net/http/httptest: don't crash in mime sniffing if HeaderMap is nil

Fixes some failing Google tests when run under Go tip (1.6). Updates #12986 Change-Id: I0ca4d20f6103d10ea9464e45730085401336dada Reviewed-on: https://go-review.googlesource.com/17698Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Nodir Turakulov <nodir@google.com> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

net/http/httptest: don't crash in mime sniffing if HeaderMap is nil
Fixes some failing Google tests when run under Go tip (1.6). Updates #12986 Change-Id: I0ca4d20f6103d10ea9464e45730085401336dada Reviewed-on: https://go-review.googlesource.com/17698Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Nodir Turakulov <nodir@google.com> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
9ccdc4ed · Brad Fitzpatrick · 8233ecd1 · 9ccdc4ed · 9ccdc4ed
Commit 9ccdc4ed authored Dec 10, 2015 by Brad Fitzpatrick
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src/net/http/httptest/recorder.go src/net/http/httptest/recorder.go +3 -0

src/net/http/httptest/recorder_test.go src/net/http/httptest/recorder_test.go +11 -0

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--- a/src/net/http/httptest/recorder.go
+++ b/src/net/http/httptest/recorder.go
@@ -65,6 +65,9 @@ func (rw *ResponseRecorder) writeHeader(b []byte, str string) {
 		if b == nil {
 			b = []byte(str)
 		}
+		if rw.HeaderMap == nil {
+			rw.HeaderMap = make(http.Header)
+		}
 		rw.HeaderMap.Set("Content-Type", http.DetectContentType(b))
 	}


--- a/src/net/http/httptest/recorder_test.go
+++ b/src/net/http/httptest/recorder_test.go
@@ -119,6 +119,17 @@ func TestRecorder(t *testing.T) {
 			},
 			check(hasHeader("Content-Type", "some/type")),
 		},
+		{
+			"Content-Type detection doesn't crash if HeaderMap is nil",
+			func(w http.ResponseWriter, r *http.Request) {
+				// Act as if the user wrote new(httptest.ResponseRecorder)
+				// rather than using NewRecorder (which initializes
+				// HeaderMap)
+				w.(*ResponseRecorder).HeaderMap = nil
+				io.WriteString(w, "<html>")
+			},
+			check(hasHeader("Content-Type", "text/html; charset=utf-8")),
+		},
 	}
 	r, _ := http.NewRequest("GET", "http://foo.com/", nil)
 	for _, tt := range tests {