feat(jsdoc-core): add Api class

Starting point for a public API for JSDoc.

packages/jsdoc-cli/lib/engine.js

@@ -15,8 +15,7 @@
 */
 
 /* eslint-disable no-process-exit */
-import EventEmitter from 'node:events';
-
+import { Api } from '@jsdoc/core';
 import { getLogFunctions } from '@jsdoc/util';
 import _ from 'lodash';
 import ow from 'ow';
@@ -130,7 +129,8 @@ export default class Engine {
     ow(opts.revision, ow.optional.date);
     ow(opts.version, ow.any(ow.optional.string, ow.optional.object));
 
-    this.emitter = opts.emitter ?? new EventEmitter();
+    this.api = opts.api ?? new Api({ emitter: opts.emitter });
+    this.emitter = this.api.emitter;
     this.flags = [];
     this.log = opts.log ?? getLogFunctions(this.emitter);
     this.#logger = new Logger({

packages/jsdoc-cli/test/specs/lib/engine.js

@@ -14,6 +14,8 @@
   limitations under the License.
 */
 
+import EventEmitter from 'node:events';
+
 import Engine from '../../../lib/engine.js';
 import flags from '../../../lib/flags.js';
 import { LEVELS } from '../../../lib/logger.js';
@@ -33,6 +35,14 @@ describe('@jsdoc/cli/lib/engine', () => {
     expect(Engine.LOG_LEVELS).toBeObject();
   });
 
+  it('has an `api` property that contains the API instance', () => {
+    expect(new Engine().api).toBeObject();
+  });
+
+  it('has an `emitter` property that contains a shared event emitter', () => {
+    expect(new Engine().emitter).toBeObject();
+  });
+
   it('has an empty array of flags by default', () => {
     expect(new Engine().flags).toBeEmptyArray();
   });
@@ -97,6 +107,49 @@ describe('@jsdoc/cli/lib/engine', () => {
     expect(() => new Engine({ version: 1 })).toThrow();
   });
 
+  describe('emitter', () => {
+    it('creates an `EventEmitter` instance by default', () => {
+      expect(new Engine().emitter).toBeInstanceOf(EventEmitter);
+    });
+
+    it('lets you provide the emitter', () => {
+      const fakeEmitter = {
+        off: () => null,
+        on: () => null,
+        once: () => null,
+      };
+      const instance = new Engine({ emitter: fakeEmitter });
+
+      expect(instance.emitter).toBe(fakeEmitter);
+    });
+
+    it('shares one emitter between the `Api` instance and the `Engine` instance', () => {
+      const instance = new Engine();
+
+      expect(instance.emitter).toBe(instance.api.emitter);
+    });
+  });
+
+  describe('exit', () => {
+    // TODO: This is testing implementation details, not behavior. Refactor the method, then rewrite
+    // this test to test the behavior.
+    it('adds one listener for `exit` events if the exit code is 0', () => {
+      spyOn(process, 'on');
+
+      new Engine().exit(0);
+
+      expect(process.on).toHaveBeenCalledTimes(1);
+    });
+
+    it('adds two listeners for `exit` events if the exit code is >0', () => {
+      spyOn(process, 'on');
+
+      new Engine().exit(1);
+
+      expect(process.on).toHaveBeenCalledTimes(2);
+    });
+  });
+
   describe('help', () => {
     const instance = new Engine();
 
@@ -132,26 +185,6 @@ describe('@jsdoc/cli/lib/engine', () => {
     });
   });
 
-  describe('exit', () => {
-    // TODO: This is testing implementation details, not behavior. Refactor the method, then rewrite
-    // this test to test the behavior.
-    it('adds one listener for `exit` events if the exit code is 0', () => {
-      spyOn(process, 'on');
-
-      new Engine().exit(0);
-
-      expect(process.on).toHaveBeenCalledTimes(1);
-    });
-
-    it('adds two listeners for `exit` events if the exit code is >0', () => {
-      spyOn(process, 'on');
-
-      new Engine().exit(1);
-
-      expect(process.on).toHaveBeenCalledTimes(2);
-    });
-  });
-
   describe('parseFlags', () => {
     it('throws with no input', () => {
       expect(() => new Engine().parseFlags()).toThrow();

packages/jsdoc-core/index.js

@@ -19,10 +19,11 @@
  *
  * @module @jsdoc/core
  */
+import Api from './lib/api.js';
 import * as config from './lib/config.js';
 import Env from './lib/env.js';
 import * as name from './lib/name.js';
 import * as plugins from './lib/plugins.js';
 
-export { config, Env, name, plugins };
-export default { config, Env, name, plugins };
+export { Api, config, Env, name, plugins };
+export default { Api, config, Env, name, plugins };

packages/jsdoc-core/lib/api.js

@@ -0,0 +1,33 @@
+/*
+  Copyright 2023 the JSDoc Authors.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      https://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+*/
+
+import EventEmitter from 'node:events';
+
+/**
+ * The API for programmatically generating documentation with JSDoc.
+ */
+export default class Api {
+  /**
+   * Creates an instance of the API.
+   *
+   * @param {?Object} opts - Options for the API instance.
+   * @param {?node:events.EventEmitter} opts.eventEmitter - The event emitter to use as a message
+   * bus for JSDoc.
+   */
+  constructor(opts) {
+    this.emitter = opts?.emitter ?? new EventEmitter();
+  }
+}

packages/jsdoc-core/test/specs/index.js

@@ -15,12 +15,19 @@
 */
 
 import core from '../../index.js';
+import Api from '../../lib/api.js';
 import * as config from '../../lib/config.js';
 import Env from '../../lib/env.js';
 import * as name from '../../lib/name.js';
 import * as plugins from '../../lib/plugins.js';
 
 describe('@jsdoc/core', () => {
+  describe('Api', () => {
+    it('is lib/api', () => {
+      expect(core.Api).toEqual(Api);
+    });
+  });
+
   describe('config', () => {
     it('is lib/config', () => {
       expect(core.config).toEqual(config);

packages/jsdoc-core/test/specs/lib/api.js

@@ -0,0 +1,53 @@
+/*
+  Copyright 2023 the JSDoc Authors.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      https://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+*/
+
+import EventEmitter from 'node:events';
+
+import Api from '../../../lib/api.js';
+
+describe('Api', () => {
+  let instance;
+
+  beforeEach(() => {
+    instance = new Api();
+  });
+
+  it('is a constructor', () => {
+    function factory() {
+      return new Api();
+    }
+
+    expect(factory).not.toThrow();
+  });
+
+  it('has an `emitter` property', () => {
+    expect(instance.emitter).toBeObject();
+  });
+
+  describe('emitter', () => {
+    it('is an instance of `EventEmitter` by default', () => {
+      expect(instance.emitter).toBeInstanceOf(EventEmitter);
+    });
+
+    it('lets you provide your own emitter', () => {
+      const fakeEmitter = {};
+
+      instance = new Api({ emitter: fakeEmitter });
+
+      expect(instance.emitter).toBe(fakeEmitter);
+    });
+  });
+});