1 files changed, 43 insertions, 35 deletions

diff --git a/src/cmd/go/list.go b/src/cmd/go/list.go
index edb59aa79..2d23d077e 100644
--- a/src/cmd/go/list.go
+++ b/src/cmd/go/list.go
@@ -9,11 +9,12 @@ import (
 	"encoding/json"
 	"io"
 	"os"
+	"strings"
 	"text/template"
 )
 
 var cmdList = &Command{
-	UsageLine: "list [-e] [-f format] [-json] [packages]",
+	UsageLine: "list [-e] [-f format] [-json] [-tags 'tag list'] [packages]",
 	Short:     "list packages",
 	Long: `
 List lists the packages named by the import paths, one per line.
@@ -24,10 +25,10 @@ The default output shows the package import path:
     code.google.com/p/goauth2/oauth
     code.google.com/p/sqlite
 
-The -f flag specifies an alternate format for the list,
-using the syntax of package template.  The default output
-is equivalent to -f '{{.ImportPath}}'.  The struct
-being passed to the template is:
+The -f flag specifies an alternate format for the list, using the
+syntax of package template.  The default output is equivalent to -f
+'{{.ImportPath}}'.  One extra template function is available, "join",
+which calls strings.Join. The struct being passed to the template is:
 
     type Package struct {
         Dir        string // directory containing package sources
@@ -41,12 +42,15 @@ being passed to the template is:
         Root       string // Go root or Go path dir containing this package
 
         // Source files
-        GoFiles  []string  // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
-        CgoFiles []string  // .go sources files that import "C"
-        CFiles   []string  // .c source files
-        HFiles   []string  // .h source files
-        SFiles   []string  // .s source files
-        SysoFiles []string // .syso object files to add to archive
+        GoFiles  []string       // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
+        CgoFiles []string       // .go sources files that import "C"
+        IgnoredGoFiles []string // .go sources ignored due to build constraints
+        CFiles   []string       // .c source files
+        HFiles   []string       // .h source files
+        SFiles   []string       // .s source files
+        SysoFiles []string      // .syso object files to add to archive
+        SwigFiles []string      // .swig files
+        SwigCXXFiles []string   // .swigcxx files
 
         // Cgo directives
         CgoCFLAGS    []string // cgo: flags for C compiler
@@ -81,6 +85,9 @@ printing.  Erroneous packages will have a non-empty ImportPath and
 a non-nil Error field; other information may or may not be missing
 (zeroed).
 
+The -tags flag specifies a list of build tags, like in the 'go build'
+command.
+
 For more about specifying packages, see 'go help packages'.
 	`,
 }
@@ -88,6 +95,7 @@ For more about specifying packages, see 'go help packages'.
 func init() {
 	cmdList.Run = runList // break init cycle
 	cmdList.Flag.Var(buildCompiler{}, "compiler", "")
+	cmdList.Flag.Var((*stringsFlag)(&buildContext.BuildTags), "tags", "")
 }
 
 var listE = cmdList.Flag.Bool("e", false, "")
@@ -96,7 +104,7 @@ var listJson = cmdList.Flag.Bool("json", false, "")
 var nl = []byte{'\n'}
 
 func runList(cmd *Command, args []string) {
-	out := newCountingWriter(os.Stdout)
+	out := newTrackingWriter(os.Stdout)
 	defer out.w.Flush()
 
 	var do func(*Package)
@@ -111,18 +119,17 @@ func runList(cmd *Command, args []string) {
 			out.Write(nl)
 		}
 	} else {
-		tmpl, err := template.New("main").Parse(*listFmt)
+		tmpl, err := template.New("main").Funcs(template.FuncMap{"join": strings.Join}).Parse(*listFmt)
 		if err != nil {
 			fatalf("%s", err)
 		}
 		do = func(p *Package) {
-			out.Reset()
 			if err := tmpl.Execute(out, p); err != nil {
 				out.Flush()
 				fatalf("%s", err)
 			}
-			if out.Count() > 0 {
-				out.w.WriteRune('\n')
+			if out.NeedNL() {
+				out.Write([]byte{'\n'})
 			}
 		}
 	}
@@ -137,32 +144,33 @@ func runList(cmd *Command, args []string) {
 	}
 }
 
-// CountingWriter counts its data, so we can avoid appending a newline
-// if there was no actual output.
-type CountingWriter struct {
-	w     *bufio.Writer
-	count int64
+// TrackingWriter tracks the last byte written on every write so
+// we can avoid printing a newline if one was already written or
+// if there is no output at all.
+type TrackingWriter struct {
+	w    *bufio.Writer
+	last byte
 }
 
-func newCountingWriter(w io.Writer) *CountingWriter {
-	return &CountingWriter{
-		w: bufio.NewWriter(w),
+func newTrackingWriter(w io.Writer) *TrackingWriter {
+	return &TrackingWriter{
+		w:    bufio.NewWriter(w),
+		last: '\n',
 	}
 }
 
-func (cw *CountingWriter) Write(p []byte) (n int, err error) {
-	cw.count += int64(len(p))
-	return cw.w.Write(p)
-}
-
-func (cw *CountingWriter) Flush() {
-	cw.w.Flush()
+func (t *TrackingWriter) Write(p []byte) (n int, err error) {
+	n, err = t.w.Write(p)
+	if n > 0 {
+		t.last = p[n-1]
+	}
+	return
 }
 
-func (cw *CountingWriter) Reset() {
-	cw.count = 0
+func (t *TrackingWriter) Flush() {
+	t.w.Flush()
 }
 
-func (cw *CountingWriter) Count() int64 {
-	return cw.count
+func (t *TrackingWriter) NeedNL() bool {
+	return t.last != '\n'
 }