feat: support import.meta.hot hmr alias

crates/rspack_core/src/options/module.rs

@@ -394,6 +394,7 @@ define_import_meta_known_properties! {
   const DIRNAME = "dirname";
   const FILENAME = "filename";
   const GLOB = "glob";
+  const HOT = "hot";
   const MAIN = "main";
   const RESOLVE = "resolve";
   const RSPACK_BASE_URI = "rspackBaseUri";
@@ -1932,4 +1933,22 @@ mod tests {
 
     assert_eq!(options.rules[0].effect.id, 0);
   }
+
+  #[test]
+  fn import_meta_hot_options_are_independent() {
+    let hot_disabled = ImportMetaOptions::new(HashMap::from_iter([("hot".to_string(), false)]));
+    assert!(!hot_disabled.is_known_property_enabled(ImportMetaKnownProperties::HOT));
+    assert!(
+      hot_disabled.is_known_property_enabled(ImportMetaKnownProperties::WEBPACK_HOT),
+      "disabling import.meta.hot should not disable import.meta.webpackHot"
+    );
+
+    let webpack_hot_disabled =
+      ImportMetaOptions::new(HashMap::from_iter([("webpackHot".to_string(), false)]));
+    assert!(webpack_hot_disabled.is_known_property_enabled(ImportMetaKnownProperties::HOT));
+    assert!(
+      !webpack_hot_disabled.is_known_property_enabled(ImportMetaKnownProperties::WEBPACK_HOT),
+      "disabling import.meta.webpackHot should not disable import.meta.hot"
+    );
+  }
 }

crates/rspack_plugin_javascript/src/parser_plugin/hot_module_replacement_plugin.rs

@@ -16,6 +16,48 @@ use crate::{
 
 type CreateDependency = fn(Atom, DependencyRange) -> BoxDependency;
 
+fn is_import_meta_hot(for_name: &str) -> bool {
+  matches!(
+    for_name,
+    expr_name::IMPORT_META_HOT | expr_name::IMPORT_META_HOT_ALIAS
+  )
+}
+
+fn is_import_meta_hot_accept(for_name: &str) -> bool {
+  matches!(
+    for_name,
+    expr_name::IMPORT_META_HOT_ACCEPT | expr_name::IMPORT_META_HOT_ALIAS_ACCEPT
+  )
+}
+
+fn is_import_meta_hot_decline(for_name: &str) -> bool {
+  matches!(
+    for_name,
+    expr_name::IMPORT_META_HOT_DECLINE | expr_name::IMPORT_META_HOT_ALIAS_DECLINE
+  )
+}
+
+fn import_meta_hot_property(for_name: &str) -> Option<ImportMetaKnownProperties> {
+  match for_name {
+    expr_name::IMPORT_META_HOT
+    | expr_name::IMPORT_META_HOT_ACCEPT
+    | expr_name::IMPORT_META_HOT_DECLINE => Some(ImportMetaKnownProperties::WEBPACK_HOT),
+    expr_name::IMPORT_META_HOT_ALIAS
+    | expr_name::IMPORT_META_HOT_ALIAS_ACCEPT
+    | expr_name::IMPORT_META_HOT_ALIAS_DECLINE => Some(ImportMetaKnownProperties::HOT),
+    _ => None,
+  }
+}
+
+fn is_import_meta_hot_enabled(parser: &JavascriptParser, for_name: &str) -> bool {
+  import_meta_hot_property(for_name).is_some_and(|property| {
+    parser
+      .javascript_options
+      .import_meta()
+      .is_known_property_enabled(property)
+  })
+}
+
 fn extract_deps(
   parser: &mut JavascriptParser,
   call_expr: &CallExpr,
@@ -211,14 +253,9 @@ impl<'p, 'a> JavascriptParserPlugin<'p, 'a> for ImportMetaHotReplacementParserPl
     start: u32,
     end: u32,
   ) -> Option<crate::utils::eval::BasicEvaluatedExpression<'p>> {
-    if for_name == expr_name::IMPORT_META_HOT
-      && parser
-        .javascript_options
-        .import_meta()
-        .is_known_property_enabled(ImportMetaKnownProperties::WEBPACK_HOT)
-    {
+    if is_import_meta_hot(for_name) && is_import_meta_hot_enabled(parser, for_name) {
       Some(eval::evaluate_to_identifier(
-        expr_name::IMPORT_META_HOT.into(),
+        for_name.into(),
         expr_name::IMPORT_META.into(),
         Some(true),
         start,
@@ -235,12 +272,7 @@ impl<'p, 'a> JavascriptParserPlugin<'p, 'a> for ImportMetaHotReplacementParserPl
     expr: &MemberExpr,
     for_name: &str,
   ) -> Option<bool> {
-    if for_name == expr_name::IMPORT_META_HOT
-      && parser
-        .javascript_options
-        .import_meta()
-        .is_known_property_enabled(ImportMetaKnownProperties::WEBPACK_HOT)
-    {
+    if is_import_meta_hot(for_name) && is_import_meta_hot_enabled(parser, for_name) {
       parser.create_hmr_expression_handler(expr.span());
       Some(true)
     } else {
@@ -254,19 +286,15 @@ impl<'p, 'a> JavascriptParserPlugin<'p, 'a> for ImportMetaHotReplacementParserPl
     call_expr: &CallExpr,
     for_name: &str,
   ) -> Option<bool> {
-    if !parser
-      .javascript_options
-      .import_meta()
-      .is_known_property_enabled(ImportMetaKnownProperties::WEBPACK_HOT)
-    {
+    if !is_import_meta_hot_enabled(parser, for_name) {
       return None;
     }
 
