Merge PR #512: perf: apply high-performance Go guidelines across five sites

merge-queue-bot · merge-queue-bot · commit a5539719d1f5 · 2026-06-06T22:57:45.000Z
diff --git a/.golangci.yml b/.golangci.yml
@@ -11,6 +11,7 @@ linters:
     - ineffassign
     - misspell
     - lll
+    - prealloc
     - revive
   settings:
     lll:
diff --git a/cmd/mdsmith/help.go b/cmd/mdsmith/help.go
@@ -69,7 +69,7 @@ func runHelpPatterns(args []string) int {
 		fmt.Fprintf(os.Stderr, "mdsmith: %v\n", err)
 		return 2
 	}
-	items := make([]patternRec, 0)
+	items := make([]patternRec, 0, len(rules))
 	for _, r := range rules {
 		if r.Maintainability == nil {
 			continue
diff --git a/cmd/mdsmith/metrics.go b/cmd/mdsmith/metrics.go
@@ -326,7 +326,7 @@ func writeMetricsListJSON(defs []metricspkg.Definition) error {
 func writeMetricsRankText(rows []metricspkg.Row, defs []metricspkg.Definition) error {
 	tw := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
 
-	var headers []string
+	headers := make([]string, 0, len(defs)+1)
 	for _, def := range defs {
 		headers = append(headers, strings.ToUpper(def.Name))
 	}
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
@@ -1320,7 +1320,7 @@ func TestYamlHasKeyRejectsAnchor(t *testing.T) {
 
 // TestTopLevelKeySet_InvalidYAML covers the yaml.Unmarshal error
 // branch of topLevelKeySet: a syntactically bad YAML payload
-// returns an empty set (not a panic) so callers can degrade
+// returns nil (not a panic) so callers can degrade
 // gracefully.
 func TestTopLevelKeySet_InvalidYAML(t *testing.T) {
 	assert.Empty(t, topLevelKeySet([]byte("{not: valid: yaml:")))
diff --git a/internal/config/convention_test.go b/internal/config/convention_test.go
@@ -175,7 +175,7 @@ func TestProvenance_ConventionLayerVisible(t *testing.T) {
 	require.True(t, ok, "rule must appear in resolution")
 	require.NotEmpty(t, rr.Layers)
 
-	var sources []string
+	sources := make([]string, 0, len(rr.Layers))
 	for _, l := range rr.Layers {
 		sources = append(sources, l.Source)
 	}
@@ -610,7 +610,7 @@ func TestProvenance_UserConventionLayerHasUserSuffix(t *testing.T) {
 	rr, ok := res.Rules["markdown-flavor"]
 	require.True(t, ok)
 
-	var sources []string
+	sources := make([]string, 0, len(rr.Layers))
 	for _, l := range rr.Layers {
 		sources = append(sources, l.Source)
 	}
diff --git a/internal/config/load.go b/internal/config/load.go
@@ -111,19 +111,19 @@ func loadFromBytes(data []byte, sourcePath string, mergeKinds bool) (*Config, er
 }
 
 // topLevelKeySet returns the set of top-level YAML mapping keys
-// present in data, or an empty set on parse error. It rejects
+// present in data, or nil on parse error. It rejects
 // anchor/alias usage for the same reason yamlHasKey does.
 func topLevelKeySet(data []byte) map[string]bool {
 	node, err := yamlutil.UnmarshalNodeSafe(data)
 	if err != nil {
-		return map[string]bool{}
+		return nil
 	}
 	if node.Kind != yaml.DocumentNode || len(node.Content) == 0 {
-		return map[string]bool{}
+		return nil
 	}
 	mapping := node.Content[0]
 	if mapping.Kind != yaml.MappingNode {
-		return map[string]bool{}
+		return nil
 	}
 	result := make(map[string]bool, len(mapping.Content)/2)
 	for i := 0; i < len(mapping.Content)-1; i += 2 {
diff --git a/internal/corpus/collect.go b/internal/corpus/collect.go
@@ -19,7 +19,7 @@ func Collect(cfg *Config, cacheDir string) ([]Record, error) {
 
 	allow := makeAllowset(cfg.LicenseAllowlist)
 
