New: Implement DotCompat class (#20)

* New: DotCompat class * More test and functionality * Dot compat cleanup * Add tests for extends * Finish up * Unignore fixture files * Update README.md Co-authored-by: Brandon Mills <[email protected]> * Update lib/dot-compat.js Co-authored-by: Brandon Mills <[email protected]> * Rename 'dot config' to 'flat config' * Allow functions in ignores array * Fix overrides behavior * Fix incorrect translation of language options * Throw errors when parser/plugin is missing * Combine ignore patterns * Fix linting errors * Fix typo * Fix failing test * Pass in pluginEnvironments to translateESLintRC() * Pass in pluginProcessors to translateESLintRC() * Code cleanup * Update README * fix errors * Cleanup package.json conflict * Finish tests * fix lint errors Co-authored-by: Brandon Mills <[email protected]>
eslint · Feb 25, 2021 · d9a527b · d9a527b
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diff --git a/README.md b/README.md
@@ -4,7 +4,7 @@ This repository contains the legacy ESLintRC configuration file format for ESLin
 
 **Note:** This package is not intended for use outside of the ESLint ecosystem. It is ESLint-specific and not intended for use in other programs.
 
-## Usage
+## Installation
 
 You can install the package as follows:
 
@@ -16,6 +16,46 @@ npm install @eslint/eslintrc --save-dev
 yarn add @eslint/eslintrc -D
 ```
 
+## Future Usage
+
+**Note:** This package is not intended for public use at this time. The following is an example of how it will be used in the future.
+
+The primary class in this package is `FlatCompat`, which is a utility to translate ESLintRC-style configs into flat configs. Here's how you use it inside of your `eslint.config.js` file:
+
+```js
+import { FlatCompat } from "@eslint/eslintrc";
+
+const compat = new FlatCompat();
+
+export default [
+
+    // mimic ESLintRC-style extends
+    compat.extends("standard", "example"),
+
+    // mimic environments
+    compat.env({
+        es2020: true,
+        node: true
+    }),
+
+    // mimic plugins
+    compat.plugins("airbnb", "react"),
+
+    // translate an entire config
+    compat.config({
+        plugins: ["airbnb", "react"],
+        extends: "standard",
+        env: {
+            es2020: true,
+            node: true
+        },
+        rules: {
+            semi: "error"
+        }
+    })
+];
+```
+
 ## License
 
 MIT License
diff --git a/conf/eslint-all.js b/conf/eslint-all.js
@@ -0,0 +1,12 @@
+/**
+ * @fileoverview Stub eslint:all config
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+module.exports = {
+    settings: {
+        "eslint:all": true
+    }
+};
diff --git a/conf/eslint-recommended.js b/conf/eslint-recommended.js
@@ -0,0 +1,12 @@
+/**
+ * @fileoverview Stub eslint:recommended config
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+module.exports = {
+    settings: {
+        "eslint:recommended": true
+    }
+};
diff --git a/lib/flat-compat.js b/lib/flat-compat.js
@@ -0,0 +1,308 @@
+/**
+ * @fileoverview Compatibility class for flat config.
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+//-----------------------------------------------------------------------------
+// Requirements
+//-----------------------------------------------------------------------------
+
+const path = require("path");
+const environments = require("../conf/environments");
+const createDebug = require("debug");
+const { ConfigArrayFactory } = require("./config-array-factory");
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+/** @typedef {import("../../shared/types").Environment} Environment */
+/** @typedef {import("../../shared/types").Processor} Processor */
+
+const debug = createDebug("eslintrc:flat-compat");
+const cafactory = Symbol("cafactory");
+
+/**
+ * Translates an ESLintRC-style config object into a flag-config-style config
+ * object.
+ * @param {Object} eslintrcConfig An ESLintRC-style config object.
+ * @param {Object} options Options to help translate the config.
+ * @param {string} options.resolveConfigRelativeTo To the directory to resolve
+ *      configs from.
+ * @param {string} options.resolvePluginsRelativeTo The directory to resolve
+ *      plugins from.
+ * @param {ReadOnlyMap<string,Environment>} options.pluginEnvironments A map of plugin environment
+ *      names to objects.
+ * @param {ReadOnlyMap<string,Processor>} options.pluginProcessors A map of plugin processor
+ *      names to objects.
+ * @returns {Object} A flag-config-style config object.
+ */
+function translateESLintRC(eslintrcConfig, {
+    resolveConfigRelativeTo,
+    resolvePluginsRelativeTo,
+    pluginEnvironments,
+    pluginProcessors
+}) {
+
+    const flatConfig = {};
+    const configs = [];
