Add native component style minification

crates/oxc_angular_compiler/Cargo.toml

@@ -26,6 +26,7 @@ oxc_sourcemap = { workspace = true }
 miette = { workspace = true }
 rustc-hash = { workspace = true }
 indexmap = { workspace = true }
+lightningcss = "1.0.0-alpha.71"
 oxc_resolver = { version = "11", optional = true }
 pathdiff = { version = "0.2", optional = true }
 semver = "1.0.27"

crates/oxc_angular_compiler/src/component/definition.rs

@@ -23,6 +23,7 @@ use super::metadata::{
     ViewEncapsulation,
 };
 use super::namespace_registry::NamespaceRegistry;
+use super::transform::TransformOptions;
 use crate::directive::{
     create_host_directive_mappings_array, create_inputs_literal, create_outputs_literal,
 };
@@ -62,6 +63,7 @@ pub struct ComponentDefinitions<'a> {
 pub fn generate_component_definitions<'a>(
     allocator: &'a Allocator,
     metadata: &ComponentMetadata<'a>,
+    options: &TransformOptions,
     job: &mut ComponentCompilationJob<'a>,
     template_fn: FunctionExpr<'a>,
     host_binding_result: Option<HostBindingCompilationResult<'a>>,
@@ -79,6 +81,7 @@ pub fn generate_component_definitions<'a>(
     let cmp_definition = generate_cmp_definition(
         allocator,
         metadata,
+        options,
         job,
         template_fn,
         host_binding_result,
@@ -109,6 +112,7 @@ pub fn generate_component_definitions<'a>(
 fn generate_cmp_definition<'a>(
     allocator: &'a Allocator,
     metadata: &ComponentMetadata<'a>,
+    options: &TransformOptions,
     job: &mut ComponentCompilationJob<'a>,
     template_fn: FunctionExpr<'a>,
     host_binding_result: Option<HostBindingCompilationResult<'a>>,
@@ -435,23 +439,17 @@ fn generate_cmp_definition<'a>(
     if !metadata.styles.is_empty() {
         let mut style_entries: OxcVec<'a, OutputExpression<'a>> = OxcVec::new_in(allocator);
         for style in &metadata.styles {
-            // Apply CSS scoping for Emulated encapsulation
-            let style_value = if metadata.encapsulation == ViewEncapsulation::Emulated {
-                // Use shim_css_text with %COMP% placeholder
-                // Angular's runtime will replace %COMP% with the actual component ID
-                let scoped = crate::styles::shim_css_text(style.as_str(), content_attr, host_attr);
-                // Skip empty styles
-                if scoped.trim().is_empty() {
-                    continue;
-                }
-                Atom::from_in(scoped.as_str(), allocator)
-            } else {
-                // For None/ShadowDom, use styles as-is
-                if style.trim().is_empty() {
-                    continue;
-                }
-                style.clone()
-            };
+            let style = crate::styles::finalize_component_style(
+                style.as_str(),
+                metadata.encapsulation == ViewEncapsulation::Emulated,
+                content_attr,
+                host_attr,
+                options.minify_component_styles,
+            );
+            if style.trim().is_empty() {
+                continue;
+            }
+            let style_value = Atom::from_in(style.as_str(), allocator);
 
             style_entries.push(OutputExpression::Literal(Box::new_in(
                 LiteralExpr { value: LiteralValue::String(style_value), source_span: None },

crates/oxc_angular_compiler/src/component/transform.rs

@@ -174,6 +174,12 @@ pub struct TransformOptions {
     ///
     /// Default: false (metadata is dev-only and usually stripped in production)
     pub emit_class_metadata: bool,
+
+    /// Minify final component styles before emitting them into `styles: [...]`.
+    ///
+    /// This runs after Angular style encapsulation, so it applies to the same
+    /// final CSS strings that are embedded in component definitions.
+    pub minify_component_styles: bool,
 }
 
