How to access info in build.zig.zon from build.zig?

dude_the_builder · November 12, 2023, 4:14pm

Continuing the discussion from New Zig Build System Documentation:

andrewrk · November 12, 2023, 9:39pm

You will be able to do @import("build.zig.zon") directly from the build.zig file, but that depends on some work-in-progress enhancements to the compiler.

ktz_alias · November 10, 2024, 8:35am

You will be able to do @import("build.zig.zon") directly from the build.zig file

I’ve tried this code.
But I’ve received a compilation error.

error: no module named 'build.zig.zon' available within module root.@build
    const bzz = @import("build.zig.zon");

Is this feature not supported yet?

Current environment:

$ zig version
0.14.0-dev.2126+e27b4647d

andrewrk · November 10, 2024, 8:33pm

github.com/ziglang/zig

ZON

ziglang:master ← MasonRemaley:zon

opened 01:14AM - 12 Jun 24 UTC

MasonRemaley

+7120 -243

# ZON This PR implements ZON, or Zig Object Notation (think JSON, but with Zig …syntax instead of Javascript.) In particular, it implements: * Runtime parsing of ZON data * Runtime stringification of ZON data * Compile time importing of ZON data A lot of files are added since I added a lot of test cases, the bulk of the work is in `src/zon.zig` and `lib/std/zon`. If there's anything I can do to make this easier to review, let me know. Tests cover all new features. ## Runtime The runtime code can be found at `lib/std/zon`. ### Parsing `lib/std/zon/parse.zig` Detailed doc comments are provided in the source. At a high level, this module provides the following functions and some configuration options: * `parseFromSlice` * `parseFromAst` * `parseFromAstNoAlloc` * `parseFromAstNode` * `parseFromAstNodeNoAlloc` * `parseFree` Most people will just want `parseFromSlice` and maybe `parseFree`, but the more fine grained functions are available for those who need `them.` ### Stringify `lib/std/zon/stringify.zig` Detailed doc comments are provided in the source. At a high level, this module provides the following functions and some configuration options: * `stringify` * `stringifyMaxDepth` * `stringifyArbitraryDepth` * `stringifier` Most users will just need stringify, or one of its variants. However, `stringifier` returns a much more fine grained interface that is used in the implementation of the other functions. It may be used directly if you need to serialize something piece by piece--perhaps to apply different configuration to different parts of the value, or because the value does not actually exist laid out in memory in the same form in which you want to stringify it. ## Compile Time Almost all of the logic for this is in `src/zon.zig`. This PR also implements importing ZON at compile time: ```zig const Foo = @import("foo.zon"); ``` ## Things that may change later... ### `&` In ZON syntax ~~Right now, ZON slices need to be prefixed with `&` to distinguish them from tuples. This is necessary because we don't know the result type when importing. In the future I think ZON should not distinguish between tuples and slices, it should just coerce to whatever the destination type is.~~ Update: `&` is not allowed in ZON, ZON will automatically coerce tuples to arrays or slices when given a destination type. ### Untagged nonexhaustive enum values not yet supported Zig does not currently have a way to represent an untagged enum value as a literal, and as such there's no way to represent one in ZON. We could resolve this by adding a syntax for untagged enum literals to Zig, or by allowing ZON to coerce integers to untagged enum literals (provided the destination type is known.) Personally I prefer the former solution. * [ ] After this PR is merged I'll file an issue to track this if still relevant. ### Type mismatches do not always point at helpful location This is an existing issue, but it can make type errors in ZON imports annoying. Consider this incorrect code: ```zig const Struct = struct { outer: struct { inner: u8 }, }; const some_value = .{ .outer = .{ .inner = 1.5 } }; const casted: Struct = some_value; ``` It produces the following error: ```sh src/main.zig:22:28: error: fractional component prevents float value '1.5' from coercion to type 'u8' const casted: Struct = some_value; ``` This isn't super helpful. The location information should be pointed to the struct literal, or a note should be added that points to the struct literal. This comes up all the time with ZON, e.g. any time you do something like this and make a mistake: ``` const Struct = struct { outer: struct { inner: u8 }, }; const casted: Struct = @import("foo.zon"); ``` * [ ] After this PR is merged I'll file an issue to track this. ### Allowing eliding outer braces may make sense There's case to be made to allow eliding braces on an outer struct in ZON, like this: ```zig .x = 10, .y = 20, ``` * [ ] I'll file an issue with some motivating use cases after this is merged, easy change if we decide to make it ### Divergences from Zig Zig has no NaN or inf literals right now. Zon does, since otherwise it would have no way to represent these values. IMO we should add the same literals to Zig. * [ ] After this PR is merged I'll file an issue to track this. ## See Also * #15552 * #17731 * #14531 * #14532 * #14534 * #5039 * #14532 * [x] #20275 (fixed, can probably parse directly as dest types now) * #20277 * #20880 * #20881