fix(linky): throw error if input is not a string

BREAKING CHANGE:

Before this change, the filter assumed that the input (if not falsy) was of type 'string' and that
certain methods (such as `.match()`) would be available on it. This would most likely result in an
not-very-useful error being thrown (trying to call a method that does not exist) or in unexpected
behavior (if the input happened to have the assumed methods).

After this change, a proper (informative) error will be thrown. If you want to pass non-string
values through `linky`, you need to explicitly convert them to strings first.

Closes angular#13547

Author: gkalpak

docs/content/error/linky/notstring.ngdoc

@@ -0,0 +1,16 @@
+@ngdoc error
+@name linky:notstring
+@fullName Not a string
+@description
+
+This error occurs when {@link ngSanitize.linky linky} is used with a non-empty, non-string value:
+```html
+<div ng-bind-html="42 | linky"></div>
+```
+
+`linky` is supposed to be used with string values only, and therefore assumes that several methods
+(such as `.match()`) are available on the passed in value.
+The value can be initialized asynchronously and therefore null or undefined won't throw this error.
+
+If you want to pass non-string values to `linky` (e.g. Objects whose `.toString()` should be
+utilized), you need to manually convert them to strings.

src/ngSanitize/filter/linky.js

@@ -134,8 +134,12 @@ angular.module('ngSanitize').filter('linky', ['$sanitize', function($sanitize) {
         /((ftp|https?):\/\/|(www\.)|(mailto:)?[A-Za-z0-9._%+-]+@)\S*[^\s.;,(){}<>"\u201d\u2019]/i,
       MAILTO_REGEXP = /^mailto:/i;
 
+  var linkyMinErr = angular.$$minErr('linky');
+
   return function(text, target, attributes) {
     if (!text) return text;
+    if (!isString(text)) throw linkyMinErr('notstring', 'Expected string but received: {0}', text);
+
     var match;
     var raw = text;
     var html = [];

test/ngSanitize/filter/linkySpec.js

@@ -20,6 +20,28 @@ describe('linky', function() {
     expect(linky(undefined)).not.toBeDefined();
   });
 
+  they('should return falsy values (such as $prop) unchanged', {
+    'undefined': undefined,
+    'null': null,
+    'false': false,
+    '0': 0,
+    '\'\'': ''
+  }, function(value) {
+    expect(value).toBeFalsy();
+    expect(linky(value)).toBe(value);
+  });
+
+  they('should throw an error when used with a non-empty, non-string value (such as $prop)', {
+    'true': true,
+    '42': 42,
+    '{}': {},
+    '[]': [],
+    'noop()': noop
+  }, function(value) {
+    expect(function() { linky(value); }).
+      toThrowMinErr('linky', 'notstring', 'Expected string but received: ' + toDebugString(value));
+  });
+
   it('should be case-insensitive', function() {
     expect(linky('WWW.example.com')).toEqual('<a href="http://WWW.example.com">WWW.example.com</a>');
     expect(linky('WWW.EXAMPLE.COM')).toEqual('<a href="http://WWW.EXAMPLE.COM">WWW.EXAMPLE.COM</a>');