Use require.resolve as a fallback of path.resolve

.github/workflows/nodejs.yml

@@ -27,8 +27,8 @@ jobs:
     - name: Install Dependencies
       run: npm install --no-package-lock
     - name: Run All Validations
-      if: ${{ matrix.node-version != '10.x' }}
+      if: ${{ matrix.node-version == '14.x' }}
       run: npm run ci
     - name: Run Tests Only
-      if: ${{ matrix.node-version == '10.x' }}
+      if: ${{ matrix.node-version != '14.x' }}
       run: npm run test

lib/markdownlint.js

@@ -895,6 +895,38 @@ function parseConfiguration(name, content, parsers) {
   };
 }
 
+/**
+ * Resolve referenced "extends" path in a configuration file
+ * using path.resolve() and require.resolve() as a fallback.
+ *
+ * @param {string} configFile Configuration file name.
+ * @param {string} referenceId Referenced identifier to resolve.
+ * @returns {string} Resolved path to file
+ */
+function resolveConfigExtends(configFile, referenceId) {
+  const configFileDirname = path.dirname(configFile);
+  const resolvedExtendsFile = path.resolve(configFileDirname, referenceId);
+
+  try {
+    if (fs.statSync(resolvedExtendsFile).isFile()) {
+      return resolvedExtendsFile;
+    }
+  // eslint-disable-next-line unicorn/prefer-optional-catch-binding
+  } catch (error) {
+    // If fs.statSync has thrown, trying require.resolve
+  }
+
+  try {
+    return require.resolve(referenceId, { "paths": [ configFileDirname ] });
+
+  // eslint-disable-next-line unicorn/prefer-optional-catch-binding
+  } catch (error) {
+    // If require.resolve throws, returning resolvedExtendsFile for BC
+  }
+
+  return resolvedExtendsFile;
+}
+
 /**
  * Read specified configuration file.
  *
@@ -925,8 +957,8 @@ function readConfig(file, parsers, callback) {
     const configExtends = config.extends;
     if (configExtends) {
       delete config.extends;
-      const extendsFile = path.resolve(path.dirname(file), configExtends);
-      return readConfig(extendsFile, parsers, (errr, extendsConfig) => {
+      const resolvedExtends = resolveConfigExtends(file, configExtends);
+      return readConfig(resolvedExtends, parsers, (errr, extendsConfig) => {
         if (errr) {
           return callback(errr);
         }
@@ -974,11 +1006,9 @@ function readConfigSync(file, parsers) {
   const configExtends = config.extends;
   if (configExtends) {
     delete config.extends;
+    const resolvedExtends = resolveConfigExtends(file, configExtends);
     return {
-      ...readConfigSync(
-        path.resolve(path.dirname(file), configExtends),
-        parsers
-      ),
+      ...readConfigSync(resolvedExtends, parsers),
       ...config
     };
   }

test/config/config-badchildpackage.json

@@ -0,0 +1,4 @@
+{
+  "extends": "@oops/markdownlint-config",
+  "default": true
+}

test/config/config-packageparent.json

@@ -0,0 +1,7 @@
+{
+  "extends": "test",
+  "MD003": false,
+  "MD007": { "indent": 4 },
+  "no-hard-tabs": true,
+  "line-length": { "line_length": 200 }
+}

test/config/pseudo-package/config-frompackage.json

@@ -0,0 +1,4 @@
+{
+  "no-hard-tabs": false,
+  "whitespace": false
+}

test/config/pseudo-package/package.json

@@ -0,0 +1,3 @@
+{
+  "main": "config-frompackage.json"
+}

test/markdownlint-test.js

@@ -1032,6 +1032,36 @@ tape("configMultiple", (test) => {
     });
 });
 
+tape("configMultipleWithRequireResolve", (test) => {
+  test.plan(2);
+
+  try {
+    fs.symlinkSync(
+      path.resolve(__dirname, "./config/pseudo-package"),
+      path.resolve(__dirname, "../node_modules/test"),
+      "dir"
+    );
+  // eslint-disable-next-line unicorn/prefer-optional-catch-binding
+  } catch (error) {
+    // Package symlink creation failed due to earlier failure
+  }
+
+  markdownlint.readConfig("./test/config/config-packageparent.json",
+    function callback(err, actual) {
+      test.ifError(err);
+      const expected = {
+        ...require("./config/pseudo-package/config-frompackage.json"),
+        ...require("./config/config-packageparent.json")
+      };
+      delete expected.extends;
+      test.deepEqual(actual, expected, "Config object not correct.");
+
+      fs.unlinkSync(path.resolve(__dirname, "../node_modules/test"));
+
+      test.end();
+    });
+});
+
 tape("configBadFile", (test) => {
   test.plan(4);
   markdownlint.readConfig("./test/config/config-badfile.json",
@@ -1059,6 +1089,20 @@ tape("configBadChildFile", (test) => {
     });
 });
 
+tape("configBadChildPackage", (test) => {
+  test.plan(4);
+  markdownlint.readConfig("./test/config/config-badchildpackage.json",
+    function callback(err, result) {
+      test.ok(err, "Did not get an error for bad child file.");
+      test.ok(err instanceof Error, "Error not instance of Error.");
+      // @ts-ignore
+      test.equal(err.code, "ENOENT",
+        "Error code for bad child file not ENOENT.");
+      test.ok(!result, "Got result for bad child file.");
+      test.end();
+    });
+});
+
 tape("configBadJson", (test) => {
   test.plan(3);
   markdownlint.readConfig("./test/config/config-badjson.json",