Support Yarn Berry

src/detectPackageManager.ts

@@ -4,7 +4,7 @@ import chalk from "chalk"
 import process from "process"
 import findWorkspaceRoot from "find-yarn-workspace-root"
 
-export type PackageManager = "yarn" | "npm" | "npm-shrinkwrap"
+export type PackageManager = "yarn" | "yarn-berry" | "npm" | "npm-shrinkwrap"
 
 function printNoYarnLockfileError() {
   console.log(`
@@ -37,6 +37,19 @@ package-lock.json if you don't need it
   )
 }
 
+function detectYarnVersion(appRootPath: string): "yarn" | "yarn-berry" {
+  try {
+    const lockfilePath = join(appRootPath, "yarn.lock")
+    const lockfileContent = fs.readFileSync(lockfilePath, "utf8")
+    if (lockfileContent.includes("__metadata:")) {
+      return "yarn-berry"
+    }
+  } catch (e) {
+    // fall through to default
+  }
+  return "yarn"
+}
+
 export const detectPackageManager = (
   appRootPath: string,
   overridePackageManager: PackageManager | null,
@@ -63,7 +76,7 @@ export const detectPackageManager = (
       return shrinkWrapExists ? "npm-shrinkwrap" : "npm"
     }
   } else if (yarnLockExists || findWorkspaceRoot()) {
-    return "yarn"
+    return detectYarnVersion(appRootPath)
   } else {
     printNoLockfilesError()
     process.exit(1)

src/makePatch.ts

@@ -193,35 +193,38 @@ export function makePatch({
     // copy .npmrc/.yarnrc in case packages are hosted in private registry
     // copy .yarn directory as well to ensure installations work in yarn 2
     // tslint:disable-next-line:align
-    ;[".npmrc", ".yarnrc", ".yarn"].forEach((rcFile) => {
+    ;[".npmrc", ".yarnrc", ".yarnrc.yml", ".yarn"].forEach((rcFile) => {
       const rcPath = join(appPath, rcFile)
       if (existsSync(rcPath)) {
         copySync(rcPath, join(tmpRepo.name, rcFile), { dereference: true })
       }
     })
 
-    if (packageManager === "yarn") {
+    if (packageManager.startsWith("yarn")) {
+      const isBerry = packageManager === "yarn-berry"
+      const installArgs = isBerry
+        ? ["install"]
+        : ["install", "--ignore-engines"]
+      const installArgsIgnoreScripts = isBerry
+        ? ["install", "--mode=skip-build"]
+        : ["install", "--ignore-engines", "--ignore-scripts"]
       console.info(
         chalk.grey("•"),
         `Installing ${packageDetails.name}@${packageVersion} with yarn`,
       )
       try {
         // try first without ignoring scripts in case they are required
         // this works in 99.99% of cases
-        spawnSafeSync(`yarn`, ["install", "--ignore-engines"], {
+        spawnSafeSync(`yarn`, installArgs, {
           cwd: tmpRepoNpmRoot,
           logStdErrOnError: false,
         })
       } catch (e) {
         // try again while ignoring scripts in case the script depends on
         // an implicit context which we haven't reproduced
-        spawnSafeSync(
-          `yarn`,
-          ["install", "--ignore-engines", "--ignore-scripts"],
-          {
-            cwd: tmpRepoNpmRoot,
-          },
-        )
+        spawnSafeSync(`yarn`, installArgsIgnoreScripts, {
+          cwd: tmpRepoNpmRoot,
+        })
       }
     } else {
       console.info(