ability to construct a LazyPath out of any file from a dependency package

[andrewrk]

The idea here is that you can put an arbitrary file contents in your build.zig.zon, like this:

.{
    .dependencies = .{
        .foo = .{
            .url = "https://example.com/foobar.tar.gz",
            .hash = "12209e851f7e2c6ba2f01de3e11b1771f03e49666065320abd8414aac152bfa75fae",
        },
    },
}

Normally, at this point, one would activate the build.zig script of the dependency like this:

    const foo_dep = b.dependency("foo", .{
        .target = target,
        .optimize = optimize,
        // ...other options...
    });

However, this issue is about the use case where the dependency is not a zig package, but a bundle of arbitrary files.

The idea is that you can access arbitrary files as std.Build.LazyPath objects, like this:

pub fn build(b: *std.Build) !void {
    // ...

    const lazy_path = b.dependencyPath("foo", "path/inside/dependency.txt");

    // now you can pass it anywhere a lazy path is accepted:
    run_step.addFileArg(lazy_path);

    // or you can access the file directly from build script logic:
    const contents = try std.fs.readFileAlloc(lazy_path.resolve());

    // ...
}

Using it via the LazyPath API would help with #14597, because resolution of the path would force the package to be downloaded.

[mitchellh]

This feature would also allow build-only projects to depend on their upstream source blobs using zon files instead of having to fork/vendor. This may be obvious, but pointing it out as a solid use case to enable the Zig build system to be used with any project.

[pfgithub]

Right now, this is possible using @import("root").dependencies.build_root.$PACKAGE_NAME, but packages require a build.zig file so an empty build.zig needs to be added:

const std = @import("std");

pub fn build(_: *std.Build) !void {}

---

I didn't notice the PR, it looks like it fixes this

[mitchellh]

but packages require a build.zig file so an empty build.zig needs to be added:

Thanks for pointing this out, but this is a key issue that I think this issue proposes to address! 😄