Fix crash with deleted file (microsoft#2934)

fix microsoft#2928

.chronus/changes/fix-crash-deleted-file-2024-1-17-1-27-24.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+[IDE] Fix issue when deleting an open file outside the IDE that would crash the language server

packages/compiler/src/core/util.ts

@@ -137,7 +137,15 @@ export function mapEquals<K, V>(
 }
 
 export async function getNormalizedRealPath(host: CompilerHost, path: string) {
-  return normalizePath(await host.realpath(path));
+  try {
+    return normalizePath(await host.realpath(path));
+  } catch (error: any) {
+    // This could mean the file got deleted but VSCode still has it in memory. So keep the original path.
+    if (error.code === "ENOENT") {
+      return normalizePath(path);
+    }
+    throw error;
+  }
 }
 
 export interface FileHandlingOptions {