Mutare.Sandbox.CompilerOptions (mutare v0.1.2)

The switches that tune the one metamutant compile for speed.

Mutare compiles the metamutant exactly once before any mutant runs, so it can afford to drop compile-time work that would be net-negative if paid per run — and everything dropped here is diagnostics-only: the metamutant is a build artifact whose warnings nobody reads, and none of it changes the compiled code a mutant run executes. Three switches, one home (this module), three delivery routes:

compiler_env/0 — the ERL_COMPILER_OPTIONS entry Mutare.Runner applies to the single mix compile (the SSA alias pass off).
compile_args/1 — extra mix compile CLI switches for the same invocation (--no-verification, Elixir ≥ 1.19: skips the Module.ParallelChecker verify pass — undefined-remote warnings and cross-module type checking).
infer_signatures_off_ast/0 — a snippet Mutare.Sandbox prefixes into the sandbox config/config.exs, turning off type-signature inference during module compilation (a project-level elixirc_options setting with no CLI or env form, so it rides the config file Mutare already owns).

The last two exist because Elixir's type checker (≥ 1.18/1.19) is pathological on metamutant-shaped code: measured on phoenix_live_view (~23k sites), inference + verification take a 14 s compile past 80 minutes; with both off it is 14 s again. See NOTES "Type inference and verification on the metamutant compile".

A per-mutant mix test never recompiles the lib (sources unchanged), so the env and args carry nothing there; the config snippet does load on every boot but only affects compilation, so it is equally inert.

Summary

Functions

compile_args(version \\ System.version())

Extra mix compile CLI switches for the metamutant compile.

compiler_env()

Env entries that tune the one metamutant compile for speed: an ERL_COMPILER_OPTIONS disabling the SSA alias-analysis pass (no_ssa_opt_alias).

erl_compiler_options(inherited)

Build the ERL_COMPILER_OPTIONS value for the metamutant compile: prepend no_ssa_opt_alias to any inherited value (an Erlang term-list string, or nil/"" for none), always returning a well-formed [...] list string. Pure, so the merge is unit-testable.

infer_signatures_off_ast()

AST that turns off type-signature inference for code compiled after it runs.

Functions

compile_args(version \\ System.version())

@spec compile_args(String.t()) :: [String.t()]

Extra mix compile CLI switches for the metamutant compile.

--no-verification (Elixir ≥ 1.19.0) skips the Module.ParallelChecker verify pass — undefined-remote-function warnings and cross-module type checking. Warnings on a build artifact are noise, and the type checker is pathological on metamutant-shaped code (measured: ~12 minutes on phoenix_live_view with inference already off). Poison detection is unaffected: it reads hard compile errors, which are raised during compilation, not verification.

version defaults to the running Elixir; it is a parameter so the gate is unit-testable.

compiler_env()

@spec compiler_env() :: [{String.t(), String.t()}]

Env entries that tune the one metamutant compile for speed: an ERL_COMPILER_OPTIONS disabling the SSA alias-analysis pass (no_ssa_opt_alias).

Read by Mutare.Runner for the single mix compile. Scoped there on purpose: a per-mutant mix test never recompiles the lib (sources unchanged), so it carries nothing. Merges with any ERL_COMPILER_OPTIONS already in the environment so a user's own compiler options survive — ours is prepended (erl_compiler_options/1).

erl_compiler_options(inherited)

@spec erl_compiler_options(String.t() | nil) :: String.t()

infer_signatures_off_ast()

@spec infer_signatures_off_ast() :: Macro.t()

AST that turns off type-signature inference for code compiled after it runs.

Mutare.Sandbox prefixes this into the sandbox config/config.exs (mix evaluates config before the compilers run), because :infer_signatures is a project-level elixirc_options setting with no CLI switch or env var — the config file is the one hook Mutare already owns. Inference feeds only type diagnostics; the compiled code is identical. On metamutant-shaped code it is pathological (measured: five phoenix_live_view modules alone push a 14 s compile past 80 minutes).

The rescue makes it a no-op wherever the option doesn't exist (Code.put_compiler_option/2 raises on unknown options pre-1.18) — the same safe-everywhere property no_ssa_opt_alias gets from unknown Erlang options being ignored. A target that sets :infer_signatures explicitly in its own elixirc_options still wins: Mix applies project options after config is loaded.