golangci-lint: add prealloc linter + manually fix problems

.golangci.yml

@@ -13,6 +13,7 @@ linters:
     - mirror
     - nolintlint
     - perfsprint
+    - prealloc
     - sqlclosecheck
     - staticcheck
     - whitespace
@@ -143,6 +144,7 @@ linters:
         path: ^go/mysql/
       - linters:
           - errcheck
+          - prealloc
         path: ^go/pools/.*_test.go
       - linters:
           - errcheck
@@ -155,6 +157,7 @@ linters:
         path: ^go/stats/statsd/
       - linters:
           - errcheck
+          - prealloc
           - sqlclosecheck
         path: ^go/test/
       - linters:
@@ -177,9 +180,11 @@ linters:
         path: ^go/vt/sqlparser/goyacc
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/throttler/.*_test.go
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/topo/.*/*._test.go
       - linters:
           - errcheck
@@ -195,12 +200,14 @@ linters:
         path: ^go/vt/vtctl/grpcvtctlserver/
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/vtctld/(schema|.*_test).go
       - linters:
           - errcheck
         path: ^go/vt/vtexplain/
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/vtgate/.*_test.go
       - linters:
           - errcheck
@@ -213,9 +220,11 @@ linters:
         path: ^go/vt/vttablet/tabletmanager/vreplication
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/vttablet/(.*endtoend.*|.*_test.go)
       - linters:
           - errcheck
+          - prealloc
         path: ^go/vt/vttest
       - linters:
           - errcheck

go/cache/theine/list_test.go

@@ -49,7 +49,7 @@ func TestList(t *testing.T) {
 	entry := l.PopTail()
 	require.Nil(t, entry)
 
-	var entries []*Entry[StringKey, string]
+	entries := make([]*Entry[StringKey, string], 0, 5)
 	for i := range 5 {
 		new := NewEntry(StringKey(strconv.Itoa(i)), "", 1)
 		evicted := l.PushFront(new)

go/cache/theine/tlfu_test.go

@@ -33,7 +33,7 @@ func TestTlfu(t *testing.T) {
 	require.Equal(t, 0, tlfu.slru.probation.len)
 	require.Equal(t, 0, tlfu.slru.protected.len)
 
-	var entries []*Entry[StringKey, string]
+	entries := make([]*Entry[StringKey, string], 0, 200)
 	for i := range 200 {
 		e := NewEntry(StringKey(strconv.Itoa(i)), "", 1)
 		evicted := tlfu.Set(e)
@@ -78,7 +78,7 @@ func TestTlfu(t *testing.T) {
 	require.Equal(t, StringKey("1a"), evicted.key)
 	require.Equal(t, 998, tlfu.slru.probation.len)
 
-	var entries2 []*Entry[StringKey, string]
+	entries2 := make([]*Entry[StringKey, string], 0, 1000)
 	for i := range 1000 {
 		e := NewEntry(StringKey(fmt.Sprintf("%d*", i)), "", 1)
 		tlfu.Set(e)

go/cmd/vtclient/cli/vtclient.go

@@ -430,7 +430,7 @@ func (r *results) print(w io.Writer) {
 		code  vtrpcpb.Code
 		count int
 	}
-	var counts []errorCounts
+	counts := make([]errorCounts, 0, len(r.errorCount))
 	for code, count := range r.errorCount {
 		counts = append(counts, errorCounts{code, count})
 	}

go/cmd/vtctldclient/command/query.go

@@ -177,7 +177,7 @@ func commandExecuteMultiFetchAsDBA(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	var qrs []*sqltypes.Result
+	qrs := make([]*sqltypes.Result, 0, len(resp.Results))
 	for _, result := range resp.Results {
 		qr := sqltypes.Proto3ToResult(result)
 		qrs = append(qrs, qr)

go/cmd/vtctldclient/command/vreplication/vdiff/vdiff.go

@@ -473,7 +473,7 @@ func getStructFieldNames(s any) []string {
 }
 
 func buildListings(listings []*listing) string {
-	var lines [][]string
+	lines := make([][]string, 0, len(listings)+1)
 	var result string
 
 	if len(listings) == 0 {

go/cmd/vtgateclienttest/services/echo.go

@@ -53,8 +53,9 @@ func newEchoClient(fallback vtgateservice.VTGateService) *echoClient {
 }
 