+    const languageOptions = {};
+    const linterOptions = {};
+    const keysToCopy = ["settings", "rules", "processor"];
+    const languageOptionsKeysToCopy = ["globals", "parser", "parserOptions"];
+    const linterOptionsKeysToCopy = ["noInlineConfig", "reportUnusedDisableDirectives"];
+
+    // check for special settings for eslint:all and eslint:recommended:
+    if (eslintrcConfig.settings) {
+        if (eslintrcConfig.settings["eslint:all"] === true) {
+            return ["eslint:all"];
+        }
+
+        if (eslintrcConfig.settings["eslint:recommended"] === true) {
+            return ["eslint:recommended"];
+        }
+    }
+
+    // copy over simple translations
+    for (const key of keysToCopy) {
+        if (key in eslintrcConfig && typeof eslintrcConfig[key] !== "undefined") {
+            flatConfig[key] = eslintrcConfig[key];
+        }
+    }
+
+    // copy over languageOptions
+    for (const key of languageOptionsKeysToCopy) {
+        if (key in eslintrcConfig && typeof eslintrcConfig[key] !== "undefined") {
+
+            // create the languageOptions key in the flat config
+            flatConfig.languageOptions = languageOptions;
+
+            if (key === "parser") {
+                debug(`Resolving parser '${languageOptions[key]}' relative to ${resolveConfigRelativeTo}`);
+
+                if (eslintrcConfig[key].error) {
+                    throw eslintrcConfig[key].error;
+                }
+
+                languageOptions[key] = eslintrcConfig[key].definition;
+                continue;
+            }
+
+            // clone any object values that are in the eslintrc config
+            if (eslintrcConfig[key] && typeof eslintrcConfig[key] === "object") {
+                languageOptions[key] = {
+                    ...eslintrcConfig[key]
+                };
+            } else {
+                languageOptions[key] = eslintrcConfig[key];
+            }
+        }
+    }
+
+    // copy over linterOptions
+    for (const key of linterOptionsKeysToCopy) {
+        if (key in eslintrcConfig && typeof eslintrcConfig[key] !== "undefined") {
+            flatConfig.linterOptions = linterOptions;
+            linterOptions[key] = eslintrcConfig[key];
+        }
+    }
+
+    // move ecmaVersion a level up
+    if (languageOptions.parserOptions) {
+
+        if ("ecmaVersion" in languageOptions.parserOptions) {
+            languageOptions.ecmaVersion = languageOptions.parserOptions.ecmaVersion;
+            delete languageOptions.parserOptions.ecmaVersion;
+        }
+
+        if ("sourceType" in languageOptions.parserOptions) {
+            languageOptions.sourceType = languageOptions.parserOptions.sourceType;
+            delete languageOptions.parserOptions.sourceType;
+        }
+
+        // check to see if we even need parserOptions anymore and remove it if not
+        if (Object.keys(languageOptions.parserOptions).length === 0) {
+            delete languageOptions.parserOptions;
+        }
+    }
+
+    // overrides
+    if (eslintrcConfig.criteria) {
+        flatConfig.files = [absoluteFilePath => eslintrcConfig.criteria.test(absoluteFilePath)];
+    }
+
+    // translate plugins
+    if (eslintrcConfig.plugins && typeof eslintrcConfig.plugins === "object") {
+        debug(`Translating plugins: ${eslintrcConfig.plugins}`);
+
+        flatConfig.plugins = {};
+
+        for (const pluginName of Object.keys(eslintrcConfig.plugins)) {
+
+            debug(`Translating plugin: ${pluginName}`);
+            debug(`Resolving plugin '${pluginName} relative to ${resolvePluginsRelativeTo}`);
+
+            const { definition: plugin, error } = eslintrcConfig.plugins[pluginName];
+
+            if (error) {
+                throw error;
+            }
+
+            flatConfig.plugins[pluginName] = plugin;
+
+            // create a config for any processors
+            if (plugin.processors) {
+                for (const processorName of Object.keys(plugin.processors)) {
+                    if (processorName.startsWith(".")) {
+                        debug(`Assigning processor: ${pluginName}/${processorName}`);
+
+                        configs.unshift({
+                            files: [`**/*${processorName}`],
+                            processor: pluginProcessors.get(`${pluginName}/${processorName}`)
+                        });
+                    }
+
+                }
+            }
+        }
+    }
+
+    // translate env - must come after plugins
+    if (eslintrcConfig.env && typeof eslintrcConfig.env === "object") {
+        for (const envName of Object.keys(eslintrcConfig.env)) {
+
+            // only add environments that are true
+            if (eslintrcConfig.env[envName]) {
