label string, total int64) *progressbar.ProgressBar {
 		opts = append(opts,
 			progressbar.OptionSetPredictTime(false),
 			progressbar.OptionSpinnerType(walkSpinnerType),
+			// Advance the spinner only on Add. The library's default
+			// redraws it from its own goroutine every 100ms, which
+			// garbles a warning printed at the same moment.
+			progressbar.OptionSetSpinnerChangeInterval(0),
 		)
 	}
 
@@ -116,29 +118,16 @@ func (p *progress) increment() {
 }
 
 // warnf prints a one-line warning to stderr without corrupting the bar.
-// The whole message is escaped like a report's path columns, so a path
-// holding a newline cannot split the warning.
 func (p *progress) warnf(format string, args ...any) {
 	if p == nil {
 		return
 	}
 
-	msg := escapePath(fmt.Sprintf(format, args...))
-
-	if p.bar != nil && p.total < 0 {
-		// The library also redraws a spinner from its own goroutine, so
-		// a direct write could land inside a redraw. The bar prints the
-		// warning itself, just before its next redraw.
-		_, _ = progressbar.Bprintln(p.bar, msg)
-
-		return
-	}
-
 	if p.bar != nil {
 		_ = p.bar.Clear()
 	}
 
-	fmt.Fprintln(os.Stderr, msg)
+	fmt.Fprintf(os.Stderr, format+"\n", args...)
 }
 
 // finish terminates the pass's display.

progress_test.go

@@ -9,9 +9,9 @@ import (
 	"time"
 )
 
-// spinnerIdle comfortably outlasts the 100ms interval at which the
+// spinnerIdle outlasts the 100ms interval at which the progressbar
-// progressbar library redraws a spinner from its own goroutine.
+// library redraws a spinner from its own goroutine unless told not to.
-const spinnerIdle = 500 * time.Millisecond
+const spinnerIdle = 300 * time.Millisecond
 
 // captureStderr points os.Stderr at a file for the rest of the test and
 // returns a function reading back everything written to it.
@@ -104,29 +104,19 @@ func TestNewProgressPrintsBeforeFirstItem(t *testing.T) {
 	}
 }
 
-// newWalkSpinner returns the walk pass's terminal display, writing to
+// TestProgressWarningsOnOwnLines drives the terminal display of the walk
-// os.Stderr whether or not it is a terminal, and stops the library's
+// pass: every warning must land on a line of its own between redraws of
-// redraws when the test ends.
+// the spinner, and nothing may redraw while no method is being called,
-func newWalkSpinner(t *testing.T) *progress {
+// or a warning could be garbled by a redraw from another goroutine.
-	t.Helper()
+//
+//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
+func TestProgressWarningsOnOwnLines(t *testing.T) {
+	stderr := captureStderr(t)
 
 	p := &progress{
 		label: "walk", total: -1, start: time.Now(),
 		bar: newBar("walk", -1),
 	}
-	t.Cleanup(p.finish)
-
-	return p
-}
-
-// TestProgressWarningsOnOwnLines drives the terminal display of the walk
-// pass: every warning must land on a line of its own, never inside a
-// redraw of the spinner.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestProgressWarningsOnOwnLines(t *testing.T) {
-	stderr := captureStderr(t)
-	p := newWalkSpinner(t)
 
 	for _, w := range []string{"first", "second", "third"} {
 		p.increment()
@@ -135,14 +125,19 @@ func TestProgressWarningsOnOwnLines(t *testing.T) {
 
 	p.increment()
 
-	// The spinner prints the warnings at its next redraw.
+	before := stderr()
+
 	time.Sleep(spinnerIdle)
 
+	if after := stderr(); after != before {
+		t.Errorf("stderr written while idle: %q", after[len(before):])
+	}
+
 	// A terminal shows each line as the text after its last carriage
 	// return.
 	var warnings []string
 
-	for line := range strings.SplitSeq(stderr(), "\n") {
+	for line := range strings.SplitSeq(before, "\n") {
 		if strings.Contains(line, "warning") {
 			warnings = append(warnings, line[strings.LastIndex(line, "\r")+1:])
 		}
@@ -153,34 +148,3 @@ func TestProgressWarningsOnOwnLines(t *testing.T) {
 		t.Errorf("warning lines = %q, want %q", warnings, want)
 	}
 }
-
-// TestSpinnerShowsCountAfterBurst checks that once a burst of items
-// faster than the redraw limit is over, the walk display shows every
-// item completed while it waits for the next one.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestSpinnerShowsCountAfterBurst(t *testing.T) {
-	stderr := captureStderr(t)
-	p := newWalkSpinner(t)
-
-	for range 50 {
-		p.increment()
-	}
-
-	time.Sleep(spinnerIdle)
-
-	// A terminal shows the last frame drawn. The library starts each
-	// frame with a carriage return and erases the previous one with
-	// spaces first.
-	var shown string
-
-	for frame := range strings.SplitSeq(stderr(), "\r") {
-		if strings.TrimSpace(frame) != "" {
-			shown = frame
-		}
-	}
-
-	if !strings.Contains(shown, "(50/-,") {
-		t.Errorf("terminal shows %q, want a count of 50", shown)
-	}
-}

