yak(make-checkverify-format-gate-rewrites-files-instead-of-checking-lnje): make check/verify format gate rewrites files instead of checking

blogex/Makefile

@@ -3,15 +3,17 @@
 MISE_BIN ?= mise
 MISE_EXEC = $(MISE_BIN) exec --
 
-.PHONY: check precommit deps compile test test.coverage coverage crap format verify
+.PHONY: check precommit deps compile test test.coverage coverage crap format format.check verify
 
 # Cheap static gate for this library (no database, no coverage). Runs from the
-# root `make check`, which loops app then blogex.
+# root `make check`, which loops app then blogex. `format.check` only reports:
+# a gate that rewrites the files it judges can never fail. Fix formatting with
+# `make format`.
 #
 # Sensor slot: add `credo` once the "credo strict, tuned config (both apps)"
 # yak lands blogex's credo dep + .credo.exs. Do not list it before then — a
 # gate that claims a check it did not run is worse than no gate.
-check: compile format
+check: compile format.check
 
 # Per-app precommit loop: same target name and alias shape as app/, so both
 # apps share one habit (compile --warning-as-errors, format, test).
@@ -58,10 +60,18 @@ crap:
 	@test -f cover/default.coverdata || { echo "crap: no exported coverage - run 'make test.coverage' first" >&2; exit 1; }
 	MIX_ENV=test $(MISE_EXEC) mix crap
 
-# Format code
+# Format code. MUTATES the tree; deliberately not part of `check` (nor of the
+# Lens pass), which must never write: a gate that fixes what it judges can never
+# fail, and would dirty the tree a push is about to send. `make check` uses
+# `format.check` below instead.
 format:
 	$(MISE_EXEC) mix format
 
+# Verify formatting without writing. Fails with the offending files, so the fix
+# is explicit: run `make format` (or `make -C blogex format`).
+format.check:
+	$(MISE_EXEC) mix format --check-formatted
+
 # =============================================================================
 # Lens pass (heavy checks; root `make verify` runs this before every push)
 # =============================================================================