Fix matrix-js-sdk linking on Windows (#33491)

* Fix matrix-js-sdk linking on Windows

* Linting

developer_guide.md

@@ -45,6 +45,8 @@ Set up your local development link by creating a `.link-config` file with conten
 matrix-js-sdk=/path/to/matrix-js-sdk
 ```
 
+**Note for Windows users**: Your link config path might need escaping. For example, `matrix-js-sdk=C:\\path\\to\\matrix-js-sdk`.
+
 Switch to the `apps/web` directory: `cd apps/web`
 
 Configure the app by copying `config.sample.json` to `config.json` and
@@ -57,6 +59,8 @@ pnpm install
 pnpm start
 ```
 
+**Note for Windows users**: `pnpm start` needs to be run from a terminal with bash/shell support.
+
 Wait a few seconds for the initial build to finish; you should see something like:
 
 ```

scripts/pnpm-link.ts

@@ -32,21 +32,31 @@ try {
         const dependencyPath = join(nodeModulesPath, dependency);
 
         try {
-            const stat = await fs.stat(dependencyPath);
-            if (stat.isSymbolicLink()) {
-                const linkPath = await fs.readlink(dependencyPath);
-                if (linkPath === path) {
-                    // already done
-                    continue;
+            try {
+                const stat = await fs.lstat(dependencyPath);
+                console.log(`Existing is ${stat.isSymbolicLink() ? "symlink" : "directory"}`);
+                if (stat.isSymbolicLink()) {
+                    const linkPath = await fs.readlink(dependencyPath);
+                    if (linkPath === path) {
+                        // already done
+                        continue;
+                    } else {
+                        await fs.unlink(dependencyPath);
+                    }
                 } else {
-                    await fs.unlink(dependencyPath);
+                    await fs.rm(dependencyPath, { recursive: true });
+                }
+            } catch (e: any) {
+                // fs.lstat throws ENOENT if the path doesn't exist (on Windows)
+                if (e.code === "ENOENT") {
+                    console.log("Received ENOENT error on dependency path - assuming it doesn't exist");
+                } else {
+                    throw e;
                 }
-            } else {
-                await fs.rm(dependencyPath, { recursive: true });
             }
 
             console.log(`Linking ${dependency} to ${path}`);
-            await fs.symlink(path, dependencyPath);
+            await fs.symlink(path, dependencyPath, "junction"); // use a junction type to avoid EPERM errors on Windows
 
             const pkgJson = await fs.readFile(join(path, "package.json"), "utf-8");
             const pkgManager = JSON.parse(pkgJson)["packageManager"]?.split("@").at(0) ?? "yarn";