PackageToJS: Import only the UWASI features Swift needs by default

The UWASI platform wrappers imported `useAll` and `MemoryFileSystem`,
so bundles always carried UWASI's in-memory file system and came out
larger than the browser_wasi_shim default. Import `useStdio`, `useArgs`,
`useEnviron`, `useClock`, `usePoll`, `useProc` and `useRandom` instead.
File syscalls now return ENOSYS.

Test builds keep the file system, because code coverage reads the
profile through `extractFile`.

Author: krodak

Plugins/PackageToJS/README.md

@@ -22,6 +22,11 @@ to generate browser and Node platform wrappers backed by `uwasi` instead:
 swift package --swift-sdk wasm32-unknown-wasi js --wasi-runtime uwasi
 ```
 
+The `uwasi` wrappers import only the stdio, args, environ, clock, poll, proc and
+random features, so bundlers can drop `uwasi`'s file system and file syscalls return
+`ENOSYS`. Test builds keep an in-memory file system for code coverage. To give an
+application a file system, pass your own `wasi` object to `instantiate`.
+
 The generated browser main-thread setup rejects blocking WASI waits. Run guests that
 require `poll_oneoff` clock waits in a worker. Node and browser workers use `uwasi`'s
 blocking implementation.

Plugins/PackageToJS/Sources/PackageToJS.swift

@@ -25,6 +25,8 @@ struct PackageToJS {
         var defaultPlatform: Platform = .browser
         /// WASI runtime used by generated JavaScript (default: browser-wasi-shim)
         var wasiRuntime: WASIRuntime = .browserWASIShim
+        /// Whether the uwasi runtime provides an in-memory file system (default: false; true for tests)
+        var wasiFilesystem: Bool = false
         /// Whether to explain the build plan (default: false)
         var explain: Bool = false
         /// Whether to print verbose output
@@ -957,6 +959,7 @@ struct PackagingPlanner {
         let staticConditions: [String: Bool] = [
             "USE_WASI_CDN": options.useCDN,
             "USE_UWASI": options.wasiRuntime == .uwasi,
+            "USE_UWASI_FILESYSTEM": options.wasiRuntime == .uwasi && options.wasiFilesystem,
             "HAS_BRIDGE": skeletons.count > 0,
             "HAS_IMPORTS": skeletons.count > 0,
             "TARGET_DEFAULT_PLATFORM_NODE": options.defaultPlatform == .node,

Plugins/PackageToJS/Sources/PackageToJSPlugin.swift

@@ -731,6 +731,7 @@ extension PackageToJS.TestOptions {
         if !options.buildOnly, !options.packageOptions.useCDN {
             options.packageOptions.useCDN = true
         }
+        options.packageOptions.wasiFilesystem = true
 
         return options
     }

Plugins/PackageToJS/Templates/platforms/browser.js

@@ -2,13 +2,24 @@
 import { MODULE_PATH /* #if USE_SHARED_MEMORY */, MEMORY_TYPE /* #endif */} from "../instantiate.js"
 /* #if IS_WASI */
 /* #if USE_UWASI */
+import { browserMainThreadSleep, createUwasi } from './uwasi.js';
+/* #if USE_UWASI_FILESYSTEM */
 /* #if USE_WASI_CDN */
 // @ts-ignore
-import { WASI, MemoryFileSystem, useAll, lineBuffered } from 'https://cdn.jsdelivr.net/npm/uwasi@1.5.2/+esm';
+import { WASI, lineBuffered, MemoryFileSystem, useAll } from 'https://cdn.jsdelivr.net/npm/uwasi@1.5.2/+esm';
 /* #else */
-import { WASI, MemoryFileSystem, useAll, lineBuffered } from 'uwasi';
+import { WASI, lineBuffered, MemoryFileSystem, useAll } from 'uwasi';
+/* #endif */
+const uwasiRuntime = { WASI, lineBuffered, MemoryFileSystem, useAll };
+/* #else */
+/* #if USE_WASI_CDN */
+// @ts-ignore
+import { WASI, lineBuffered, useStdio, useArgs, useEnviron, useClock, usePoll, useProc, useRandom } from 'https://cdn.jsdelivr.net/npm/uwasi@1.5.2/+esm';
+/* #else */
+import { WASI, lineBuffered, useStdio, useArgs, useEnviron, useClock, usePoll, useProc, useRandom } from 'uwasi';
+/* #endif */
+const uwasiRuntime = { WASI, lineBuffered, useStdio, useArgs, useEnviron, useClock, usePoll, useProc, useRandom };
 /* #endif */
-import { browserMainThreadSleep, createUwasi } from './uwasi.js';
 /* #else */
 /* #if USE_WASI_CDN */
 // @ts-ignore
@@ -38,10 +49,7 @@ export async function defaultBrowserThreadSetup() {
 
 /* #if IS_WASI */
 /* #if USE_UWASI */
-    const { wasi } = createUwasi(
-        { WASI, MemoryFileSystem, useAll, lineBuffered },
-        { modulePath: MODULE_PATH }
-    )
+    const { wasi } = createUwasi(uwasiRuntime, { modulePath: MODULE_PATH })
 /* #else */
     const wasi = new WASI(/* args */[MODULE_PATH], /* env */[], /* fd */[
         new OpenFile(new File([])), // stdin
@@ -127,16 +135,13 @@ export async function defaultBrowserSetup(options) {
     const onStdoutLine = options.onStdoutLine ?? ((line) => console.log(line))
     const onStderrLine = options.onStderrLine ?? ((line) => console.error(line))
 /* #if USE_UWASI */
-    const { wasi } = createUwasi(
-        { WASI, MemoryFileSystem, useAll, lineBuffered },
-        {
-            modulePath: MODULE_PATH,
-            args,
-            onStdoutLine,
-            onStderrLine,
