misc/wasm: Go's WASM shim breaks in Node v19

[evanw]

What version of Go are you using (go version)?

$ go version
go version go1.19.1 linux/amd64

Does this issue reproduce with the latest release?

Presumably, because the problematic code is still there in the latest commit.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/evan/.cache/go-build"
GOENV="/home/evan/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/evan/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/evan/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/evan/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/evan/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.19.1"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build4187052113=/tmp/go-build -gno-record-gcc-switches"

What did you do?

1. Install node v19 from here: https://nodejs.org/dist/v19.1.0/
2. Make a simple hello world go program
3. Built it with GOOS=js GOARCH=wasm go build main.go
4. Run it with node $(go env GOPATH)/misc/wasm/wasm_exec_node.js main

What did you expect to see?

Hello world

What did you see instead?

/home/evan/go/misc/wasm/wasm_exec_node.js:25
globalThis.crypto = {
                  ^

TypeError: Cannot set property crypto of #<Object> which has only a getter
    at Object.<anonymous> (/home/evan/go/misc/wasm/wasm_exec_node.js:25:19)
    at Module._compile (node:internal/modules/cjs/loader:1205:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1259:10)
    at Module.load (node:internal/modules/cjs/loader:1068:32)
    at Module._load (node:internal/modules/cjs/loader:909:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:82:12)
    at node:internal/main/run_main_module:23:47

Node.js v19.1.0

I assume this recent Node change is the cause: nodejs/node#44897. Here's one possible fix:

diff --git a/wasm_exec_node.js b/wasm_exec_node.js
index f9200ca..2b424a2 100644
--- a/wasm_exec_node.js
+++ b/wasm_exec_node.js
@@ -22,11 +22,13 @@ globalThis.performance = {
 };
 
 const crypto = require("crypto");
-globalThis.crypto = {
-       getRandomValues(b) {
-               crypto.randomFillSync(b);
+Object.defineProperty(globalThis, 'crypto', {
+       value: {
+               getRandomValues(b) {
+                       crypto.randomFillSync(b);
+               },
        },
-};
+});
 
 require("./wasm_exec");

For further context, this bug was reported to me by a user of esbuild here: evanw/esbuild#2683

[seankhliao]

cc @golang/wasm

[neelance]

I think we can simply drop these shims because the latest Node.js v18 LTS already has them built-in. Our support policy is only to support the active LTS version.

[neelance]

Oops, not entirely true. Node.js v18 has crypto.getRandomValues, but it does not load crypto by default. So we still need:

globalThis.crypto ??= require('crypto');

[johanbrandhorst]

Using the suggested fix would require upgrading our js-wasm builders to LTS 18, so I've opened #57017 to track this effort. Assuming we can get that done I have confirmed locally that the suggested fix works (for both 18 and 19).

[gopherbot]

Change https://go.dev/cl/455415 mentions this issue: misc/wasm: migrate support to Node 18 LTS

[dmitshur]

As I understand, the fix suggested in #56860 (comment) (and currently implemented in CL 455415) intentionally drops compatibility with Node 14 ('??=' is too new of a syntax for it; see log). That's fine to do if desired, but submitting that CL will require us to turn off the TryBot part of the current js-wasm builder with Node 14.

Note that the new js-wasm-node18 builder can't be made a TryBot until all.bash is passing on it. If that will take some investigation work (see #57614), maybe it'd be worth it to have all that ready first, to keep a small gap in TryBot coverage during the time when neither js-wasm nor js-wasm-node18 builder is passing.

Another possible path is to maintain compatibility with Node 18 and 14 only during the transition, and then drop anything only needed for Node 14 afterwards.

I think whichever path is easier for the CL author(s) is fine.