Mutare.Gettext (mutare_gettext v0.1.0)

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A Mutare extension that teaches Mutare to read Gettext's translation macros, so the built-in mutators land on a use Gettext module without poisoning the single metamutant build.

It is an extension, not a mutator: it produces no mutations, is charged no slot, and never appears in a report — it only makes the built-in mutators' work land (the bare gettext calls resolve; the right arguments are offered). List it under :extensions (in .mutare.exs or Mutare.run/2):

# .mutare.exs
[extensions: [Mutare.Gettext]]

What it does

Two capability behaviours, one per half of the Gettext problem (see Mutare.Extension):

  • Mutare.UseExpansion.expand_use/3 — takes over every use Gettext line and injects the import Gettext.Macros directive it would. Gettext (>= 0.26) compiles use Gettext, backend: MyApp.Gettext by mutating the caller module to register the backend, which raises when Mutare expands it in the scan process (the caller is already compiled), so the import never surfaces and the bare gettext/ngettext calls never resolve. (The backend: value is a module alias, not a compile-time literal, so Mutare's static-literal opts gate would skip the expansion regardless.) Re-injecting the import directly is the fix — now the calls resolve and route.

  • Mutare.CallRouting.call_routes/0 — routes each Gettext macro's arguments. The compile-time literal positions — message id, plural id, domain, context, backend — must never be mutated: they have to stay literals, and splicing a mutation selector there makes the macro raise while expanding and poisons the build. The runtime positions — the ngettext plural count and the interpolation bindings — are mutated, so a stale plural threshold or a wrong interpolation value still gets caught.

This is expressed as a whole-module :raw baseline ({Gettext.Macros, :*, :raw} — every argument of every macro left untouched, the safe default) plus a per-position override for each arity that carries a count/bindings, routing just those trailing positions :expression (a more specific route wins; see Mutare.CallRouting). For example ngettext/4 routes [:raw, :raw, :expression, :expression] — the two msgids stay literal, the count and bindings mutate. The overrides are derived from the Gettext macro families rather than hand-listed, so a position can't drift (the package's test cross-checks every one against the real Gettext.Macros).

Targets Gettext >= 0.26 (the Gettext.Macros era). On an older Gettext the injected import Gettext.Macros names a module that isn't loaded, so resolution conservatively raws it and the extension degrades to a harmless no-op.