Niklas Mischkulnig

This commit introduces a **new capability** to **Turbopack** by enhancing its **JavaScript downleveling** for older browser targets. It enables conditional emission of modern syntax, specifically **arrow functions** and **block-scoped declarations (`const`/`let`)**, replacing them with regular functions and `var` when the target environment lacks support. This involves significant updates to the `turbopack-core` environment detection and various `turbopack-ecmascript` modules responsible for code generation and chunking. The `turbopack-ecmascript-runtime` is also modified to conditionally generate browser runtime code. This change ensures that applications built with Turbopack can achieve **broader compatibility** with older browsers, improving the overall reach and robustness of generated bundles.

This commit introduces **support for `createRequire` calls** that utilize `new URL("...", import.meta.url)` for dynamic path resolution, representing a **new capability** within Turbopack. It **enhances the `turbopack-ecmascript` crate's analyzer** to recognize these patterns and implements the corresponding **resolution logic** in the references module. This improvement is vital for achieving **parity with `@vercel/nft`**, ensuring more complex module resolution scenarios are correctly handled. Comprehensive **new test cases** have been added to validate this behavior, improving the robustness of **Turbopack's module resolution**.

This commit introduces a **fix** to ensure consistent hashing within **Turbopack's asset management** for Next.js applications. It updates the `crates/next-api` module to use the `Xxh3Hash128Base38` algorithm for asset content, aligning it with the hashing used for `immutable-static-hashes.json` and preventing potential inconsistencies in asset identification. This change is crucial for reliable caching and deployment of static assets. To validate this behavior, **new integration tests** have been added to the `deployment-id-handling` suite, which verify that immutable asset hashes are correctly emitted to a custom Next.js adapter, enhancing the robustness of the build process.

This commit introduces a **new capability** to **Turbopack's ECMAScript analyzer** by enabling the static evaluation of `path.sep` based on the compile target's platform, aiming for better parity with `@vercel/nft`. A new `path_separator` function was added to the `Platform` enum in `turbopack-core` to provide the appropriate separator, which is then utilized by the `path_module_member` analysis in `turbopack-ecmascript`. This enhancement improves **dependency tracing accuracy** and ensures more reliable builds when `path.sep` is used in modules. Additionally, the `turbopack-tracing` crate received a new `similar` dependency and an enabled `path-sep` test case to validate this functionality.

This commit **fixes** an issue in **Next.js telemetry** where the `turboFlag` was incorrectly hardcoded to `false` during the export process. It introduces a `bundler` property to the `ExportAppOptions` interface and updates the `exportAppImpl` function in `packages/next/src/export/index.ts` to dynamically determine and set the `turboFlag` based on the actual bundler in use. This **enhancement** ensures that **telemetry data** accurately reflects whether **Turbopack** is being utilized during builds. Corresponding **integration tests** have been updated to verify this conditional behavior, improving the reliability of usage reporting.

This commit significantly **enhances the test coverage** for **Turbopack's Node.js file tracing** by pulling in updated and new test cases from `vercel/nft`. It introduces a wide array of **integration and unit tests**, including scenarios for AWS SDK, `sharp-pnpm`, `pino` transports, and complex module resolution involving symlinks and package directories, alongside general updates to existing tests. This is a **maintenance and testing enhancement** that ensures the accuracy and robustness of **Turbopack's dependency tracing** for Node.js applications. The `turbopack-tracing` crate now depends on `turbopack-node` to support these expanded tracing tests.

This commit **fixes a critical bug** in **Turbopack's Webpack loader integration** that previously led to an infinite loop or `Dependency tracking is disabled` error when `turbopack.rules.loader` and `turbopackLoader` were used simultaneously. The **bug fix** addresses a conflict in the internal loader runner layer by **renaming** the `turbopack_use_loaders` layer to `webpack_loaders` within the `process_default_internal` function in `turbopack/crates/turbopack/src/lib.rs`. This change ensures correct layer identification and prevents the aforementioned build failures. New test cases have been added to the `turbopack-import-assertions-use` suite to validate that identity loader rules are now correctly applied.

