feat(angular): add angular builder to start storybook

The builder allows to add a "architect" in angular.json to start storybook
config ex :
```
"storybook": {
 "builder": "@storybook/angular:start-storybook",
  "options": {
  "browserTarget": "angular-cli:build",
  "port": 4400
}
```
cmd : `ng run angular-cli:storybook`

With this solution it is possible to have several angular projects using different assets and style

app/angular/package.json

@@ -22,6 +22,7 @@
   "main": "dist/ts3.9/client/index.js",
   "module": "dist/ts3.9/client/index.js",
   "types": "dist/ts3.9/client/index.d.ts",
+  "builders": "dist/ts3.9/builders/builders.json",
   "typesVersions": {
     "<3.8": {
       "*": [

app/angular/src/builders/builders.json

@@ -0,0 +1,9 @@
+{
+  "builders": {
+    "start-storybook": {
+      "implementation": "./start-storybook",
+      "schema": "./start-storybook/schema.json",
+      "description": "Start storybook"
+    }
+  }
+}

app/angular/src/builders/start-storybook/index.spec.ts

@@ -0,0 +1,54 @@
+import { Architect } from '@angular-devkit/architect';
+import { TestingArchitectHost } from '@angular-devkit/architect/testing';
+import { schema } from '@angular-devkit/core';
+import * as path from 'path';
+
+const buildStandaloneMock = jest.fn().mockImplementation((_options: unknown) => Promise.resolve());
+
+jest.mock('@storybook/angular/standalone', () => buildStandaloneMock);
+
+describe('Start Storybook Builder', () => {
+  let architect: Architect;
+  let architectHost: TestingArchitectHost;
+
+  beforeEach(async () => {
+    const registry = new schema.CoreSchemaRegistry();
+    registry.addPostTransform(schema.transforms.addUndefinedDefaults);
+
+    architectHost = new TestingArchitectHost();
+    architect = new Architect(architectHost, registry);
+
+    // This will either take a Node package name, or a path to the directory
+    // for the package.json file.
+    await architectHost.addBuilderFromPackage(path.join(__dirname, '../../..'));
+  });
+
+  it('should work', async () => {
+    const run = await architect.scheduleBuilder('@storybook/angular:start-storybook', {
+      browserTarget: 'angular-cli:build-2',
+      port: 4400,
+    });
+
+    const output = await run.result;
+
+    await run.stop();
+
+    expect(output.success).toBeTruthy();
+    expect(buildStandaloneMock).toHaveBeenCalledWith({
+      angularBrowserTarget: 'angular-cli:build-2',
+      browserTarget: 'angular-cli:build-2',
+      ci: false,
+      configDir: '.storybook',
+      docs: false,
+      host: 'localhost',
+      https: false,
+      port: 4400,
+      quiet: false,
+      smokeTest: false,
+      sslCa: undefined,
+      sslCert: undefined,
+      sslKey: undefined,
+      staticDir: [],
+    });
+  });
+});

app/angular/src/builders/start-storybook/index.ts

@@ -0,0 +1,56 @@
+import { BuilderContext, BuilderOutput, createBuilder } from '@angular-devkit/architect';
+import { JsonObject } from '@angular-devkit/core';
+import { Observable, of } from 'rxjs';
+import { CLIOptions } from '@storybook/core-common';
+import { map, switchMap, tap } from 'rxjs/operators';
+
+// TODO: find a better way 🤷‍♂️
+// eslint-disable-next-line import/no-extraneous-dependencies
+import buildStandalone, { StandaloneOptions } from '@storybook/angular/standalone';
+
+export type StorybookBuilderOptions = JsonObject & {
+  browserTarget: string;
+} & Pick<
+    // makes sure the option exists
+    CLIOptions,
+    | 'port'
+    | 'host'
+    | 'staticDir'
+    | 'configDir'
+    | 'https'
+    | 'sslCa'
+    | 'sslCert'
+    | 'sslKey'
+    | 'smokeTest'
+    | 'ci'
+    | 'quiet'
+    | 'docs'
+  >;
+
+export type StorybookBuilderOutput = JsonObject & BuilderOutput & {};
+
+export default createBuilder(commandBuilder);
+
+function commandBuilder(
+  options: StorybookBuilderOptions,
+  _context: BuilderContext
+): Observable<StorybookBuilderOutput> {
+  return of({}).pipe(
+    map(() => ({
+      ...options,
+      angularBrowserTarget: options.browserTarget,
+    })),
+    switchMap((standaloneOptions) => runInstance(standaloneOptions)),
+    map(() => {
+      return { success: true };
+    })
+  );
+}
+
+function runInstance(options: StandaloneOptions) {
+  return new Observable<unknown>((obs) => {
+    buildStandalone({ ...options })
+      .then((sucess: unknown) => obs.next(sucess))
+      .catch((err: unknown) => obs.error(err));
+  });
+}

