wasi: introduce initial WASI support

Co-authored-by: Gus Caplan <me@gus.host>
Co-authored-by: Daniel Bevenius <daniel.bevenius@gmail.com>
Co-authored-by: Jiawen Geng <technicalcute@gmail.com>
Co-authored-by: Tobias Nießen <tniessen@tnie.de>
Co-authored-by: Chengzhong Wu <legendecas@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/30258
Refs: https://github.com/nodejs/node/pull/27850
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Wyatt Preul <wpreul@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

4 files changed, 114 insertions, 0 deletions

diff --git a/lib/internal/bootstrap/loaders.js b/lib/internal/bootstrap/loaders.js
index cfefc56bd8..044bea3114 100644
--- a/lib/internal/bootstrap/loaders.js
+++ b/lib/internal/bootstrap/loaders.js
@@ -157,6 +157,9 @@ function NativeModule(id) {
   this.loaded = false;
   this.loading = false;
   this.canBeRequiredByUsers = !id.startsWith('internal/');
+
+  if (id === 'wasi')
+    this.canBeRequiredByUsers = !!internalBinding('config').experimentalWasi;
 }
 
 // To be called during pre-execution when --expose-internals is on.
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
index ee467f31f3..88a38f5e1d 100644
--- a/lib/internal/errors.js
+++ b/lib/internal/errors.js
@@ -1229,6 +1229,7 @@ E('ERR_VM_MODULE_LINKING_ERRORED',
 E('ERR_VM_MODULE_NOT_MODULE',
   'Provided module is not an instance of Module', Error);
 E('ERR_VM_MODULE_STATUS', 'Module status %s', Error);
+E('ERR_WASI_ALREADY_STARTED', 'WASI instance has already started', Error);
 E('ERR_WORKER_INVALID_EXEC_ARGV', (errors) =>
   `Initiated Worker with invalid execArgv flags: ${errors.join(', ')}`,
   Error);
diff --git a/lib/internal/modules/cjs/helpers.js b/lib/internal/modules/cjs/helpers.js
index f7155c4aa1..2d73219a77 100644
--- a/lib/internal/modules/cjs/helpers.js
+++ b/lib/internal/modules/cjs/helpers.js
@@ -117,6 +117,11 @@ const builtinLibs = [
   'v8', 'vm', 'worker_threads', 'zlib'
 ];
 
+if (internalBinding('config').experimentalWasi) {
+  builtinLibs.push('wasi');
+  builtinLibs.sort();
+}
+
 if (typeof internalBinding('inspector').open === 'function') {
   builtinLibs.push('inspector');
   builtinLibs.sort();
diff --git a/lib/wasi.js b/lib/wasi.js
new file mode 100644
index 0000000000..65b8473624
--- /dev/null
+++ b/lib/wasi.js
@@ -0,0 +1,105 @@
+'use strict';
+/* global WebAssembly */
+const {
+  ArrayIsArray,
+  ArrayPrototypeForEach,
+  ArrayPrototypeMap,
+  FunctionPrototypeBind,
+  ObjectKeys
+} = primordials;
+const {
+  ERR_INVALID_ARG_TYPE,
+  ERR_WASI_ALREADY_STARTED
+} = require('internal/errors').codes;
+const { emitExperimentalWarning } = require('internal/util');
+const { WASI: _WASI } = internalBinding('wasi');
+const kSetMemory = Symbol('setMemory');
+const kStarted = Symbol('started');
+
+emitExperimentalWarning('WASI');
+
+
+class WASI {
+  constructor(options = {}) {
+    if (options === null || typeof options !== 'object')
+      throw new ERR_INVALID_ARG_TYPE('options', 'object', options);
+
+    // eslint-disable-next-line prefer-const
+    let { args, env, preopens } = options;
+
+    if (ArrayIsArray(args))
+      args = ArrayPrototypeMap(args, (arg) => { return String(arg); });
+    else if (args === undefined)
+      args = [];
+    else
+      throw new ERR_INVALID_ARG_TYPE('options.args', 'Array', args);
+
+    const envPairs = [];
+
+    if (env !== null && typeof env === 'object') {
+      for (const key in env) {
+        const value = env[key];
+        if (value !== undefined)
+          envPairs.push(`${key}=${value}`);
+      }
+    } else if (env !== undefined) {
+      throw new ERR_INVALID_ARG_TYPE('options.env', 'Object', env);
+    }
+
+    const preopenArray = [];
+
+    if (typeof preopens === 'object' && preopens !== null) {
+      ArrayPrototypeForEach(ObjectKeys(preopens), (key) => {
+        preopenArray.push(String(key));
+        preopenArray.push(String(preopens[key]));
+      });
+    } else if (preopens !== undefined) {
+      throw new ERR_INVALID_ARG_TYPE('options.preopens', 'Object', preopens);
+    }
+
+    const wrap = new _WASI(args, envPairs, preopenArray);
+
+    for (const prop in wrap) {
+      wrap[prop] = FunctionPrototypeBind(wrap[prop], wrap);
+    }
+
+    this[kSetMemory] = wrap._setMemory;
+    delete wrap._setMemory;
+    this.wasiImport = wrap;
+    this[kStarted] = false;
+  }
+
+  start(instance) {
+    if (!(instance instanceof WebAssembly.Instance)) {
+      throw new ERR_INVALID_ARG_TYPE(
+        'instance', 'WebAssembly.Instance', instance);
+    }
+
+    const exports = instance.exports;
+
+    if (exports === null || typeof exports !== 'object')
+      throw new ERR_INVALID_ARG_TYPE('instance.exports', 'Object', exports);
+
+    const { memory } = exports;
+
+    if (!(memory instanceof WebAssembly.Memory)) {
+      throw new ERR_INVALID_ARG_TYPE(
+        'instance.exports.memory', 'WebAssembly.Memory', memory);
+    }
+
+    if (this[kStarted]) {
+      throw new ERR_WASI_ALREADY_STARTED();
+    }
+
+    this[kStarted] = true;
+    this[kSetMemory](memory);
+
+    if (exports._start)
+      exports._start();
+    else if (exports.__wasi_unstable_reactor_start)
+      exports.__wasi_unstable_reactor_start();
+  }
+}
+
+
+module.exports = { WASI };