report.go

@@ -31,9 +31,9 @@ type scanRec struct {
 // loadRecords opens the database and reads every file record for the
 // report and trees subcommands. Any database problem — including a
 // missing database — is fatal. The error is returned rather than
-// exiting, so that the deferred close always runs; the database is
+// exiting, so that the deferred close — which checkpoints the SQLite
-// closed before the caller formats its output, so it stays closed even
+// WAL — always runs; the database is closed before the caller formats
-// if that output fails.
+// its output, so it stays closed even if that output fails.
 func loadRecords(ctx context.Context) ([]scanRec, error) {
 	dbPath := databasePath()
 
@@ -87,7 +87,7 @@ func runReport(ctx context.Context) error {
 	for _, g := range dupes {
 		for _, p := range g.paths[1:] {
 			_, err = fmt.Fprintf(out, "%s\t%s\t%d\n",
-				escapePath(g.paths[0]), escapePath(p), g.size)
+				g.paths[0], p, g.size)
 			if err != nil {
 				return fmt.Errorf("write stdout: %w", err)
 			}
@@ -156,21 +156,6 @@ func collectDupeGroups(recs []scanRec) []dupeGroup {
 	return dupes
 }
 
-// escapePath returns a path as it is written in a report column (README
-// "Report output format"): a backslash, tab, newline or carriage return
-// becomes \\, \t, \n or \r, and every other byte is kept as it is.
-// Grouping and sorting use the raw path, never this form.
-func escapePath(p string) string {
-	// Most paths need no escaping; skip building a replacer for them.
-	if !strings.ContainsAny(p, "\\\t\n\r") {
-		return p
-	}
-
-	return strings.NewReplacer(
-		`\`, `\\`, "\t", `\t`, "\n", `\n`, "\r", `\r`,
-	).Replace(p)
-}
-
 // humanBytes formats a byte count in human units (binary prefixes).
 func humanBytes(n int64) string {
 	const unit = 1024

report_test.go

@@ -1,128 +1,10 @@
 package main
 
 import (
-	"bytes"
-	"io"
-	"os"
-	"path/filepath"
 	"slices"
 	"testing"
 )
 
-// awkwardDir is a directory name holding every byte the reports escape.
-const awkwardDir = "/d/\tone\ntwo\rthree\\four"
-
-// awkwardPairRecs is a duplicate pair in sibling directories /d/A and
-// awkwardDir. A raw tab sorts before "A" but its escaped form `\t`
-// sorts after it, so awkwardDir coming first shows that sorting uses
-// the raw path.
-func awkwardPairRecs() []scanRec {
-	return []scanRec{
-		{size: 5, head: "h", tail: "t", content: "c", path: "/d/A/f"},
-		{size: 5, head: "h", tail: "t", content: "c", path: awkwardDir + "/f"},
-	}
-}
-
-// seedDatabase writes recs into a fresh database and returns its path.
-func seedDatabase(t *testing.T, recs []scanRec) string {
-	t.Helper()
-
-	path := testDBPath(t)
-
-	db, err := openScanDatabase(t.Context(), path)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = applyChanges(t.Context(), db, recs, nil, nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = db.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	return path
-}
-
-func TestRunReportEscapesPaths(t *testing.T) {
-	t.Setenv(databaseEnv, seedDatabase(t, awkwardPairRecs()))
-
-	var stderr bytes.Buffer
-
-	stdout := captureStdout(t)
-
-	code := run([]string{cmdReport}, &stderr)
-	if code != exitOK {
-		t.Fatalf("run(report) = %d, want %d; stderr: %s",
-			code, exitOK, stderr.String())
-	}
-
-	want := "first\tdupe\tsize\n" +
-		`/d/\tone\ntwo\rthree\\four/f` + "\t/d/A/f\t5\n"
-	if got := stdout(); got != want {
-		t.Errorf("stdout = %q, want %q", got, want)
-	}
-}
-
-func TestEscapePath(t *testing.T) {
-	t.Parallel()
-
-	cases := map[string]string{
-		"/srv/plain":    "/srv/plain",
-		"/a\tb":         `/a\tb`,
-		"/a\nb":         `/a\nb`,
-		"/a\rb":         `/a\rb`,
-		`/a\b`:          `/a\\b`,
-		`/a\tb`:         `/a\\tb`,
-		"/not-utf8\xff": "/not-utf8\xff",
-	}
-	for in, want := range cases {
-		if got := escapePath(in); got != want {
-			t.Errorf("escapePath(%q) = %q, want %q", in, got, want)
-		}
-	}
-}
-
-// TestWarnfEscapes checks that a warning naming a path that holds a
-// newline is still one line.
-//
-//nolint:paralleltest // replaces the process-wide os.Stderr
-func TestWarnfEscapes(t *testing.T) {
-	f, err := os.Create(filepath.Join(t.TempDir(), "stderr"))
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	saved := os.Stderr
-	os.Stderr = f
-
-	t.Cleanup(func() {
-		os.Stderr = saved
-
-		_ = f.Close()
-	})
-
-	(&progress{}).warnf("stat %s: %s", "/d/a\nb", "gone")
-
-	_, err = f.Seek(0, io.SeekStart)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	got, err := io.ReadAll(f)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	want := `stat /d/a\nb: gone` + "\n"
-	if string(got) != want {
-		t.Errorf("warning = %q, want %q", got, want)
-	}
-}
-
 func TestCollectDupeGroups(t *testing.T) {
 	t.Parallel()
 

