Adopt package manger definition from root manifest (#78)

src/isolate.ts

@@ -50,11 +50,11 @@ export async function isolate(
 
   const log = useLogger();
 
-  const thisPackageManifest = await readTypedJson<PackageManifest>(
+  const { version: libraryVersion } = await readTypedJson<PackageManifest>(
     path.join(path.join(__dirname, "..", "package.json"))
   );
 
-  log.debug("Using isolate-package version", thisPackageManifest.version);
+  log.debug("Using isolate-package version", libraryVersion);
 
   /**
    * If a targetPackagePath is set, we assume the configuration lives in the

src/lib/manifest/adapt-target-package-manifest.ts

@@ -45,6 +45,8 @@ export async function adaptTargetPackageManifest({
 
   return {
     ...adaptedManifest,
+    /** Adopt the package manager definition from the root manifest if available. */
+    packageManager: packageManager.packageManagerString,
     /**
      * Scripts are removed by default if not explicitly picked or omitted via
      * config.

src/lib/package-manager/helpers/infer-from-manifest.ts

@@ -11,16 +11,17 @@ import { getLockfileFileName, supportedPackageManagerNames } from "../names";
 export function inferFromManifest(workspaceRoot: string) {
   const log = useLogger();
 
-  const rootManifest = readTypedJsonSync<PackageManifest>(
-    path.join(workspaceRoot, "package.json")
-  );
+  const { packageManager: packageManagerString } =
+    readTypedJsonSync<PackageManifest>(
+      path.join(workspaceRoot, "package.json")
+    );
 
-  if (!rootManifest.packageManager) {
+  if (!packageManagerString) {
     log.debug("No packageManager field found in root manifest");
     return;
   }
 
-  const [name, version = "*"] = rootManifest.packageManager.split("@") as [
+  const [name, version = "*"] = packageManagerString.split("@") as [
     PackageManagerName,
     string,
   ];
@@ -37,5 +38,10 @@ export function inferFromManifest(workspaceRoot: string) {
     `Manifest declares ${name} to be the packageManager, but failed to find ${lockfileName} in workspace root`
   );
 
-  return { name, version, majorVersion: getMajorVersion(version) };
+  return {
+    name,
+    version,
+    majorVersion: getMajorVersion(version),
+    packageManagerString,
+  };
 }

src/lib/package-manager/names.ts

@@ -6,6 +6,7 @@ export type PackageManager = {
   name: PackageManagerName;
   version: string;
   majorVersion: number;
+  packageManagerString?: string;
 };
 
 export function getLockfileFileName(name: PackageManagerName) {