-	records := make([]Record, 0)
+	records := make([]Record, 0, len(cfg.Sources))
 	for idx, source := range cfg.Sources {
 		sourceRecords, err := collectSource(
 			cfg,
diff --git a/internal/corpus/qa.go b/internal/corpus/qa.go
@@ -90,7 +90,7 @@ func validateAnnotationsAgainstSample(
 	annotations []QAAnnotation,
 ) error {
 	seenIDs := make(map[string]struct{}, len(annotations))
-	extraIDs := make([]string, 0)
+	extraIDs := make([]string, 0, len(annotations))
 
 	for _, annotation := range annotations {
 		recordID := annotation.RecordID
diff --git a/internal/cuetemplate/cuetemplate.go b/internal/cuetemplate/cuetemplate.go
@@ -173,7 +173,7 @@ func buildSource(fm map[string]any, expr string) string {
 	if err != nil {
 		panic(fmt.Errorf("cuetemplate: encoding frontmatter: %w", err))
 	}
-	var src []byte
+	var src []byte //nolint:prealloc
 	src = append(src, []byte(
 		"import \"strings\"\n\n"+
 			"_strings_used: strings.Join([], \"\")\n")...)
diff --git a/internal/engine/check_test.go b/internal/engine/check_test.go
@@ -443,7 +443,7 @@ func (r *mockMultiLineRule) ID() string       { return r.id }
 func (r *mockMultiLineRule) Name() string     { return r.name }
 func (r *mockMultiLineRule) Category() string { return "test" }
 func (r *mockMultiLineRule) Check(f *lint.File) []lint.Diagnostic {
-	var diags []lint.Diagnostic
+	diags := make([]lint.Diagnostic, 0, len(r.lines))
 	for _, l := range r.lines {
 		diags = append(diags, lint.Diagnostic{
 			File:     f.Path,
diff --git a/internal/engine/intrafile_test.go b/internal/engine/intrafile_test.go
@@ -234,7 +234,7 @@ func TestRunner_IntraFileConcurrencyByteIdentical(t *testing.T) {
 	}
 	cfg := config.Defaults()
 	dir := t.TempDir()
-	var paths []string
+	paths := make([]string, 0, len(files))
 	for name, body := range files {
 		p := filepath.Join(dir, name)
 		require.NoError(t, os.WriteFile(p, []byte(body), 0o644))
diff --git a/internal/integration/rule_walk_audit_test.go b/internal/integration/rule_walk_audit_test.go
@@ -515,7 +515,7 @@ func loadBadFixtureInputs(t *testing.T, dir string) []auditProbeInput {
 		paths = append(paths, single)
 	}
 
-	var inputs []auditProbeInput
+	inputs := make([]auditProbeInput, 0, len(paths))
 	for _, p := range paths {
 		raw, err := os.ReadFile(p) //nolint:gosec // test fixture path
 		require.NoError(t, err)
diff --git a/internal/lsp/symbols_navigation.go b/internal/lsp/symbols_navigation.go
@@ -387,7 +387,7 @@ func (s *Server) locationsForFileTop(file string, idx *index.Index) []location {
 // file path.
 func (s *Server) locationsForFileReferences(file string, idx *index.Index) []location {
 	edges := idx.IncomingEdges(file, "")
-	var out []location
+	out := make([]location, 0, len(edges))
 	for _, e := range edges {
 		switch e.Kind {
 		case index.EdgeFileLink:
diff --git a/internal/metrics/collect_authored_test.go b/internal/metrics/collect_authored_test.go
@@ -3,6 +3,7 @@ package metrics
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -16,10 +17,7 @@ func TestCollect_AuthoredMetrics(t *testing.T) {
 	dir := t.TempDir()
 
 	// hostFull.md has an <?include?> section with 100 lines of content.
-	bigContent := ""
-	for i := 0; i < 100; i++ {
-		bigContent += "Generated line with some words here.\n"
-	}
+	bigContent := strings.Repeat("Generated line with some words here.\n", 100)
 	hostFull := "# Host\n\nAuthor wrote this.\n\n" +
 		"<?include\nfile: frag.md\n?>\n" +
 		bigContent +
diff --git a/internal/release/buildnpm_test.go b/internal/release/buildnpm_test.go
@@ -164,7 +164,8 @@ func TestNpmChannelDocMatchesPlatformBuilds(t *testing.T) {
 	}
 	require.NotEmpty(t, actual, "npm.md: no bullet list found")
 
