Shader Processor: process imported shader (#3290)

# Objective

- I want to be able to use `#ifdef` and other processor directives in an imported shader

## Solution

- Process imported shader strings


Co-authored-by: François <8672791+mockersf@users.noreply.github.com>

crates/bevy_render/src/render_resource/shader.rs

@@ -360,16 +360,16 @@ impl ShaderProcessor {
             }
         };
 
-        let shader_defs = HashSet::<String>::from_iter(shader_defs.iter().cloned());
+        let shader_defs_unique = HashSet::<String>::from_iter(shader_defs.iter().cloned());
         let mut scopes = vec![true];
         let mut final_string = String::new();
         for line in shader_str.split('\n') {
             if let Some(cap) = self.ifdef_regex.captures(line) {
                 let def = cap.get(1).unwrap();
-                scopes.push(*scopes.last().unwrap() && shader_defs.contains(def.as_str()));
+                scopes.push(*scopes.last().unwrap() && shader_defs_unique.contains(def.as_str()));
             } else if let Some(cap) = self.ifndef_regex.captures(line) {
                 let def = cap.get(1).unwrap();
-                scopes.push(*scopes.last().unwrap() && !shader_defs.contains(def.as_str()));
+                scopes.push(*scopes.last().unwrap() && !shader_defs_unique.contains(def.as_str()));
             } else if self.else_regex.is_match(line) {
                 let mut is_parent_scope_truthy = true;
                 if scopes.len() > 1 {
@@ -388,19 +388,32 @@ impl ShaderProcessor {
                 .captures(line)
             {
                 let import = ShaderImport::AssetPath(cap.get(1).unwrap().as_str().to_string());
-                apply_import(import_handles, shaders, &import, shader, &mut final_string)?;
+                self.apply_import(
+                    import_handles,
+                    shaders,
+                    &import,
+                    shader,
+                    shader_defs,
+                    &mut final_string,
+                )?;
             } else if let Some(cap) = SHADER_IMPORT_PROCESSOR
                 .import_custom_path_regex
                 .captures(line)
             {
                 let import = ShaderImport::Custom(cap.get(1).unwrap().as_str().to_string());
-                apply_import(import_handles, shaders, &import, shader, &mut final_string)?;
+                self.apply_import(
+                    import_handles,
+                    shaders,
+                    &import,
+                    shader,
+                    shader_defs,
+                    &mut final_string,
+                )?;
             } else if *scopes.last().unwrap() {
                 final_string.push_str(line);
                 final_string.push('\n');
             }
         }
-
         final_string.pop();
 
         if scopes.len() != 1 {
@@ -417,45 +430,51 @@ impl ShaderProcessor {
             }
         }
     }
-}
 
-fn apply_import(
-    import_handles: &HashMap<ShaderImport, Handle<Shader>>,
-    shaders: &HashMap<Handle<Shader>, Shader>,
-    import: &ShaderImport,
-    shader: &Shader,
-    final_string: &mut String,
-) -> Result<(), ProcessShaderError> {
-    let imported_shader = import_handles
-        .get(import)
-        .and_then(|handle| shaders.get(handle))
-        .ok_or_else(|| ProcessShaderError::UnresolvedImport(import.clone()))?;
-    match &shader.source {
-        Source::Wgsl(_) => {
-            if let Source::Wgsl(import_source) = &imported_shader.source {
-                final_string.push_str(import_source);
-            } else {
-                return Err(ProcessShaderError::MismatchedImportFormat(import.clone()));
+    fn apply_import(
+        &self,
+        import_handles: &HashMap<ShaderImport, Handle<Shader>>,
+        shaders: &HashMap<Handle<Shader>, Shader>,
+        import: &ShaderImport,
+        shader: &Shader,
+        shader_defs: &[String],
+        final_string: &mut String,
+    ) -> Result<(), ProcessShaderError> {
+        let imported_shader = import_handles
+            .get(import)
+            .and_then(|handle| shaders.get(handle))
+            .ok_or_else(|| ProcessShaderError::UnresolvedImport(import.clone()))?;
+        let imported_processed =
+            self.process(imported_shader, shader_defs, shaders, import_handles)?;
+
+        match &shader.source {
+            Source::Wgsl(_) => {
+                if let ProcessedShader::Wgsl(import_source) = &imported_processed {
+                    final_string.push_str(import_source);
+                } else {
+                    return Err(ProcessShaderError::MismatchedImportFormat(import.clone()));
+                }
             }
-        }
-        Source::Glsl(_, _) => {
-            if let Source::Glsl(import_source, _) = &imported_shader.source {
-                final_string.push_str(import_source);
-            } else {
-                return Err(ProcessShaderError::MismatchedImportFormat(import.clone()));
+            Source::Glsl(_, _) => {
+                if let ProcessedShader::Glsl(import_source, _) = &imported_processed {
+                    final_string.push_str(import_source);
+                } else {
+                    return Err(ProcessShaderError::MismatchedImportFormat(import.clone()));
+                }
+            }
+            Source::SpirV(_) => {
+                return Err(ProcessShaderError::ShaderFormatDoesNotSupportImports);
             }
         }
-        Source::SpirV(_) => {
-            return Err(ProcessShaderError::ShaderFormatDoesNotSupportImports);
-        }
-    }
 
