all: start using Go 1.21 std APIs

A lot of simplifications this time around.

expand/braces.go

@@ -29,11 +29,7 @@ func Braces(word *syntax.Word) []*syntax.Word {
 
 			fromLit := br.Elems[0].Lit()
 			toLit := br.Elems[1].Lit()
-			zeros := extraLeadingZeros(fromLit)
-			// TODO: use max when we can assume Go 1.21
-			if z := extraLeadingZeros(toLit); z > zeros {
-				zeros = z
-			}
+			zeros := max(extraLeadingZeros(fromLit), extraLeadingZeros(toLit))
 
 			from, err1 := strconv.Atoi(fromLit)
 			to, err2 := strconv.Atoi(toLit)

expand/environ.go

@@ -5,6 +5,7 @@ package expand
 
 import (
 	"runtime"
+	"slices"
 	"sort"
 	"strings"
 )
@@ -152,7 +153,7 @@ func ListEnviron(pairs ...string) Environ {
 // listEnvironWithUpper implements ListEnviron, but letting the tests specify
 // whether to uppercase all names or not.
 func listEnvironWithUpper(upper bool, pairs ...string) Environ {
-	list := append([]string{}, pairs...)
+	list := slices.Clone(pairs)
 	if upper {
 		// Uppercase before sorting, so that we can remove duplicates
 		// without the need for linear search nor a map.

expand/environ_test.go

@@ -18,7 +18,7 @@ func TestListEnviron(t *testing.T) {
 		{
 			name:  "Empty",
 			pairs: nil,
-			want:  []string{},
+			want:  nil,
 		},
 		{
 			name:  "Simple",
@@ -62,7 +62,7 @@ func TestListEnviron(t *testing.T) {
 			gotEnv := listEnvironWithUpper(tc.upper, tc.pairs...)
 			got := []string(gotEnv.(listEnviron))
 			if !reflect.DeepEqual(got, tc.want) {
-				t.Fatalf("ListEnviron(%t, %q) wanted %q, got %q",
+				t.Fatalf("ListEnviron(%t, %q) wanted %#v, got %#v",
 					tc.upper, tc.pairs, tc.want, got)
 			}
 		})

expand/expand.go

@@ -731,12 +731,14 @@ func (cfg *Config) quotedElemFields(pe *syntax.ParamExp) []string {
 			switch vr := cfg.Env.Get(name); vr.Kind {
 			case Indexed:
 				keys := make([]string, 0, len(vr.Map))
+				// TODO: maps.Keys if it makes it into Go 1.23
 				for key := range vr.List {
 					keys = append(keys, strconv.Itoa(key))
 				}
 				return keys
 			case Associative:
 				keys := make([]string, 0, len(vr.Map))
+				// TODO: maps.Keys if it makes it into Go 1.23
 				for key := range vr.Map {
 					keys = append(keys, key)
 				}
@@ -757,6 +759,7 @@ func (cfg *Config) quotedElemFields(pe *syntax.ParamExp) []string {
 		case Indexed:
 			return vr.List
 		case Associative:
+			// TODO: maps.Values if it makes it into Go 1.23
 			elems := make([]string, 0, len(vr.Map))
 			for _, elem := range vr.Map {
 				elems = append(elems, elem)

interp/api.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"maps"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -667,9 +668,7 @@ func (r *Runner) Reset() {
 	if r.Vars == nil {
 		r.Vars = make(map[string]expand.Variable)
 	} else {
-		for k := range r.Vars {
-			delete(r.Vars, k)
-		}
+		clear(r.Vars)
 	}
 	// TODO(v4): Use the supplied Env directly if it implements enough methods.
 	r.writeEnv = &overlayEnviron{parent: r.Env}
@@ -818,17 +817,9 @@ func (r *Runner) Subshell() *Runner {
 	// Env vars aren't copied; setVar will copy lists and maps as needed.
 	oenv := &overlayEnviron{parent: r.writeEnv}
 	r2.writeEnv = oenv
-	r2.Funcs = make(map[string]*syntax.Stmt, len(r.Funcs))
-	for k, v := range r.Funcs {
-		r2.Funcs[k] = v
-	}
+	r2.Funcs = maps.Clone(r.Funcs)
 	r2.Vars = make(map[string]expand.Variable)
-	if l := len(r.alias); l > 0 {
-		r2.alias = make(map[string]alias, l)
-		for k, v := range r.alias {
-			r2.alias[k] = v
-		}
-	}
+	r2.alias = maps.Clone(r.alias)
 
 	r2.dirStack = append(r2.dirBootstrap[:0], r.dirStack...)
 	r2.fillExpandConfig(r.ectx)

interp/vars.go

@@ -5,8 +5,10 @@ package interp
 
 import (
 	"fmt"
+	"maps"
 	"os"
 	"runtime"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -228,9 +230,8 @@ func (r *Runner) setVar(name string, index syntax.ArithmExpr, vr expand.Variable
 	case expand.String:
 		list = append(list, cur.Str)
 	case expand.Indexed:
-		// TODO: slices.Clone
 		// TODO: only clone when inside a subshell and getting a var from outside for the first time
-		list = append([]string(nil), cur.List...)
+		list = slices.Clone(cur.List)
 	case expand.Associative:
 		// if the existing variable is already an AssocArray, try our
 		// best to convert the key to a string
@@ -240,13 +241,8 @@ func (r *Runner) setVar(name string, index syntax.ArithmExpr, vr expand.Variable
 		}
 		k := r.literal(w)
 