 /// Input for host metadata when passed via TransformOptions.
@@ -223,6 +229,7 @@ impl Default for TransformOptions {
             resolved_imports: None,
             // Class metadata for TestBed support (disabled by default)
             emit_class_metadata: false,
+            minify_component_styles: false,
         }
     }
 }
@@ -2453,6 +2460,7 @@ fn compile_component_full<'a>(
     let definitions = generate_component_definitions(
         allocator,
         metadata,
+        options,
         &mut job,
         compiled.template_fn,
         host_binding_result,

crates/oxc_angular_compiler/src/styles/minify.rs

@@ -0,0 +1,68 @@
+use lightningcss::stylesheet::{MinifyOptions, ParserOptions, PrinterOptions, StyleSheet};
+
+const COMPONENT_PLACEHOLDER: &str = "%COMP%";
+const MINIFY_PLACEHOLDER: &str = "OXCANGULARCOMPONENT";
+
+/// Apply Angular style encapsulation and optionally minify the final CSS.
+pub fn finalize_component_style(
+    style: &str,
+    encapsulate: bool,
+    content_attr: &str,
+    host_attr: &str,
+    minify: bool,
+) -> String {
+    let style = if encapsulate {
+        super::shim_css_text(style, content_attr, host_attr)
+    } else {
+        style.to_string()
+    };
+
+    if !minify || style.trim().is_empty() {
+        return style;
+    }
+
+    minify_component_style(&style).unwrap_or(style)
+}
+
+/// Minify a final component CSS string while preserving Angular's `%COMP%` placeholder.
+pub fn minify_component_style(style: &str) -> Option<String> {
+    let css = style.replace(COMPONENT_PLACEHOLDER, MINIFY_PLACEHOLDER);
+    let mut stylesheet = StyleSheet::parse(&css, ParserOptions::default()).ok()?;
+    stylesheet.minify(MinifyOptions::default()).ok()?;
+
+    let code =
+        stylesheet.to_css(PrinterOptions { minify: true, ..PrinterOptions::default() }).ok()?.code;
+
+    Some(code.replace(MINIFY_PLACEHOLDER, COMPONENT_PLACEHOLDER))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{finalize_component_style, minify_component_style};
+
+    #[test]
+    fn minifies_css_with_component_placeholders() {
+        let minified = minify_component_style(
+            "[_ngcontent-%COMP%] {\n  color: red;\n  background: transparent;\n}\n",
+        )
+        .expect("style should minify");
+
+        assert_eq!(minified, "[_ngcontent-%COMP%]{color:red;background:0 0}");
+    }
+
+    #[test]
+    fn finalizes_emulated_styles_before_minifying() {
+        let finalized = finalize_component_style(
+            ":host {\n  display: block;\n}\n.button {\n  color: red;\n}\n",
+            true,
+            "_ngcontent-%COMP%",
+            "_nghost-%COMP%",
+            true,
+        );
+
+        assert_eq!(
+            finalized,
+            "[_nghost-%COMP%]{display:block}.button[_ngcontent-%COMP%]{color:red}"
+        );
+    }
+}

crates/oxc_angular_compiler/src/styles/mod.rs

@@ -5,5 +5,7 @@
 //! - CSS transformation for component-scoped styles
 
 mod encapsulation;
+mod minify;
 
 pub use encapsulation::{encapsulate_style, shim_css_text};
+pub use minify::{finalize_component_style, minify_component_style};

crates/oxc_angular_compiler/tests/integration_test.rs

@@ -1524,6 +1524,34 @@ export class MultiStyledComponent {}
     insta::assert_snapshot!("component_with_multiple_styles", result.code);
 }
 
+#[test]
+fn test_component_with_minified_styles() {
+    let allocator = Allocator::default();
+    let source = r#"
+import { Component } from '@angular/core';
+
+@Component({
+    selector: 'app-styled',
+    template: '<div class="container">Hello</div>',
+    styles: ['.container { color: red; background: transparent; }']
+})
+export class StyledComponent {}
+"#;
+
+    let mut options = ComponentTransformOptions::default();
+    options.minify_component_styles = true;
+
+    let result = transform_angular_file(&allocator, "styled.component.ts", source, &options, None);
+
+    assert_eq!(result.component_count, 1);
+    assert!(!result.has_errors(), "Should not have errors: {:?}", result.diagnostics);
+    assert!(
+        result.code.contains(".container[_ngcontent-%COMP%]{color:red;background:0 0}"),
+        "Generated code should contain minified component styles: {}",
+        result.code
+    );
+}
+
 #[test]
 fn test_component_without_styles_downgrades_encapsulation() {
     let allocator = Allocator::default();

napi/angular-compiler/README.md

@@ -139,6 +139,9 @@ interface TransformOptions {
   // i18n
   i18nUseExternalIds?: boolean
 
