Angular: Introduce argsToTemplate for property and event Bindings

code/frameworks/angular/src/client/argsToTemplate.test.ts

@@ -0,0 +1,102 @@
+import { argsToTemplate, ArgsToTemplateOptions } from './argsToTemplate'; // adjust path
+
+describe('argsToTemplate', () => {
+  it('should correctly convert args to template string and exclude undefined values', () => {
+    const args: Record<string, any> = {
+      prop1: 'value1',
+      prop2: undefined,
+      prop3: 'value3',
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {};
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1" [prop3]="prop3"');
+  });
+
+  it('should include properties from include option', () => {
+    const args = {
+      prop1: 'value1',
+      prop2: 'value2',
+      prop3: 'value3',
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {
+      include: ['prop1', 'prop3'],
+    };
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1" [prop3]="prop3"');
+  });
+
+  it('should include non-undefined properties from include option', () => {
+    const args: Record<string, any> = {
+      prop1: 'value1',
+      prop2: 'value2',
+      prop3: undefined,
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {
+      include: ['prop1', 'prop3'],
+    };
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1"');
+  });
+
+  it('should exclude properties from exclude option', () => {
+    const args = {
+      prop1: 'value1',
+      prop2: 'value2',
+      prop3: 'value3',
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {
+      exclude: ['prop2'],
+    };
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1" [prop3]="prop3"');
+  });
+
+  it('should exclude properties from exclude option and undefined properties', () => {
+    const args: Record<string, any> = {
+      prop1: 'value1',
+      prop2: 'value2',
+      prop3: undefined,
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {
+      exclude: ['prop2'],
+    };
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1"');
+  });
+
+  it('should prioritize include over exclude when both options are given', () => {
+    const args = {
+      prop1: 'value1',
+      prop2: 'value2',
+      prop3: 'value3',
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {
+      include: ['prop1', 'prop2'],
+      exclude: ['prop2', 'prop3'],
+    };
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1" [prop2]="prop2"');
+  });
+
+  it('should work when neither include nor exclude options are given', () => {
+    const args = {
+      prop1: 'value1',
+      prop2: 'value2',
+    };
+    const options: ArgsToTemplateOptions<keyof typeof args> = {};
+    const result = argsToTemplate(args, options);
+    expect(result).toBe('[prop1]="prop1" [prop2]="prop2"');
+  });
+
+  it('should bind events correctly when value is a function', () => {
+    const args = { event1: () => {}, event2: () => {} };
+    const result = argsToTemplate(args, {});
+    expect(result).toEqual('(event1)="event1($event)" (event2)="event2($event)"');
+  });
+
+  it('should mix properties and events correctly', () => {
+    const args = { input: 'Value1', event1: () => {} };
+    const result = argsToTemplate(args, {});
+    expect(result).toEqual('[input]="input" (event1)="event1($event)"');
+  });
+});