scan.go

@@ -87,9 +87,8 @@ type fileMeta struct {
 // hash only when its size, head, and tail match another file's. Flag
 // parsing and the at-least-one-operand check are done by cobra. Errors
 // are returned rather than exiting, so that the deferred close — which
-// takes the database out of WAL mode — always runs. Cancelling ctx
+// checkpoints the SQLite WAL — always runs. Cancelling ctx unwinds the
-// unwinds the worker pools and aborts the scan with the context's
+// worker pools and aborts the scan with the context's error.
-// error.
 func runScan(ctx context.Context, roots []string, workers int,
 	oneFS bool,
 ) error {
@@ -109,7 +108,7 @@ func runScan(ctx context.Context, roots []string, workers int,
 		return err
 	}
 
-	defer closeScanDatabase(ctx, db, dbPath)
+	defer func() { _ = db.Close() }()
 
 	st, err := syncScan(ctx, db, roots, workers, oneFS)
 	if err != nil {

trees.go

@@ -62,8 +62,7 @@ func runTrees(ctx context.Context) error {
 		first := g[0]
 		for _, n := range g[1:] {
 			_, err = fmt.Fprintf(out, "%s\t%s\t%d\t%d\n",
-				escapePath(first.path), escapePath(n.path),
+				first.path, n.path, first.fileCount, first.totalSize)
-				first.fileCount, first.totalSize)
 			if err != nil {
 				return fmt.Errorf("write stdout: %w", err)
 			}
@@ -88,8 +87,8 @@ func runTrees(ctx context.Context) error {
 
 // buildHierarchy reconstructs the directory hierarchy from the record
 // paths under a synthetic super-root. Paths are split on "/"; for
-// absolute paths the first component is empty, which becomes the
+// absolute paths the first component is empty, which simply becomes a
-// top-level node with path "/". It returns the super-root and every
+// top-level node representing "/". It returns the super-root and every
 // directory node created.
 func buildHierarchy(recs []scanRec) (*treeNode, []*treeNode) {
 	super := &treeNode{}
@@ -103,17 +102,9 @@ func buildHierarchy(recs []scanRec) (*treeNode, []*treeNode) {
 		for _, c := range comps[:len(comps)-1] {
 			child := node.dirs[c]
 			if child == nil {
-				childPath := node.path + "/" + c
+				childPath := c
-
+				if node != super {
-				// The root directory's path is "/", not empty, and its
+					childPath = node.path + "/" + c
-				// children's paths start with one slash, not two.
-				switch {
-				case node == super && c == "":
-					childPath = "/"
-				case node == super:
-					childPath = c
-				case node.path == "/":
-					childPath = "/" + c
 				}
 
 				child = &treeNode{path: childPath, parent: node}

trees_test.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"bytes"
 	"slices"
 	"testing"
 )
@@ -85,46 +84,6 @@ func TestBuildHierarchyCounts(t *testing.T) {
 	}
 }
 
-func TestBuildHierarchyRootPath(t *testing.T) {
-	t.Parallel()
-
-	// The root directory's path is "/", never empty, and its
-	// children's paths start with a single slash.
-	_, dirs := buildHierarchy([]scanRec{{path: "/f"}, {path: "/srv/g"}})
-
-	got := make([]string, 0, len(dirs))
-	for _, d := range dirs {
-		got = append(got, d.path)
-	}
-
-	slices.Sort(got)
-
-	want := []string{"/", "/srv"}
-	if !slices.Equal(got, want) {
-		t.Fatalf("directory paths = %q, want %q", got, want)
-	}
-}
-
-func TestRunTreesEscapesPaths(t *testing.T) {
-	t.Setenv(databaseEnv, seedDatabase(t, awkwardPairRecs()))
-
-	var stderr bytes.Buffer
-
-	stdout := captureStdout(t)
-
-	code := run([]string{cmdTrees}, &stderr)
-	if code != exitOK {
-		t.Fatalf("run(trees) = %d, want %d; stderr: %s",
-			code, exitOK, stderr.String())
-	}
-
-	want := "first\tdupe\tfiles\tsize\n" +
-		`/d/\tone\ntwo\rthree\\four` + "\t/d/A\t1\t5\n"
-	if got := stdout(); got != want {
-		t.Errorf("stdout = %q, want %q", got, want)
-	}
-}
-
 func TestTreeDigests(t *testing.T) {
 	t.Parallel()