Packages depending on other packages doesn't work

[Hejsil]

Three file example:
a.zig:

const b = @import("b");
pub fn main() void { b.something(); }

b.zig:

const c = @import("c");
pub fn something() void { c.something(); }

c.zig:

pub fn something() void { }

build.zig:

const std = @import("std");

pub fn build(b: *std.Build) void {
    const optimize = b.standardOptimizeOption(.{});
    const exe = b.addExecutable(.{
        .name = "a",
        .root_source_file = .{ .path = "a.zig" },
        .optimize = optimize,
    });
    const mod_c = b.addModule("c", .{
        .source_file = .{ .path = "c.zig" },
    });
    const mod_b = b.addModule("b", .{
        .source_file = .{ .path = "b.zig" },
        .dependencies = &.{
            .{
                .name = "c",
                .module = mod_c,
            },
        },
    });
    exe.addModule("b", mod_b);

    b.default_step.dependOn(&exe.step);
}

When using zig build I get:

b.zig:1:11: error: unable to find 'c'
const c = @import("c");

I've looked around in build.zig, but it doesn't seem like there is a way to add package path c.zig to b. Actually, it seems that build.zig just passes the info to the zig compiler through command line args:

zig build-exe a.zig --cache-dir zig-cache --output zig-cache/a --name a --pkg-begin b b.zig --pkg-end --pkg-begin c c.zig --pkg-end

[andrewrk]

I think we need to add support for it in std/build.zig but here's the command line options you want (note the recursive --pkg-begin):

zig build-exe a.zig --cache-dir zig-cache --output zig-cache/a --name a --pkg-begin b b.zig --pkg-begin c c.zig  --pkg-end --pkg-end

This puts c as a sub-package in b.

[andrewrk]

I think this is #353

[emekoi]

should we add a package object similar to the executable and library object? furthermore, does --pkg-begin and --pkg-end allow for specifying build flags unique to that package?

[BenoitJGirard]

As Windows has a maximum size for the command (8K from cmd.exe, 32K from StartProcess()), seems to me that "--pkg-begin" and "--pkg-end" will not scale for large projects with many edges in their package dependency graph.

Unless I am missing something?

Maybe the tree described by "--pkg-begin" and "--pkg-end" should be imported from a file, instead?

[andrewrk]

@BenoitJGirard you are correct.

How packages work for zig is still in the design phase. The command line interface is one of the things that will be addressed. I'm planning on publishing a detailed design specification proposal for the zig package manager shortly after 0.4.0 is released.

[BenoitJGirard]

@andrewrk Understood.

I like how "--pkg-begin" and "--pkg-end" force the explicit listing of the dependencies all the way down the dependency graph. Policing the dependency graph for large projects is one of the headaches we have at my day job. I hope your upcoming design keeps that mindset.

[SamTebbs33]

The command used is now zig build-exe a.zig --cache-dir zig-cache --name a --pkg-begin b b.zig --pkg-end --pkg-begin c c.zig --pkg-end --cache on and interestingly, re-ordering the calls to addPackagePath doesn't give the same issue.

[andrewrk]

This might be working today. Here's what needs to happen for this to be closed:

• Investigate whether there is still an error trying to do this with the zig build system.
• Make sure there is test coverage in test/standalone/* (perhaps it already has coverage?)
  • add test coverage if not

[nektro]

this happened because addPackagePath adds a package with no dependencies. so the tree looks like this

root
  -> b
  -> c

but what you really need is

root
  -> b
    -> c

so what they need to do is

const pkg_c = Pkg{ .name = "c", .path = .{ .path = "c.zig" } };
const pkg_b = Pkg{ .name = "b", .path = .{ .path = "b.zig" }, .dependencies = &[_]Pkg{ pkg_c } };
exe.addPackage(pkg_b);

[andrewrk]

This indeed works today, and has test coverage via these files:

$ grep -RI addModule ../test/standalone
../test/standalone/dep_recursive/build.zig:    exe.addModule("foo", foo);
../test/standalone/dep_triangle/build.zig:    exe.addModule("shared", shared);
../test/standalone/dep_mutually_recursive/build.zig:    exe.addModule("foo", foo);
../test/standalone/test_runner_module_imports/build.zig:    t.addModule("module2", module2);