go/build: add AllTags to Package

AllTags lists all the tags that can affect the decision
about which files to include. Tools scanning packages
can use this to decide how many variants there are
and what they are.

R=bradfitz
CC=golang-dev
https://golang.org/cl/12703044

src/pkg/go/build/build.go

@@ -337,16 +337,17 @@ const (
 
 // A Package describes the Go package found in a directory.
 type Package struct {
-	Dir        string // directory containing package sources
+	Dir        string   // directory containing package sources
-	Name       string // package name
+	Name       string   // package name
-	Doc        string // documentation synopsis
+	Doc        string   // documentation synopsis
-	ImportPath string // import path of package ("" if unknown)
+	ImportPath string   // import path of package ("" if unknown)
-	Root       string // root of Go tree where this package lives
+	Root       string   // root of Go tree where this package lives
-	SrcRoot    string // package source root directory ("" if unknown)
+	SrcRoot    string   // package source root directory ("" if unknown)
-	PkgRoot    string // package install root directory ("" if unknown)
+	PkgRoot    string   // package install root directory ("" if unknown)
-	BinDir     string // command install directory ("" if unknown)
+	BinDir     string   // command install directory ("" if unknown)
-	Goroot     bool   // package found in Go root
+	Goroot     bool     // package found in Go root
-	PkgObj     string // installed .a file
+	PkgObj     string   // installed .a file
+	AllTags    []string // tags that can influence file selection in this directory
 
 	// Source files
 	GoFiles        []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
@@ -578,6 +579,7 @@ Found:
 	imported := make(map[string][]token.Position)
 	testImported := make(map[string][]token.Position)
 	xTestImported := make(map[string][]token.Position)
+	allTags := make(map[string]bool)
 	fset := token.NewFileSet()
 	for _, d := range dirs {
 		if d.IsDir() {
@@ -595,7 +597,7 @@ Found:
 		}
 		ext := name[i:]
 
-		if !ctxt.UseAllFiles && !ctxt.goodOSArchFile(name) {
+		if !ctxt.goodOSArchFile(name, allTags) && !ctxt.UseAllFiles {
 			if ext == ".go" {
 				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
 			}
@@ -634,7 +636,7 @@ Found:
 		}
 
 		// Look for +build comments to accept or reject the file.
-		if !ctxt.UseAllFiles && !ctxt.shouldBuild(data) {
+		if !ctxt.shouldBuild(data, allTags) && !ctxt.UseAllFiles {
 			if ext == ".go" {
 				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
 			}
@@ -736,6 +738,7 @@ Found:
 			}
 		}
 		if isCgo {
+			allTags["cgo"] = true
 			if ctxt.CgoEnabled {
 				p.CgoFiles = append(p.CgoFiles, name)
 			}
@@ -751,6 +754,11 @@ Found:
 		return p, &NoGoError{p.Dir}
 	}
 
+	for tag := range allTags {
+		p.AllTags = append(p.AllTags, tag)
+	}
+	sort.Strings(p.AllTags)
+
 	p.Imports, p.ImportPos = cleanImports(imported)
 	p.TestImports, p.TestImportPos = cleanImports(testImported)
 	p.XTestImports, p.XTestImportPos = cleanImports(xTestImported)
@@ -800,7 +808,7 @@ var slashslash = []byte("//")
 //
 // marks the file as applicable only on Windows and Linux.
 //
-func (ctxt *Context) shouldBuild(content []byte) bool {
+func (ctxt *Context) shouldBuild(content []byte, allTags map[string]bool) bool {
 	// Pass 1. Identify leading run of // comments and blank lines,
 	// which must be followed by a blank line.
 	end := 0
@@ -825,6 +833,7 @@ func (ctxt *Context) shouldBuild(content []byte) bool {
 
 	// Pass 2.  Process each line in the run.
 	p = content
+	allok := true
 	for len(p) > 0 {
 		line := p
 		if i := bytes.IndexByte(line, '\n'); i >= 0 {
@@ -841,19 +850,19 @@ func (ctxt *Context) shouldBuild(content []byte) bool {
 				if f[0] == "+build" {
 					ok := false
 					for _, tok := range f[1:] {
-						if ctxt.match(tok) {
+						if ctxt.match(tok, allTags) {
 							ok = true
-							break
 						}
 					}
 					if !ok {
-						return false // this one doesn't match
+						allok = false
 					}
 				}
 			}
 		}
 	}
-	return true // everything matches
+
+	return allok
 }
 
