Allow browsers to specify fd preopens

package.json

@@ -43,7 +43,7 @@
   "author": "The Extism Authors <[email protected]>",
   "license": "BSD-3-Clause",
   "devDependencies": {
-    "@bjorn3/browser_wasi_shim": "^0.2.17",
+    "@bjorn3/browser_wasi_shim": "^0.2.20",
     "@playwright/test": "^1.39.0",
     "@types/node": "^20.8.7",
     "@typescript-eslint/eslint-plugin": "^6.8.0",

src/foreground-plugin.ts

@@ -156,7 +156,7 @@ async function instantiateModule(
         }
 
         if (wasi === null) {
-          wasi = await loadWasi(opts.allowedPaths, opts.enableWasiOutput);
+          wasi = await loadWasi(opts.allowedPaths, opts.enableWasiOutput, opts.wasiOptions);
           wasiList.push(wasi);
           imports.wasi_snapshot_preview1 = await wasi.importObject();
         }
@@ -211,9 +211,9 @@ async function instantiateModule(
       const instance = providerExports.find((xs) => xs.name === '_start')
         ? await instantiateModule([...current, module], provider, imports, opts, wasiList, names, modules, new Map())
         : !linked.has(provider)
-        ? (await instantiateModule([...current, module], provider, imports, opts, wasiList, names, modules, linked),
-          linked.get(provider))
-        : linked.get(provider);
+          ? (await instantiateModule([...current, module], provider, imports, opts, wasiList, names, modules, linked),
+            linked.get(provider))
+          : linked.get(provider);
 
       if (!instance) {
         // circular import, either make a trampoline or bail
@@ -254,10 +254,10 @@ async function instantiateModule(
   const guestType = instance.exports.hs_init
     ? 'haskell'
     : instance.exports._initialize
-    ? 'reactor'
-    : instance.exports._start
-    ? 'command'
-    : 'none';
+      ? 'reactor'
+      : instance.exports._start
+        ? 'command'
+        : 'none';
 
   if (wasi) {
     await wasi?.initialize(instance);

src/interfaces.ts

@@ -123,6 +123,19 @@ export interface Plugin {
   reset(): Promise<boolean>;
 }
 
+/**
+ * Options for initializing WASI.
+ */
+export interface WASIOptions {
+  /**
+   * A list of file descriptors; only available in browser environments.
+   *
+   * See [`@bjorn3/browser_wasi_shim`](https://github.com/bjorn3/browser_wasi_shim) for more
+   * details on use.
+   */
+  fileDescriptors: any[];
+}
+
 /**
  * Options for initializing an Extism plugin.
  */
@@ -167,6 +180,7 @@ export interface ExtismPluginOptions {
   functions?: { [key: string]: { [key: string]: (callContext: CallContext, ...args: any[]) => any } } | undefined;
   allowedPaths?: { [key: string]: string } | undefined;
   allowedHosts?: string[] | undefined;
+  wasiOptions?: WASIOptions;
 
   /**
    * Whether WASI stdout should be forwarded to the host.
@@ -189,6 +203,7 @@ export interface InternalConfig {
   wasiEnabled: boolean;
   config: PluginConfig;
   sharedArrayBufferSize: number;
+  wasiOptions: WASIOptions | null;
 }
 
 export interface InternalWasi {

src/mod.ts

@@ -99,6 +99,7 @@ export async function createPlugin(
     config: opts.config,
     enableWasiOutput: opts.enableWasiOutput,
     sharedArrayBufferSize: Number(opts.sharedArrayBufferSize) || 1 << 16,
+    wasiOptions: opts.wasiOptions ?? null,
   };
 
   return (opts.runInWorker ? _createBackgroundPlugin : _createForegroundPlugin)(ic, names, moduleData);

src/polyfills/browser-wasi.ts

@@ -1,48 +1,29 @@
-import { WASI, Fd, File, OpenFile, wasi } from '@bjorn3/browser_wasi_shim';
-import { type InternalWasi } from '../mod.ts';
-
-class Output extends Fd {
-  #mode: string;
-
-  constructor(mode: string) {
-    super();
-    this.#mode = mode;
-  }
-
-  fd_write(view8: Uint8Array, iovs: [wasi.Iovec]): { ret: number; nwritten: number } {
-    let nwritten = 0;
-    const decoder = new TextDecoder();
-    const str = iovs.reduce((acc, iovec, idx, all) => {
-      nwritten += iovec.buf_len;
-      const buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-      return acc + decoder.decode(buffer, { stream: idx !== all.length - 1 });
-    }, '');
-
-    (console[this.#mode] as any)(str);
-
-    return { ret: 0, nwritten };
-  }
-}
+import { WASI, Fd, File, OpenFile, ConsoleStdout } from '@bjorn3/browser_wasi_shim';
+import { type WASIOptions, type InternalWasi } from '../interfaces.ts';
 
