go/buildutil, cmd/guru: resolve symlinks in filenames through build.Context

Resolve symlinks in source directories (GOPATH, GOROOT, etc.) and source
files in order to find correct package. All I/O performed through
build.Context. Also add minor fix to guru unit tests in order to pass on
Windows.

Change-Id: Ie6134b9cd74eb7386e1d93603eb37c8e44b083b8
Reviewed-on: https://go-review.googlesource.com/33924
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/guru/unit_test.go

@@ -9,6 +9,7 @@ import (
 	"go/build"
 	"io/ioutil"
 	"os"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
@@ -46,7 +47,7 @@ func TestIssue17515(t *testing.T) {
 	}
 
 	successTests := []SuccessTest{
-		{home + "/go", home + "/go/src/test/test.go", home + "/go/src"},
+		{home + "/go", home + "/go/src/test/test.go", filepath.FromSlash(home + "/go/src")},
 	}
 
 	// Add symlink cases if not on Windows, Plan 9
@@ -57,9 +58,9 @@ func TestIssue17515(t *testing.T) {
 		}
 
 		successTests = append(successTests, []SuccessTest{
-			{home + "/go", home + "/src/test/test.go", home + "/go/src"},
-			{home, home + "/go/src/test/test.go", home + "/src"},
-			{home, home + "/src/test/test.go", home + "/src"},
+			{home + "/go", home + "/src/test/test.go", filepath.FromSlash(home + "/go/src")},
+			{home, home + "/go/src/test/test.go", filepath.FromSlash(home + "/src")},
+			{home, home + "/src/test/test.go", filepath.FromSlash(home + "/src")},
 		}...)
 	}
 
@@ -67,7 +68,7 @@ func TestIssue17515(t *testing.T) {
 		buildContext.GOPATH = test.gopath
 		srcdir, importPath, err := guessImportPath(test.filename, &buildContext)
 		if srcdir != test.wantSrcdir || importPath != "test" || err != nil {
-			t.Errorf("guessImportPath(%v, %v) = %v, %v, %v; want %v, %v, %v",
+			t.Errorf("guessImportPath(%q, %q) = %q, %q, %q; want %q, %q, %q",
 				test.filename, test.gopath, srcdir, importPath, err, test.wantSrcdir, "test", "nil")
 		}
 	}
@@ -82,14 +83,14 @@ func TestIssue17515(t *testing.T) {
 	}
 
 	failTests := []FailTest{
-		{home + "/go", home + "/go/src/fake/test.go", errFormat(home + "/go/src/fake")},
+		{home + "/go", home + "/go/src/fake/test.go", errFormat(filepath.FromSlash(home + "/go/src/fake"))},
 	}
 
 	if runtime.GOOS != "windows" && runtime.GOOS != "plan9" {
 		failTests = append(failTests, []FailTest{
-			{home + "/go", home + "/src/fake/test.go", errFormat(home + "/src/fake")},
-			{home, home + "/src/fake/test.go", errFormat(home + "/src/fake")},
-			{home, home + "/go/src/fake/test.go", errFormat(home + "/go/src/fake")},
+			{home + "/go", home + "/src/fake/test.go", errFormat(filepath.FromSlash(home + "/src/fake"))},
+			{home, home + "/src/fake/test.go", errFormat(filepath.FromSlash(home + "/src/fake"))},
+			{home, home + "/go/src/fake/test.go", errFormat(filepath.FromSlash(home + "/go/src/fake"))},
 		}...)
 	}
 
@@ -97,7 +98,7 @@ func TestIssue17515(t *testing.T) {
 		buildContext.GOPATH = test.gopath
 		srcdir, importPath, err := guessImportPath(test.filename, &buildContext)
 		if !strings.HasPrefix(fmt.Sprint(err), test.wantErr) {
-			t.Errorf("guessImportPath(%v, %v) = %v, %v, %v; want %v, %v, %v",
+			t.Errorf("guessImportPath(%q, %q) = %q, %q, %q; want %q, %q, %q",
 				test.filename, test.gopath, srcdir, importPath, err, "", "", test.wantErr)
 		}
 	}

go/buildutil/util.go

@@ -71,8 +71,7 @@ func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Packag
 	// We assume that no source root (GOPATH[i] or GOROOT) contains any other.
 	for _, srcdir := range ctxt.SrcDirs() {
 		srcdirSlash := filepath.ToSlash(srcdir) + "/"
-		if dirHasPrefix(dirSlash, srcdirSlash) {
-			importPath := dirSlash[len(srcdirSlash) : len(dirSlash)-len("/")]
+		if importPath, ok := HasSubdir(ctxt, srcdirSlash, dirSlash); ok {
 			return ctxt.Import(importPath, dir, build.FindOnly)
 		}
 	}
@@ -92,7 +91,47 @@ func dirHasPrefix(dir, prefix string) bool {
 
 // (go/build.Context defines these as methods, but does not export them.)
 
