feat: preserve tla expr for EsmLibrary

[JSerFeng]

Summary

Preserve top level await expr as is, support scope hoist async modules.

Related links

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[Copilot]

Pull request overview

This PR adds support for preserving top-level await (TLA) expressions in ESM library output and enables scope hoisting for async modules. The main issue being addressed is that when using TLA, available modules optimization was incorrectly removing dependencies from child chunks, even though those modules weren't actually loaded yet when the child chunk was being loaded.

Changes:

• Tracks top-level await context through a new in_top_level_await field in the JavaScript parser
• Propagates the TLA flag through dependency blocks and import dependencies
• Modifies build chunk graph logic to skip available modules optimization when dependencies are within TLA expressions
• Removes the async module bailout from ESM library plugin to enable scope hoisting for async modules
• Refactors re-export logic from ChunkLinkContext methods to standalone functions in link.rs

Reviewed changes

Copilot reviewed 52 out of 53 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
.vscode/settings.json	Adds Rust formatter configuration (unrelated to PR purpose)
crates/rspack_core/src/compilation/build_chunk_graph/code_splitter.rs	Adds logic to skip available modules merging for TLA dependencies
crates/rspack_core/src/compilation/build_chunk_graph/mod.rs	Adds hook system for controlling TLA behavior and makes function async
crates/rspack_core/src/compilation/build_chunk_graph/pass.rs	Updates to call async build_chunk_graph
crates/rspack_core/src/compilation/mod.rs	Minor formatting change
crates/rspack_core/src/context_module.rs	Adds in_top_level_await field to ContextOptions and passes to blocks
crates/rspack_core/src/dependencies_block.rs	Adds in_top_level_await parameter to AsyncDependenciesBlock
crates/rspack_core/src/plugin/context.rs	Adds build_chunk_graph_hooks to ApplyContext
crates/rspack_core/src/plugin/plugin_driver.rs	Registers build_chunk_graph_hooks
crates/rspack_plugin_esm_library/src/chunk_link.rs	Removes re-export methods (moved to link.rs) and adds re_exports_mut accessor
crates/rspack_plugin_esm_library/src/lib.rs	Renames module from ensure_entry_exports to optimize_chunks
crates/rspack_plugin_esm_library/src/link.rs	Refactors export tracking to use ExportsContext struct and moves re-export methods here
crates/rspack_plugin_esm_library/src/optimize_chunks.rs	File rename from ensure_entry_exports.rs
crates/rspack_plugin_esm_library/src/plugin.rs	Removes async module bailout and adds ignore_top_level_await hook returning false
crates/rspack_plugin_javascript/src/dependency/esm/import_dependency.rs	Adds in_top_level_await field and accessor method
crates/rspack_plugin_javascript/src/parser_plugin/*.rs	Updates all dependency/block creation sites to pass in_top_level_await
crates/rspack_plugin_javascript/src/visitors/dependency/parser/mod.rs	Adds in_top_level_await field to JavascriptParser
crates/rspack_plugin_javascript/src/visitors/dependency/parser/walk.rs	Tracks TLA state when walking await expressions
crates/rspack_plugin_javascript/src/visitors/dependency/parser/walk_pre.rs	Tracks TLA state when pre-walking for-await-of statements
crates/rspack_plugin_lazy_compilation/src/module.rs	Adds in_top_level_await field and passes to blocks
crates/rspack_plugin_lazy_compilation/src/plugin.rs	Extracts TLA flag from ImportDependency
crates/rspack_plugin_mf/src/*.rs	Updates AsyncDependenciesBlock calls to pass false for TLA
crates/rspack_plugin_rstest/src/parser_plugin.rs	Updates dependency/block creation to pass in_top_level_await
tests/rspack-test/esmOutputCases/basic/async-modules/__snapshots__/esm.snap.txt	Updated snapshot showing scope-hoisted async modules
tests/rspack-test/esmOutputCases/top-level-await/*	New test cases for TLA scenarios

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[github-actions]

Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 0 projects with changes.

📊 Quick Summary

Project	Total Size	Change
react-10k	5.7 MB	0
react-1k	825.4 KB	0
react-5k	2.7 MB	0
rome	984.2 KB	0
ui-components	2.2 MB	0

Generated by Rsdoctor GitHub Action

[github-actions]

📦 Binary Size-limit

Comparing aed151a to refactor: use runtime template for context module codegen (#12957) by Gengkun

❌ Size increased by 1.75KB from 48.56MB to 48.56MB (⬆️0.00%)

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing feat/esm-tla (aed151a) with main (0f251ee)}

Summary

✅ 16 untouched benchmarks
⏩ 1 skipped benchmark¹

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[JSerFeng]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

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