1 files changed, 85 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/util/module-resolver.js b/tools/node_modules/eslint/lib/util/module-resolver.js
new file mode 100644
index 0000000000..470a54f7c4
--- /dev/null
+++ b/tools/node_modules/eslint/lib/util/module-resolver.js
@@ -0,0 +1,85 @@
+/**
+ * @fileoverview Implements the Node.js require.resolve algorithm
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const Module = require("module");
+
+//------------------------------------------------------------------------------
+// Private
+//------------------------------------------------------------------------------
+
+const DEFAULT_OPTIONS = {
+
+    /*
+     * module.paths is an array of paths to search for resolving things relative
+     * to this file. Module.globalPaths contains all of the special Node.js
+     * directories that can also be searched for modules.
+     *
+     * Need to check for existence of module.paths because Jest seems not to
+     * include it. See https://github.com/eslint/eslint/issues/5791.
+     */
+    lookupPaths: module.paths ? module.paths.concat(Module.globalPaths) : Module.globalPaths.concat()
+};
+
+/**
+ * Resolves modules based on a set of options.
+ */
+class ModuleResolver {
+
+    /**
+     * Resolves modules based on a set of options.
+     * @param {Object} options The options for resolving modules.
+     * @param {string[]} options.lookupPaths An array of paths to include in the
+     *      lookup with the highest priority paths coming first.
+     */
+    constructor(options) {
+        this.options = Object.assign({}, DEFAULT_OPTIONS, options || {});
+    }
+
+    /**
+     * Resolves the file location of a given module relative to the configured
+     * lookup paths.
+     * @param {string} name The module name to resolve.
+     * @param {string} extraLookupPath An extra path to look into for the module.
+     *      This path is used with the highest priority.
+     * @returns {string} The resolved file path for the module.
+     * @throws {Error} If the module cannot be resolved.
+     */
+    resolve(name, extraLookupPath) {
+
+        /*
+         * First, clone the lookup paths so we're not messing things up for
+         * subsequent calls to this function. Then, move the extraLookupPath to the
+         * top of the lookup paths list so it will be searched first.
+         */
+        const lookupPaths = this.options.lookupPaths.concat();
+
+        lookupPaths.unshift(extraLookupPath);
+
+        /**
+         * Module._findPath is an internal method to Node.js, then one they use to
+         * lookup file paths when require() is called. So, we are hooking into the
+         * exact same logic that Node.js uses.
+         */
+        const result = Module._findPath(name, lookupPaths); // eslint-disable-line no-underscore-dangle
+
+        if (!result) {
+            throw new Error(`Cannot find module '${name}'`);
+        }
+
+        return result;
+    }
+}
+
+//------------------------------------------------------------------------------
+// Public API
+//------------------------------------------------------------------------------
+
+module.exports = ModuleResolver;