-	expected := []string{"- `@mdsmith/cli` — root, contains the shim"}
+	expected := make([]string, 0, 1+len(npmPlatformBuilds))
+	expected = append(expected, "- `@mdsmith/cli` — root, contains the shim")
 	for _, pb := range npmPlatformBuilds {
 		expected = append(expected, "- `@mdsmith/"+pb.NodeTarget+"`")
 	}
diff --git a/internal/release/buildwheels_test.go b/internal/release/buildwheels_test.go
@@ -63,7 +63,7 @@ func zipFileNames(t *testing.T, whlPath string) []string {
 	r, err := zip.OpenReader(whlPath)
 	require.NoError(t, err, "open %s", whlPath)
 	defer func() { _ = r.Close() }()
-	var names []string
+	names := make([]string, 0, len(r.File))
 	for _, f := range r.File {
 		names = append(names, f.Name)
 	}
@@ -132,7 +132,7 @@ func assertWheel(t *testing.T, out string, entries []os.DirEntry, c wheelCase) {
 		}
 	}
 	if match == "" {
-		names := []string{}
+		names := make([]string, 0, len(entries))
 		for _, e := range entries {
 			names = append(names, e.Name())
 		}
diff --git a/internal/release/messaging_targets.go b/internal/release/messaging_targets.go
@@ -39,11 +39,15 @@ type MessagingTarget struct {
 // included content is up to date before the consuming file is
 // re-read.
 func MessagingTargets(root string) []MessagingTarget {
-	var out []MessagingTarget
-	out = append(out, messagingFragmentTargets(root)...)
-	out = append(out, messagingWebsiteTargets(root)...)
-	out = append(out, messagingPackageTargets(root)...)
-	out = append(out, messagingEditorTargets(root)...)
+	frags := messagingFragmentTargets(root)
+	web := messagingWebsiteTargets(root)
+	pkgs := messagingPackageTargets(root)
+	eds := messagingEditorTargets(root)
+	out := make([]MessagingTarget, 0, len(frags)+len(web)+len(pkgs)+len(eds))
+	out = append(out, frags...)
+	out = append(out, web...)
+	out = append(out, pkgs...)
+	out = append(out, eds...)
 	return out
 }
 
diff --git a/internal/rename/rename.go b/internal/rename/rename.go
@@ -220,7 +220,7 @@ func linkRefEdits(source []byte, oldLabel, newName string) []Edit {
 	body, fmOffset := bodyAndFMOffset(source)
 	root := lint.NewParser().Parse(text.NewReader(body), parser.WithContext(parser.NewContext()))
 	lines := splitLines(source)
-	var out []Edit
+	out := make([]Edit, 0, 8)
 	out = append(out, refDefEditsInBody(body, lines, fmOffset, oldLabel, newName)...)
 	out = append(out, refUseEditsInBody(root, body, lines, fmOffset, oldLabel, newName)...)
 	return out
diff --git a/internal/rules/horizontalrulestyle/rule.go b/internal/rules/horizontalrulestyle/rule.go
@@ -69,7 +69,7 @@ func (r *Rule) checkHR(f *lint.File, line int) []lint.Diagnostic {
 	_, token := splitHRLine(rawLine)
 	delimiter, count, hasSpaces := parseHR(token)
 
-	var diags []lint.Diagnostic
+	diags := make([]lint.Diagnostic, 0, 4)
 	diags = append(diags, r.checkDelimiter(f, line, delimiter)...)
 	diags = append(diags, r.checkSpaces(f, line, hasSpaces)...)
 	diags = append(diags, r.checkLength(f, line, count)...)
diff --git a/internal/rules/include/rule.go b/internal/rules/include/rule.go
@@ -275,7 +275,7 @@ func (r *Rule) checkCycleOrDepth(
 			fmt.Sprintf("include depth exceeds maximum (%d)", maxIncludeDepth))}
 	}
 	if r.visited[resolvedFile] {
-		chain := make([]string, len(r.chain))
+		chain := make([]string, len(r.chain), len(r.chain)+1)
 		copy(chain, r.chain)
 		chain = append(chain, resolvedFile)
 		return []lint.Diagnostic{makeDiag(filePath, line,
diff --git a/internal/rules/linkvalidity/rule.go b/internal/rules/linkvalidity/rule.go
@@ -222,7 +222,7 @@ func (r *Rule) Fix(f *lint.File) []byte {
 			out[i] = line
 			continue
 		}
-		var b []byte
+		b := make([]byte, 0, len(line))
 		prev := 0
 		for _, mm := range matches {
 			b = append(b, line[prev:mm.col0]...)
diff --git a/internal/rules/paragraphstructure/rule.go b/internal/rules/paragraphstructure/rule.go
@@ -71,7 +71,6 @@ func (r *Rule) EnabledByDefault() bool { return false }
 
