[lukesandberg]

Summary

Export circuit breakers protect evaluation cycles by exposing lazy export getters before module execution. A cycle that closes only through a deferred module edge cannot be traversed during evaluation, so applying circuit-breaker code generation to it adds unnecessary early export setup and getters.

This change reuses the evaluation timing recorded on module-reference binding metadata when selecting circuit-breaker cycles. The cycle detector still considers only parallel, used edges, and now also excludes edges proven to execute after their parent module finishes evaluating. Deferred references remain in every reachability, export-usage, chunking, and runtime-loading path; only evaluation-cycle detection is narrowed.

Separate scope-hoisting fixtures pin both sides of the behavior: a cycle closed by a deferred require() uses normal bottom-of-factory value exports, while an all-eager cycle retains early getter initialization.

Verification

• cargo test -p turbopack-core module_graph --lib
• cargo nextest run -p turbopack-tests -E 'test(snapshot) | test(/circuit_breaker_(deferred|eager)_edge/) | test(/side_effect_optimization|side_effects_optimization/) | test(/async_modules/) | test(/execution__turbopack__scope_hoisting/) | test(/cjs_remove_unused_imports/)'
• cargo check -p turbopack-core -p turbopack-ecmascript -p turbopack-tests

[github-actions]

Failing test suites

Commit: e6b43fb | About building and testing Next.js

pnpm test-dev-experimental-turbo test/development/app-dir/lazy-dynamic-imports/lazy-dynamic-imports.test.ts (turbopack) (Experimental) (job)

• lazy-dynamic-imports > does not parse a dynamic import target before activation (DD)

Expand output

● lazy-dynamic-imports › does not parse a dynamic import target before activation

expect(received).toContain(expected) // indexOf

Matcher error: received value must not be null nor undefined

Received has value: null

  257 |         await browser.elementByCss('#load-parse-error').click()
  258 |         await waitForRedbox(browser)
> 259 |         expect(await getRedboxSource(browser)).toContain(
      |                                                ^
  260 |           'parse-error-proves-target-was-analyzed'
  261 |         )
  262 |       } finally {

  at Object.toContain (development/app-dir/lazy-dynamic-imports/lazy-dynamic-imports.test.ts:259:48)