Parsing ZON files (NOT build.zig.zon) from Zig code

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1

Could somebody please point me in the direction of ZON parsing functionality in stdlib (I hope it’s there, where else would it be)?

I have found myself in need of a ‘config’ file format, and while I have used JSON, YAML, TOML and my own homegrown file formats in the past for this purpose, I think ZON is the obvious choice in Zig programs.

Upd: these seem to be relevant:
https://github.com/ziglang/zig/blob/master/lib/std/zig/Parse.zig
https://github.com/ziglang/zig/blob/master/lib/std/zig/Ast.zig
but for me they’re a ball of yarn I’d have to untangle. Not that I don’t want to learn (I do), but abstract syntax trees are not my primary focus right now, and so I would be grateful if I could just throw a ZON file at a function and get some form of parsed result in return.

2

Maybe reading the loadManifest function can help in Fetch.zig?

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3

Thank you.
I’m currently looking at fn parse in Ast.zig: zig/lib/std/zig/Ast.zig at master · ziglang/zig · GitHub , at it uses std.zig.Parse, hoping I can copy from it.

Update: well, this does do something:

    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const alloc8r = gpa.allocator();

    const zon_txt =
        \\.{
        \\    .name = "libffmpeg",
        \\    .version = "5.1.2",
        \\}
        ;

    var ast = try std.zig.Ast.parse(alloc8r, zon_txt, .zon);
    defer ast.deinit(alloc8r);
    std.debug.print("{}\n", .{ ast });

$ zig run zon_parse.zig 
zig.Ast{ .source = { 46, 123, 10, 32, 32, 32, 32, 46, 110, 97, 109, 101, 32, 61, 32, 34, 108, 105, 98, 102, 102, 109, 112, 101, 103, 34, 44, 10, 32, 32, 32, 32, 46, 118, 101, 114, 115, 105, 111, 110, 32, 61, 32, 34, 53, 46, 49, 46, 50, 34, 44, 10, 125 }, .tokens = multi_array_list.MultiArrayList(zig.Ast.TokenList__struct_4036).Slice{ .ptrs = { u8@7f8bf672b050, u8@7f8bf672b000 }, .len = 14, .capacity = 20 }, .nodes = multi_array_list.MultiArrayList(zig.Ast.Node).Slice{ .ptrs = { u8@7f8bf672b0e0, u8@7f8bf672b080, u8@7f8bf672b0a0 }, .len = 4, .capacity = 8 }, .extra_data = {  }, .mode = zig.Ast.Mode.zon, .errors = {  } }
4

You can have a look at what Manifest does and you’re all set.

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5

I have found this post - Zig Parser – Mitchell Hashimoto

BTW, it looks like Parse struct is not public, meaning that ZON parsing functionality is for not for external use either :cry:

6

Just wanted to share that I’m making some progress by following @figsoda’s zon2nix, more specifically, function parse: zon2nix/src/parse.zig at main · nix-community/zon2nix · GitHub

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7

BTW, does ZON support arrays?

Both .uint_arr = { 1, 2, 3, 4 }, and .uint_arr = .{ 1, 2, 3, 4 }, seem to be passing std.zig.Ast.parse with flying colors.

I wonder which of them (if any) is correct.
With .uint_arr = .{ I’m getting zig.Ast.Node.Tag.array_init_dot, and with .uint_arr_2 = { - zig.Ast.Node.Tag.block_two, so I guess .{ is correct. Maybe.

Or is it something like [_]{ 1, 2, 3, 4 } ?

8

Ok, never mind that last question about arrays (yes, they are supported).

I think I have achieved what I wanted, here’s the link - ZON field value extractor (for the lack of better name) - zon_get_fields

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9

I made zon2json tool for my zig2nix repo zig2nix/tools/zon2json at master · Cloudef/zig2nix · GitHub

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10

I split it into separate module zig2nix/tools/zon2json/src at master · Cloudef/zig2nix · GitHub
Not sure if zig package manager can access subpaths in git repo though.
It’s mainly used to generate lockfiles for nix zig2nix/tools/fixtures/2.zig.zon2json-lock at master · Cloudef/zig2nix · GitHub

Though I may eventually replace this tool, reason here:

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