 // Check implements rule.Rule.
 func (r *Rule) Check(f *lint.File) []lint.Diagnostic {
-	var diags []lint.Diagnostic
 	// Iterate the per-File memoized non-table paragraph collection so
 	// the AST walk is shared with the other paragraph-walking rules
 	// (MDS023 paragraph-readability, MDS057 required-text-patterns,
@@ -91,6 +90,7 @@ func (r *Rule) Check(f *lint.File) []lint.Diagnostic {
 	// collector keeps MDS024 inside the budget; the extra
 	// extraction cost when MDS057/MDS058 are co-enabled is paid
 	// per-paragraph in the bare ExtractText calls.
+	var diags []lint.Diagnostic //nolint:prealloc // pre-sizing would exceed the 9-alloc/op budget (plan 193)
 	for _, p := range astutil.CollectSectionParagraphs(f) {
 		diags = append(diags, r.checkParagraph(p.ExtractText(f.Source), p.Line, f.Path)...)
 	}
diff --git a/internal/rules/recipesafety/rule.go b/internal/rules/recipesafety/rule.go
@@ -191,7 +191,7 @@ func (r *Rule) validateRecipes(filePath string) []lint.Diagnostic {
 	}
 	sort.Strings(names)
 
-	var diags []lint.Diagnostic
+	diags := make([]lint.Diagnostic, 0, len(names))
 	for _, name := range names {
 		diags = append(diags, r.checkRecipe(filePath, name, r.Recipes[name])...)
 	}
diff --git a/internal/rules/requiredstructure/compose_test.go b/internal/rules/requiredstructure/compose_test.go
@@ -596,7 +596,7 @@ func TestBodySyncDiagnostics_ParseError(t *testing.T) {
 	// The compose-path reports the parse failure; the
 	// body-sync path swallows it (the swallowed branch is what
 	// this test covers).
-	var msgs []string
+	msgs := make([]string, 0, len(diags))
 	for _, d := range diags {
 		msgs = append(msgs, d.Message)
 	}
diff --git a/internal/rules/requiredstructure/rule.go b/internal/rules/requiredstructure/rule.go
@@ -648,7 +648,7 @@ func (r *Rule) isAnySchemaFile(f *lint.File) bool {
 // sync (no source body content) so the legacy syncPoints code path
 // is skipped.
 func (r *Rule) checkSingleInlineSchema(f *lint.File, sch *schema.Schema) []lint.Diagnostic {
-	var diags []lint.Diagnostic
+	diags := make([]lint.Diagnostic, 0, 8)
 	docFMRaw, fmDiags := readDocFrontMatterRaw(f)
 	diags = append(diags, fmDiags...)
 	fmIsCUE := placeholders.HasCUEFrontmatter(r.Placeholders)
@@ -1622,7 +1622,7 @@ func expandSchemaInclude(
 			"schema include depth exceeds maximum (%d)", maxSchemaIncludeDepth)
 	}
 	if visited[includedPath] {
-		chainCopy := make([]string, len(chain))
+		chainCopy := make([]string, len(chain), len(chain)+1)
 		copy(chainCopy, chain)
 		chainCopy = append(chainCopy, includedPath)
 		return nil, "", includedPath, nil, fmt.Errorf(
diff --git a/internal/rules/tableformat/structure.go b/internal/rules/tableformat/structure.go
@@ -61,7 +61,7 @@ func (t tableBlock) end() int   { return t.rows[len(t.rows)-1].lineNum }
 func structureDiagnostics(f *lint.File, style, ruleID, ruleName string) []lint.Diagnostic {
 	skip := structureSkipFunc(f)
 	tables := findStructureTables(f.Lines, skip)
-	var diags []lint.Diagnostic
+	diags := make([]lint.Diagnostic, 0, len(tables))
 	for _, t := range tables {
 		diags = append(diags, checkPipeStyle(f, t, style, ruleID, ruleName)...)
 		diags = append(diags, checkColumnCount(f, t, ruleID, ruleName)...)
diff --git a/internal/schema/compose.go b/internal/schema/compose.go
@@ -543,7 +543,11 @@ func cloneSettingsMap(m map[string]any) map[string]any {
 }
 