-    if for_name == expr_name::IMPORT_META_HOT_ACCEPT {
+    if is_import_meta_hot_accept(for_name) {
       parser.create_accept_handler(call_expr, |request, range| {
         Box::new(ImportMetaHotAcceptDependency::new(request, range))
       })
-    } else if for_name == expr_name::IMPORT_META_HOT_DECLINE {
+    } else if is_import_meta_hot_decline(for_name) {
       parser.create_decline_handler(call_expr, |request, range| {
         Box::new(ImportMetaHotDeclineDependency::new(request, range))
       })

crates/rspack_plugin_javascript/src/parser_plugin/import_meta_plugin.rs

@@ -297,7 +297,11 @@ impl ImportMetaPlugin {
     if let Some(api) = import_meta_runtime_api_from_name(name) {
       return Some(api.property);
     }
-    None
+    match name {
+      expr_name::IMPORT_META_HOT => Some(ImportMetaKnownProperties::WEBPACK_HOT),
+      expr_name::IMPORT_META_HOT_ALIAS => Some(ImportMetaKnownProperties::HOT),
+      _ => None,
+    }
   }
 
   fn preserve_property(&self, property: Option<&str>) -> bool {
@@ -488,6 +492,12 @@ impl<'p, 'a> JavascriptParserPlugin<'p, 'a> for ImportMetaPlugin {
       && self.runtime_api_enabled(api)
     {
       evaluated = Some(api.type_of.to_string())
+    } else if Self::known_property_from_name(for_name)
+      .is_some_and(|property| self.known_property_enabled(property))
+    {
+      // HMR fields are evaluated by HotModuleReplacementPlugin. Keep `typeof`
+      // unknown here so the member expression can be rewritten to `module.hot`.
+      return None;
     } else if let Some(member_expr) = expr.arg.as_member()
       && let Some(meta_expr) = member_expr.obj.as_meta_prop()
       && meta_expr