 // saveCgo saves the information from the #cgo lines in the import "C" comment.
@@ -893,7 +902,7 @@ func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup)
 		if len(cond) > 0 {
 			ok := false
 			for _, c := range cond {
-				if ctxt.match(c) {
+				if ctxt.match(c, nil) {
 					ok = true
 					break
 				}
@@ -1018,19 +1027,28 @@ func splitQuoted(s string) (r []string, err error) {
 //	!tag (if tag is not listed in ctxt.BuildTags or ctxt.ReleaseTags)
 //	a comma-separated list of any of these
 //
-func (ctxt *Context) match(name string) bool {
+func (ctxt *Context) match(name string, allTags map[string]bool) bool {
 	if name == "" {
+		if allTags != nil {
+			allTags[name] = true
+		}
 		return false
 	}
 	if i := strings.Index(name, ","); i >= 0 {
 		// comma-separated list
-		return ctxt.match(name[:i]) && ctxt.match(name[i+1:])
+		ok1 := ctxt.match(name[:i], allTags)
+		ok2 := ctxt.match(name[i+1:], allTags)
+		return ok1 && ok2
 	}
 	if strings.HasPrefix(name, "!!") { // bad syntax, reject always
 		return false
 	}
 	if strings.HasPrefix(name, "!") { // negation
-		return len(name) > 1 && !ctxt.match(name[1:])
+		return len(name) > 1 && !ctxt.match(name[1:], allTags)
+	}
+
+	if allTags != nil {
+		allTags[name] = true
 	}
 
 	// Tags must be letters, digits, underscores or dots.
@@ -1075,7 +1093,7 @@ func (ctxt *Context) match(name string) bool {
 //     name_$(GOARCH)_test.*
 //     name_$(GOOS)_$(GOARCH)_test.*
 //
-func (ctxt *Context) goodOSArchFile(name string) bool {
+func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
 	if dot := strings.Index(name, "."); dot != -1 {
 		name = name[:dot]
 	}
@@ -1085,12 +1103,16 @@ func (ctxt *Context) goodOSArchFile(name string) bool {
 	}
 	n := len(l)
 	if n >= 2 && knownOS[l[n-2]] && knownArch[l[n-1]] {
+		allTags[l[n-2]] = true
+		allTags[l[n-1]] = true
 		return l[n-2] == ctxt.GOOS && l[n-1] == ctxt.GOARCH
 	}
 	if n >= 1 && knownOS[l[n-1]] {
+		allTags[l[n-1]] = true
 		return l[n-1] == ctxt.GOOS
 	}
 	if n >= 1 && knownArch[l[n-1]] {
+		allTags[l[n-1]] = true
 		return l[n-1] == ctxt.GOARCH
 	}
 	return true

src/pkg/go/build/build_test.go

@@ -7,6 +7,7 @@ package build
 import (
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"testing"
 )
@@ -14,29 +15,37 @@ import (
 func TestMatch(t *testing.T) {
 	ctxt := Default
 	what := "default"
-	match := func(tag string) {
+	match := func(tag string, want map[string]bool) {
-		if !ctxt.match(tag) {
+		m := make(map[string]bool)
+		if !ctxt.match(tag, m) {
 			t.Errorf("%s context should match %s, does not", what, tag)
 		}
+		if !reflect.DeepEqual(m, want) {
+			t.Errorf("%s tags = %v, want %v", tag, m, want)
+		}
 	}
-	nomatch := func(tag string) {
+	nomatch := func(tag string, want map[string]bool) {
-		if ctxt.match(tag) {
+		m := make(map[string]bool)
+		if ctxt.match(tag, m) {
 			t.Errorf("%s context should NOT match %s, does", what, tag)
 		}
+		if !reflect.DeepEqual(m, want) {
+			t.Errorf("%s tags = %v, want %v", tag, m, want)
+		}
 	}
 
