CodyC Posts

CodyC

•Created by CodyC on 1/12/2025 in #help

Reliable pattern for cleaning up resources as process exists?

I'm using Explicit Resource Management (await using resource = ...), but [Symbol.asyncDispose] doesn't get called if my program is killed with SIGINT or other signals. Is there a known/good pattern for making sure some resource gets cleaned up, even if the process is dying? I'm familiar with window.onunload, but since that's a global, it feels unreliable to rely on, since anything else in my dependencies might overwrite it during a lengthy runtime. I may also have more than one thing that I want to clean up. (never mind, unload doesn't fire during SIGINT) I also know about Deno.addSignalListener() but there are an awful lot of signals I'd need to listen to.

5 replies

DDeno

•Created by CodyC on 4/1/2024 in #help

How to open a file as blob?

Docs for Blob (https://deno.land/api@v1.42.0?s=Blob) say that File implements Blob. But the docs for Deno.File (https://deno.land/api@v1.42.0?s=Deno.File) say that it's deprecated and you should use FsFile instead. But FsFile (https://deno.land/api@v1.42.0?s=Deno.FsFile) doesn't implement Blob. I could probably write my own wrapper that will make FsFile conform to Blob, but that feels like something that might already be in std somewhere? (update: the important part here is that I want to wrap a file-like object, not read the entire file's contents into memory, since I'm working with potentially large files.)

20 replies

DDeno

•Created by CodyC on 4/4/2023 in #help

Is there a way to lint check unnecessary `await`s?

1 replies

DDeno

•Created by CodyC on 3/24/2023 in #help

Help debugging command that doesn't exit.

Is there a way to have Deno tell me what async tasks are still pending when a program ends? I'm using a third-party API, and AFAICT awaiting all the promises I can, but I still get to the end of my main() and deno doesn't exit. So I've got:

async function main() {
    // [snip]
    console.log("Done")
    showPending()
}

function showPending() {
    let {ops} = Deno.metrics()
    for (let [key, value] of Object.entries(ops)) {
        if (value.opsDispatched != value.opsCompleted) {
            console.log(key, value)
        }
    }
    console.log(Deno.resources())
}

async function main() {
    // [snip]
    console.log("Done")
    showPending()
}

function showPending() {
    let {ops} = Deno.metrics()
    for (let [key, value] of Object.entries(ops)) {
        if (value.opsDispatched != value.opsCompleted) {
            console.log(key, value)
        }
    }
    console.log(Deno.resources())
}

Which gives me:

[snip]
Done
op_read {
  opsDispatched: 14,
  opsDispatchedSync: 0,
  opsDispatchedAsync: 14,
  opsDispatchedAsyncUnref: 0,
  opsCompleted: 13,
  opsCompletedSync: 0,
  opsCompletedAsync: 13,
  opsCompletedAsyncUnref: 0,
  bytesSentControl: 0,
  bytesSentData: 0,
  bytesReceived: 0
}
{
  "0": "stdin",
  "1": "stdout",
  "2": "stderr",
  "8": "childStdin",
  "9": "childStdout",
  "10": "child"
}

[snip]
Done
op_read {
  opsDispatched: 14,
  opsDispatchedSync: 0,
  opsDispatchedAsync: 14,
  opsDispatchedAsyncUnref: 0,
  opsCompleted: 13,
  opsCompletedSync: 0,
  opsCompletedAsync: 13,
  opsCompletedAsyncUnref: 0,
  bytesSentControl: 0,
  bytesSentData: 0,
  bytesReceived: 0
}
{
  "0": "stdin",
  "1": "stdout",
  "2": "stderr",
  "8": "childStdin",
  "9": "childStdout",
  "10": "child"
}

Any suggestions? I guess I'll fire up a debugger...

4 replies

DDeno

•Created by CodyC on 12/23/2022 in #help

Lint for if you forgot to `await` a Promise?

If you have async methods that you call for their side effects, it's easy to forget to await them. Is there a lint rule that I can enable for that? (Sort of like Rust's rules about unused Results?) ex:

async myFn() {
    // code

    // oops, I forgot to await:
    doThing()

    // more code
    // fails at runtime because doThing()
    // hasn't finished yet.

}

async myFn() {
    // code

    // oops, I forgot to await:
    doThing()

    // more code
    // fails at runtime because doThing()
    // hasn't finished yet.

}

7 replies