[Fetch API] Appending headers of the same name should have their values

third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js

 if (self.importScripts) {
   importScripts('../resources/fetch-test-helpers.js');
 }
 
 test(function() {
     var expectedValueMap = {
       'content-language': 'ja',
       'content-type': 'text/html; charset=UTF-8',
       'x-fetch-test': 'response test field'
     };
@@ skipping 118 matching lines @@
     }, thisObject);
 
     // 'append()', 'getAll()'
     var allValues = headers.getAll('X-Fetch-Test');
     assert_equals(allValues.length, 1);
     assert_equals(size(headers), 4);
     headers.append('X-FETCH-TEST', 'response test field - append');
     headers.append('X-FETCH-TEST-2', 'response test field - append');
     assert_equals(size(headers), 5, 'headers size should increase by 1.');
     assert_equals(headers.get('X-FETCH-Test'),
-                  'response test field - updated',
+                  'response test field - updated,response test field - append',
                   'the value of the first header added should be returned.');
     allValues = headers.getAll('X-FETch-TEST');
     assert_equals(allValues.length, 2);
     assert_equals(allValues[0], 'response test field - updated');
     assert_equals(allValues[1], 'response test field - append');
     headers.set('X-FETch-Test', 'response test field - set');
     assert_equals(size(headers), 5, 'the second header should be deleted');
     allValues = headers.getAll('X-Fetch-Test');
     assert_equals(allValues.length, 1, 'the second header should be deleted');
     assert_equals(allValues[0], 'response test field - set');
     headers.append('X-Fetch-TEST', 'response test field - append');
     assert_equals(size(headers), 5, 'headers size should not increase by 1.');
     headers.delete('X-FeTCH-Test');
     assert_equals(size(headers), 4, 'two headers should be deleted.');
 
     // new Headers with sequence<sequence<ByteString>>
     headers = new Headers([['a', 'b'], ['c', 'd'], ['c', 'e']]);
     assert_equals(size(headers), 2, 'headers size should match');
     assert_equals(headers.get('a'), 'b');
-    assert_equals(headers.get('c'), 'd');
+    assert_equals(headers.get('c'), 'd,e');
     assert_equals(headers.getAll('c')[0], 'd');
     assert_equals(headers.getAll('c')[1], 'e');
 
     // new Headers with Headers
     var headers2 = new Headers(headers);
     assert_equals(size(headers2), 2, 'headers size should match');
     assert_equals(headers2.get('a'), 'b');
-    assert_equals(headers2.get('c'), 'd');
+    assert_equals(headers2.get('c'), 'd,e');
     assert_equals(headers2.getAll('c')[0], 'd');
     assert_equals(headers2.getAll('c')[1], 'e');
     headers.set('a', 'x');
     assert_equals(headers.get('a'), 'x');
     assert_equals(headers2.get('a'), 'b');
 
+    var headers3 = new Headers();
+    headers3.append('test', 'a');
+    headers3.append('test', '');

[jsbell, 2016/12/16 22:29:37]

Hrm... I think this should throw TypeError:

https://fetch.spec.whatwg.org/#concept-headers-append

"If name is not a name or value is not a value, then throw a TypeError."

https://fetch.spec.whatwg.org/#concept-header-value

"A value is a byte sequence that matches the field-content token production."

https://tools.ietf.org/html/rfc7230#section-3.2

field-content  = field-vchar [ 1*( SP / HTAB ) field-vchar ]
field-vchar    = VCHAR / obs-text

... which seems to me that it must be non-empty.

+    headers3.append('test', 'b');
+    assert_equals(headers3.get('test'), 'a,b');
     // new Headers with Dictionary
     headers = new Headers({'a': 'b', 'c': 'd'});
     assert_equals(size(headers), 2, 'headers size should match');
     assert_equals(headers.get('a'), 'b');
     assert_equals(headers.get('c'), 'd');
 
     // Throw errors
     INVALID_HEADER_NAMES.forEach(function(name) {
         assert_throws({name: 'TypeError'},
                       function() {
@@ skipping 71 matching lines @@
         values.push(value);
     }
     assert_array_equals(keys, ['a', 'b', 'c'],
                         'The pairs to iterate over should be the return ' +
                         'value of an algorithm that implicitly makes a copy.');
     assert_array_equals(values, ['1,2,3', '2', '3'],
                         "The values should be combined and separated by ','.");
 }, 'Iteration mutation');
 
 done();