[BUGFIX beta] Allow optional spaces when parsing response headers

Fixes #4122

- Allows header field-value without preceding whitespace
- Removes leading/trailing whitespace from header field-names
- Removes leading/trailing whitespace from header field-values
- Moves `parseResponseHeaders` function out of `DS.RestAdapter` to its
  own module

The main reason for moving to a module was to make it easier to unit
test in order to document current behavior before making the fix. Let me
know if this is undesirable.

(cherry picked from commit dce22e3)

Author: HeroicEric

addon/-private/utils/parse-response-headers.js

@@ -0,0 +1,26 @@
+import EmptyObject from 'ember-data/-private/system/empty-object';
+
+const CLRF = '\u000d\u000a';
+
+export default function parseResponseHeaders(headersString) {
+  let headers = new EmptyObject();
+
+  if (!headersString) {
+    return headers;
+  }
+
+  let headerPairs = headersString.split(CLRF);
+
+  headerPairs.forEach((header) => {
+    let [field, ...value] = header.split(':');
+
+    field = field.trim();
+    value = value.join(':').trim();
+
+    if (value) {
+      headers[field] = value;
+    }
+  });
+
+  return headers;
+}

addon/adapters/rest.js

@@ -10,9 +10,9 @@ import {
   TimeoutError,
   AbortError
 } from 'ember-data/-private/adapters/errors';
-import EmptyObject from "ember-data/-private/system/empty-object";
 import BuildURLMixin from "ember-data/-private/adapters/build-url-mixin";
 import isEnabled from 'ember-data/-private/features';
+import parseResponseHeaders from 'ember-data/-private/utils/parse-response-headers';
 
 const {
   MapWithDefault,
@@ -1006,26 +1006,6 @@ export default Adapter.extend(BuildURLMixin, {
   }
 });
 
-function parseResponseHeaders(headerStr) {
-  var headers = new EmptyObject();
-  if (!headerStr) { return headers; }
-
-  var headerPairs = headerStr.split('\u000d\u000a');
-  for (var i = 0; i < headerPairs.length; i++) {
-    var headerPair = headerPairs[i];
-    // Can't use split() here because it does the wrong thing
-    // if the header value has the string ": " in it.
-    var index = headerPair.indexOf('\u003a\u0020');
-    if (index > 0) {
-      var key = headerPair.substring(0, index);
-      var val = headerPair.substring(index + 2);
-      headers[key] = val;
-    }
-  }
-
-  return headers;
-}
-
 //From http://stackoverflow.com/questions/280634/endswith-in-javascript
 function endsWith(string, suffix) {
   if (typeof String.prototype.endsWith !== 'function') {

tests/unit/utils/parse-response-headers-test.js

@@ -0,0 +1,67 @@
+import EmptyObject from 'ember-data/-private/system/empty-object';
+import parseResponseHeaders from 'ember-data/-private/utils/parse-response-headers';
+import { module, test } from 'qunit';
+
+const CRLF = '\u000d\u000a';
+
+module('unit/adapters/parse-response-headers');
+
+test('returns an EmptyObject when headersString is undefined', function(assert) {
+  let headers = parseResponseHeaders(undefined);
+
+  assert.deepEqual(headers, new EmptyObject(), 'EmptyObject is returned');
+});
+
+test('header parsing', function(assert) {
+  let headersString = [
+    'Content-Encoding: gzip',
+    'content-type: application/json; charset=utf-8',
+    'date: Fri, 05 Feb 2016 21:47:56 GMT'
+  ].join(CRLF);
+
+  let headers = parseResponseHeaders(headersString);
+
+  assert.equal(headers['Content-Encoding'], 'gzip', 'parses basic header pair');
+  assert.equal(headers['content-type'], 'application/json; charset=utf-8', 'parses header with complex value');
+  assert.equal(headers['date'], 'Fri, 05 Feb 2016 21:47:56 GMT', 'parses header with date value');
+});
+
+test('field-name parsing', function(assert) {
+  let headersString = [
+    '  name-with-leading-whitespace: some value',
+    'name-with-whitespace-before-colon : another value'
+  ].join(CRLF);
+
+  let headers = parseResponseHeaders(headersString);
+
+  assert.equal(headers['name-with-leading-whitespace'], 'some value', 'strips leading whitespace from field-name');
+  assert.equal(headers['name-with-whitespace-before-colon'], 'another value', 'strips whitespace before colon from field-name');
+});
+
+test('field-value parsing', function(assert) {
+  let headersString = [
+    'value-with-leading-space: value with leading whitespace',
+    'value-without-leading-space:value without leading whitespace',
+    'value-with-colon: value with: a colon',
+    'value-with-trailing-whitespace: banana   '
+  ].join(CRLF);
+
+  let headers = parseResponseHeaders(headersString);
+
+  assert.equal(headers['value-with-leading-space'], 'value with leading whitespace', 'strips leading whitespace in field-value');
+  assert.equal(headers['value-without-leading-space'], 'value without leading whitespace', 'works without leaading whitespace in field-value');
+  assert.equal(headers['value-with-colon'], 'value with: a colon', 'has correct value when value contains a colon');
+  assert.equal(headers['value-with-trailing-whitespace'], 'banana', 'strips trailing whitespace from field-value');
+});
+
+test('ignores headers that do not contain a colon', function(assert) {
+  let headersString = [
+    'Content-Encoding: gzip',
+    'I am ignored because I do not contain a colon'
+  ].join(CRLF);
+
+  let headers = parseResponseHeaders(headersString);
+
+  assert.deepEqual(headers['Content-Encoding'], 'gzip', 'parses basic header pair');
+  assert.equal(Object.keys(headers).length, 1, 'only has the one valid header');
+});