-	match(runtime.GOOS + "," + runtime.GOARCH)
+	match(runtime.GOOS+","+runtime.GOARCH, map[string]bool{runtime.GOOS: true, runtime.GOARCH: true})
-	match(runtime.GOOS + "," + runtime.GOARCH + ",!foo")
+	match(runtime.GOOS+","+runtime.GOARCH+",!foo", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "foo": true})
-	nomatch(runtime.GOOS + "," + runtime.GOARCH + ",foo")
+	nomatch(runtime.GOOS+","+runtime.GOARCH+",foo", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "foo": true})
 
 	what = "modified"
 	ctxt.BuildTags = []string{"foo"}
-	match(runtime.GOOS + "," + runtime.GOARCH)
+	match(runtime.GOOS+","+runtime.GOARCH, map[string]bool{runtime.GOOS: true, runtime.GOARCH: true})
-	match(runtime.GOOS + "," + runtime.GOARCH + ",foo")
+	match(runtime.GOOS+","+runtime.GOARCH+",foo", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "foo": true})
-	nomatch(runtime.GOOS + "," + runtime.GOARCH + ",!foo")
+	nomatch(runtime.GOOS+","+runtime.GOARCH+",!foo", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "foo": true})
-	match(runtime.GOOS + "," + runtime.GOARCH + ",!bar")
+	match(runtime.GOOS+","+runtime.GOARCH+",!bar", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "bar": true})
-	nomatch(runtime.GOOS + "," + runtime.GOARCH + ",bar")
+	nomatch(runtime.GOOS+","+runtime.GOARCH+",bar", map[string]bool{runtime.GOOS: true, runtime.GOARCH: true, "bar": true})
-	nomatch("!")
+	nomatch("!", map[string]bool{})
 }
 
 func TestDotSlashImport(t *testing.T) {
@@ -92,28 +101,44 @@ func TestLocalDirectory(t *testing.T) {
 func TestShouldBuild(t *testing.T) {
 	const file1 = "// +build tag1\n\n" +
 		"package main\n"
+	want1 := map[string]bool{"tag1": true}
 
 	const file2 = "// +build cgo\n\n" +
 		"// This package implements parsing of tags like\n" +
 		"// +build tag1\n" +
 		"package build"
+	want2 := map[string]bool{"cgo": true}
 
 	const file3 = "// Copyright The Go Authors.\n\n" +
 		"package build\n\n" +
 		"// shouldBuild checks tags given by lines of the form\n" +
 		"// +build tag\n" +
 		"func shouldBuild(content []byte)\n"
+	want3 := map[string]bool{}
 
 	ctx := &Context{BuildTags: []string{"tag1"}}
-	if !ctx.shouldBuild([]byte(file1)) {
+	m := map[string]bool{}
-		t.Errorf("should not build file1, expected the contrary")
+	if !ctx.shouldBuild([]byte(file1), m) {
+		t.Errorf("shouldBuild(file1) = false, want true")
 	}
-	if ctx.shouldBuild([]byte(file2)) {
+	if !reflect.DeepEqual(m, want1) {
-		t.Errorf("should build file2, expected the contrary")
+		t.Errorf("shoudBuild(file1) tags = %v, want %v", m, want1)
 	}
 
+	m = map[string]bool{}
+	if ctx.shouldBuild([]byte(file2), m) {
+		t.Errorf("shouldBuild(file2) = true, want fakse")
+	}
+	if !reflect.DeepEqual(m, want2) {
+		t.Errorf("shoudBuild(file2) tags = %v, want %v", m, want2)
+	}
+
+	m = map[string]bool{}
 	ctx = &Context{BuildTags: nil}
-	if !ctx.shouldBuild([]byte(file3)) {
+	if !ctx.shouldBuild([]byte(file3), m) {
-		t.Errorf("should not build file3, expected the contrary")
+		t.Errorf("shouldBuild(file3) = false, want true")
+	}
+	if !reflect.DeepEqual(m, want3) {
+		t.Errorf("shoudBuild(file3) tags = %v, want %v", m, want3)
 	}
 }

src/pkg/go/build/syslist_test.go

@@ -55,7 +55,7 @@ var tests = []GoodFileTest{
 
 func TestGoodOSArch(t *testing.T) {
 	for _, test := range tests {
-		if Default.goodOSArchFile(test.name) != test.result {
+		if Default.goodOSArchFile(test.name, make(map[string]bool)) != test.result {
 			t.Fatalf("goodOSArchFile(%q) != %v", test.name, test.result)
 		}
 	}