net/http, net/textproto: add Header.Values, MIMEHeader.Values methods

Fixes #34799

Change-Id: I134b2717fa90c8955902e7eeaaf8510dcc28340e
Reviewed-on: https://go-review.googlesource.com/c/go/+/200760
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

4 files changed, 78 insertions, 40 deletions

diff --git a/src/net/http/header.go b/src/net/http/header.go
index 230ca03d4f..4a4ebbcf2f 100644
--- a/src/net/http/header.go
+++ b/src/net/http/header.go
@@ -40,13 +40,21 @@ func (h Header) Set(key, value string) {
 // Get gets the first value associated with the given key. If
 // there are no values associated with the key, Get returns "".
 // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
-// used to canonicalize the provided key. To access multiple
-// values of a key, or to use non-canonical keys, access the
-// map directly.
+// used to canonicalize the provided key. To use non-canonical keys,
+// access the map directly.
 func (h Header) Get(key string) string {
 	return textproto.MIMEHeader(h).Get(key)
 }
 
+// Values returns all values associated with the given key.
+// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical
+// keys, access the map directly.
+// The returned slice is not a copy.
+func (h Header) Values(key string) []string {
+	return textproto.MIMEHeader(h).Values(key)
+}
+
 // get is like Get, but key must already be in CanonicalHeaderKey form.
 func (h Header) get(key string) string {
 	if v := h[key]; len(v) > 0 {
diff --git a/src/net/textproto/header.go b/src/net/textproto/header.go
index ed096d9a3c..a58df7aebc 100644
--- a/src/net/textproto/header.go
+++ b/src/net/textproto/header.go
@@ -26,8 +26,7 @@ func (h MIMEHeader) Set(key, value string) {
 // It is case insensitive; CanonicalMIMEHeaderKey is used
 // to canonicalize the provided key.
 // If there are no values associated with the key, Get returns "".
-// To access multiple values of a key, or to use non-canonical keys,
-// access the map directly.
+// To use non-canonical keys, access the map directly.
 func (h MIMEHeader) Get(key string) string {
 	if h == nil {
 		return ""
@@ -39,6 +38,18 @@ func (h MIMEHeader) Get(key string) string {
 	return v[0]
 }
 
+// Values returns all values associated with the given key.
+// It is case insensitive; CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical
+// keys, access the map directly.
+// The returned slice is not a copy.
+func (h MIMEHeader) Values(key string) []string {
+	if h == nil {
+		return nil
+	}
+	return h[CanonicalMIMEHeaderKey(key)]
+}
+
 // Del deletes the values associated with key.
 func (h MIMEHeader) Del(key string) {
 	delete(h, CanonicalMIMEHeaderKey(key))
diff --git a/src/net/textproto/header_test.go b/src/net/textproto/header_test.go
new file mode 100644
index 0000000000..de9405ca86
--- /dev/null
+++ b/src/net/textproto/header_test.go
@@ -0,0 +1,54 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import "testing"
+
+type canonicalHeaderKeyTest struct {
+	in, out string
+}
+
+var canonicalHeaderKeyTests = []canonicalHeaderKeyTest{
+	{"a-b-c", "A-B-C"},
+	{"a-1-c", "A-1-C"},
+	{"User-Agent", "User-Agent"},
+	{"uSER-aGENT", "User-Agent"},
+	{"user-agent", "User-Agent"},
+	{"USER-AGENT", "User-Agent"},
+
+	// Other valid tchar bytes in tokens:
+	{"foo-bar_baz", "Foo-Bar_baz"},
+	{"foo-bar$baz", "Foo-Bar$baz"},
+	{"foo-bar~baz", "Foo-Bar~baz"},
+	{"foo-bar*baz", "Foo-Bar*baz"},
+
+	// Non-ASCII or anything with spaces or non-token chars is unchanged:
+	{"üser-agenT", "üser-agenT"},
+	{"a B", "a B"},
+
+	// This caused a panic due to mishandling of a space:
+	{"C Ontent-Transfer-Encoding", "C Ontent-Transfer-Encoding"},
+	{"foo bar", "foo bar"},
+}
+
+func TestCanonicalMIMEHeaderKey(t *testing.T) {
+	for _, tt := range canonicalHeaderKeyTests {
+		if s := CanonicalMIMEHeaderKey(tt.in); s != tt.out {
+			t.Errorf("CanonicalMIMEHeaderKey(%q) = %q, want %q", tt.in, s, tt.out)
+		}
+	}
+}
+
+// Issue #34799 add a Header method to get multiple values []string, with canonicalized key
+func TestMIMEHeaderMultipleValues(t *testing.T) {
+	testHeader := MIMEHeader{
+		"Set-Cookie": {"cookie 1", "cookie 2"},
+	}
+	values := testHeader.Values("set-cookie")
+	n := len(values)
+	if n != 2 {
+		t.Errorf("count: %d; want 2", n)
+	}
+}
diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go
index 595d94f938..3124d438fa 100644
--- a/src/net/textproto/reader_test.go
+++ b/src/net/textproto/reader_test.go
@@ -13,41 +13,6 @@ import (
 	"testing"
 )
 
-type canonicalHeaderKeyTest struct {
-	in, out string
-}
-
-var canonicalHeaderKeyTests = []canonicalHeaderKeyTest{
-	{"a-b-c", "A-B-C"},
-	{"a-1-c", "A-1-C"},
-	{"User-Agent", "User-Agent"},
-	{"uSER-aGENT", "User-Agent"},
-	{"user-agent", "User-Agent"},
-	{"USER-AGENT", "User-Agent"},
-
-	// Other valid tchar bytes in tokens:
-	{"foo-bar_baz", "Foo-Bar_baz"},
-	{"foo-bar$baz", "Foo-Bar$baz"},
-	{"foo-bar~baz", "Foo-Bar~baz"},
-	{"foo-bar*baz", "Foo-Bar*baz"},
-
-	// Non-ASCII or anything with spaces or non-token chars is unchanged:
-	{"üser-agenT", "üser-agenT"},
-	{"a B", "a B"},
-
-	// This caused a panic due to mishandling of a space:
-	{"C Ontent-Transfer-Encoding", "C Ontent-Transfer-Encoding"},
-	{"foo bar", "foo bar"},
-}
-
-func TestCanonicalMIMEHeaderKey(t *testing.T) {
-	for _, tt := range canonicalHeaderKeyTests {
-		if s := CanonicalMIMEHeaderKey(tt.in); s != tt.out {
-			t.Errorf("CanonicalMIMEHeaderKey(%q) = %q, want %q", tt.in, s, tt.out)
-		}
-	}
-}
-
 func reader(s string) *Reader {
 	return NewReader(bufio.NewReader(strings.NewReader(s)))
 }