-		// TODO: maps.Clone
 		// TODO: only clone when inside a subshell and getting a var from outside for the first time
-		m2 := make(map[string]string, len(cur.Map))
-		for k, vr := range cur.Map {
-			m2[k] = vr
-		}
-		cur.Map = m2
+		cur.Map = maps.Clone(cur.Map)
 		cur.Map[k] = valStr
 		r.setVarInternal(name, cur)
 		return
@@ -355,9 +351,7 @@ func (r *Runner) assignVal(as *syntax.Assign, valType string) expand.Variable {
 		}
 		elemValues[i].index = index
 		index += len(elemValues[i].values)
-		if index > maxIndex {
-			maxIndex = index
-		}
+		maxIndex = max(maxIndex, index)
 	}
 	// Flatten down the values.
 	strs := make([]string, maxIndex)

syntax/fuzz_test.go

@@ -44,13 +44,13 @@ func FuzzQuote(f *testing.F) {
 		var shellProgram string
 		switch lang {
 		case LangBash:
-			hasBash51(t)
+			requireBash52(t)
 			shellProgram = "bash"
 		case LangPOSIX:
-			hasDash059(t)
+			requireDash059(t)
 			shellProgram = "dash"
 		case LangMirBSDKorn:
-			hasMksh59(t)
+			requireMksh59(t)
 			shellProgram = "mksh"
 		case LangBats:
 			t.Skip() // bats has no shell and its syntax is just bash

syntax/parser_test.go

@@ -164,43 +164,36 @@ func TestMain(m *testing.M) {
 }
 
 var (
-	storedHasBash52 bool
-	onceHasBash52   sync.Once
+	onceHasBash52 = sync.OnceValue(func() bool {
+		return cmdContains("version 5.2", "bash", "--version")
+	})
 
-	storedHasDash059 bool
-	onceHasDash059   sync.Once
+	onceHasDash059 = sync.OnceValue(func() bool {
+		// dash provides no way to check its version, so we have to
+		// check if it's new enough as to not have the bug that breaks
+		// our integration tests.
+		// This also means our check does not require a specific version.
+		return cmdContains("Bad subst", "dash", "-c", "echo ${#<}")
+	})
 
-	storedHasMksh59 bool
-	onceHasMksh59   sync.Once
+	onceHasMksh59 = sync.OnceValue(func() bool {
+		return cmdContains(" R59 ", "mksh", "-c", "echo $KSH_VERSION")
+	})
 )
 
-func hasBash51(tb testing.TB) {
-	onceHasBash52.Do(func() {
-		storedHasBash52 = cmdContains("version 5.2", "bash", "--version")
-	})
-	if !storedHasBash52 {
-		tb.Skipf("bash 5.1 required to run")
+func requireBash52(tb testing.TB) {
+	if !onceHasBash52() {
+		tb.Skipf("bash 5.2 required to run")
 	}
 }
-
-func hasDash059(tb testing.TB) {
-	// dash provides no way to check its version, so we have to
-	// check if it's new enough as to not have the bug that breaks
-	// our integration tests.
-	// This also means our check does not require a specific version.
-	onceHasDash059.Do(func() {
-		storedHasDash059 = cmdContains("Bad subst", "dash", "-c", "echo ${#<}")
-	})
-	if !storedHasDash059 {
+func requireDash059(tb testing.TB) {
+	if !onceHasDash059() {
 		tb.Skipf("dash 0.5.9+ required to run")
 	}
 }
 
-func hasMksh59(tb testing.TB) {
-	onceHasMksh59.Do(func() {
-		storedHasMksh59 = cmdContains(" R59 ", "mksh", "-c", "echo $KSH_VERSION")
-	})
-	if !storedHasMksh59 {
+func requireMksh59(tb testing.TB) {
+	if !onceHasMksh59() {
 		tb.Skipf("mksh 59 required to run")
 	}
 }
@@ -265,7 +258,7 @@ func TestParseBashConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling bash is slow.")
 	}
-	hasBash51(t)
+	requireBash52(t)
 	i := 0
 	for _, c := range append(fileTests, fileTestsNoPrint...) {
 		if c.Bash == nil {
@@ -283,7 +276,7 @@ func TestParsePosixConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling dash is slow.")
 	}
-	hasDash059(t)
+	requireDash059(t)
 	i := 0
 	for _, c := range append(fileTests, fileTestsNoPrint...) {
 		if c.Posix == nil {
@@ -301,7 +294,7 @@ func TestParseMirBSDKornConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling mksh is slow.")
 	}
-	hasMksh59(t)
+	requireMksh59(t)
 	i := 0
 	for _, c := range append(fileTests, fileTestsNoPrint...) {
 		if c.MirBSDKorn == nil {
@@ -319,7 +312,7 @@ func TestParseErrBashConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling bash is slow.")
 	}
-	hasBash51(t)
+	requireBash52(t)
 	for _, c := range shellTests {
 		want := c.common
 		if c.bsmk != nil {
@@ -340,7 +333,7 @@ func TestParseErrPosixConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling dash is slow.")
 	}
-	hasDash059(t)
+	requireDash059(t)
 	for _, c := range shellTests {
 		want := c.common
 		if c.posix != nil {
@@ -358,7 +351,7 @@ func TestParseErrMirBSDKornConfirm(t *testing.T) {
 	if testing.Short() {
 		t.Skip("calling mksh is slow.")
 	}
-	hasMksh59(t)
+	requireMksh59(t)
 	for _, c := range shellTests {
 		want := c.common
 		if c.bsmk != nil {