refactor(configuration): migrate algorithm to Chain of Responsibility…

… pattern for improved extensibility and separation of concerns

lib/src/runner/configuration-loaders/configuration-loader.ts

@@ -0,0 +1,85 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+import { CypressRunnerConfig } from '../cypress-runner-config';
+
+/**
+ * Object delegated to load CypressRunnerConfig.
+ * Each loader in the chain is responsible for attempting to load a configuration file
+ * based on its specific file extension. If a loader cannot find or parse the file,
+ * it delegates the responsibility to the next loader in the chain.
+ */
+export abstract class ConfigurationLoader {
+  private static readonly CYPRESS_RUNNER_CONFIG_FILENAME = '.cypressrunnerrc';
+
+  private _next: ConfigurationLoader | undefined;
+  private _parent: ConfigurationLoader | undefined;
+  private get supportedExtensions(): string[] {
+    const parentFormats = this._parent?.supportedExtensions ?? [];
+
+    return [...parentFormats, this.extension];
+  }
+
+  /**
+   * The file extension supported by this loader.
+   */
+  protected abstract readonly extension: string;
+
+  /**
+   * Parse the configuration file at the given path.
+   */
+  protected abstract parse(path: string): CypressRunnerConfig;
+
+  /**
+   * Attempts to load the configuration file. If the file is found and valid,
+   * it is parsed and returned. Otherwise, the responsibility is delegated
+   * to the next loader in the chain.
+   */
+  public load(): CypressRunnerConfig {
+    const jsonPath = this.resolveConfigurationPath();
+    if (fs.existsSync(jsonPath)) {
+      return this.parse(jsonPath);
+    }
+
+    return this.next();
+  }
+
+  /**
+   * Sets the next loader in the chain and establishes a parent-child relationship.
+   */
+  public setNext(loader: ConfigurationLoader): ConfigurationLoader {
+    this._next = loader;
+    loader._parent = this;
+
+    return loader;
+  }
+
+  /**
+   * Delegates the loading process to the next loader in the chain.
+   * Throws an error if no configuration file is found by any loader in the chain.
+   */
+  protected next(): CypressRunnerConfig {
+    const { CYPRESS_RUNNER_CONFIG_FILENAME } = ConfigurationLoader;
+    if (!this._next) {
+      const supportedExtensions = this.supportedExtensions
+        .filter((extension) => extension.trim().length > 0)
+        .join('|');
+
+      throw new Error(
+        `No configuration file found. Please create a ${CYPRESS_RUNNER_CONFIG_FILENAME} file with the appropriate format: ${CYPRESS_RUNNER_CONFIG_FILENAME}{${supportedExtensions}}?.`,
+      );
+    }
+
+    return this._next.load();
+  }
+
+  /**
+   * Resolves the path to the configuration file based on the current working directory
+   * and the file extension supported by this loader.
+   */
+  protected resolveConfigurationPath(): string {
+    const { CYPRESS_RUNNER_CONFIG_FILENAME } = ConfigurationLoader;
+
+    return path.resolve(process.cwd(), CYPRESS_RUNNER_CONFIG_FILENAME + this.extension);
+  }
+}

lib/src/runner/configuration-loaders/default.ts

@@ -0,0 +1,12 @@
+import * as fs from 'fs';
+
+import { CypressRunnerConfig } from '../cypress-runner-config';
+import { JsonConfigurationLoader } from './json';
+
+export class DefaultConfigurationLoader extends JsonConfigurationLoader {
+  protected extension = '';
+
+  protected parse(path: string): CypressRunnerConfig {
+    return JSON.parse(fs.readFileSync(path, 'utf-8'));
+  }
+}

lib/src/runner/configuration-loaders/index.ts

@@ -0,0 +1,18 @@
+import { DefaultConfigurationLoader } from './default';
+import { JavaScriptConfigurationLoader } from './javascript';
+import { JsonConfigurationLoader } from './json';
+import { TypeScriptConfigurationLoader } from './typescript';
+
+export * from './configuration-loader';
+export * from './default';
+export * from './javascript';
+export * from './json';
+export * from './typescript';
+
+const defaultLoader = new DefaultConfigurationLoader();
+defaultLoader
+  .setNext(new JsonConfigurationLoader())
+  .setNext(new JavaScriptConfigurationLoader())
+  .setNext(new TypeScriptConfigurationLoader());
+
+export const loader = defaultLoader;

lib/src/runner/configuration-loaders/javascript.ts

@@ -0,0 +1,10 @@
+import { CypressRunnerConfig } from '../cypress-runner-config';
+import { ConfigurationLoader } from './configuration-loader';
+
+export class JavaScriptConfigurationLoader extends ConfigurationLoader {
+  protected extension = '.js';
+
+  protected parse(path: string): CypressRunnerConfig {
+    return require(path);
+  }
+}

lib/src/runner/configuration-loaders/json.ts

@@ -0,0 +1,12 @@
+import * as fs from 'fs';
+
+import { CypressRunnerConfig } from '../cypress-runner-config';
+import { ConfigurationLoader } from './configuration-loader';
+
+export class JsonConfigurationLoader extends ConfigurationLoader {
+  protected extension = '.json';
+
+  protected parse(path: string): CypressRunnerConfig {
+    return JSON.parse(fs.readFileSync(path, 'utf-8'));
+  }
+}

lib/src/runner/configuration-loaders/typescript.ts

@@ -0,0 +1,24 @@
+import { register } from 'ts-node';
+
+import { CypressRunnerConfig } from '../cypress-runner-config';
+import { ConfigurationLoader } from './configuration-loader';
+
+export class TypeScriptConfigurationLoader extends ConfigurationLoader {
+  protected extension = '.ts';
+
+  protected parse(path: string): CypressRunnerConfig {
+    register({
+      transpileOnly: true,
+      compilerOptions: {
+        module: 'commonjs',
+      },
+    });
+
+    const config = require(path).default;
+    if (!config) {
+      throw new Error('Missing default export configuration');
+    }
+
+    return config;
+  }
+}

lib/src/runner/index.ts

@@ -1,7 +1,6 @@
 export * from './banner';
 export * from './cypress-runner-config';
 export * from './kill-concurrently-result';
-export * from './load-configuration';
 export * from './runner';
 export * from './start-web-server-commands';
 export * from './wait-web-services';

lib/src/runner/runner.ts

@@ -1,8 +1,8 @@
 import { execSync } from 'child_process';
 
 import { printBanner } from './banner';
+import { loader } from './configuration-loaders';
 import { CypressRunnerConfig } from './cypress-runner-config';
-import { loadConfiguration } from './load-configuration';
 import { startWebServerCommands } from './start-web-server-commands';
 import { waitWebServices } from './wait-web-services';
 
@@ -15,7 +15,7 @@ export const cypressRunner = async (): Promise<void> => {
   const processArguments = [...process.argv];
   processArguments.splice(0, SCRIPT_ARG_START_INDEX);
 
-  const configuration: CypressRunnerConfig = loadConfiguration();
+  const configuration: CypressRunnerConfig = loader.load();
   const isDebug = configuration.debug;
 
   if (isDebug) {