code/frameworks/angular/src/client/argsToTemplate.ts

@@ -0,0 +1,74 @@
+/**
+ * Options for controlling the behavior of the argsToTemplate function.
+ *
+ * @template T The type of the keys in the target object.
+ */
+export interface ArgsToTemplateOptions<T> {
+  /**
+   * An array of keys to specifically include in the output.
+   * If provided, only the keys from this array will be included in the output,
+   * irrespective of the `exclude` option. Undefined values will still be excluded from the output.
+   */
+  include?: Array<T>;
+  /**
+   * An array of keys to specifically exclude from the output.
+   * If provided, these keys will be omitted from the output. This option is
+   * ignored if the `include` option is also provided
+   */
+  exclude?: Array<T>;
+}
+
+/**
+ * Converts an object of arguments to a string of property and event bindings and excludes undefined values.
+ * Why? Because Angular treats undefined values in property bindings as an actual value
+ * and does not apply the default value of the property as soon as the binding is set.
+ * This feels counter-intuitive and is a common source of bugs in stories.
+ * @example
+ * ```ts
+ * // component.ts
+ *ㅤ@Component({ selector: 'example' })
+ *  export class ExampleComponent {
+ *   ㅤ@Input() input1: string = 'Default Input1';
+ *   ㅤ@Input() input2: string = 'Default Input2';
+ *   ㅤ@Output() click = new EventEmitter();
+ *  }
+ *
+ * // component.stories.ts
+ * import { argsToTemplate } from '@storybook/angular';
+ * export const Input1: Story = {
+ *  render: (args) => ({
+ *    props: args,
+ *    // Problem1: <example [input1]="input1" [input2]="input2" (click)="click($event)"></example>
+ *    // This will set input2 to undefined and the internal default value will not be used.
+ *    // Problem2: <example [input1]="input1" (click)="click($event)"></example>
+ *    // The default value of input2 will be used, but it is not overridable by the user via controls.
+ *    // Solution: Now the controls will be applicable to both input1 and input2, and the default values will be used if the user does not override them.
+ *    template: `<example ${argsToTemplate(args)}"></example>`,
+ *  }),
+ *  args: {
+ *    // In this Story, we want to set the input1 property, and the internal default property of input2 should be used.
+ *    input1: 'Input 1',
+ *    click: { action: 'clicked' },
+ *  },
+ *};
+ * ```
+ */
+export function argsToTemplate<A extends Record<string, any>>(
+  args: A,
+  options: ArgsToTemplateOptions<keyof A> = {}
+) {
+  const includeSet = options.include ? new Set(options.include) : null;
+  const excludeSet = options.exclude ? new Set(options.exclude) : null;
+
+  return Object.entries(args)
+    .filter(([key]) => args[key] !== undefined)
+    .filter(([key]) => {
+      if (includeSet) return includeSet.has(key);
+      if (excludeSet) return !excludeSet.has(key);
+      return true;
+    })
+    .map(([key, value]) =>
+      typeof value === 'function' ? `(${key})="${key}($event)"` : `[${key}]="${key}"`
+    )
+    .join(' ');
+}

code/frameworks/angular/src/client/index.ts

@@ -10,6 +10,7 @@ export * from './public-types';
 export type { StoryFnAngularReturnType as IStory } from './types';
 
 export { moduleMetadata, componentWrapperDecorator, applicationConfig } from './decorators';
+export { argsToTemplate } from './argsToTemplate';
 
 // optimization: stop HMR propagation in webpack
 if (typeof module !== 'undefined') module?.hot?.decline();

code/frameworks/angular/template/stories/argTypes/doc-button/doc-button.stories.ts

@@ -1,24 +1,29 @@
-import { Args } from '@storybook/angular';
+import { Meta, StoryObj, argsToTemplate } from '@storybook/angular';
 import { DocButtonComponent } from './doc-button.component';
 
-export default {
+const meta: Meta<DocButtonComponent<any>> = {
   component: DocButtonComponent,
 };
 
-export const Basic = (args: Args) => ({
-  props: args,
-});
-Basic.args = { label: 'Args test', isDisabled: false };
-Basic.ArgTypes = {
-  theDefaultValue: {
-    table: {
-      defaultValue: { summary: 'Basic default value' },
+export default meta;
+
+type Story = StoryObj<DocButtonComponent<any>>;
+
+export const Basic: Story = {
+  args: { label: 'Args test', isDisabled: false },
+  argTypes: {
+    theDefaultValue: {
+      table: {
+        defaultValue: { summary: 'Basic default value' },
+      },
     },
   },
 };
 
-export const WithTemplate = (args: Args) => ({
-  props: args,
-  template: '<my-button [label]="label" [appearance]="appearance"></my-button>',
-});
-WithTemplate.args = { label: 'Template test', appearance: 'primary' };
+export const WithTemplate: Story = {
+  args: { label: 'Template test', appearance: 'primary' },
+  render: (args) => ({
+    props: args,
+    template: `<my-button ${argsToTemplate(args)}></my-button>`,
+  }),
+};

code/frameworks/angular/template/stories/argTypes/doc-directive/doc-directive.stories.ts

@@ -1,14 +1,19 @@
+import { Meta, StoryObj } from '@storybook/angular';
 import { DocDirective } from './doc-directive.directive';
 
-export default {
+const meta: Meta<DocDirective> = {
   component: DocDirective,
 };
 
