Windtrap_runtimeSourceThe runtime library that instrumented code links.
Code instrumented by ppx_windtrap.coverage calls Coverage, and code instrumented by ppx_windtrap.mutate calls Mutate, at module load and then at every point or site. The mutation loop of the windtrap library drives Mutate and writes what it finds through Verdicts, and the windtrap command merges the files of both formats. Instr is what the two formats share.
The library depends on the standard library only, so it cannot call the windtrap library. It writes its warnings itself, on the standard error of the instrumented process and behind the windtrap: prefix, whatever the flags of a run. It reads one environment variable, WINDTRAP_COVERAGE_FILE, at the first Coverage.register of the process. It never decides which mutants a run tests nor which one a process arms. Its caller does, with Mutate.catalogue and Mutate.arm.
Loading the library has one effect, the registration of the printer of Mutate.Runaway.
Generated code. The ppx_windtrap package depends on the windtrap package at its own version, so the rewriters and this library are released together. That pairing is why generated code may name Coverage.register, Coverage.visit and the fields of Coverage.point, and Mutate.register and the fields of Mutate.site. No stability of these names is promised from one version to the next.
What the two file formats share: build paths, writer identities, atomic writes and the scanner. It also holds the warning line of the runtime.
Expression coverage: the point registry, the dump written at exit and the report data.
Mutation: the mutant catalogue, the arming guard and the reach map.