fix(yarn): yarn v2 yarnrc support

lib/manager/common.ts

@@ -93,7 +93,7 @@ export interface PackageFile<T = Record<string, any>>
   packageFileVersion?: string;
   parent?: string;
   skipInstalls?: boolean;
-  yarnrc?: string;
+  yarnrc?: RcFile;
   yarnWorkspacesPackages?: string[] | string;
   matchStrings?: string[];
 }
@@ -263,3 +263,8 @@ export interface PostUpdateConfig extends ManagerConfig, Record<string, any> {
   branchName?: string;
   reuseExistingBranch?: boolean;
 }
+
+export interface RcFile {
+  content: string;
+  fileName: string;
+}

lib/manager/npm/extract/index.ts

@@ -23,6 +23,7 @@ import { NpmPackage, NpmPackageDependency } from './common';
 import { getLockedVersions } from './locked-versions';
 import { detectMonorepos } from './monorepo';
 import { mightBeABrowserLibrary } from './type';
+import { getYarnRc } from './yarn';
 
 function parseDepName(depType: string, key: string): string {
   if (depType !== 'resolutions') {
@@ -117,11 +118,8 @@ export async function extractPackageFile(
       npmrc = undefined;
     }
   }
-  const yarnrcFileName = getSiblingFileName(fileName, '.yarnrc');
-  let yarnrc;
-  if (!is.string(config.yarnrc)) {
-    yarnrc = (await readLocalFile(yarnrcFileName, 'utf8')) || undefined;
-  }
+
+  const yarnrc = await getYarnRc(fileName, config);
 
   let lernaDir: string;
   let lernaPackages: string[];

lib/manager/npm/extract/yarn.ts

@@ -1,7 +1,12 @@
+import * as path from 'path';
+import is from '@sindresorhus/is';
 import { structUtils } from '@yarnpkg/core';
 import { parseSyml } from '@yarnpkg/parsers';
+import findUp from 'find-up';
+import { getEnv } from '../../../../tools/utils';
 import { logger } from '../../../logger';
-import { readLocalFile } from '../../../util/fs';
+import { readFile, readLocalFile } from '../../../util/fs';
+import { ExtractConfig, RcFile } from '../../common';
 
 export async function getYarnLock(
   filePath: string
@@ -41,3 +46,29 @@ export async function getYarnLock(
     return { isYarn1: true, cacheVersion: NaN, lockedVersions: {} };
   }
 }
+
+export async function getYarnRc(
+  packageFilePath: string,
+  config: ExtractConfig
+): Promise<RcFile> {
+  if (is.string(config.yarnrc) || config.localDir === undefined) {
+    return undefined;
+  }
+  const yarnRcFileNames = [
+    '.yarnrc',
+    '.yarnrc.yml',
+    getEnv('YARN_RC_FILENAME'),
+  ];
+  const yarnRcPath = await findUp(yarnRcFileNames, {
+    cwd: path.dirname(path.join(config.localDir, packageFilePath)),
+    type: 'file',
+  });
+  if (yarnRcPath?.startsWith(config.localDir) !== true) {
+    return undefined;
+  }
+  logger.debug({ yarnRcPath }, 'found Yarn config file');
+  return {
+    content: await readFile(yarnRcPath, 'utf8'),
+    fileName: yarnRcPath,
+  };
+}

lib/manager/npm/post-update/index.ts

@@ -158,12 +158,15 @@ export async function writeExistingFiles(
       }
     }
     if (packageFile.yarnrc) {
-      logger.debug(`Writing .yarnrc to ${basedir}`);
-      const yarnrcFilename = upath.join(basedir, '.yarnrc');
+      const {
+        fileName: yarnrcFilename,
+        content: yarnrcContent,
+      } = packageFile.yarnrc;
+      logger.debug(`Writing ${yarnrcFilename} to ${basedir}`);
       try {
         await outputFile(
           yarnrcFilename,
-          packageFile.yarnrc
+          yarnrcContent
             .replace('--install.pure-lockfile true', '')
             .replace('--install.frozen-lockfile true', '')
         );