+  // Final component style output
+  minifyComponentStyles?: boolean
+
   // Component metadata
   selector?: string
   standalone?: boolean
@@ -176,6 +179,7 @@ interface AngularPluginOptions {
 
   // Style processing
   inlineStylesExtension?: string
+  minifyComponentStyles?: boolean | 'auto'
 
   // File replacements
   fileReplacements?: Array<{
@@ -185,6 +189,14 @@ interface AngularPluginOptions {
 }
 ```
 
+`minifyComponentStyles` resolves like this:
+
+- `true`: always minify component styles
+- `false`: never minify component styles
+- `"auto"` or `undefined`: follow the resolved Vite minification settings
+
+For `"auto"`, the plugin uses `build.cssMinify` when it is set, otherwise it falls back to `build.minify`. In dev, `"auto"` defaults to `false`.
+
 ## Vite Plugin Architecture
 
 The Vite plugin consists of three sub-plugins:

napi/angular-compiler/e2e/tests/build-minify-component-styles.spec.ts

@@ -0,0 +1,97 @@
+import { execSync } from 'node:child_process'
+import { existsSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import { test, expect } from '@playwright/test'
+
+const __dirname = fileURLToPath(new URL('.', import.meta.url))
+const APP_DIR = join(__dirname, '../app')
+const BUILD_OUT_DIR = join(APP_DIR, 'dist-minify')
+const TEMP_CONFIG = join(APP_DIR, 'vite.config.minify.ts')
+
+function writeBuildConfig(minify: boolean): void {
+  writeFileSync(
+    TEMP_CONFIG,
+    `
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+import { angular } from '@oxc-angular/vite';
+import { defineConfig } from 'vite';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const tsconfig = path.resolve(__dirname, './tsconfig.json');
+
+export default defineConfig({
+  plugins: [
+    angular({
+      tsconfig,
+      liveReload: false,
+      minifyComponentStyles: 'auto',
+    }),
+  ],
+  build: {
+    minify: ${minify},
+    outDir: 'dist-minify',
+    rollupOptions: {
+      external: [/^@angular\\/.+$/, /^rxjs(?:\\/.+)?$/, /^tslib$/],
+    },
+  },
+});
+`.trim(),
+    'utf-8',
+  )
+}
+
+function cleanup(): void {
+  rmSync(TEMP_CONFIG, { force: true })
+  rmSync(BUILD_OUT_DIR, { recursive: true, force: true })
+}
+
+function readBuiltJs(): string {
+  const assetDir = join(BUILD_OUT_DIR, 'assets')
+  const files = existsSync(assetDir) ? readdirSync(assetDir) : []
+  const jsFiles = files.filter((file) => file.endsWith('.js'))
+
+  expect(jsFiles.length).toBeGreaterThan(0)
+
+  return jsFiles.map((file) => readFileSync(join(assetDir, file), 'utf-8')).join('\n')
+}
+
+test.describe('build auto minify component styles', () => {
+  test.afterEach(() => {
+    cleanup()
+  })
+
+  test('minifies embedded component styles when build.minify is true', () => {
+    writeBuildConfig(true)
+
+    execSync('npx vite build --config vite.config.minify.ts', {
+      cwd: APP_DIR,
+      stdio: 'pipe',
+      timeout: 60000,
+    })
+
+    const output = readBuiltJs()
+
+    expect(output).toContain('.card-title[_ngcontent-%COMP%]{color:green;margin:0}')
+  })
+
+  test('keeps embedded component styles unminified when build.minify is false', () => {
+    writeBuildConfig(false)
+
+    execSync('npx vite build --config vite.config.minify.ts', {
+      cwd: APP_DIR,
+      stdio: 'pipe',
+      timeout: 60000,
+    })
+
+    const output = readBuiltJs()
+
+    expect(output).toContain(
+      '.card-title[_ngcontent-%COMP%] {\\n  color: green;\\n  margin: 0;\\n}',
+    )
+  })
+})

napi/angular-compiler/index.d.ts

@@ -826,6 +826,13 @@ export interface TransformOptions {
    * Default: false (metadata is dev-only and usually stripped in production)
    */
   emitClassMetadata?: boolean
+  /**
+   * Minify final component styles before emitting them into `styles: [...]`.
+   *
+   * This runs after Angular style encapsulation, so it applies to the same
+   * final CSS strings that are embedded in generated component definitions.
+   */
+  minifyComponentStyles?: boolean
   /**
    * Resolved import paths for host directives and other imports.
    *