 func printSortedMap(val reflect.Value) []byte {
-	var keys []string
-	for _, key := range val.MapKeys() {
+	mapKeys := val.MapKeys()
+	keys := make([]string, 0, len(mapKeys))
+	for _, key := range mapKeys {
 		keys = append(keys, key.String())
 	}
 	sort.Strings(keys)
@@ -73,7 +74,7 @@ func printSortedMap(val reflect.Value) []byte {
 func echoQueryResult(vals map[string]any) *sqltypes.Result {
 	qr := &sqltypes.Result{}
 
-	var row []sqltypes.Value
+	row := make([]sqltypes.Value, 0, len(vals)+2)
 
 	// The first two returned fields are always a field with a MySQL NULL value,
 	// and another field with a zero-length string.

go/cmd/vttablet/cli/cli_test.go

@@ -53,7 +53,7 @@ func TestRunFailsToStartTabletManager(t *testing.T) {
 		"--init-tablet-type":           "replica",
 	}
 
-	var flagArgs []string
+	flagArgs := make([]string, 0, len(flags))
 	for flag, value := range flags {
 		flagArgs = append(flagArgs, flag, value)
 	}

go/event/syslogger/fake_logger.go

@@ -77,7 +77,7 @@ func (tl *testLogger) getLog() loggerMsg {
 }
 
 func (tl *testLogger) GetAllLogs() []string {
-	var logs []string
+	logs := make([]string, 0, len(tl.logs))
 	for _, l := range tl.logs {
 		logs = append(logs, l.level+":"+l.msg)
 	}

go/flagutil/flagutil.go

@@ -42,8 +42,7 @@ func (value StringListValue) Get() any {
 
 func parseListWithEscapes(v string, delimiter rune) (value []string) {
 	var escaped, lastWasDelimiter bool
-	var current []rune
-
+	current := make([]rune, 0, len(v))
 	for _, r := range v {
 		lastWasDelimiter = false
 		if !escaped {

go/mysql/binlog/binlog_json.go

@@ -512,12 +512,15 @@ func binparserString(_ jsonDataType, data []byte, pos int) (node *json.Value, er
 // arrays are stored thus:
 // | type_identifier(one of [2,3]) | elem count | obj size | list of offsets+lengths of values | actual values |
 func binparserArray(typ jsonDataType, data []byte, pos int) (node *json.Value, err error) {
-	var nodes []*json.Value
 	var elem *json.Value
 	var elementCount int
 	large := typ == jsonLargeArray
 	elementCount, pos = readInt(data, pos, large)
 	_, pos = readInt(data, pos, large)
+	nodes := make([]*json.Value, 0, elementCount)
+	if elementCount == 0 {
+		nodes = nil
+	}
 	for range elementCount {
 		elem, pos, err = binparserElement(data, pos, large)
 		if err != nil {

go/mysql/collations/colldata/uca_contraction_test.go

@@ -194,7 +194,7 @@ func (s *strgen) withText(in string) *strgen {
 }
 
 func (s *strgen) generate(length int, freq float64) (out []byte) {
-	var flat []rune
+	flat := make([]rune, 0, len(s.repertoire))
 	for r := range s.repertoire {
 		flat = append(flat, r)
 	}

go/mysql/collations/colldata/wildcard_test.go

@@ -366,7 +366,7 @@ func BenchmarkWildcardMatching(b *testing.B) {
 		m2    WildcardPattern
 	}
 
-	var patterns []bench
+	patterns := make([]bench, 0, len(wildcardTestCases))
 	for _, tc := range wildcardTestCases {
 		patterns = append(patterns, bench{
 			input: []byte(tc.in),

go/mysql/collations/golden_test.go

@@ -84,12 +84,12 @@ func XTestSupportTables(t *testing.T) {
 		collverMariaDB100,
 	}
 
-	var envs []*Environment
+	envs := make([]*Environment, 0, len(versions))
 	for _, v := range versions {
 		envs = append(envs, makeEnv(v))
 	}
 
