[naga-cli] add --defines options for the glsl parser (#5859)

Author: theomonnom

CHANGELOG.md

@@ -47,7 +47,7 @@ TODO(wumpf): This is still work in progress. Should write a bit more about it. A
 
 `wgpu::ComputePass` recording methods (e.g. `wgpu::ComputePass:set_render_pipeline`) no longer impose a lifetime constraint passed in resources.
 
-Furthermore, you can now opt out of `wgpu::ComputePass`'s lifetime dependency on its parent `wgpu::CommandEncoder` using `wgpu::ComputePass::forget_lifetime`:  
+Furthermore, you can now opt out of `wgpu::ComputePass`'s lifetime dependency on its parent `wgpu::CommandEncoder` using `wgpu::ComputePass::forget_lifetime`:
 ```rust
 fn independent_cpass<'enc>(encoder: &'enc mut wgpu::CommandEncoder) -> wgpu::ComputePass<'static> {
     let cpass: wgpu::ComputePass<'enc> = encoder.begin_compute_pass(&wgpu::ComputePassDescriptor::default());
@@ -126,6 +126,7 @@ By @atlv24 in [#5383](https://github.com/gfx-rs/wgpu/pull/5383)
 
 #### Naga
 
+- Added -D, --defines option to naga CLI to define preprocessor macros by @theomonnom in [#5859](https://github.com/gfx-rs/wgpu/pull/5859)
 - Added type upgrades to SPIR-V atomic support. Added related infrastructure. Tracking issue is [here](https://github.com/gfx-rs/wgpu/issues/4489). By @schell in [#5775](https://github.com/gfx-rs/wgpu/pull/5775).
 - Implement `WGSL`'s `unpack4xI8`,`unpack4xU8`,`pack4xI8` and `pack4xU8`. By @VlaDexa in [#5424](https://github.com/gfx-rs/wgpu/pull/5424)
 - Began work adding support for atomics to the SPIR-V frontend. Tracking issue is [here](https://github.com/gfx-rs/wgpu/issues/4489). By @schell in [#5702](https://github.com/gfx-rs/wgpu/pull/5702).

naga-cli/src/bin/naga.rs

@@ -132,6 +132,10 @@ struct Args {
     /// In bulk validation mode, these are all input files to be validated.
     #[argh(positional)]
     files: Vec<String>,
+
+    /// defines to be passed to the parser (only glsl is supported)
+    #[argh(option, short = 'D')]
+    defines: Vec<Defines>,
 }
 
 /// Newtype so we can implement [`FromStr`] for `BoundsCheckPolicy`.
@@ -285,6 +289,27 @@ impl FromStr for Overrides {
     }
 }
 
+#[derive(Clone, Debug)]
+struct Defines {
+    pairs: Vec<(String, String)>,
+}
+
+impl FromStr for Defines {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut pairs = vec![];
+        for pair in s.split(',') {
+            let (name, value) = match pair.split_once('=') {
+                Some((name, value)) => (name, value),
+                None => (pair, ""), // Default to an empty string if no '=' is found
+            };
+            pairs.push((name.trim().to_string(), value.trim().to_string()));
+        }
+        Ok(Defines { pairs })
+    }
+}
+
 #[derive(Default)]
 struct Parameters<'a> {
     validation_flags: naga::valid::ValidationFlags,
@@ -300,6 +325,7 @@ struct Parameters<'a> {
     hlsl: naga::back::hlsl::Options,
     input_kind: Option<InputKind>,
     shader_stage: Option<ShaderStage>,
+    defines: FastHashMap<String, String>,
 }
 
 trait PrettyResult {
@@ -393,6 +419,14 @@ fn run() -> anyhow::Result<()> {
         .flat_map(|o| &o.pairs)
         .cloned()
         .collect();
+
+    params.defines = args
+        .defines
+        .iter()
+        .flat_map(|o| &o.pairs)
+        .cloned()
+        .collect();
+
     params.spv_in = naga::front::spv::Options {
         adjust_coordinate_space: !args.keep_coordinate_space,
         strict_capabilities: false,
@@ -611,7 +645,7 @@ fn parse_input(input_path: &Path, input: Vec<u8>, params: &Parameters) -> anyhow
                     .parse(
                         &naga::front::glsl::Options {
                             stage: shader_stage.0,
-                            defines: Default::default(),
+                            defines: params.defines.clone(),
                         },
                         &input,
                     )
@@ -859,7 +893,7 @@ use codespan_reporting::{
         termcolor::{ColorChoice, StandardStream},
     },
 };
-use naga::WithSpan;
+use naga::{FastHashMap, WithSpan};
 
 pub fn emit_annotated_error<E: Error>(ann_err: &WithSpan<E>, filename: &str, source: &str) {
     let files = SimpleFile::new(filename, source);