Lifting files and directories

[eladb]

Use Case

I am looking for a way to reference files or directories (relative to source file).

Proposed Solution

Latest and greatest:

bring fs;

// file (which is also a directory) or path, std.File or std.Path
let public = file!("./public");

test "print the index file" {
  // public is now just a string, or could be an inflight client with a .path property
  // It's a (new) absolute path that the lifter has taken care getting into the runtime for you
  let index = fs.readFile("{public}/index.html");
  log(index);
}

test "print all files" {
  for f in fs.readdir(public) {
    // The nice part about this is that any fs operations should still work as expected
    let data = fs.readFile("{public}/{f}");
    log(f);
  }
}

Component

Language Design, Compiler

Community Notes

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[eladb]

BTW, I think this might be a reasonable and simple solution until we have something more formal for https://github.com/winglang/wing/issues/3736

[Chriscbr]

Related-ish https://twitter.com/meijer_s/status/1745727753964462431

[skyrpex]

I didn't know that, Chris! I prefer something along the modern syntax.

[eladb]

@skyrpex any suggestions?

[skyrpex]

What about a syntax similar to ESM's import.meta, but with wing flavour?

For example, bring.meta.filename and bring.meta.dirname.

[yoav-steinberg]

I'm trying to better understand this:

• In preflight __dirname should just return the dir name of the file. I guess this should and can work (with extern). Doesn't it?
• In inflight, what do we want? The dir name of the wing source file (same as preflight) or the runtime dirname (like node)?
  • if we want the location of wing source file, there's no issue, same as preflight.
  • if we want the runtime location, I think we're doing something wrong since this might not even be a file system. What does __dirname in JS do when running on a browser? Can you elaborate why this is useful?

If we don't care about runtime location, just build time location then I'm for just using __dirname, __filename (and __linenum and __columnnum). I think that's the best DX, even though I think it's pretty ugly.

[eladb]

The location is actually not the important piece (at least in most cases).

If we go back to the fundamentals. What's the use case for __dirname? It's basically accessing assets (files and directories) that are part of the source tree.

This use case is relevant both for inflight and preflight of course (e.g. I want to bundle a .png as part of my inflight and use it).

I am wondering if perhaps we need something a bit more higher level that will allow the compiler/bundler to do the right thing and package the assets into the relevant runtime context.

Maybe something like:

// this returns an `std.Asset` that represents the entire directory.
// "asset" is a builtin because the path it takes is relative to the *source file*.
let public = asset("./public");

test "print the index file" {
  let index = public.readFile("index.html");
  log(index);
}

test "print all files" {
  for f in public.readdir() {
    log(f);
  }
}

What do you all think?

[MarkMcCulloh]

I like the asset idea and the solution probably has to be something like that (preflight relative path thing that binds into inflight with a way to access the data).

I think it's unfortunate that we'd basically be duplicating the fs API on this though, and limiting to directories seems unnecessary. What if we do keep this scoped to paths and say "if you reference the lifted path inflight, it will exist"

bring fs;

// file (which is also a directory) or path, std.File or std.Path
let public = file("./public");

test "print the index file" {
  // public is now just a string, or could be an inflight client with a .path property
  // It's a (new) absolute path that the lifter has taken care getting into the runtime for you
  let index = fs.readFile("{public}/index.html");
  log(index);
}

test "print all files" {
  for f in fs.readdir(public) {
    // The nice part about this is that any fs operations should still work as expected
    let data = fs.readFile("{public}/{f}");
    log(f);
  }
}

[eladb]

@MarkMcCulloh I like this direction. It does imply that we won't be able to do any optimizations (i.e. just lift a single file instead of a directory) but it sounds like a premature optimization.

In a sense, this is basically the use case of "lifting files" into inflight, which is not the same as referencing files in the project directory during preflight.

I'll split into two issues.

[MarkMcCulloh]

I like this direction. It does imply that we won't be able to do any optimizations (i.e. just lift a single file instead of a directory) but it sounds like a premature optimization.

It's not part of the API but the user does still have the single-file option since there's no reason this can't work for individual files too. You're right though, I think the optimizations available to a "lazy-phantom filesystem" with asset() would be very interesting. Strong OCI vibes.

In a sense, this is basically the use case of "lifting files" into inflight, which is not the same as referencing files in the project directory during preflight.