crates/rspack_plugin_javascript/src/visitors/dependency/util.rs

@@ -32,6 +32,9 @@ pub mod expr_name {
   pub const IMPORT_META_HOT: &str = "import.meta.webpackHot";
   pub const IMPORT_META_HOT_ACCEPT: &str = "import.meta.webpackHot.accept";
   pub const IMPORT_META_HOT_DECLINE: &str = "import.meta.webpackHot.decline";
+  pub const IMPORT_META_HOT_ALIAS: &str = "import.meta.hot";
+  pub const IMPORT_META_HOT_ALIAS_ACCEPT: &str = "import.meta.hot.accept";
+  pub const IMPORT_META_HOT_ALIAS_DECLINE: &str = "import.meta.hot.decline";
   pub const IMPORT_META_CONTEXT: &str = "import.meta.webpackContext";
   pub const IMPORT_META_GLOB: &str = "import.meta.glob";
 }

packages/rspack/module.d.ts

@@ -229,6 +229,7 @@ declare namespace Rspack {
 
 interface ImportMeta {
   url: string;
+  hot?: Rspack.Hot;
   webpackHot?: Rspack.Hot;
   webpackContext: (
     request: string,

packages/rspack/src/config/types.ts

@@ -1199,6 +1199,11 @@ export type ImportMetaParserOptions = {
    */
   glob?: boolean;
 
+  /**
+   * Enable/disable evaluating import.meta.hot.
+   */
+  hot?: boolean;
+
   /**
    * Enable/disable evaluating import.meta.main.
    */

tests/rspack-test/configCases/parsing/import-meta-hot/dep.js

@@ -0,0 +1 @@
+export default "import.meta.hot";

tests/rspack-test/configCases/parsing/import-meta-hot/index.js

@@ -0,0 +1,32 @@
+import value from "./dep";
+
+const fs = require("fs");
+
+let typeofGuardMatched = false;
+let webpackHotTypeofGuardMatched = false;
+
+if (typeof import.meta.hot !== "undefined") {
+	typeofGuardMatched = true;
+}
+
+if (typeof import.meta.webpackHot !== "undefined") {
+	webpackHotTypeofGuardMatched = true;
+}
+
+if (import.meta.hot) {
+	import.meta.hot.accept(["./dep"], () => {});
+}
+
+it("should support import.meta.hot as an HMR alias", () => {
+	expect(value).toBe("import.meta.hot");
+	expect(typeofGuardMatched).toBe(true);
+	expect(webpackHotTypeofGuardMatched).toBe(true);
+	expect(typeof import.meta.hot).toBe("object");
+	expect(typeof import.meta.hot.accept).toBe("function");
+	expect(typeof import.meta.webpackHot).toBe("object");
+
+	const source = fs.readFileSync(__filename, "utf-8");
+	const typeofKeyword = ["type", "of"].join("");
+	const runtimeTypeof = `${typeofKeyword} module.hot !== "undefined"`;
+	expect(source.split(runtimeTypeof)).toHaveLength(3);
+});

tests/rspack-test/configCases/parsing/import-meta-hot/parser-options.js

@@ -0,0 +1,15 @@
+const fs = require("fs");
+
+it("should disable the hot alias independently from the canonical HMR field", () => {
+	expect(typeof import.meta.hot).toBe("undefined");
+	expect(typeof import.meta.webpackHot).toBe("object");
+	if (import.meta.hot) {
+		import.meta.hot.accept();
+		import.meta.hot.decline();
+	}
+
+	const source = fs.readFileSync(__filename, "utf-8");
+	const importMeta = ["import", "meta"].join(".");
+	expect(source.split(`${importMeta}.hot`)).toHaveLength(5);
+	expect(source).not.toContain(`${importMeta}.webpackHot`);
+});

tests/rspack-test/configCases/parsing/import-meta-hot/production.js

@@ -0,0 +1,9 @@
+it("should transform import.meta.hot to false without HMR", () => {
+	let hot = false;
+	if (import.meta.hot) {
+		hot = true;
+		import.meta.hot.accept();
+	}
+
+	expect(hot).toBe(false);
+});

