panic: mkdir /tmp/jsii-runtime: not implemented on js wasm_exec.js

[Hunter-Thompson]

🐛 Bug Report

Affected Languages

• TypeScript or Javascript
• Python
• Java
• .NET (C#, F#, ...)
• Go

General Information

• JSII Version: 1.46.0
• Platform: Firefox on Ubuntu Linux : )

What is the problem?

While running cdk8s synth from the browser using web assembly for Golang, I get the following JSII Runtime errors.

Verbose Log

panic: mkdir /tmp/jsii-runtime.843980924: not implemented on js wasm_exec.js:51:14
<empty string> wasm_exec.js:51:14
goroutine 1 [running]: wasm_exec.js:51:14
github.com/aws/jsii-runtime-go/internal/kernel.GetClient.func1() wasm_exec.js:51:14
	/build/vendor/github.com/aws/jsii-runtime-go/internal/kernel/client.go:44 +0xd wasm_exec.js:51:14
sync.(*Once).doSlow(0x2372058, 0x690828) wasm_exec.js:51:14
	/usr/local/go/src/sync/once.go:68 +0x9 wasm_exec.js:51:14
sync.(*Once).Do(0x2372058, 0x690828) wasm_exec.js:51:14
	/usr/local/go/src/sync/once.go:59 +0x6 wasm_exec.js:51:14
github.com/aws/jsii-runtime-go/internal/kernel.GetClient() wasm_exec.js:51:14
	/build/vendor/github.com/aws/jsii-runtime-go/internal/kernel/client.go:37 +0x2 wasm_exec.js:51:14
github.com/aws/jsii-runtime-go/runtime.RegisterClass({0x458a63, 0x14}, {0x8d1d30, 0x26fdc0}, {0x24a3750, 0x4, 0x4}, 0x6907e0) wasm_exec.js:51:14
	/build/vendor/github.com/aws/jsii-runtime-go/runtime/runtime.go:50 +0x2 wasm_exec.js:51:14
github.com/aws/constructs-go/constructs/v3.init.0() wasm_exec.js:51:14
	/build/vendor/github.com/aws/constructs-go/constructs/v3/constructs.init.go:10 +0x12

Notes

1. The stack traces to a function called TempDir() which calls os.MkdirTemp()
2. Related issue: Support creating temporary files and directories WebAssembly/WASI#306

Reproduction Repo

https://github.com/Hunter-Thompson/jsii-webasembly-bug

[Hunter-Thompson]

I can write a small example project that can be viewed publicly so that this issue can be reproduced if required.

[NGL321]

Thank you for reporting this @Hunter-Thompson!

A gist or repo with reproduction code and steps would almost certainly be helpful!

[Hunter-Thompson]

@NGL321 I created a repo with all the code, and very minimal reproduction steps.

https://github.com/Hunter-Thompson/jsii-webasembly-bug

[RomainMuller]

Yeah, the jsii runtime needs to be able to access the file system in order to operate properly. It creates a temporary directory in which it will unpack NPM modules to load them up in a Node/JS VM.

If your environment does not support the fs module of the node standard library, then it is not supported at the moment, unfortunately.

[Hunter-Thompson]

Yeah, the jsii runtime needs to be able to access the file system in order to operate properly. It creates a temporary directory in which it will unpack NPM modules to load them up in a Node/JS VM.

This seems to be quite an important step. Maintainers can close this issue if they don't think there is an alternative to this in the near future.

[github-actions]

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