shim more buffer methods, and fs methods

getting importer plugin to work,

src/shims/fs/fd.js

@@ -0,0 +1,153 @@
+// File descriptor shim  -  maps fake integer fds to in-memory file buffers.
+// Enables libraries like yauzl that use fs.open/fs.read/fs.close to seek
+// around files without loading them via readFileSync upfront.
+
+let nextFd = 100;
+const openFiles = new Map();
+
+export function createFdOps(metadataCache, contentCache, transport) {
+  function ensureData(path) {
+    const cached = contentCache.get(path);
+
+    if (cached !== null) {
+      if (typeof cached === "string") {
+        return new TextEncoder().encode(cached);
+      }
+
+      return cached;
+    }
+
+    // Synchronous fetch fallback
+    console.warn("[shim:fs] fd open cache miss, using sync XHR:", path);
+    const data = transport.readFileSync(path);
+    contentCache.set(path, data);
+
+    return data;
+  }
+
+  function getEntry(fd) {
+    const entry = openFiles.get(fd);
+
+    if (!entry) {
+      const err = new Error(`EBADF: bad file descriptor, fd ${fd}`);
+      err.code = "EBADF";
+      throw err;
+    }
+
+    return entry;
+  }
+
+  // --- Sync ---
+
+  function openSync(path, flags, mode) {
+    if (!metadataCache.has(path)) {
+      const err = new Error(
+        `ENOENT: no such file or directory, open '${path}'`,
+      );
+      err.code = "ENOENT";
+      throw err;
+    }
+
+    const data = ensureData(path);
+    const fd = nextFd++;
+    openFiles.set(fd, { path, data });
+
+    return fd;
+  }
+
+  function readSync(fd, buffer, offset, length, position) {
+    const entry = getEntry(fd);
+    const available = Math.min(length, entry.data.length - position);
+
+    if (available <= 0) {
+      return 0;
+    }
+
+    const slice = entry.data.subarray(position, position + available);
+    buffer.set(slice, offset);
+
+    return available;
+  }
+
+  function closeSync(fd) {
+    openFiles.delete(fd);
+  }
+
+  function fstatSync(fd) {
+    const entry = getEntry(fd);
+    const stat = metadataCache.toStat(entry.path);
+
+    if (stat) {
+      return stat;
+    }
+
+    // Fallback: construct minimal stat from the buffer
+    return {
+      size: entry.data.length,
+      isFile: () => true,
+      isDirectory: () => false,
+    };
+  }
+
+  // --- Async (callback style) ---
+
+  function open(path, flags, modeOrCb, cb) {
+    if (typeof modeOrCb === "function") {
+      cb = modeOrCb;
+    }
+
+    try {
+      const fd = openSync(path, flags);
+      queueMicrotask(() => cb(null, fd));
+    } catch (e) {
+      queueMicrotask(() => cb(e));
+    }
+  }
+
+  function read(fd, buffer, offset, length, position, cb) {
+    try {
+      const bytesRead = readSync(fd, buffer, offset, length, position);
+      queueMicrotask(() => cb(null, bytesRead, buffer));
+    } catch (e) {
+      queueMicrotask(() => cb(e));
+    }
+  }
+
+  function close(fd, cb) {
+    try {
+      closeSync(fd);
+
+      if (cb) {
+        queueMicrotask(() => cb(null));
+      }
+    } catch (e) {
+      if (cb) {
+        queueMicrotask(() => cb(e));
+      }
+    }
+  }
+
+  function fstat(fd, optionsOrCb, cb) {
+    if (typeof optionsOrCb === "function") {
+      cb = optionsOrCb;
+    }
+
+    try {
+      const stat = fstatSync(fd);
+      queueMicrotask(() => cb(null, stat));
+    } catch (e) {
+      queueMicrotask(() => cb(e));
+    }
+  }
+
+  return {
+    openSync,
+    readSync,
+    closeSync,
+    fstatSync,
+    open,
+    read,
+    close,
+    fstat,
+  };
+}

src/shims/fs/index.js

@@ -4,6 +4,7 @@ import { transport } from "./transport.js";
 import { createFsPromises } from "./promises.js";
 import { createFsSync } from "./sync.js";
 import { createFsWatch } from "./watch.js";
+import { createFdOps } from "./fd.js";
 import { constants } from "./constants.js";
 
 const metadataCache = new MetadataCache();
@@ -12,6 +13,7 @@ const contentCache = new ContentCache();
 const fsPromises = createFsPromises(metadataCache, contentCache, transport);
 const fsSync = createFsSync(metadataCache, contentCache, transport);
 const fsWatch = createFsWatch(transport);
+const fdOps = createFdOps(metadataCache, contentCache, transport);
 
 export const fsShim = {
   promises: fsPromises,
@@ -24,6 +26,15 @@ export const fsShim = {
   statSync: fsSync.statSync,
   readdirSync: fsSync.readdirSync,
 
+  open: fdOps.open,
+  openSync: fdOps.openSync,
+  read: fdOps.read,
+  readSync: fdOps.readSync,
+  close: fdOps.close,
+  closeSync: fdOps.closeSync,
+  fstat: fdOps.fstat,
+  fstatSync: fdOps.fstatSync,
+
   watch: fsWatch.watch,
   constants,
 

src/shims/fs/promises.js

@@ -197,5 +197,48 @@ export function createFsPromises(metadataCache, contentCache, transport) {
         metadataCache.set(path, meta);
       }
     },
+
+    async open(path, flags) {
+      if (!metadataCache.has(path)) {
+        const err = new Error(
+          `ENOENT: no such file or directory, open '${path}'`,
+        );
+        err.code = "ENOENT";
+        throw err;
+      }
+
+      const data = await this.readFile(path);
+      const fileData =
+        typeof data === "string" ? new TextEncoder().encode(data) : data;
+
+      const fileStat = metadataCache.toStat(path) || {
+        size: fileData.length,
+        isFile: () => true,
+        isDirectory: () => false,
+      };
+
+      return {
+        async stat() {
+          return fileStat;
+        },
+
+        async read(buffer, offset, length, position) {
+          const available = Math.min(length, fileData.length - position);
+
+          if (available <= 0) {
+            return { bytesRead: 0, buffer };
+          }
+
+          const slice = fileData.subarray(position, position + available);
+          buffer.set(slice, offset);
+
+          return { bytesRead: available, buffer };
+        },
+
+        async close() {
+          // Nothing to clean up  -  data is in memory
+        },
+      };
+    },
   };
 }