This commit delivers a **bug fix** and **improvement** to **Turbopack's metadata processing**, resolving a regression related to how metadata imports and **Top-Level Await (TLA)** modules are handled. It modifies the `crates/next-core` module import generation to use lazy `() => require()` for metadata, mirroring the approach for layout segments, and ensures proper awaiting of async metadata modules. This change enhances **Turbopack's compatibility** with Next.js applications utilizing **dynamic routes and asynchronous metadata dependencies**, aligning its behavior with Webpack. A new e2e test suite has been added to validate the correct handling of dynamic routes with async metadata.

This commit **improves Turbopack's CSS processing** by **reclassifying unknown CSS selectors** from fatal errors to warnings. Specifically, unsupported pseudo-classes and pseudo-elements encountered during CSS parsing are now treated as non-blocking warnings, preventing builds from failing due to modern CSS syntax. This **enhancement to error handling** within the `turbopack-css` crate allows developers to use newer CSS features without blocking the build process, providing a more flexible development experience. The core logic change is in `turbopack/crates/turbopack-css/src/process.rs`, with corresponding updates to snapshot tests in `turbopack-tests` to reflect the new warning behavior.

This commit **refactors the Turbopack snapshot testing suite** to **correctly apply effects** when validating issue snapshots. Specifically, it modifies `turbopack-tests/tests/snapshot.rs` by adjusting the return type of `inner_operation` and introducing an `extract_effects` function to ensure effects are properly captured. This **correctness improvement** addresses an issue where effects were not accurately applied during snapshot generation or updates, particularly when `UPDATE=1` is active. The change significantly enhances the reliability of **Turbopack's testing infrastructure** by ensuring accurate validation of issue handling.

This commit performs a **refactoring** by **removing the unused `layer` property** from the **server actions manifest generation** logic. The `build_manifest` function in `crates/next-api/src/server_actions.rs` no longer includes this property, which was deemed unnecessary for internal Webpack usage and unable to accurately model complex action layering. This **maintenance** effort streamlines the internal manifest structure, reducing unnecessary data within the **Next.js API crate**. Consequently, **action type definitions** and numerous **snapshot tests** within the `app-dir/actions-tree-shaking` test suite have been updated to reflect the removal of this property, ensuring consistency across the **server actions subsystem**. The change has no direct user-facing impact, as the `layer` property was an internal detail not relied upon externally.

This commit **refactors Turbopack's chunking strategy** for **Next.js Server Components** and **Server Actions**, acting as a **bug fix** and **maintenance** task to correct module graph entry types. It adjusts the use of `ChunkGroupEntry::Shared` to ensure the client reference transform can correctly infer parent server components during graph traversal, particularly for `layout.js [app-rsc]` modules. This change, affecting **Turbopack's** internal module representation in `crates/next-core` and `crates/next-api`, improves the robustness of **App Router** features and enables better chunk deduplication through turbotask caching.

This commit significantly **improves the testing infrastructure for App Router's server actions tree-shaking**. It **refactors test setup utilities** in `test/production/app-dir/actions-tree-shaking/_testing/utils.ts` to streamline test execution by avoiding redundant builds and introduces the `nextTestSetupActionTreeShaking` utility. This **test refactoring** also enhances the debuggability of test failures by replacing numerical snapshot assertions with detailed inline snapshots that include action names. Consequently, various `actions-tree-shaking` test cases are updated to leverage these improvements, making the tests more robust, efficient, and easier to diagnose.

