Deno: Cannot get output from a process executing 'deno eval' command.

[Ayfri]

Hi, I'm trying to do a discord bot that can perform great eval as the one by default does not accept imports.
So I made a code that creates a process executing the code via deno eval, but whatever I do, I can't get the proper output.

This is my code :

const process = Deno.run({
    cwd:    Deno.cwd(),
    cmd:    [
        'cmd', // I have to this else it says that 'deno' cannot be found ¯\_(ツ)_/¯
        '/c',
        `deno eval ${code} --ts --print`
    ],
    stdout: 'piped',
    stderr: 'piped',
    stdin: 'piped'
});

const decoder: TextDecoder = new TextDecoder('utf8');
const output: string = decoder.decode(await process.output());
const errors: string = decoder.decode(await process.stderrOutput());

If I execute this code with code = "\"console.log('test')\"", it's sending me console.log('test') as the output, I do not understand why and I need help 👀

[MarkTiedemann]

You're passing a literal string to Deno. (The outer pair of quotes is for the cmd string. The inner escaped pair of quotes is for the JS string.)

C:\>deno eval --print "\"I'm a string\""
I'm a string

I have to this else it says that 'deno' cannot be found ¯_(ツ)_/¯

Can you run where deno in cmd.exe? It seems like deno.exe is not in your %path%.

Alternatively you can use Deno.execPath(), e.g.

// hi.ts
await Deno.run({ cmd: [Deno.execPath(), "eval", "console.log('hi')"], stdout: "inherit" }).status();

C:\>C:\directory\that\is\not\in\path\deno.exe run -A hi.ts
hi

[Ayfri]

where deno is sending me this :
C:\Users\Pierre\.deno\bin\deno.exe

Thanks, I was not knowing the Deno.execPath function it will helps me ^^

[MarkTiedemann]

It seems like deno.exe is indeed in your %path%.

What command did you use to execute the example code you copy-pasted above? Which shell did you run it in?

[Ayfri]

I run it via deno run from the webstorm terminal.

[MarkTiedemann]

Can you try running from default cmd.exe? This might be an issue with the webstorm terminal. Using just "deno" as the first cmd array item should work.

C:\>deno eval "await Deno.run({ cmd: ['deno', '-V'], stdout: 'inherit' }).status();"
deno 1.5.1

[Ayfri]

Nothing appears in the terminal.

[MarkTiedemann]

Does the command above work for you in cmd.exe?

deno eval "await Deno.run({ cmd: ['deno', '-V'], stdout: 'inherit' }).status();"

[Ayfri]

In cmd it's sending me deno 1.5.1, in webstorm terminal it's not sending anything.

[MarkTiedemann]

Well, no idea what Webstorm is doing, but this doesn't seem to be a Deno issue.

[Ayfri]

Yeah...

Anyway, my issue was not getting what the code sends to the console from the await process.output().
So what do I do wrong?

[bartlomieju]

@Ayfri call await process.status() before reading from stdio

[MarkTiedemann]

As I said in my first comment, you were passing a string to Deno eval.

C:\>deno eval "\"I'm a string\""

is equivalent to executing

// string.ts
"I'm a string"

C:\>deno run string.ts

What you want to do is

Deno.run({ cmd: [Deno.execPath(), "eval", code] // ...

You don't need to escape code with extra quotes.

[Ayfri]

Oh, I see my problem now, thanks for all it works now!