-// TODO(adonovan): HasSubdir?
+// hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
+// the local file system to answer the question.
+func HasSubdir(ctxt *build.Context, root, dir string) (rel string, ok bool) {
+	if f := ctxt.HasSubdir; f != nil {
+		return f(root, dir)
+	}
+
+	// Try using paths we received.
+	if rel, ok = hasSubdir(root, dir); ok {
+		return
+	}
+
+	// Try expanding symlinks and comparing
+	// expanded against unexpanded and
+	// expanded against expanded.
+	rootSym, _ := filepath.EvalSymlinks(root)
+	dirSym, _ := filepath.EvalSymlinks(dir)
+
+	if rel, ok = hasSubdir(rootSym, dir); ok {
+		return
+	}
+	if rel, ok = hasSubdir(root, dirSym); ok {
+		return
+	}
+	return hasSubdir(rootSym, dirSym)
+}
+
+func hasSubdir(root, dir string) (rel string, ok bool) {
+	const sep = string(filepath.Separator)
+	root = filepath.Clean(root)
+	if !strings.HasSuffix(root, sep) {
+		root += sep
+	}
+
+	dir = filepath.Clean(dir)
+	if !strings.HasPrefix(dir, root) {
+		return "", false
+	}
+
+	return filepath.ToSlash(dir[len(root):]), true
+}
 
 // FileExists returns true if the specified file exists,
 // using the build context's file system interface.

go/buildutil/util_test.go

@@ -2,14 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Incomplete source tree on Android.
-
-// +build !android
-
 package buildutil_test
 
 import (
 	"go/build"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -23,22 +20,51 @@ func TestContainingPackage(t *testing.T) {
 	goroot := runtime.GOROOT()
 	gopath := filepath.SplitList(os.Getenv("GOPATH"))[0]
 
-	tests := [][2]string{
-		{goroot + "/src/fmt/print.go", "fmt"},
-		{goroot + "/src/encoding/json/foo.go", "encoding/json"},
-		{goroot + "/src/encoding/missing/foo.go", "(not found)"},
-		{gopath + "/src/golang.org/x/tools/go/buildutil/util_test.go",
+	type Test struct {
+		gopath, filename, wantPkg string
+	}
+
+	tests := []Test{
+		{gopath, goroot + "/src/fmt/print.go", "fmt"},
+		{gopath, goroot + "/src/encoding/json/foo.go", "encoding/json"},
+		{gopath, goroot + "/src/encoding/missing/foo.go", "(not found)"},
+		{gopath, gopath + "/src/golang.org/x/tools/go/buildutil/util_test.go",
 			"golang.org/x/tools/go/buildutil"},
 	}
+
+	if runtime.GOOS != "windows" && runtime.GOOS != "plan9" {
+		// Make a symlink to gopath for test
+		tmp, err := ioutil.TempDir(os.TempDir(), "go")
+		if err != nil {
+			t.Errorf("Unable to create a temporary directory in %s", os.TempDir())
+		}
+
+		defer os.RemoveAll(tmp)
+
+		// symlink between $GOPATH/src and /tmp/go/src
+		// in order to test all possible symlink cases
+		if err := os.Symlink(gopath+"/src", tmp+"/src"); err != nil {
+			t.Fatal(err)
+		}
+		tests = append(tests, []Test{
+			{gopath, tmp + "/src/golang.org/x/tools/go/buildutil/util_test.go", "golang.org/x/tools/go/buildutil"},
+			{tmp, gopath + "/src/golang.org/x/tools/go/buildutil/util_test.go", "golang.org/x/tools/go/buildutil"},
+			{tmp, tmp + "/src/golang.org/x/tools/go/buildutil/util_test.go", "golang.org/x/tools/go/buildutil"},
+		}...)
+	}
+
 	for _, test := range tests {
-		file, want := test[0], test[1]
-		bp, err := buildutil.ContainingPackage(&build.Default, ".", file)
-		got := bp.ImportPath
+		var got string
+		var buildContext = build.Default
+		buildContext.GOPATH = test.gopath
+		bp, err := buildutil.ContainingPackage(&buildContext, ".", test.filename)
 		if err != nil {
 			got = "(not found)"
+		} else {
+			got = bp.ImportPath
 		}
-		if got != want {
-			t.Errorf("ContainingPackage(%q) = %s, want %s", file, got, want)
+		if got != test.wantPkg {
+			t.Errorf("ContainingPackage(%q) = %s, want %s", test.filename, got, test.wantPkg)
 		}
 	}