zarara

This repository is a focused fuzzing harness for Rolldown output graph behavior.

It generates random module graphs, bundles them with Rolldown, and asserts:

• input static graph is acyclic
• output static chunk-import graph is also acyclic
• output chunks contain valid JavaScript (parsed with oxc_parser)
• entry chunks preserve all expected exports (when preserveEntrySignatures: "strict")
• output is deterministic (bundling twice produces identical results)

When a failure is found, the test prints markdown with:

• failed seed
• minimized graph structure
• detected output cycle path
• REPL URL (repl.rolldown.rs) for quick inspection
• fixture generation command

Repository Layout

• output_fuzz_common/
  • Shared fuzz infrastructure (GraphCase, materialization, case-spec encoding, generate_fixture binary)
• acyclic_output_fuzz/
  • Acyclic-input/acyclic-output property test + cycle checker
• deterministic_output_fuzz/
  • Determinism property test (covers rolldown#9754)
• rolldown/
  • Rolldown source as a submodule dependency for the harness
• .github/workflows/output_fuzz.yml
  • scheduled fuzz workflow + issue tracking

Fuzz Tests

Test	What it checks
acyclic_input_produces_acyclic_output	Acyclic input graphs produce acyclic output chunk-import graphs, valid JS, entry export preservation.
deterministic_output	Bundling the same graph twice produces identical chunks (filenames, code, imports, exports). Covers rolldown#9754 via static default imports from the same external module under different local names per importer.

Run Locally

Run all fuzz tests:

cargo test --workspace -- --nocapture

Run a specific test:

cargo test -p acyclic_output_fuzz acyclic_input_produces_acyclic_output -- --nocapture
cargo test -p deterministic_output_fuzz deterministic_output -- --nocapture

Increase search space:

PROPTEST_CASES=2000 cargo test --workspace -- --nocapture

Use a deterministic RNG seed:

PROPTEST_RNG_SEED=123456 cargo test --workspace -- --nocapture

Reproduce a Failure

Use the command printed in ### Generate Fixture, for example:

cargo run -p output_fuzz_common --bin generate_fixture -- --seed <u64> --case '<case-spec>' --out ./fixtures/seed-<u64>

That writes:

• generated input modules (node*.js)
• rolldown.config.js with matching fuzz options

You can also open the printed ### REPL URL directly in https://repl.rolldown.rs/.

CI Workflow

The workflow in .github/workflows/output_fuzz.yml:

• runs daily and on manual dispatch
• uploads the fuzz log artifact
• creates/updates a tracking issue in the current repository on failure
• posts the exact failure markdown as an issue comment