+                debug(`Translating environment: ${envName}`);
+
+                if (environments.has(envName)) {
+
+                    // built-in environments should be defined first
+                    configs.unshift(...translateESLintRC(environments.get(envName), {
+                        resolveConfigRelativeTo,
+                        resolvePluginsRelativeTo
+                    }));
+                } else if (pluginEnvironments.has(envName)) {
+
+                    // if the environment comes from a plugin, it should come after the plugin config
+                    configs.push(...translateESLintRC(pluginEnvironments.get(envName), {
+                        resolveConfigRelativeTo,
+                        resolvePluginsRelativeTo
+                    }));
+                }
+            }
+        }
+    }
+
+    // only add if there are actually keys in the config
+    if (Object.keys(flatConfig).length > 0) {
+        configs.push(flatConfig);
+    }
+
+    return configs;
+}
+
+
+//-----------------------------------------------------------------------------
+// Exports
+//-----------------------------------------------------------------------------
+
+/**
+ * A compatibility class for working with configs.
+ */
+class FlatCompat {
+
+    constructor({
+        baseDirectory = process.cwd(),
+        resolvePluginsRelativeTo = baseDirectory
+    } = {}) {
+        this.baseDirectory = baseDirectory;
+        this.resolvePluginsRelativeTo = resolvePluginsRelativeTo;
+        this[cafactory] = new ConfigArrayFactory({
+            cwd: baseDirectory,
+            resolvePluginsRelativeTo,
+            eslintAllPath: path.resolve(__dirname, "../conf/eslint-all.js"),
+            eslintRecommendedPath: path.resolve(__dirname, "../conf/eslint-recommended.js")
+        });
+    }
+
+    /**
+     * Translates an ESLintRC-style config into a flag-config-style config.
+     * @param {Object} eslintrcConfig The ESLintRC-style config object.
+     * @returns {Object} A flag-config-style config object.
+     */
+    config(eslintrcConfig) {
+        const eslintrcArray = this[cafactory].create(eslintrcConfig, {
+            basePath: this.baseDirectory
+        });
+
+        const flatArray = [];
+        let hasIgnorePatterns = false;
+
+        eslintrcArray.forEach(configData => {
+            if (configData.type === "config") {
+                hasIgnorePatterns = hasIgnorePatterns || configData.ignorePattern;
+                flatArray.push(...translateESLintRC(configData, {
+                    resolveConfigRelativeTo: path.join(this.baseDirectory, "__placeholder.js"),
+                    resolvePluginsRelativeTo: path.join(this.resolvePluginsRelativeTo, "__placeholder.js"),
+                    pluginEnvironments: eslintrcArray.pluginEnvironments,
+                    pluginProcessors: eslintrcArray.pluginProcessors
+                }));
+            }
+        });
+
+        // combine ignorePatterns to emulate ESLintRC behavior better
+        if (hasIgnorePatterns) {
+            flatArray.unshift({
+                ignores: [filePath => {
+
+                    // Compute the final config for this file.
+                    // This filters config array elements by `files`/`excludedFiles` then merges the elements.
+                    const finalConfig = eslintrcArray.extractConfig(filePath);
+
+                    // Test the `ignorePattern` properties of the final config.
+                    return Boolean(finalConfig.ignores) && finalConfig.ignores(filePath);
+                }]
+            });
+        }
+
+        return flatArray;
+    }
+
+    /**
+     * Translates the `env` section of an ESLintRC-style config.
+     * @param {Object} envConfig The `env` section of an ESLintRC config.
+     * @returns {Object} A flag-config object representing the environments.
+     */
+    env(envConfig) {
+        return this.config({
+            env: envConfig
+        });
+    }
+
+    /**
+     * Translates the `extends` section of an ESLintRC-style config.
+     * @param {...string} configsToExtend The names of the configs to load.
+     * @returns {Object} A flag-config object representing the config.
+     */
+    extends(...configsToExtend) {
+        return this.config({
+            extends: configsToExtend
+        });
+    }
+
+    /**
+     * Translates the `plugins` section of an ESLintRC-style config.
+     * @param {...string} plugins The names of the plugins to load.
+     * @returns {Object} A flag-config object representing the plugins.
+     */
+    plugins(...plugins) {
+        return this.config({
+            plugins
+        });
+    }
+}
+
+exports.FlatCompat = FlatCompat;