internal/versions: add a new versions package

Adds a new versions package to provide x/tools a way to
deal with new GoVersion() and FileVersions API from go/types
and the new go/version standard library.

This provides a stable API until 1.26.

Updates golang/go#63374
Updates golang/go#62605

Change-Id: I4de54df00ea0f4363c0383cbdc917186277bfd0a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/533056
Run-TryBot: Tim King <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

internal/versions/gover.go

@@ -0,0 +1,172 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This is a fork of internal/gover for use by x/tools until
+// go1.21 and earlier are no longer supported by x/tools.
+
+package versions
+
+import "strings"
+
+// A gover is a parsed Go gover: major[.Minor[.Patch]][kind[pre]]
+// The numbers are the original decimal strings to avoid integer overflows
+// and since there is very little actual math. (Probably overflow doesn't matter in practice,
+// but at the time this code was written, there was an existing test that used
+// go1.99999999999, which does not fit in an int on 32-bit platforms.
+// The "big decimal" representation avoids the problem entirely.)
+type gover struct {
+	major string // decimal
+	minor string // decimal or ""
+	patch string // decimal or ""
+	kind  string // "", "alpha", "beta", "rc"
+	pre   string // decimal or ""
+}
+
+// compare returns -1, 0, or +1 depending on whether
+// x < y, x == y, or x > y, interpreted as toolchain versions.
+// The versions x and y must not begin with a "go" prefix: just "1.21" not "go1.21".
+// Malformed versions compare less than well-formed versions and equal to each other.
+// The language version "1.21" compares less than the release candidate and eventual releases "1.21rc1" and "1.21.0".
+func compare(x, y string) int {
+	vx := parse(x)
+	vy := parse(y)
+
+	if c := cmpInt(vx.major, vy.major); c != 0 {
+		return c
+	}
+	if c := cmpInt(vx.minor, vy.minor); c != 0 {
+		return c
+	}
+	if c := cmpInt(vx.patch, vy.patch); c != 0 {
+		return c
+	}
+	if c := strings.Compare(vx.kind, vy.kind); c != 0 { // "" < alpha < beta < rc
+		return c
+	}
+	if c := cmpInt(vx.pre, vy.pre); c != 0 {
+		return c
+	}
+	return 0
+}
+
+// lang returns the Go language version. For example, lang("1.2.3") == "1.2".
+func lang(x string) string {
+	v := parse(x)
+	if v.minor == "" || v.major == "1" && v.minor == "0" {
+		return v.major
+	}
+	return v.major + "." + v.minor
+}
+
+// isValid reports whether the version x is valid.
+func isValid(x string) bool {
+	return parse(x) != gover{}
+}
+
+// parse parses the Go version string x into a version.
+// It returns the zero version if x is malformed.
+func parse(x string) gover {
+	var v gover
+
+	// Parse major version.
+	var ok bool
+	v.major, x, ok = cutInt(x)
+	if !ok {
+		return gover{}
+	}
+	if x == "" {
+		// Interpret "1" as "1.0.0".
+		v.minor = "0"
+		v.patch = "0"
+		return v
+	}
+
+	// Parse . before minor version.
+	if x[0] != '.' {
+		return gover{}
+	}
+
+	// Parse minor version.
+	v.minor, x, ok = cutInt(x[1:])
+	if !ok {
+		return gover{}
+	}
+	if x == "" {
+		// Patch missing is same as "0" for older versions.
+		// Starting in Go 1.21, patch missing is different from explicit .0.
+		if cmpInt(v.minor, "21") < 0 {
+			v.patch = "0"
+		}
+		return v
+	}
+
+	// Parse patch if present.
+	if x[0] == '.' {
+		v.patch, x, ok = cutInt(x[1:])
+		if !ok || x != "" {
+			// Note that we are disallowing prereleases (alpha, beta, rc) for patch releases here (x != "").
+			// Allowing them would be a bit confusing because we already have:
+			//	1.21 < 1.21rc1
+			// But a prerelease of a patch would have the opposite effect:
+			//	1.21.3rc1 < 1.21.3
+			// We've never needed them before, so let's not start now.
+			return gover{}
+		}
+		return v
+	}
+
+	// Parse prerelease.
+	i := 0
+	for i < len(x) && (x[i] < '0' || '9' < x[i]) {
+		if x[i] < 'a' || 'z' < x[i] {
+			return gover{}
+		}
+		i++
+	}
+	if i == 0 {
+		return gover{}
+	}
+	v.kind, x = x[:i], x[i:]
+	if x == "" {
+		return v
+	}
+	v.pre, x, ok = cutInt(x)
+	if !ok || x != "" {
+		return gover{}
+	}
+
+	return v
+}
+
+// cutInt scans the leading decimal number at the start of x to an integer
+// and returns that value and the rest of the string.
+func cutInt(x string) (n, rest string, ok bool) {
+	i := 0
+	for i < len(x) && '0' <= x[i] && x[i] <= '9' {
+		i++
+	}
+	if i == 0 || x[0] == '0' && i != 1 { // no digits or unnecessary leading zero
+		return "", "", false
+	}
+	return x[:i], x[i:], true
+}
+
+// cmpInt returns cmp.Compare(x, y) interpreting x and y as decimal numbers.
+// (Copied from golang.org/x/mod/semver's compareInt.)
+func cmpInt(x, y string) int {
+	if x == y {
+		return 0
+	}
+	if len(x) < len(y) {
+		return -1
+	}
+	if len(x) > len(y) {
+		return +1
+	}
+	if x < y {
+		return -1
+	} else {
+		return +1
+	}
+}

