fix(daemon): node makeFilePowers uses mutex for serial file updates

packages/daemon/src/daemon-node-powers.js

@@ -9,6 +9,7 @@ import { makeReaderRef } from './reader-ref.js';
 import { makePetStoreMaker } from './pet-store.js';
 import { servePrivatePortHttp } from './serve-private-port-http.js';
 import { servePrivatePath } from './serve-private-path.js';
+import { makeMutex } from './mutex.js';
 
 const { quote: q } = assert;
 
@@ -354,6 +355,8 @@ export const makeNetworkPowers = ({ http, ws, net }) => {
 };
 
 export const makeFilePowers = ({ fs, path: fspath }) => {
+  const writeLock = makeMutex();
+
   /**
    * @param {string} path
    */
@@ -376,7 +379,9 @@ export const makeFilePowers = ({ fs, path: fspath }) => {
    * @param {string} text
    */
   const writeFileText = async (path, text) => {
-    await fs.promises.writeFile(path, text);
+    await writeLock.enqueue(async () => {
+      await fs.promises.writeFile(path, text);
+    });
   };
 
   /**
@@ -418,11 +423,16 @@ export const makeFilePowers = ({ fs, path: fspath }) => {
    * @param {string} path
    */
   const removePath = async path => {
-    return fs.promises.rm(path);
+    await writeLock.enqueue(async () => {
+      return fs.promises.rm(path);
+    });
   };
 
-  const renamePath = async (source, target) =>
-    fs.promises.rename(source, target);
+  const renamePath = async (source, target) => {
+    await writeLock.enqueue(async () => {
+      return fs.promises.rename(source, target);
+    });
+  };
 
   const joinPath = (...components) => fspath.join(...components);
 

packages/daemon/src/mutex.js

@@ -0,0 +1,30 @@
+import { makeQueue } from '@endo/stream';
+
+/**
+ * @returns {{ lock: () => Promise<void>, unlock: () => void, enqueue: (asyncFn: () => Promise<any>) => Promise<any> }}
+ */
+export const makeMutex = () => {
+  /** @type {import('@endo/stream').AsyncQueue<void>} */
+  const queue = makeQueue();
+  const lock = () => {
+    return queue.get();
+  };
+  const unlock = () => {
+    queue.put();
+  };
+  unlock();
+
+  return {
+    lock,
+    unlock,
+    // helper for correct usage
+    enqueue: async asyncFn => {
+      await lock();
+      try {
+        return await asyncFn();
+      } finally {
+        unlock();
+      }
+    },
+  };
+};