[rush-resolver-cache] Fix projectFolder on Windows (#4931)

Co-authored-by: David Michon <dmichon-msft@users.noreply.github.com>

common/changes/@microsoft/rush/fix-project-folder_2024-09-20-00-10.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Fix a bug that caused rush-resolver-cache-plugin to crash on Windows.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush"
+}

rush-plugins/rush-resolver-cache-plugin/src/computeResolverCacheFromLockfileAsync.ts

@@ -136,6 +136,15 @@ export interface IComputeResolverCacheFromLockfileOptions {
   ) => Promise<void>;
 }
 
+/**
+ * Copied from `@rushstack/node-core-library/src/Path.ts` to avoid expensive dependency
+ * @param path - Path using backslashes as path separators
+ * @returns The same string using forward slashes as path separators
+ */
+function convertToSlashes(path: string): string {
+  return path.replace(/\\/g, '/');
+}
+
 /**
  * Given a lockfile and information about the workspace and platform, computes the resolver cache file.
  * @param params - The options for computing the resolver cache
@@ -146,9 +155,9 @@ export async function computeResolverCacheFromLockfileAsync(
 ): Promise<IResolverCacheFile> {
   const { platformInfo, projectByImporterPath, lockfile, afterExternalPackagesAsync } = params;
   // Needs to be normalized to `/` for path.posix.join to work correctly
-  const workspaceRoot: string = params.workspaceRoot.replace(/\\/g, '/');
+  const workspaceRoot: string = convertToSlashes(params.workspaceRoot);
   // Needs to be normalized to `/` for path.posix.join to work correctly
-  const commonPrefixToTrim: string = params.commonPrefixToTrim.replace(/\\/g, '/');
+  const commonPrefixToTrim: string = convertToSlashes(params.commonPrefixToTrim);
 
   const contexts: Map<string, IResolverContext> = new Map();
   const missingOptionalDependencies: Set<string> = new Set();
@@ -218,8 +227,10 @@ export async function computeResolverCacheFromLockfileAsync(
       throw new Error(`Missing project for importer ${importerPath}`);
     }
 
+    const descriptionFileRoot: string = convertToSlashes(project.projectFolder);
+
     const context: IResolverContext = {
-      descriptionFileRoot: project.projectFolder,
+      descriptionFileRoot,
       descriptionFileHash: undefined, // Not needed anymore
       name: project.packageJson.name,
       isProject: true,
@@ -227,7 +238,7 @@ export async function computeResolverCacheFromLockfileAsync(
       ordinal: -1
     };
 
-    contexts.set(project.projectFolder, context);
+    contexts.set(descriptionFileRoot, context);
 
     if (importer.dependencies) {
       resolveDependencies(workspaceRoot, importer.dependencies, context);

rush-plugins/rush-resolver-cache-plugin/src/test/computeResolverCacheFromLockfileAsync.test.ts

@@ -107,7 +107,8 @@ describe(computeResolverCacheFromLockfileAsync.name, () => {
       for (const importerPath of lockfile.importers.keys()) {
         const remainder: string = importerPath.slice(importerPath.lastIndexOf('../') + 3);
         projectByImporterPath.setItem(importerPath, {
-          projectFolder: `${commonPrefixToTrim.replace(/\\/g, '/')}${remainder}`,
+          // Normalization is the responsibility of the implementation
+          projectFolder: `${commonPrefixToTrim}${remainder}`,
           packageJson: {
             name: `@local/${remainder.replace(/\//g, '+')}`
           }