app/angular/src/builders/start-storybook/schema.json

@@ -0,0 +1,74 @@
+{
+  "$schema": "http://json-schema.org/schema",
+  "title": "Start Storybook",
+  "description": "Serve up storybook in development mode.",
+  "type": "object",
+  "properties": {
+    "browserTarget": {
+      "type": "string",
+      "description": "Build target to be served in project-name:builder:config format. Should generally target on the builder: '@angular-devkit/build-angular:browser'. Useful for Storybook to use options (styles, assets, ...).",
+      "pattern": "^[^:\\s]+:[^:\\s]+(:[^\\s]+)?$"
+    },
+    "port": {
+      "type": "number",
+      "description": "Port to listen on.",
+      "default": 9009
+    },
+    "host": {
+      "type": "string",
+      "description": "Host to listen on.",
+      "default": "localhost"
+    },
+    "staticDir": {
+      "type": "array",
+      "description": "Directory where to load static files from, array of strings.",
+      "items": {
+        "type": "string"
+      }
+    },
+    "configDir": {
+      "type": "string",
+      "description": "Directory where to load Storybook configurations from.",
+      "default": ".storybook"
+    },
+    "https": {
+      "type": "boolean",
+      "description": "Serve Storybook over HTTPS. Note: You must provide your own certificate information.",
+      "default": false
+    },
+    "sslCa": {
+      "type": "string",
+      "description": "Provide an SSL certificate authority. (Optional with --https, required if using a self-signed certificate)."
+    },
+    "sslCert": {
+      "type": "string",
+      "description": "Provide an SSL certificate. (Required with --https)."
+    },
+    "sslKey": {
+      "type": "string",
+      "description": "SSL key to use for serving HTTPS."
+    },
+    "smokeTest": {
+      "type": "boolean",
+      "description": "Exit after successful start.",
+      "default": false
+    },
+    "ci": {
+      "type": "boolean",
+      "description": "CI mode (skip interactive prompts, don't open browser).",
+      "default": false
+    },
+    "quiet": {
+      "type": "boolean",
+      "description": "Suppress verbose build output.",
+      "default": false
+    },
+    "docs": {
+      "type": "boolean",
+      "description": "Starts Storybook in documentation mode. Learn more about it : https://storybook.js.org/docs/react/writing-docs/build-documentation#preview-storybooks-documentation.",
+      "default": false
+    }
+  },
+  "additionalProperties": false,
+  "required": ["browserTarget"]
+}

app/angular/standalone.d.ts

@@ -0,0 +1,13 @@
+import { CLIOptions, LoadOptions, BuilderOptions } from '@storybook/core-common';
+
+export type StandaloneOptions = Partial<
+  CLIOptions &
+    LoadOptions &
+    BuilderOptions & {
+      angularBrowserTarget: string;
+    }
+>;
+
+declare module '@storybook/angular/standalone' {
+  export default function buildStandalone(options: StandaloneOptions): Promise<unknown>;
+}

app/angular/tsconfig.json

@@ -6,5 +6,6 @@
     "types": ["webpack-env", "node"],
     "rootDir": "./src",
     "resolveJsonModule": true
-  }
+  },
+  "include": ["src/**/*", "src/**/*.json"]
 }

examples/angular-cli/angular.json

@@ -74,6 +74,13 @@
             "scripts": [],
             "assets": ["src/favicon.ico", "src/assets"]
           }
+        },
+        "storybook": {
+          "builder": "@storybook/angular:start-storybook",
+          "options": {
+            "browserTarget": "angular-cli:build",
+            "port": 4400
+          }
         }
       }
     },