internal/versions/types.go

@@ -0,0 +1,19 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package versions
+
+import (
+	"go/types"
+)
+
+// GoVersion returns the Go version of the type package.
+// It returns zero if no version can be determined.
+func GoVersion(pkg *types.Package) string {
+	// TODO(taking): x/tools can call GoVersion() [from 1.21] after 1.25.
+	if pkg, ok := any(pkg).(interface{ GoVersion() string }); ok {
+		return pkg.GoVersion()
+	}
+	return ""
+}

internal/versions/types_go121.go

@@ -0,0 +1,20 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.22
+// +build !go1.22
+
+package versions
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+// FileVersions always reports the a file's Go version as the
+// zero version at this Go version.
+func FileVersions(info *types.Info, file *ast.File) string { return "" }
+
+// InitFileVersions is a noop at this Go version.
+func InitFileVersions(*types.Info) {}

internal/versions/types_go122.go

@@ -0,0 +1,24 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.22
+// +build go1.22
+
+package versions
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+// FileVersions maps a file to the file's semantic Go version.
+// The reported version is the zero version if a version cannot be determined.
+func FileVersions(info *types.Info, file *ast.File) string {
+	return info.FileVersions[file]
+}
+
+// InitFileVersions initializes info to record Go versions for Go files.
+func InitFileVersions(info *types.Info) {
+	info.FileVersions = make(map[*ast.File]string)
+}

internal/versions/types_test.go

@@ -0,0 +1,87 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package versions_test
+
+import (
+	"fmt"
+	"go/ast"
+	"go/importer"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"testing"
+
+	"golang.org/x/tools/internal/testenv"
+	"golang.org/x/tools/internal/versions"
+)
+
+func Test(t *testing.T) {
+	testenv.NeedsGo1Point(t, 22)
+
+	var contents = map[string]string{
+		"gobuild.go": `
+	//go:build go1.23
+	package p
+	`,
+		"noversion.go": `
+	package p
+	`,
+	}
+	type fileTest struct {
+		fname string
+		want  string
+	}
+	for _, item := range []struct {
+		goversion string
+		pversion  string
+		tests     []fileTest
+	}{
+		{"", "", []fileTest{{"noversion.go", ""}, {"gobuild.go", ""}}},
+		{"go1.22", "go1.22", []fileTest{{"noversion.go", "go1.22"}, {"gobuild.go", "go1.23"}}},
+	} {
+		name := fmt.Sprintf("types.Config{GoVersion:%q}", item.goversion)
+		t.Run(name, func(t *testing.T) {
+			fset := token.NewFileSet()
+			files := make([]*ast.File, len(item.tests))
+			for i, test := range item.tests {
+				files[i] = parse(t, fset, test.fname, contents[test.fname])
+			}
+			pkg, info := typeCheck(t, fset, files, item.goversion)
+			if got, want := versions.GoVersion(pkg), item.pversion; versions.Compare(got, want) != 0 {
+				t.Errorf("GoVersion()=%q. expected %q", got, want)
+			}
+			if got := versions.FileVersions(info, nil); got != "" {
+				t.Errorf(`FileVersions(nil)=%q. expected ""`, got)
+			}
+			for i, test := range item.tests {
+				if got, want := versions.FileVersions(info, files[i]), test.want; got != want {
+					t.Errorf("FileVersions(%s)=%q. expected %q", test.fname, got, want)
+				}
+			}
+		})
+	}
+}
+
+func parse(t *testing.T, fset *token.FileSet, name, src string) *ast.File {
+	file, err := parser.ParseFile(fset, name, src, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return file
+}
+
+func typeCheck(t *testing.T, fset *token.FileSet, files []*ast.File, goversion string) (*types.Package, *types.Info) {
+	conf := types.Config{
+		Importer:  importer.Default(),
+		GoVersion: goversion,
+	}
+	info := types.Info{}
+	versions.InitFileVersions(&info)
+	pkg, err := conf.Check("", fset, files, &info)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return pkg, &info
+}

internal/versions/versions_go121.go

@@ -0,0 +1,34 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.22
+// +build !go1.22
+
+package versions
+
+// Lang returns the Go language version for version x.
+// If x is not a valid version, Lang returns the empty string.
+// For example:
+//
+//	Lang("go1.21rc2") = "go1.21"
+//	Lang("go1.21.2") = "go1.21"
+//	Lang("go1.21") = "go1.21"
+//	Lang("go1") = "go1"
+//	Lang("bad") = ""
+//	Lang("1.21") = ""
+func Lang(x string) string { return lang(x) }
+
+// Compare returns -1, 0, or +1 depending on whether
+// x < y, x == y, or x > y, interpreted as Go versions.
+// The versions x and y must begin with a "go" prefix: "go1.21" not "1.21".
+// Invalid versions, including the empty string, compare less than
+// valid versions and equal to each other.
+// The language version "go1.21" compares less than the
+// release candidate and eventual releases "go1.21rc1" and "go1.21.0".
+// Custom toolchain suffixes are ignored during comparison:
+// "go1.21.0" and "go1.21.0-bigcorp" are equal.
+func Compare(x, y string) int { return compare(x, y) }
+
+// IsValid reports whether the version x is valid.
+func IsValid(x string) bool { return isValid(x) }