-            sleep: browserMainThreadSleep(),
-        }
-    )
+    const { wasi } = createUwasi(uwasiRuntime, {
+        modulePath: MODULE_PATH,
+        args,
+        onStdoutLine,
+        onStderrLine,
+        sleep: browserMainThreadSleep(),
+    })
 /* #else */
     const wasi = new WASI(/* args */[MODULE_PATH, ...args], /* env */[], /* fd */[
         new OpenFile(new File([])), // stdin

Plugins/PackageToJS/Templates/platforms/node.js

@@ -4,8 +4,14 @@ import { Worker, parentPort } from "node:worker_threads";
 import { MODULE_PATH /* #if USE_SHARED_MEMORY */, MEMORY_TYPE /* #endif */} from "../instantiate.js"
 /* #if IS_WASI */
 /* #if USE_UWASI */
-import { WASI, MemoryFileSystem, useAll, lineBuffered } from 'uwasi';
 import { createUwasi } from './uwasi.js';
+/* #if USE_UWASI_FILESYSTEM */
+import { WASI, lineBuffered, MemoryFileSystem, useAll } from 'uwasi';
+const uwasiRuntime = { WASI, lineBuffered, MemoryFileSystem, useAll };
+/* #else */
+import { WASI, lineBuffered, useStdio, useArgs, useEnviron, useClock, usePoll, useProc, useRandom } from 'uwasi';
+const uwasiRuntime = { WASI, lineBuffered, useStdio, useArgs, useEnviron, useClock, usePoll, useProc, useRandom };
+/* #endif */
 /* #else */
 import { WASI, File, OpenFile, ConsoleStdout, PreopenDirectory, Directory, Inode } from '@bjorn3/browser_wasi_shim';
 /* #endif */
@@ -28,10 +34,7 @@ export async function defaultNodeThreadSetup() {
     }
 
 /* #if USE_UWASI */
-    const { wasi } = createUwasi(
-        { WASI, MemoryFileSystem, useAll, lineBuffered },
-        { modulePath: MODULE_PATH }
-    )
+    const { wasi } = createUwasi(uwasiRuntime, { modulePath: MODULE_PATH })
 /* #else */
     const wasi = new WASI(/* args */[MODULE_PATH], /* env */[], /* fd */[
         new OpenFile(new File([])), // stdin
@@ -136,14 +139,11 @@ export async function defaultNodeSetup(options = {}) {
 
     const args = options.args ?? process.argv.slice(2)
 /* #if USE_UWASI */
-    const { wasi } = createUwasi(
-        { WASI, MemoryFileSystem, useAll, lineBuffered },
-        {
-            modulePath: MODULE_PATH,
-            args,
-            withExtractFile: true,
-        }
-    )
+    const { wasi } = createUwasi(uwasiRuntime, {
+        modulePath: MODULE_PATH,
+        args,
+        withExtractFile: true,
+    })
 /* #else */
     const rootFs = new Map();
     const wasi = new WASI(/* args */[MODULE_PATH, ...args], /* env */[], /* fd */[

Plugins/PackageToJS/Templates/platforms/uwasi.js

@@ -17,7 +17,19 @@ export function browserMainThreadSleep() {
 }
 
 /**
- * @param {{ WASI: any, MemoryFileSystem: any, useAll: any, lineBuffered: any }} runtime
+ * @param {{
+ *   WASI: any,
+ *   lineBuffered: any,
+ *   MemoryFileSystem?: any,
+ *   useAll?: any,
+ *   useStdio?: any,
+ *   useArgs?: any,
+ *   useEnviron?: any,
+ *   useClock?: any,
+ *   usePoll?: any,
+ *   useProc?: any,
+ *   useRandom?: any,
+ * }} runtime
  * @param {{
  *   modulePath: string,
  *   args?: string[],
@@ -32,27 +44,39 @@ export function createUwasi(runtime, options) {
     const onStdoutLine = options.onStdoutLine ?? ((line) => console.log(line));
     const onStderrLine =
         options.onStderrLine ?? ((line) => console.error(line));
-    const fileSystem = new runtime.MemoryFileSystem({ "/": "/" });
-    const stdout = runtime.lineBuffered(onStdoutLine);
-    const stderr = runtime.lineBuffered(onStderrLine);
+    const stdio = {
+        stdin: () => "",
+        stdout: runtime.lineBuffered(onStdoutLine),
+        stderr: runtime.lineBuffered(onStderrLine),
+        outputBuffers: true,
+    };
+    const fileSystem = runtime.MemoryFileSystem
+        ? new runtime.MemoryFileSystem({ "/": "/" })
+        : undefined;
+    const features = fileSystem
+        ? [
+              runtime.useAll({
+                  withFileSystem: fileSystem,
+                  withStdio: stdio,
+                  sleep: options.sleep,
+              }),
+          ]
+        : [
+              runtime.useStdio(stdio),
+              runtime.useArgs(),
+              runtime.useEnviron(),
+              runtime.useClock(),
+              runtime.usePoll({ sleep: options.sleep }),
+              runtime.useProc(),
+              runtime.useRandom(),
+          ];
     const wasi = new runtime.WASI({
         args: [options.modulePath, ...args],
         env: {},
-        features: [
-            runtime.useAll({
-                withFileSystem: fileSystem,
-                withStdio: {
-                    stdin: () => "",
-                    stdout,
-                    stderr,
-                    outputBuffers: true,
-                },
-                sleep: options.sleep,
-            }),
-        ],
+        features,
     });
 
-    if (options.withExtractFile) {
+    if (fileSystem && options.withExtractFile) {
         Object.assign(wasi, {
             extractFile(filePath) {
                 const node = fileSystem.lookup(filePath);