The proposed solution of assert()/file() covers both cases, no? As far as a user is concerned I don't see the difference between those cases.

[yoav-steinberg]

I like these ideas. Note that in many cases a better dx would be if file/asset were more like keywords expecting a string literal and not builtins expecting a string type. That way you can get IDE path autocomplete and squiggly red line in case the path is wrong (like what we have for extern "file.js"):

let public = asset "./public";
                //  ^^^^^ path "./public" not found in current_file_name.w's path

[MarkMcCulloh]

That way you can get IDE path autocomplete and squiggly red line in case the path is wrong

IDE path completion doesn't require special syntax, right now it's sufficient to be in a string and start with ./. Special syntax would avoid the need for that trigger though.

Also, unlike extern, these paths will probably be resolved during synthesis (or one of the hooks), so users will not see any squiggles in the IDE without a full wing compile. IMO I wouldn't want them to resolve before that because preflight itself could be building these files.

I'm not against special syntax, I think it'd be pretty cool, just want to make sure we choose it for a good reason.

[eladb]

I am repurposing this issue to focus on lifting files and directories instead of __dirname because that's actually much more interesting and the discussion here is focused on this.

[eladb]

Y'all know I think we made a mistake with extern "foo"...

Maybe all these global builtins function-like should have some mark:

1. extern!(), file!(), assert!()
2. ~assert()
3. file~("./path")
4. $file("./path")
5. #file("./path");
6. "file#("./path");`
7. _file("./path");

The ! suffix feels cleanest to me.

[skyrpex]

Interesting discussion. So basically, file("./path") will bundle a directory or file during preflight, and make it available during inflight.

Reminds me of the different asset handling techniques in bundlers. For example, see Vite's Static Asset Handling. You can import an image from a JavaScript file and what you get is the final URL:

import imgUrl from './img.png'
document.getElementById('hero-img').src = imgUrl

You can also use import suffixes to customize what's being imported:

import workletURL from 'extra-scalloped-border/worklet.js?url'
CSS.paintWorklet.addModule(workletURL)

or

import shaderString from './shader.glsl?raw'

[MarkMcCulloh]

Y'all know I think we made a mistake with extern "foo"

The distinction with extern is that it's part of a declaration, not a plain expression. This kinda shows how the different syntax is useful, because the expectation of what extern does WRT outside files should be different than file() with the currently implementation.

If the mistake with extern is that it's declarative, then fair enough. I do think there should be some fundamental rework of extern, but the problem isn't just if it looks like extern "foo" or extern("foo").

Maybe all these global builtins function-like should have some mark

This was discussed before when the first globals were added. IMO a marker implies these things are special, but they're just global. file is not functionally different than user-defined functions/closures. Also to be consistent we'd have to have log!() too, which seems off,

[Chriscbr]

file is not functionally different than user-defined functions/closures.

I guess the difference is that the string passed to file is evaluated with respect to the current source file, no? It sounds like that's the motivation for a dedicated syntax (like Yoav suggested)

If it were a plain function, then it could be used as a value (passed to higher order functions, etc) and would produce the same asset when called in different directories with the same path argument, which sounds like it isn't the case.

// dir1/mod.w
let a = asset "./flower.png"; // dir1/flower.png

// dir2/mod.w
let a = asset "./flower.png"; // dir2/flower.png

It seems like the function is doing something special that can't be achieved in Wing userland

[MarkMcCulloh]

It seems like the function is doing something special that can't be achieved in Wing userland

That's fair, I was more arguing against the ! marker concept for globals like assert/log. "Special" here is subjective.

I do still think treating file like a regular function is feasible, akin to CJS require, which can work as expected even when passing the function around.

[eladb]

I guess the difference is that the string passed to file is evaluated with respect to the current source file, no? It sounds like that's the motivation for a dedicated syntax (like Yoav suggested)

Yes, that's why I think it must be a special thing.

Another way to think about it is to think about it as a primitive type (file):

let myFile: file = f"./my-file";

myFile.read();
myFile.path
myFile.extname
myFile.dirname

The compiler compiles this to:

const myFile = new std.File(path.join(__dirname, "./my-file"));

Or something like this.

What do y'all think? I kind of like the idea of a file being a primitive type.

[Chriscbr]

Related: https://github.com/winglang/wing/issues/6108

[ekeren]

Also Related: https://github.com/winglang/wing/issues/6380

(TSOA resource)