Feature request - Allow watching files outside of the module graph

[bebraw]

I am reading JSON files that then affect what Deno serves. The problem is that the operation is outside of Deno's module graph and the watch feature won't notice these type of changes.

Based on #2401 (comment) I was thinking patterns are supported already but looking at the source (

deno/cli/flags.rs

Line 226 in 3c97dbf

pub watch: bool,

) they are not.

Therefore I would propose adding support to --watch=./**/*.ts,./**/*.tsx kind of syntax (i.e. watch would accept a string of globs) to allow watching arbitrary files even outside of Deno's module graph.

Related to jurassiscripts/velociraptor#80.

[bebraw]

I found a good workaround for this. Consider the code below:

async function watch(
  directory: string,
  extension: string,
  handler: (path: string) => void,
) {
  const watcher = Deno.watchFs(directory);

  for await (const event of watcher) {
    event.paths.forEach((p) => p.endsWith(extension) && handler(p));
  }
}

Then at mod.ts (my server):

function main() {
  // Touch this file if any json file in the project changes to trigger a rebuild.
  watch(
    ".",
    ".json",
    () => Deno.run({ cmd: ["touch", new URL("", import.meta.url).pathname] }),
  );

  ...
}

[lucacasonato]

I think this is a really useful feature. We should add it. Would be tremendously useful for fresh: https://fresh.deno.dev.

[bartlomieju]

I think this is a really useful feature. We should add it. Would be tremendously useful for fresh: https://fresh.deno.dev.

How do you propose we do this? Accept arguments to the --watch flag?

[bebraw]

@bartlomieju As mentioned in the issue, I would go with something like --watch=./**/*.ts,./**/*.tsx (i.e. a list of globs). That would resolve the files to watch against the project root.

[bartlomieju]

The thing is we don't really support globs in any of the CLI flags - it's up to your shell to expand them. I can see the value of this feature, but we need to be careful considering what can be delivered.

[lucacasonato]

@bartlomieju let's just start with individual files and folders in the arguments to --watch, and go from there.

[bartlomieju]

@bartlomieju let's just start with individual files and folders in the arguments to --watch, and go from there.

Sounds good to me, PRs are welcome

[bartlomieju]

For anyone interested in tackling this issue, here are some some pointers how to do it:

In cli/flags.rs:

• change watch_arg() function to accept values, and update the description that passing values has only effect on the deno run subcommand
• change watch field in Flags struct to accept Option<Vec<PathBuf>> instead of a bool
• in run_parse change parsing logic to create a vector of paths
• in other functions that parse watch flag they should set watch equal to Some(vec![]) is "watch" flag is present

In cli/main.rs:

• change run_with_watch function to extend paths_to_watch with the value of vector from Flags::watch

Add a test to cli/tests/integration/watcher_tests.rs that verifies that additional files passed to the flag actually cause the process to restart.

I'm going to mark this as a "good first issue", even though it's on the harder spectrum of "first issues".

[jespertheend]

I'd like to have a go at this if that's ok!

[lucacasonato]

@jespertheend Please do! If you need some more guidance, please hop into the #dev channel on Discord: https://discord.gg/deno