-const modules = {
-  declarations: [DocDirective],
-};
+export default meta;
+
+type Story = StoryObj<DocDirective>;
 
-export const Basic = () => ({
-  moduleMetadata: modules,
-  template: '<div docDirective [hasGrayBackground]="true"><h1>DocDirective</h1></div>',
-});
+export const Basic: Story = {
+  render: () => ({
+    moduleMetadata: {
+      declarations: [DocDirective],
+    },
+    template: '<div docDirective [hasGrayBackground]="true"><h1>DocDirective</h1></div>',
+  }),
+};

code/frameworks/angular/template/stories/argTypes/doc-injectable/doc-injectable.stories.ts

@@ -1,14 +1,19 @@
+import { Meta, StoryObj } from '@storybook/angular';
 import { DocInjectableService } from './doc-injectable.service';
 
-export default {
+const meta: Meta<DocInjectableService> = {
   component: DocInjectableService,
 };
 
-const modules = {
-  provider: [DocInjectableService],
-};
+export default meta;
+
+type Story = StoryObj<DocInjectableService>;
 
-export const Basic = () => ({
-  moduleMetadata: modules,
-  template: '<div><h1>DocInjectable</h1></div>',
-});
+export const Basic: Story = {
+  render: () => ({
+    moduleMetadata: {
+      providers: [DocInjectableService],
+    },
+    template: '<div><h1>DocInjectable</h1></div>',
+  }),
+};

code/frameworks/angular/template/stories/argTypes/doc-pipe/doc-pipe.stories.ts

@@ -1,14 +1,19 @@
+import { Meta, StoryObj } from '@storybook/angular';
 import { DocPipe } from './doc-pipe.pipe';
 
-export default {
+const meta: Meta<DocPipe> = {
   component: DocPipe,
 };
 
-const modules = {
-  declarations: [DocPipe],
-};
+export default meta;
+
+type Story = StoryObj<DocPipe>;
 
-export const Basic = () => ({
-  moduleMetadata: modules,
-  template: `<div><h1>{{ 'DocPipe' | docPipe }}</h1></div>`,
-});
+export const Basic: Story = {
+  render: () => ({
+    moduleMetadata: {
+      declarations: [DocPipe],
+    },
+    template: `<div><h1>{{ 'DocPipe' | docPipe }}</h1></div>`,
+  }),
+};

code/frameworks/angular/template/stories/basics/angular-forms/customControlValueAccessor/custom-cva-component.stories.ts

@@ -1,8 +1,8 @@
 import { FormsModule } from '@angular/forms';
-import { Meta, StoryFn, moduleMetadata } from '@storybook/angular';
+import { Meta, StoryFn, StoryObj, moduleMetadata } from '@storybook/angular';
 import { CustomCvaComponent } from './custom-cva.component';
 
-export default {
+const meta: Meta<CustomCvaComponent> = {
   // title: 'Basics / Angular forms / ControlValueAccessor',
   component: CustomCvaComponent,
   decorators: [
@@ -17,11 +17,16 @@ export default {
   ],
 } as Meta;
 
-export const SimpleInput: StoryFn = () => ({
-  props: {
-    ngModel: 'Type anything',
-    ngModelChange: () => {},
-  },
-});
+export default meta;
 
-SimpleInput.storyName = 'Simple input';
+type Story = StoryObj<CustomCvaComponent>;
+
+export const SimpleInput: Story = {
+  name: 'Simple input',
+  render: () => ({
+    props: {
+      ngModel: 'Type anything',
+      ngModelChange: () => {},
+    },
+  }),
+};

code/frameworks/angular/template/stories/basics/component-with-complex-selectors/attribute-selectors.component.stories.ts

@@ -1,8 +1,13 @@
+import { Meta, StoryObj } from '@storybook/angular';
 import { AttributeSelectorComponent } from './attribute-selector.component';
 
-export default {
+const meta: Meta<AttributeSelectorComponent> = {
   // title: 'Basics / Component / With Complex Selectors',
   component: AttributeSelectorComponent,
 };
 
-export const AttributeSelectors = {};
+export default meta;
+
+type Story = StoryObj<AttributeSelectorComponent>;
+
+export const AttributeSelectors: Story = {};