Duplicate header handling (#874)

* Update parseHeaders to match node http behavior

Node ignores duplicate entries for certain HTTP headers.

It also always converts the `set-cookie` header into an array.

* add tests for new duplicate header handling

* clarify comment

lib/helpers/parseHeaders.js

@@ -2,6 +2,15 @@
 
 var utils = require('./../utils');
 
+// Headers whose duplicates are ignored by node
+// c.f. https://nodejs.org/api/http.html#http_message_headers
+var ignoreDuplicateOf = [
+  'age', 'authorization', 'content-length', 'content-type', 'etag',
+  'expires', 'from', 'host', 'if-modified-since', 'if-unmodified-since',
+  'last-modified', 'location', 'max-forwards', 'proxy-authorization',
+  'referer', 'retry-after', 'user-agent'
+];
+
 /**
  * Parse headers into an object
  *
@@ -29,7 +38,14 @@ module.exports = function parseHeaders(headers) {
     val = utils.trim(line.substr(i + 1));
 
     if (key) {
-      parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
+      if (parsed[key] && ignoreDuplicateOf.indexOf(key) >= 0) {
+        return;
+      }
+      if (key === 'set-cookie') {
+        parsed[key] = (parsed[key] ? parsed[key] : []).concat([val]);
+      } else {
+        parsed[key] = parsed[key] ? parsed[key] + ', ' + val : val;
+      }
     }
   });
 

test/specs/helpers/parseHeaders.spec.js

@@ -15,5 +15,31 @@ describe('helpers::parseHeaders', function () {
     expect(parsed['connection']).toEqual('keep-alive');
     expect(parsed['transfer-encoding']).toEqual('chunked');
   });
-});
 
+  it('should use array for set-cookie', function() {
+    var parsedZero = parseHeaders('');
+    var parsedSingle = parseHeaders(
+      'Set-Cookie: key=val;'
+    );
+    var parsedMulti = parseHeaders(
+      'Set-Cookie: key=val;\n' +
+      'Set-Cookie: key2=val2;\n'
+    );
+
+    expect(parsedZero['set-cookie']).toBeUndefined();
+    expect(parsedSingle['set-cookie']).toEqual(['key=val;']);
+    expect(parsedMulti['set-cookie']).toEqual(['key=val;', 'key2=val2;']);
+  });
+
+  it('should handle duplicates', function() {
+    var parsed = parseHeaders(
+      'Age: age-a\n' + // age is in ignore duplicates blacklist
+      'Age: age-b\n' +
+      'Foo: foo-a\n' +
+      'Foo: foo-b\n'
+    );
+
+    expect(parsed['age']).toEqual('age-a');
+    expect(parsed['foo']).toEqual('foo-a, foo-b');
+  });
+});