-    Ok(())
+        Ok(())
+    }
 }
 
 #[cfg(test)]
 mod tests {
-    use bevy_asset::Handle;
+    use bevy_asset::{Handle, HandleUntyped};
+    use bevy_reflect::TypeUuid;
     use bevy_utils::HashMap;
     use naga::ShaderStage;
 
@@ -1081,4 +1100,106 @@ fn vertex(
             .unwrap();
         assert_eq!(result.get_wgsl_source().unwrap(), EXPECTED);
     }
+
+    #[test]
+    fn process_import_ifdef() {
+        #[rustfmt::skip]
+        const FOO: &str = r"
+#ifdef IMPORT_MISSING
+fn in_import_missing() { }
+#endif
+#ifdef IMPORT_PRESENT
+fn in_import_present() { }
+#endif
+";
+        #[rustfmt::skip]
+        const INPUT: &str = r"
+#import FOO
+#ifdef MAIN_MISSING
+fn in_main_missing() { }
+#endif
+#ifdef MAIN_PRESENT
+fn in_main_present() { }
+#endif
+";
+        #[rustfmt::skip]
+        const EXPECTED: &str = r"
+
+fn in_import_present() { }
+fn in_main_present() { }
+";
+        let processor = ShaderProcessor::default();
+        let mut shaders = HashMap::default();
+        let mut import_handles = HashMap::default();
+        let foo_handle = Handle::<Shader>::default();
+        shaders.insert(foo_handle.clone_weak(), Shader::from_wgsl(FOO));
+        import_handles.insert(
+            ShaderImport::Custom("FOO".to_string()),
+            foo_handle.clone_weak(),
+        );
+        let result = processor
+            .process(
+                &Shader::from_wgsl(INPUT),
+                &["MAIN_PRESENT".to_string(), "IMPORT_PRESENT".to_string()],
+                &shaders,
+                &import_handles,
+            )
+            .unwrap();
+        assert_eq!(result.get_wgsl_source().unwrap(), EXPECTED);
+    }
+
+    #[test]
+    fn process_import_in_import() {
+        #[rustfmt::skip]
+        const BAR: &str = r"
+#ifdef DEEP
+fn inner_import() { }
+#endif
+";
+        const FOO: &str = r"
+#import BAR
+fn import() { }
+";
+        #[rustfmt::skip]
+        const INPUT: &str = r"
+#import FOO
+fn in_main() { }
+";
+        #[rustfmt::skip]
+        const EXPECTED: &str = r"
+
+
+fn inner_import() { }
+fn import() { }
+fn in_main() { }
+";
+        let processor = ShaderProcessor::default();
+        let mut shaders = HashMap::default();
+        let mut import_handles = HashMap::default();
+        {
+            let bar_handle = Handle::<Shader>::default();
+            shaders.insert(bar_handle.clone_weak(), Shader::from_wgsl(BAR));
+            import_handles.insert(
+                ShaderImport::Custom("BAR".to_string()),
+                bar_handle.clone_weak(),
+            );
+        }
+        {
+            let foo_handle = HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 1).typed();
+            shaders.insert(foo_handle.clone_weak(), Shader::from_wgsl(FOO));
+            import_handles.insert(
+                ShaderImport::Custom("FOO".to_string()),
+                foo_handle.clone_weak(),
+            );
+        }
+        let result = processor
+            .process(
+                &Shader::from_wgsl(INPUT),
+                &["DEEP".to_string()],
+                &shaders,
+                &import_handles,
+            )
+            .unwrap();
+        assert_eq!(result.get_wgsl_source().unwrap(), EXPECTED);
+    }
 }