 func composeCrossRefs(schemas []*Schema) []CrossRef {
-	var out []CrossRef
+	total := 0
+	for _, s := range schemas {
+		total += len(s.CrossReferences)
+	}
+	out := make([]CrossRef, 0, total)
 	for _, s := range schemas {
 		out = append(out, s.CrossReferences...)
 	}
diff --git a/pkg/markdown/flavor/detect_pin_test.go b/pkg/markdown/flavor/detect_pin_test.go
@@ -93,7 +93,7 @@ func TestDetectByteIdenticalPin(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			doc := markdown.Parse([]byte(tc.src))
 			got := Detect(doc, nil)
-			var gotShapes []findingShape
+			var gotShapes []findingShape //nolint:prealloc
 			for _, f := range got {
 				gotShapes = append(gotShapes,
 					findingShape{f.Feature, f.Line, f.Column})

Original file line number	Diff line number	Diff line change
`@@ -69,7 +69,7 @@ func runHelpPatterns(args []string) int {`
`69`	`69`	`fmt.Fprintf(os.Stderr, "mdsmith: %v\n", err)`
`70`	`70`	`return 2`
`71`	`71`	`}`
`72`		`- items := make([]patternRec, 0)`
	`72`	`+ items := make([]patternRec, 0, len(rules))`
`73`	`73`	`for _, r := range rules {`
`74`	`74`	`if r.Maintainability == nil {`
`75`	`75`	`continue`
Original file line number	Diff line number	Diff line change
`@@ -326,7 +326,7 @@ func writeMetricsListJSON(defs []metricspkg.Definition) error {`
`326`	`326`	`func writeMetricsRankText(rows []metricspkg.Row, defs []metricspkg.Definition) error {`
`327`	`327`	`tw := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)`
`328`	`328`
`329`		`- var headers []string`
	`329`	`+ headers := make([]string, 0, len(defs)+1)`
`330`	`330`	`for _, def := range defs {`
`331`	`331`	`headers = append(headers, strings.ToUpper(def.Name))`
`332`	`332`	`}`
Original file line number	Diff line number	Diff line change
`@@ -111,19 +111,19 @@ func loadFromBytes(data []byte, sourcePath string, mergeKinds bool) (*Config, er`
`111`	`111`	`}`
`112`	`112`
`113`	`113`	`// topLevelKeySet returns the set of top-level YAML mapping keys`
`114`		`-// present in data, or an empty set on parse error. It rejects`
	`114`	`+// present in data, or nil on parse error. It rejects`
`115`	`115`	`// anchor/alias usage for the same reason yamlHasKey does.`
`116`	`116`	`func topLevelKeySet(data []byte) map[string]bool {`
`117`	`117`	`node, err := yamlutil.UnmarshalNodeSafe(data)`
`118`	`118`	`if err != nil {`
`119`		`- return map[string]bool{}`
	`119`	`+ return nil`
`120`	`120`	`}`
`121`	`121`	`if node.Kind != yaml.DocumentNode \|\| len(node.Content) == 0 {`
`122`		`- return map[string]bool{}`
	`122`	`+ return nil`
`123`	`123`	`}`
`124`	`124`	`mapping := node.Content[0]`
`125`	`125`	`if mapping.Kind != yaml.MappingNode {`
`126`		`- return map[string]bool{}`
	`126`	`+ return nil`
`127`	`127`	`}`
`128`	`128`	`result := make(map[string]bool, len(mapping.Content)/2)`
`129`	`129`	`for i := 0; i < len(mapping.Content)-1; i += 2 {`
Original file line number	Diff line number	Diff line change
`@@ -173,7 +173,7 @@ func buildSource(fm map[string]any, expr string) string {`
`173`	`173`	`if err != nil {`
`174`	`174`	`panic(fmt.Errorf("cuetemplate: encoding frontmatter: %w", err))`
`175`	`175`	`}`
`176`		`- var src []byte`
	`176`	`+ var src []byte //nolint:prealloc`
`177`	`177`	`src = append(src, []byte(`
`178`	`178`	`"import \"strings\"\n\n"+`
`179`	`179`	`"_strings_used: strings.Join([], \"\")\n")...)`