cmd/go: do not panic on template I/O error

Fixes #11839.

Change-Id: Ie092a3a512a2d35967364b41081a066ab3a6aab4
Reviewed-on: https://go-review.googlesource.com/12571
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index e07651bb026b787b923d0ea7f0ea610b018ca327..88a94417d74a85eabe4abb6889ed814421351e2b 100644 (file)
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -235,12 +235,35 @@ var documentationTemplate = `// Copyright 2011 The Go Authors.  All rights reser
 package main
 `
 
+// An errWriter wraps a writer, recording whether a write error occurred.
+type errWriter struct {
+       w   io.Writer
+       err error
+}
+
+func (w *errWriter) Write(b []byte) (int, error) {
+       n, err := w.w.Write(b)
+       if err != nil {
+               w.err = err
+       }
+       return n, err
+}
+
 // tmpl executes the given template text on data, writing the result to w.
 func tmpl(w io.Writer, text string, data interface{}) {
        t := template.New("top")
        t.Funcs(template.FuncMap{"trim": strings.TrimSpace, "capitalize": capitalize})
        template.Must(t.Parse(text))
-       if err := t.Execute(w, data); err != nil {
+       ew := &errWriter{w: w}
+       err := t.Execute(ew, data)
+       if ew.err != nil {
+               // I/O error writing. Ignore write on closed pipe.
+               if strings.Contains(ew.err.Error(), "pipe") {
+                       os.Exit(1)
+               }
+               fatalf("writing output: %v", ew.err)
+       }
+       if err != nil {
                panic(err)
        }
 }