misc/wasm: better adapt to different JavaScript environments

This change adds support for using wasm with Electron. It refactors
environment detection to a more modular approach instead of explicitly
testing for Node.js.

Fixes #29404

Change-Id: I882a9c56523744e7fd7cb2013d158df91cf91d14
Reviewed-on: https://go-review.googlesource.com/c/164665
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index 165d567750506b58450e4b90735b71925c949355..8eff751d62a14b2daa3a39a8171f09107900fee4 100644 (file)
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -3,6 +3,15 @@
 // license that can be found in the LICENSE file.
 
 (() => {
+       // Map multiple JavaScript environments to a single common API,
+       // preferring web standards over Node.js API.
+       //
+       // Environments considered:
+       // - Browsers
+       // - Node.js
+       // - Electron
+       // - Parcel
+
        if (typeof global !== "undefined") {
                // global already exists
        } else if (typeof window !== "undefined") {
@@ -13,30 +22,15 @@
                throw new Error("cannot export Go (neither global, window nor self is defined)");
        }
 
-       // Map web browser API and Node.js API to a single common API (preferring web standards over Node.js API).
-       const isNodeJS = global.process && global.process.title === "node";
-       if (isNodeJS) {
+       if (!global.require && typeof require !== "undefined") {
                global.require = require;
-               global.fs = require("fs");
-
-               const nodeCrypto = require("crypto");
-               global.crypto = {
-                       getRandomValues(b) {
-                               nodeCrypto.randomFillSync(b);
-                       },
-               };
+       }
 
-               global.performance = {
-                       now() {
-                               const [sec, nsec] = process.hrtime();
-                               return sec * 1000 + nsec / 1000000;
-                       },
-               };
+       if (!global.fs && global.require) {
+               global.fs = require("fs");
+       }
 
-               const util = require("util");
-               global.TextEncoder = util.TextEncoder;
-               global.TextDecoder = util.TextDecoder;
-       } else {
+       if (!global.fs) {
                let outputBuf = "";
                global.fs = {
                        constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
@@ -72,6 +66,34 @@
                };
        }
 
+       if (!global.crypto) {
+               const nodeCrypto = require("crypto");
+               global.crypto = {
+                       getRandomValues(b) {
+                               nodeCrypto.randomFillSync(b);
+                       },
+               };
+       }
+
+       if (!global.performance) {
+               global.performance = {
+                       now() {
+                               const [sec, nsec] = process.hrtime();
+                               return sec * 1000 + nsec / 1000000;
+                       },
+               };
+       }
+
+       if (!global.TextEncoder) {
+               global.TextEncoder = require("util").TextEncoder;
+       }
+
+       if (!global.TextDecoder) {
+               global.TextDecoder = require("util").TextDecoder;
+       }
+
+       // End of polyfills for common API.
+
        const encoder = new TextEncoder("utf-8");
        const decoder = new TextDecoder("utf-8");
 
@@ -439,7 +461,13 @@
                }
        }
 
-       if (isNodeJS) {
+       if (
+               global.require &&
+               global.require.main === module &&
+               global.process &&
+               global.process.versions &&
+               !global.process.versions.electron
+       ) {
                if (process.argv.length < 3) {
                        process.stderr.write("usage: go_js_wasm_exec [wasm binary] [arguments]\n");
                        process.exit(1);