-	var all []ID
+	all := make([]ID, 0, len(globalVersionInfo))
 	for id := range globalVersionInfo {
 		all = append(all, id)
 	}

go/mysql/collations/integration/coercion_test.go

@@ -124,7 +124,6 @@ func (tc *testComparison) Test(t *testing.T, remote *RemoteCoercionResult, local
 
 func TestComparisonSemantics(t *testing.T) {
 	const BaseString = "abcdABCD01234"
-	var testInputs []*TextWithCollation
 
 	conn := mysqlconn(t)
 	defer conn.Close()
@@ -133,7 +132,9 @@ func TestComparisonSemantics(t *testing.T) {
 		t.Skipf("The behavior of Coercion Semantics is not correct before 8.0.31")
 	}
 
-	for _, coll := range colldata.All(collations.MySQL8()) {
+	allCollations := colldata.All(collations.MySQL8())
+	testInputs := make([]*TextWithCollation, 0, len(allCollations))
+	for _, coll := range allCollations {
 		text := verifyTranscoding(t, coll, remote.NewCollation(conn, coll.Name()), []byte(BaseString))
 		testInputs = append(testInputs, &TextWithCollation{Text: text, Collation: coll.ID()})
 	}

go/mysql/collations/integration/weight_string_test.go

@@ -76,7 +76,7 @@ func TestWeightStringsComprehensive(t *testing.T) {
 		c4cs.remotes = append(c4cs.remotes, remote.NewCollation(conn, coll.Name()))
 	}
 
-	var allCharsets []*collationsForCharset
+	allCharsets := make([]*collationsForCharset, 0, len(charsetMap))
 	for _, c4cs := range charsetMap {
 		allCharsets = append(allCharsets, c4cs)
 	}

go/mysql/collations/tools/makecolldata/codegen/codegen.go

@@ -92,7 +92,7 @@ func (g *Generator) WriteToFile(out string) {
 	fmt.Fprintf(&file, "package %s\n\n", g.local.Name())
 	fmt.Fprintf(&file, "import (\n")
 
-	var sortedPackages []Package
+	sortedPackages := make([]Package, 0, len(g.imported))
 	for pkg := range g.imported {
 		sortedPackages = append(sortedPackages, pkg)
 	}

go/mysql/collations/tools/makecolldata/codegen/tablegen.go

@@ -251,7 +251,7 @@ func (tg *TableGenerator) writePage(g *Generator, p *page, layout uca.Layout) st
 }
 
 func (tg *TableGenerator) WriteTables(g *Generator, layout uca.Layout) {
-	var pagePtrs []string
+	pagePtrs := make([]string, 0, len(tg.pages))
 	for _, page := range tg.pages {
 		pagePtrs = append(pagePtrs, tg.writePage(g, &page, layout))
 	}

go/mysql/collations/tools/makecolldata/mysqlversions.go

@@ -117,7 +117,7 @@ func makeversions(output string) {
 		}
 	}
 
-	var versions []string
+	versions := make([]string, 0, len(versionfiles))
 	for _, versionCsv := range versionfiles {
 		base := filepath.Base(versionCsv)
 		base = strings.TrimPrefix(base, "collations_")
@@ -158,7 +158,7 @@ func makeversions(output string) {
 	g.P()
 	g.P("var globalVersionInfo = map[ID]struct{alias []collalias; isdefault collver}{")
 
-	var sorted []*versionInfo
+	sorted := make([]*versionInfo, 0, len(versioninfo))
 	for _, vi := range versioninfo {
 		sorted = append(sorted, vi)
 	}

go/mysql/collations/tools/maketestdata/maketestdata.go

@@ -96,7 +96,7 @@ func getTextFromWikipedia(lang testutil.Lang, article string) (string, error) {
 		return "", err
 	}
 
-	var chunks []string
+	chunks := make([]string, 0, len(response.Query.Pages))
 	for _, page := range response.Query.Pages {
 		chunks = append(chunks, page.Extract)
 	}

go/mysql/fakesqldb/server.go

@@ -846,7 +846,7 @@ func (db *DB) MockQueriesForTable(table string, result *sqltypes.Result) {
 	db.AddQueryPattern(selectQueryPattern, result)
 
