Move form-wide response error code to formHelpers

Add an (optional) third argument to the method
`formHelpers#applyValidationErrors()` that can take an error string,
``reason``, to set on the form itself, rather than any particular
field. Remove the duplicate code in the auth directive to reset
the response errors on each field, which is handled already in the
``form-input`` directive.

h/static/scripts/auth/auth.coffee

@@ -15,19 +15,12 @@ class AuthController
 
     failure = (form, response) ->
       {errors, reason} = response.data
-
-      if reason
-        if reason == 'Invalid username or password.'
-          form.password.$setValidity('response', false)
-          form.password.responseErrorMessage = reason
-        else
-          form.responseErrorMessage = reason
-      else
-        form.responseErrorMessage = null
-
-      formHelpers.applyValidationErrors(form, errors)
+      formHelpers.applyValidationErrors(form, errors, reason)
 
     this.submit = (form) ->
+      delete form.responseErrorMessage
+      form.$setValidity('response', true)
+
       return unless form.$valid
 
       data = {}
@@ -62,12 +55,6 @@ authDirective = ['$timeout', ($timeout) ->
       scope.$apply ->
         $target = angular.element event.target
         $form = $target.controller('form')
-
-        delete $form.responseErrorMessage
-
-        for ctrl in $form.$error.response?.slice?() or []
-          ctrl.$setValidity('response', true)
-
         auth.submit($form)
 
     scope.model = {}

h/static/scripts/helpers/form-helpers.coffee

@@ -4,11 +4,15 @@ createFormHelpers = ->
   # API and updates the validity of the form. The field.$errors.response
   # property will be true if there are errors and the responseErrorMessage
   # will contain the API error message.
-  applyValidationErrors: (form, errors) ->
+  applyValidationErrors: (form, errors, reason) ->
     for own field, error of errors
       form[field].$setValidity('response', false)
       form[field].responseErrorMessage = error
 
+    if reason
+      form.$setValidity('response', false)
+      form.responseErrorMessage = reason
+
 
 angular.module('h.helpers.formHelpers', [])
 .factory('formHelpers', createFormHelpers)

tests/js/auth-test.coffee

@@ -46,6 +46,7 @@ describe 'h.auth', ->
         auth.submit
           $name: 'login'
           $valid: true
+          $setValidity: sandbox.stub()
 
         assert.called session.$login
 
@@ -53,13 +54,15 @@ describe 'h.auth', ->
         auth.submit
           $name: 'login'
           $valid: false
+          $setValidity: sandbox.stub()
 
         assert.notCalled session.$login
 
-      it 'should set response errors', ->
+      it 'should apply validation errors on submit', ->
         form =
           $name: 'register'
           $valid: true
+          $setValidity: sandbox.stub()
           username:
             $setValidity: sandbox.stub()
           email:
@@ -68,8 +71,8 @@ describe 'h.auth', ->
         auth.submit(form)
 
         assert.calledWith mockFormHelpers.applyValidationErrors, form,
-          username: 'taken'
-        assert.equal form.responseErrorMessage, 'registration error'
+          {username: 'taken'},
+          'registration error'
 
     describe 'timeout', ->
       it 'should happen after a period of inactivity', ->
@@ -120,17 +123,6 @@ describe 'h.auth', ->
 
       $scope = elem.isolateScope()
 
-    it 'should reset response errors before submit', ->
-      $scope.login.username.$setViewValue('test')
-      $scope.login.password.$setViewValue('1234')
-      $scope.login.responseErrorMessage = 'test'
-      $scope.login.username.$setValidity('response', false)
-      assert.isFalse $scope.login.$valid
-
-      elem.find('input').trigger('submit')
-      assert.isTrue $scope.login.$valid
-      assert.isUndefined $scope.login.responseErrorMessage
-
     it 'should invoke handlers set by attributes', ->
       $rootScope.stub = sandbox.stub()
       for event in ['error', 'success', 'timeout']