fix(expressions): change model reference in string hideExpression and watcher expression for nested models

BREAKING CHANGE: reference to 'model' in string hideExpressions and watchers on fields with nested models now points to field.model just as in expressionProperties

Author: kwypchlo

src/directives/formly-form.js

@@ -42,7 +42,7 @@ function formlyForm(formlyUsability, formlyWarn, $parse, formlyConfig, $interpol
                ${getHideDirective()}="!field.hide"
                class="formly-field"
                options="field"
-               model="field.model || model"
+               model="field.model"
                original-model="model"
                fields="fields"
                form="theFormlyForm"
@@ -265,6 +265,8 @@ function formlyForm(formlyUsability, formlyWarn, $parse, formlyConfig, $interpol
 
         isNewModel = !referencesCurrentlyWatchedModel(expression)
 
+        // temporary assign $scope.model as field.model to evaluate the expression in correct context
+        field.model = $scope.model
         field.model = evalCloseToFormlyExpression(expression, undefined, field, index)
         if (!field.model) {
           throw formlyUsability.getFieldError(
@@ -273,6 +275,8 @@ function formlyForm(formlyUsability, formlyWarn, $parse, formlyConfig, $interpol
             ' expression must have been initialized ahead of time.',
             field)
         }
+      } else if (!field.model) {
+        field.model = $scope.model
       }
       return isNewModel
     }
@@ -328,6 +332,8 @@ function formlyForm(formlyUsability, formlyWarn, $parse, formlyConfig, $interpol
           return originalExpression(...args)
         }
         watchExpression.displayName = `Formly Watch Expression for field for ${field.key}`
+      } else if (field.model) {
+        watchExpression = $parse(watchExpression).bind(null, $scope, {model: field.model})
       }
       return watchExpression
     }
@@ -366,6 +372,7 @@ function formlyForm(formlyUsability, formlyWarn, $parse, formlyConfig, $interpol
     function getFormlyFieldLikeLocals(field, index) {
       // this makes it closer to what a regular formlyExpression would be
       return {
+        model: field.model,
         options: field,
         index,
         formState: $scope.options.formState,

src/directives/formly-form.test.js

@@ -597,17 +597,21 @@ describe('formly-form', () => {
     })
 
     it('ensures that hideExpression has all the expressionProperties values', () => {
+      scope.model = {nested: {foo: 'bar', baz: []}}
       scope.options = {formState: {}}
       scope.fields = [{
         template: input,
         key: 'test',
+        model: 'model.nested',
         hideExpression: `
+        model === options.data.model &&
         options === options.data.field &&
         index === 0 &&
         formState === options.data.formOptions.formState &&
         originalModel === options.data.originalModel &&
         formOptions === options.data.formOptions`,
         data: {
+          model: scope.model.nested,
           originalModel: scope.model,
           formOptions: scope.options,
         },
@@ -1196,7 +1200,7 @@ describe('formly-form', () => {
         }
         scope.fields[0].model = model
         scope.fields[0].watcher = [{
-          expression: 'model.nested.foo',
+          expression: 'model.foo',
           runFieldExpressions: true,
         }]
         scope.fields[0].expressionProperties = {
@@ -1363,7 +1367,7 @@ describe('formly-form', () => {
         const field = scope.fields[0]
 
         field.model = 'model.baz'
-        field.hideExpression = 'model.baz.buzz === "bar"'
+        field.hideExpression = 'model.buzz === "bar"'
 
         compileAndDigest()
         $timeout.flush()