 export async function loadWasi(
   _allowedPaths: { [from: string]: string },
   enableWasiOutput: boolean,
+  wasiOptions: WASIOptions | null
 ): Promise<InternalWasi> {
   const args: Array<string> = [];
   const envVars: Array<string> = [];
+  const fileDescriptors = (wasiOptions?.fileDescriptors || []) as Fd[]
   const fds: Fd[] = enableWasiOutput
     ? [
-        new Output('log'), // fd 0 is dup'd to stdout
-        new Output('log'),
-        new Output('error'),
-      ]
+      ConsoleStdout.lineBuffered((msg) => console.log(msg)), // fd 0 is dup'd to stdout
+      ConsoleStdout.lineBuffered((msg) => console.log(msg)),
+      ConsoleStdout.lineBuffered((msg) => console.warn(msg)),
+      ...fileDescriptors,
+    ]
     : [
-        new OpenFile(new File([])), // stdin
-        new OpenFile(new File([])), // stdout
-        new OpenFile(new File([])), // stderr
-      ];
+      new OpenFile(new File([])), // stdin
+      new OpenFile(new File([])), // stdout
+      new OpenFile(new File([])), // stderr
+      ...fileDescriptors,
+    ];
 
-  const context = new WASI(args, envVars, fds);
+  const context = new WASI(args, envVars, fds, { debug: false });
 
   return {
     async importObject() {
@@ -78,7 +59,7 @@ export async function loadWasi(
         context.start({
           exports: {
             memory,
-            _start: () => {},
+            _start: () => { },
           },
         });
       }

src/polyfills/deno-wasi.ts

@@ -1,5 +1,5 @@
 import Context from './deno-snapshot_preview1.ts';
-import { type InternalWasi } from '../interfaces.ts';
+import { type WASIOptions, type InternalWasi } from '../interfaces.ts';
 import { devNull } from 'node:os';
 import { open } from 'node:fs/promises';
 import { closeSync } from 'node:fs';
@@ -20,7 +20,7 @@ async function createDevNullFDs() {
   return {
     async close() {
       needsClose = false;
-      await Promise.all([stdin.close(), stdout.close()]).catch(() => {});
+      await Promise.all([stdin.close(), stdout.close()]).catch(() => { });
     },
     fds: [stdin.fd, stdout.fd, stdout.fd],
   };
@@ -29,11 +29,12 @@ async function createDevNullFDs() {
 export async function loadWasi(
   allowedPaths: { [from: string]: string },
   enableWasiOutput: boolean,
+  _wasiOptions: WASIOptions | null,
 ): Promise<InternalWasi> {
   const {
     close,
     fds: [stdin, stdout, stderr],
-  } = enableWasiOutput ? { async close() {}, fds: [0, 1, 2] } : await createDevNullFDs();
+  } = enableWasiOutput ? { async close() { }, fds: [0, 1, 2] } : await createDevNullFDs();
   const context = new Context({
     preopens: allowedPaths,
     exitOnReturn: false,
@@ -76,7 +77,7 @@ export async function loadWasi(
         context.start({
           exports: {
             memory,
-            _start: () => {},
+            _start: () => { },
           },
         });
       }

src/polyfills/node-wasi.ts

@@ -1,5 +1,5 @@
 import { WASI } from 'wasi';
-import { type InternalWasi } from '../interfaces.ts';
+import { type WASIOptions, type InternalWasi } from '../interfaces.ts';
 import { devNull } from 'node:os';
 import { open } from 'node:fs/promises';
 import { closeSync } from 'node:fs';
@@ -26,7 +26,7 @@ async function createDevNullFDs() {
     fr.register(stdout, stdout.fd);
     close = async () => {
       needsClose = false;
-      await Promise.all([stdin.close(), stdout.close()]).catch(() => {});
+      await Promise.all([stdin.close(), stdout.close()]).catch(() => { });
     };
   }
 
@@ -39,11 +39,12 @@ async function createDevNullFDs() {
 export async function loadWasi(
   allowedPaths: { [from: string]: string },
   enableWasiOutput: boolean,
+  _wasiOptions: WASIOptions | null,
 ): Promise<InternalWasi> {
   const {
     close,
     fds: [stdin, stdout, stderr],
-  } = enableWasiOutput ? { async close() {}, fds: [0, 1, 2] } : await createDevNullFDs();
+  } = enableWasiOutput ? { async close() { }, fds: [0, 1, 2] } : await createDevNullFDs();
 
   const context = new WASI({
     version: 'preview1',
@@ -87,7 +88,7 @@ export async function loadWasi(
         context.start({
           exports: {
             memory,
-            _start: () => {},
+            _start: () => { },
           },
         });
       }