syscall/js: make wasm_exec.js compatible with Webpack

In Webpack, require("fs") will always be empty. This behavior throws an error: "fs.writeSync is not function". It happens when you did "fmt.Println".
This PR avoids such problem and use polyfill in wasm_exec.js on Webpack.

Change-Id: I55f2c75ce86b7f84d2d92e8e217b5decfbe3c8a1
GitHub-Last-Rev: aecc847e3f9d5617ea4b00196ef2810c2458f085
GitHub-Pull-Request: golang/go#35805
Reviewed-on: https://go-review.googlesource.com/c/go/+/208600
Reviewed-by: Richard Musiol <neelance@gmail.com>

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index 8cb297f3793f6fbf454489616785cdaceaa365c2..a99aaeda071876154af07eb7265341faee6e03ea 100644 (file)
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -27,7 +27,10 @@
        }
 
        if (!global.fs && global.require) {
-               global.fs = require("fs");
+               const fs = require("fs");
+               if (Object.keys(fs) !== 0) {
+                       global.fs = fs;
+               }
        }
 
        const enosys = () => {