 	// mock query for returning columns from information_schema.columns based on specified result
-	var cols []string
+	cols := make([]string, 0, len(result.Fields))
 	for _, field := range result.Fields {
 		cols = append(cols, field.Name)
 	}

go/sqltypes/marshal.go

@@ -99,14 +99,14 @@ func ReplaceFields(result *Result, remap map[string]string) *Result {
 		}
 	}
 
-	var fields []*querypb.Field
+	fields := make([]*querypb.Field, 0, len(fieldIdx))
 	for _, name := range fieldIdx {
 		fields = append(fields, result.Fields[orig[name]])
 	}
 
 	fields = fields[:len(result.Fields)-len(remap)]
 
-	var rows []Row
+	rows := make([]Row, 0, len(result.Rows))
 	for _, origRow := range result.Rows {
 		var row []Value
 		for _, name := range rowIdx {
@@ -142,13 +142,15 @@ func MarshalResult(v any) (*Result, error) {
 	elem := val.Type().Elem()
 	elemType := elem.Elem()
 
+	visibleFields := reflect.VisibleFields(elemType)
+
 	var (
-		exportedStructFields []reflect.StructField
-		fields               []*querypb.Field
-		rows                 []Row
+		exportedStructFields = make([]reflect.StructField, 0, len(visibleFields))
+		fields               = make([]*querypb.Field, 0, len(visibleFields))
+		rows                 = make([]Row, 0, val.Len())
 	)
 
-	for _, field := range reflect.VisibleFields(elemType) {
+	for _, field := range visibleFields {
 		if !field.IsExported() {
 			continue
 		}

go/sqltypes/testing.go

@@ -46,7 +46,7 @@ import (
 func MakeTestFields(names, types string) []*querypb.Field {
 	n := split(names)
 	t := split(types)
-	var fields []*querypb.Field
+	fields := make([]*querypb.Field, 0, len(n))
 	for i := range n {
 		fields = append(fields, &querypb.Field{
 			Name: n[i],

go/stats/statsd/statsd.go

@@ -61,7 +61,7 @@ func makeLabels(labelNames []string, labelValsCombined string) []string {
 }
 
 func makeCommonTags(tags map[string]string) []string {
-	var commonTags []string
+	commonTags := make([]string, 0, len(tags))
 	for k, v := range tags {
 		commonTag := fmt.Sprintf("%s:%s", k, v)
 		commonTags = append(commonTags, commonTag)

go/tools/asthelpergen/integration/types.go

@@ -131,7 +131,7 @@ func (r ValueSliceContainer) String() string {
 }
 
 func (r InterfaceSlice) String() string {
-	var elements []string
+	elements := make([]string, 0, len(r))
 	for _, el := range r {
 		elements = append(elements, el.String())
 	}
@@ -144,7 +144,7 @@ func (r Bytes) String() string {
 }
 
 func (r LeafSlice) String() string {
-	var elements []string
+	elements := make([]string, 0, len(r))
 	for _, el := range r {
 		elements = append(elements, el.String())
 	}

go/tools/asthelpergen/paths_gen.go

@@ -148,8 +148,7 @@ func (p *pathGen) basicMethod(t types.Type, basic *types.Basic, spi generatorSPI
 }
 
 func (p *pathGen) debugString() *jen.Statement {
-	var switchCases []jen.Code
-
+	switchCases := make([]jen.Code, 0, len(p.steps)+1)
 	for _, step := range p.steps {
 		stepName := step.AsEnum()
 
@@ -230,8 +229,7 @@ func (p *pathGen) generateGetNodeFromPath(spi generatorSPI) *jen.Statement {
 }
 
 func (p *pathGen) generateWalkCases(spi generatorSPI) []jen.Code {
-	var cases []jen.Code
-
+	cases := make([]jen.Code, 0, len(p.steps)+2)
 	for _, step := range p.steps {
 		stepName := step.AsEnum()
 

go/tools/release-notes/release_notes.go

@@ -264,7 +264,7 @@ func groupPRs(pris []pullRequestInformation) prsByType {
 }
 
 func createSortedPrTypeSlice(prPerType prsByType) []sortedPRType {
-	var data []sortedPRType
+	data := make([]sortedPRType, 0, len(prPerType))
 	for typeKey, typeElem := range prPerType {
 		newPrType := sortedPRType{
 			Name: typeKey,