This commit introduces a **new capability** to specify module chunking types within **Turbopack's ECMAScript module analysis**. It extends support for `turbopack-chunking-type` annotations to **CommonJS `require` and `require.resolve` calls**, mirroring existing ESM `import` functionality, and adds a new `shared` chunking type. This allows developers to explicitly define how modules are chunked using annotations like `/* turbopackChunkingType: parallel */` or `/* turbopackChunkingType: shared */` in `require` calls, and `with { "turbopack-chunking-type": "shared" }` in `import` statements. Additionally, it **improves error messages** for invalid chunking type annotations, enhancing developer experience and debugging.

This commit introduces a **performance optimization** within the **Turbopack ECMAScript analyzer** by **refactoring** how import attributes are stored. It wraps `ImportAnnotations` in an `Option<Arc<ImportAnnotations>>`, leveraging the fact that most imports lack explicit attributes like `import ... with {}` or `require(/*webpackIgnore: true*/...)`. This change avoids unnecessary memory allocations and has a significant **downstream impact**, leading to a **23% speedup** in the JS analyze microbenchmark for `jsonwebtoken.js/full`. The **Turbopack ECMAScript analysis** and reference handling modules are primarily affected, with updates across `turbopack-ecmascript/src/analyzer` and `turbopack-ecmascript/src/references` to accommodate the new optional pointer structure.

This commit introduces an **optimization** to **Turbopack's bundle generation** process by preventing the emission of polyfill chunks specifically for **Next.js API routes**. Previously, these unnecessary polyfills were included, contributing to larger bundle sizes and providing misleading information within the bundle analyzer. The change in `crates/next-api/src/app.rs` now ensures polyfill chunks are conditionally emitted only for page endpoints, effectively **reducing the overall bundle size** for applications heavily utilizing API routes. This enhancement improves build efficiency and provides more accurate bundle analysis for Next.js projects.

This commit performs a significant **refactoring** within the **Turbopack CSS processing pipeline** by renaming several core structs and enums for improved clarity and consistency. Specifically, `CssModuleAsset` is now `CssModule`, `ModuleCssAsset` has become `EcmascriptCssModule`, and `CssModuleAssetType` is renamed to `CssModuleType`. These changes propagate across the `turbopack-css`, `turbopack`, `next-api`, and `next-core` crates, updating all type references, imports, and related comments. This is a purely **semantic change** aimed at enhancing code readability and maintainability without altering any existing functionality.

This commit provides a **bug fix** for the **Next.js custom transforms** specifically addressing issues within the **server actions** transformation logic. It corrects the creation of `Ident` instances in `crates/next-custom-transforms/src/transforms/server_actions.rs` by ensuring they are initialized with the appropriate `SyntaxContext` rather than `SyntaxContext::default()`. This is crucial for maintaining correct variable resolution and semantic understanding of the code, particularly for **Turbopack**, where `SyntaxContext` plays a vital role. The fix prevents potential problems where variables might be incorrectly identified, ensuring proper code transformation and execution.

This commit introduces **new `ast-grep` linting rules** to enforce best practices for error handling, specifically preventing the eager evaluation of error messages when using `.context()` with `format!` or `turbofmt!`. This **new capability** encourages the use of `.with_context()` for lazy evaluation, improving performance by only formatting error messages when they are actually consumed. As part of this **refactoring** effort, several modules within `next-api`, `next-core`, and `turbopack` have been updated to align with the new lint, while `ast-grep-ignore` comments were added in some areas to temporarily bypass the rules due to current false positives. This change significantly enhances the **error handling quality and efficiency** across the codebase by promoting on-demand message generation.

This commit **introduces a new `ReferenceTypeCondition` enum** to enhance **Turbopack's module rule matching system**, addressing previous limitations where specific or complex `ReferenceType` variants were difficult to match precisely. This **refactoring** provides a more robust and accurate mechanism for defining conditions, improving the reliability of module processing. The change is integrated across various **Next.js subsystems**, including app transitions, server-side module resolution, and transformation rules, ensuring correct handling of diverse reference types like CSS, ECMAScript, and URLs. This enables more flexible and precise rule definitions for how modules and assets are processed.