@systemfsoftware/stryker-js-instrumenter

Parses source files, applies their configured mutators, and produces the mutant set for a mutation run.

Install

pnpm add @systemfsoftware/stryker-js-instrumenter

Entry points

• @systemfsoftware/stryker-js-instrumenter

Use

The instrumenter is used internally by the Stryker mutation testing framework to instrument source files with mutant coverage and switching logic.

File formats resolve through a format registry: coreFormatRegistry carries the built-in js/ts/tsx entries, frameworkEntryOf adapts a framework's Framework object into an entry, and registerEntries folds additions into a registry (an extension already claimed stays with the earlier entry). instrument(files, options, registry) and disableTypeChecks(file, registry) accept that registry — defaulting to the core one — and instrument returns the files it skipped because no entry claimed their extension.

options.mutantSetPolicy states which mutant set the run wants and is required: 'default' is the product default, and 'full' turns off the mutant-set pruning the instrumenter would otherwise apply, so the run keeps every mutation the selected mutators can plant.

Opt-in mutators

Three mutators that plant Effect concurrency faults are available on request and stay out of the default set. Enable any subset in your Stryker config:

{
  "mutator": {
    "optInMutations": ["AtomicUpdateSplit", "SynchronizationRemoval", "FinalizerEscape"]
  }
}

• AtomicUpdateSplit turns read-modify-write calls such as Ref.update or SynchronizedRef.modify into a separate read, a yield, and a separate write, so an interleaved mutation can lose an update.
• SynchronizationRemoval drops the guarding effect of Semaphore.withPermits/withPermit and Effect.uninterruptible, letting code that assumed exclusivity or uninterruptibility run without it.
• FinalizerEscape weakens Effect.ensuring, Effect.onExit, Effect.onError, and Effect.onInterrupt so their cleanup no longer runs on interruption.

Naming a mutator that does not exist fails the run before instrumentation, as a config failure naming the entry. The replacements these mutators plant use Effect 4 APIs, so a repository on Effect 3.x must not opt in.

License

Apache-2.0. Part of systemfsoftware.