tests/rspack-test/configCases/parsing/import-meta-hot/rspack.config.js

@@ -0,0 +1,47 @@
+const { HotModuleReplacementPlugin } = require('@rspack/core');
+
+/** @type {import("@rspack/core").Configuration[]} */
+module.exports = [
+  {
+    entry: './index.js',
+    devtool: false,
+    externals: {
+      fs: 'node-commonjs fs',
+    },
+    node: {
+      __filename: false,
+    },
+    plugins: [new HotModuleReplacementPlugin()],
+  },
+  {
+    entry: './production.js',
+    mode: 'production',
+    target: 'web',
+    devServer: {
+      hot: true,
+    },
+  },
+  {
+    entry: './parser-options.js',
+    mode: 'development',
+    devtool: false,
+    target: 'node',
+    experiments: {
+      outputModule: true,
+    },
+    output: {
+      module: true,
+      chunkFormat: 'module',
+    },
+    module: {
+      parser: {
+        javascript: {
+          importMeta: {
+            hot: false,
+          },
+        },
+      },
+    },
+    plugins: [new HotModuleReplacementPlugin()],
+  },
+];

website/docs/en/api/runtime-api/hmr.mdx

@@ -10,9 +10,11 @@ import WebpackLicense from '@components/WebpackLicense';
 
 Rspack provides the same interface as webpack for implementing HMR.
 
-If you've enabled Hot Module Replacement via the [HotModuleReplacementPlugin](/plugins/webpack/hot-module-replacement-plugin), its interface is exposed on the `module.hot` and `import.meta.webpackHot` objects.
+If you've enabled Hot Module Replacement via the [HotModuleReplacementPlugin](/plugins/webpack/hot-module-replacement-plugin), its interface is exposed on the `module.hot`, `import.meta.webpackHot`, and `import.meta.hot` objects.
 
-In ESM, use `import.meta.webpackHot` instead of `module.hot`.
+In ESM, use `import.meta.webpackHot` or `import.meta.hot` instead of `module.hot`.
+
+`import.meta.hot` is available since Rspack 2.1.5.
 
 ## Example
 
@@ -33,7 +35,7 @@ if (import.meta.webpackHot) {
 }
 ```
 
-The following methods are supported by `module.hot` and `import.meta.webpackHot`.
+The following methods are supported by `module.hot`, `import.meta.webpackHot`, and `import.meta.hot`.
 
 ## Module API
 

website/docs/zh/api/runtime-api/hmr.mdx

@@ -10,9 +10,11 @@ import WebpackLicense from '@components/WebpackLicense';
 
 Rspack 提供了与 webpack 相同的接口来实现模块热替换。
 
-如果你通过 [HotModuleReplacementPlugin](/plugins/webpack/hot-module-replacement-plugin) 启用了模块热替换，它的接口将暴露在 `module.hot` 和 `import.meta.webpackHot` 对象下。
+如果你通过 [HotModuleReplacementPlugin](/plugins/webpack/hot-module-replacement-plugin) 启用了模块热替换，它的接口将暴露在 `module.hot`、`import.meta.webpackHot` 和 `import.meta.hot` 对象下。
 
-注意，在 ESM 中请使用 `import.meta.webpackHot` 来代替 `module.hot`。
+注意，在 ESM 中请使用 `import.meta.webpackHot` 或 `import.meta.hot` 来代替 `module.hot`。
+
+`import.meta.hot` 从 Rspack 2.1.5 开始可用。
 
 ## 示例
 
@@ -33,7 +35,7 @@ if (import.meta.webpackHot) {
 }
 ```
 
-`module.hot` 和 `import.meta.webpackHot` 支持以下方法。
+`module.hot`、`import.meta.webpackHot` 和 `import.meta.hot` 支持以下方法。
 
 ## 模块 API