Fix: Compiler couldn't resolve files at a long path(256+) on window (#…

…2797)

fix #2783

common/changes/@typespec/compiler/fix-realpath-long-path-windows_2024-01-17-15-46.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@typespec/compiler",
+      "comment": "Fix: Compiler couldn't resolve files at a long path(256+) on windows",
+      "type": "none"
+    }
+  ],
+  "packageName": "@typespec/compiler"
+}

packages/compiler/src/core/node-host.ts

@@ -1,4 +1,5 @@
-import { mkdir, readdir, readFile, realpath, rm, stat, writeFile } from "fs/promises";
+import { realpath } from "fs";
+import { mkdir, readdir, readFile, rm, stat, writeFile } from "fs/promises";
 import { fileURLToPath, pathToFileURL } from "url";
 import { createSourceFile } from "./diagnostics.js";
 import { fetch } from "./fetch.js";
@@ -33,7 +34,17 @@ export const NodeHost: CompilerHost = {
     return stat(path);
   },
   realpath(path) {
-    return realpath(path);
+    // BUG in the promise version of realpath https://github.com/microsoft/typespec/issues/2783
+    // Fix was only made to node 21.6 at this time. https://github.com/nodejs/node/issues/51031
+    return new Promise((resolve, reject) => {
+      realpath(path, (err, resolvedPath) => {
+        if (err) {
+          reject(err);
+        } else {
+          resolve(resolvedPath);
+        }
+      });
+    });
   },
   getSourceFileKind: getSourceFileKindFromExt,
   mkdirp: (path: string) => mkdir(path, { recursive: true }),