Inject stdout/stderr as character device by consolePrinter

Since the upstream `@bjorn3/browser_wasi_shim` intentionally offloads
stdout/stderr handling to application, we need to do it in our side.

Author: kateinoigakukun

packages/npm-packages/ruby-wasm-wasi/src/browser.ts

@@ -1,4 +1,4 @@
-import { Fd, File, OpenFile, WASI } from "@bjorn3/browser_wasi_shim";
+import { Fd, WASI } from "@bjorn3/browser_wasi_shim";
 import { RubyVM } from "./index.js";
 import { consolePrinter } from "./console.js";
 
@@ -18,31 +18,7 @@ export const DefaultRubyVM = async (
     ([k, v]) => `${k}=${v}`,
   );
 
-  // WORKAROUND: `@bjorn3/browser_wasi_shim` does not set proper rights
-  // and filetypes for stdout and stderr, but wasi-libc's fcntl(2) respects
-  // rights and  CRuby checks it. So we need to override `fd_fdstat_get` here.
-  const FILETYPE_CHARACTER_DEVICE = 2;
-  class Stdout extends OpenFile {
-    fd_filestat_get() {
-      const { ret, filestat } = super.fd_filestat_get();
-      filestat.filetype = FILETYPE_CHARACTER_DEVICE;
-      return { ret, filestat };
-    }
-
-    fd_fdstat_get() {
-      const { ret, fdstat } = super.fd_fdstat_get();
-      const RIGHTS_FD_WRITE = BigInt(1);
-      fdstat.fs_filetype = FILETYPE_CHARACTER_DEVICE;
-      fdstat.fs_rights_base = RIGHTS_FD_WRITE;
-      return { ret, fdstat };
-    }
-  }
-
-  const fds: Fd[] = [
-    new OpenFile(new File([])), // stdin
-    new Stdout(new File([])), // stdout
-    new Stdout(new File([])), // stderr
-  ];
+  const fds: Fd[] = [];
   const wasi = new WASI(args, env, fds, { debug: false });
   const vm = new RubyVM();
 

packages/npm-packages/ruby-wasm-wasi/src/console.ts

@@ -37,35 +37,39 @@ export function consolePrinter(
   },
 ) {
   let memory: WebAssembly.Memory | undefined = undefined;
-  let view: DataView | undefined = undefined;
+  let _view: DataView | undefined = undefined;
+
+  function getMemoryView(): DataView {
+    if (typeof memory === "undefined") {
+      throw new Error("Memory is not set");
+    }
+    if (_view === undefined || _view.buffer.byteLength === 0) {
+      _view = new DataView(memory.buffer);
+    }
+    return _view;
+  }
 
   const decoder = new TextDecoder();
 
   return {
     addToImports(imports: WebAssembly.Imports): void {
-      const original = imports.wasi_snapshot_preview1.fd_write as (
-        fd: number,
-        iovs: number,
-        iovsLen: number,
-        nwritten: number,
-      ) => number;
-      imports.wasi_snapshot_preview1.fd_write = (
-        fd: number,
-        iovs: number,
-        iovsLen: number,
-        nwritten: number,
-      ): number => {
+      const wasiImport = imports.wasi_snapshot_preview1 as {
+        fd_write: (
+          fd: number,
+          iovs: number,
+          iovsLen: number,
+          nwritten: number,
+        ) => number;
+        fd_filestat_get: (fd: number, filestat: number) => number;
+        fd_fdstat_get: (fd: number, fdstat: number) => number;
+      };
+      const original_fd_write = wasiImport.fd_write;
+      wasiImport.fd_write = (fd, iovs, iovsLen, nwritten): number => {
         if (fd !== 1 && fd !== 2) {
-          return original(fd, iovs, iovsLen, nwritten);
-        }
-
-        if (typeof memory === "undefined" || typeof view === "undefined") {
-          throw new Error("Memory is not set");
-        }
-        if (view.buffer.byteLength === 0) {
-          view = new DataView(memory.buffer);
+          return original_fd_write(fd, iovs, iovsLen, nwritten);
         }
 
+        const view = getMemoryView();
         const buffers = Array.from({ length: iovsLen }, (_, i) => {
           const ptr = iovs + i * 8;
           const buf = view.getUint32(ptr, true);
@@ -86,10 +90,44 @@ export function consolePrinter(
 
         return 0;
       };
+
+      const original_fd_filestat_get = wasiImport.fd_filestat_get;
+      wasiImport.fd_filestat_get = (fd, filestat): number => {
+        if (fd !== 1 && fd !== 2) {
+          return original_fd_filestat_get(fd, filestat);
+        }
+
+        const view = getMemoryView();
+        const result = original_fd_filestat_get(fd, filestat);
+        if (result !== 0) {
+          return result;
+        }
+
+        const filetypePtr = filestat + 0;
+        view.setUint8(filetypePtr, 2); // FILETYPE_CHARACTER_DEVICE
+
+        return 0;
+      };
+
+      const original_fd_fdstat_get = wasiImport.fd_fdstat_get;
+      wasiImport.fd_fdstat_get = (fd, fdstat): number => {
+        if (fd !== 1 && fd !== 2) {
+          return original_fd_fdstat_get(fd, fdstat);
+        }
+
+        const view = getMemoryView();
+
+        const fs_filetypePtr = fdstat + 0;
+        view.setUint8(fs_filetypePtr, 2); // FILETYPE_CHARACTER_DEVICE
+
+        const fs_rights_basePtr = fdstat + 8;
+        view.setBigUint64(fs_rights_basePtr, BigInt(1)); // RIGHTS_FD_WRITE
+
+        return 0;
+      };
     },
     setMemory(m: WebAssembly.Memory) {
       memory = m;
-      view = new DataView(m.buffer);
     },
   };
 }

packages/npm-packages/ruby-wasm-wasi/tools/run-test-unit.mjs

@@ -109,31 +109,11 @@ const instantiateWasmerWasi = async (rootTestFile) => {
     "RUBY_FIBER_MACHINE_STACK_SIZE": String(1024 * 1024 * 20),
   }).map(([key, value]) => `${key}=${value}`);
 
-  // WORKAROUND: `@bjorn3/browser_wasi_shim` does not set proper rights
-  // for stdout and stderr, but wasi-libc's fcntl(2) respects rights and
-  // CRuby checks it. So we need to override `fd_fdstat_get` here.
-  const FILETYPE_CHARACTER_DEVICE = 2;
-  class Stdout extends browserWasi.OpenFile {
-    fd_filestat_get() {
-      const { ret, filestat } = super.fd_filestat_get();
-      filestat.filetype = FILETYPE_CHARACTER_DEVICE;
-      return { ret, filestat };
-    }
-
-    fd_fdstat_get() {
-      const { ret, fdstat } = super.fd_fdstat_get();
-      const RIGHTS_FD_WRITE = BigInt(1);
-      const RIGHTS_FD_TELL = BigInt(1) << BigInt(5);
-      fdstat.fs_filetype = FILETYPE_CHARACTER_DEVICE;
-      fdstat.fs_rights_base = RIGHTS_FD_WRITE;
-      return { ret, fdstat };
-    }
-  }
 
   const fds = [
     new browserWasi.OpenFile(new browserWasi.File([])),
-    new Stdout(new browserWasi.File([])),
-    new Stdout(new browserWasi.File([])),
+    new browserWasi.OpenFile(new browserWasi.File([])),
+    new browserWasi.OpenFile(new browserWasi.File([])),
     new browserWasi.PreopenDirectory("/__root__", __root__.contents)
   ]