Is it possible to write files from within a plugin?

[ole-treichel]

I want to use a plugin to extract things from a JS file (e.g. ˋpropTypesˋ) and write them to a seperate file on disk.

[kwonoj]

There is a limited filesystem access for /cwd to current working directory, if plugin is compiled as wasi target.

[kwonoj]

There isn't so far I know, except PR enables /cwd alias itself if you'd like to see how it is exposed. Using fs access is not much different anyway other than it only allows known explicit path alias.

[ole-treichel]

Thanks. I still can't make it work, sorry if I misunderstood. I tried the following in my plugin:

let data = "Some data";
let out_path = env::current_dir().expect("Failed to get cwd").join("test.txt");

println!("out_path: {}", out_path.display());

fs::write(out_path, data).expect("Unable to write file");

This does not work, permission is denied:

thread '<unnamed>' panicked at 'Unable to write file: Os { code: 2, kind: PermissionDenied, message: "Permission denied" }'

I can also see that cwd is just /. I tried hardcoding the path to the project directory, but no luck either. It cannot find the directory then (which I guess makes sense if the cwd is "mounted" inside wasi as /.

I am using (almost) the latest swc crates / npm-packages:

swc_plugin = "=0.57.0"
serde = "1.0.117"

"devDependencies": {
    "@swc/cli": "0.1.57",
    "@swc/core": "1.2.204"
}

[kwonoj]

You should use mounted dir, any attempt to calculate actual physical path including env::current_dir is expected to fail. Since plugin runs in the sandboxed context, you only get access to current dir's mounted alias.

[ole-treichel]

Could you give an example with fs? Sorry, I don't really understand what you mean by "mounted" directory, is this a special path?

[ole-treichel]

Nvm got it: the mounted directory is /cwd, so this works:

let data = "Some data";

println!("out_path: {}", out_path.display());

fs::write("/cwd/test.txt", data).expect("Unable to write file");

Appreciate your help!

[romanusname]

I can't add text to a file. fs::write("/cwd/test.txt", data).expect("Unable to write file"); completely overwrites it. And when I try to read I get an error. Can you add new text to a file?

[kwonoj]

https://doc.rust-lang.org/std/fs/fn.write.html

This function will create a file if it does not exist, and will entirely replace its contents if it does.

[romanusname]

https://doc.rust-lang.org/std/fs/fn.write.html

This function will create a file if it does not exist, and will entirely replace its contents if it does.

"Write a slice as the entire contents of a file.". The file says "Hello", you need to add "World". CWS does not read files. I created a separate question. Look here please. i really need help #7359

[kwonoj]

Now I understood q, it's not about fs more about the approach: if components are separated into different files, no, there's no global lifetime you can expect to store-at-read once some states.

[romanusname]

Now I understood q, it's not about fs more about the approach: if components are separated into different files, no, there's no global lifetime you can expect to store-at-read once some states.

Can't read the file? Or am I doing something wrong? let r = fs::read("test.txt").expect("test"); test without error but next js thread '<unnamed>' panicked at 'failed to invoke plugin...