imports: add configuration mechanism to exclude directories

Each $GOPATH entry may have a file $GOPATH/src/.goimportsignore which
may contain blank lines, #comment lines, or lines naming a directory
relative to the configuration file to ignore when scanning.  No
globbing or regex patterns are allowed.

Updates golang/go#16367 (goimports speed)
Fixes golang/go#16386 (add mechanism to ignore directories)

Change-Id: I8f1a88ae6c4d0ed3075444d70aec3e2228c5ce6a
Reviewed-on: https://go-review.googlesource.com/24971
Reviewed-by: Rob Pike <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

cmd/goimports/doc.go

@@ -27,6 +27,18 @@ For GoSublime, follow the steps described here:
 
 For other editors, you probably know what to do.
 
+To exclude directories in your $GOPATH from being scanned for Go
+files, goimports respects a configuration file at
+$GOPATH/src/.goimportsignore which may contain blank lines, comment
+lines (beginning with '#'), or lines naming a directory relative to
+the configuration file to ignore when scanning. No globbing or regex
+patterns are allowed. Use the "-v" verbose flag to verify it's
+working and see what goimports is doing.
+
+File bugs or feature requests at:
+
+    https://golang.org/issues/new?title=x/tools/cmd/goimports:+
+
 Happy hacking!
 
 */

imports/fix.go

@@ -5,6 +5,8 @@
 package imports
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
 	"go/ast"
 	"go/build"
@@ -311,10 +313,47 @@ var visitedSymlinks struct {
 	m map[string]struct{}
 }
 
+var ignoredDirs []os.FileInfo
+
+// populateIgnoredDirs reads an optional config file at <path>/.goimportsignore
+// of relative directories to ignore when scanning for go files.
+// The provided path is one of the $GOPATH entries with "src" appended.
+func populateIgnoredDirs(path string) {
+	slurp, err := ioutil.ReadFile(filepath.Join(path, ".goimportsignore"))
+	if err != nil {
+		return
+	}
+	bs := bufio.NewScanner(bytes.NewReader(slurp))
+	for bs.Scan() {
+		line := strings.TrimSpace(bs.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		if fi, err := os.Stat(filepath.Join(path, line)); err == nil {
+			ignoredDirs = append(ignoredDirs, fi)
+		}
+	}
+}
+
+func skipDir(fi os.FileInfo) bool {
+	for _, ignoredDir := range ignoredDirs {
+		if os.SameFile(fi, ignoredDir) {
+			return true
+		}
+	}
+	return false
+}
+
 // shouldTraverse checks if fi, found in dir, is a directory or a symlink to a directory.
 // It makes sure symlinks were never visited before to avoid symlink loops.
 func shouldTraverse(dir string, fi os.FileInfo) bool {
 	if fi.IsDir() {
+		if skipDir(fi) {
+			if Debug {
+				log.Printf("skipping directory %q under %s", fi.Name(), dir)
+			}
+			return false
+		}
 		return true
 	}
 
@@ -382,6 +421,9 @@ func scanGoDirs(goRoot bool) {
 		if isGoroot != goRoot {
 			continue
 		}
+		if !goRoot {
+			populateIgnoredDirs(path)
+		}
 		fsgate.enter()
 		testHookScanDir(path)
 		if Debug {
@@ -554,7 +596,7 @@ func loadExportsGoPath(expectPackage, dir string) map[string]bool {
 			exportList = append(exportList, k)
 		}
 		sort.Strings(exportList)
-		log.Printf("scanned dir %v (package %v): exports = %v", dir, expectPackage, strings.Join(exportList, ", "))
+		log.Printf("loaded exports in dir %v (package %v): %v", dir, expectPackage, strings.Join(exportList, ", "))
 	}
 	return exports
 }

imports/fix_test.go

@@ -985,6 +985,7 @@ func withEmptyGoPath(fn func()) {
 	scanGoRootOnce = &sync.Once{}
 	scanGoPathOnce = &sync.Once{}
 	dirScan = nil
+	ignoredDirs = nil
 	dirScanMu.Unlock()
 
 	oldGOPATH := build.Default.GOPATH
@@ -1304,6 +1305,26 @@ func TestImportPathToNameGoPathParse(t *testing.T) {
 	})
 }
 
+func TestIgnoreConfiguration(t *testing.T) {
+	testConfig{
+		gopathFiles: map[string]string{
+			".goimportsignore":                                     "# comment line\n\n example.net", // tests comment, blank line, whitespace trimming
+			"example.net/pkg/pkg.go":                               "package pkg\nconst X = 1",
+			"otherwise-longer-so-worse.example.net/foo/pkg/pkg.go": "package pkg\nconst X = 1",
+		},
+	}.test(t, func(t *goimportTest) {
+		const in = "package x\n\nconst _ = pkg.X\n"
+		const want = "package x\n\nimport \"otherwise-longer-so-worse.example.net/foo/pkg\"\n\nconst _ = pkg.X\n"
+		buf, err := Process(t.gopath+"/src/x/x.go", []byte(in), nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(buf) != want {
+			t.Errorf("wrong output.\ngot:\n%q\nwant:\n%q\n", buf, want)
+		}
+	})
+}
+
 func strSet(ss []string) map[string]bool {
 	m := make(map[string]bool)
 	for _, s := range ss {