ci: a changed directory in a nested module is not a package of the root module

.github/workflows/ci.yml

@@ -229,6 +229,21 @@ jobs:
             dirs="$(printf '%s\n' "$changed" | { grep '\.go$' || true; } | xargs -r -n1 dirname | sort -u)"
             pkgs=""
             for dir in $dirs; do
+              # A DIRECTORY UNDER ITS OWN go.mod IS ANOTHER MODULE, not a package
+              # of this one, and `go test ./that/dir` from the root answers
+              # "main module does not contain package" and fails the job as a
+              # setup error. The bench fixtures under bench/bashloop/fixtures
+              # are exactly that: small programs the task door edits, each with
+              # a go.mod of its own. Walking up from the directory to the first
+              # go.mod is what tells the two apart. This walk is the same one
+              # the Makefile's test-touched target does, and the two must keep
+              # deriving the same set or `make pr-ready` stops predicting CI.
+              nested=0; walk="$dir"
+              while [ "$walk" != "." ] && [ "$walk" != "/" ]; do
+                if [ -f "$walk/go.mod" ]; then nested=1; break; fi
+                walk="$(dirname "$walk")"
+              done
+              if [ "$nested" = 1 ]; then continue; fi
               # A directory the change emptied has no package left to test.
               if ls "$dir"/*.go >/dev/null 2>&1; then pkgs="$pkgs ./$dir"; fi
             done

Makefile

@@ -185,6 +185,9 @@ test-touched-preflight:
 		exit 2; \
 	fi
 
+# A directory under its own go.mod is another module — a bench fixture the
+# task door edits, not a package of this one — and `go test ./that/dir` from
+# here answers "does not contain package". The walk skips those.
 test-touched: test-touched-preflight
 	@set -eu; \
 	base="$${BASE:-origin/dev}"; \
@@ -197,6 +200,12 @@ test-touched: test-touched-preflight
 		done | sort -u)"; \
 		pkgs=""; \
 		for dir in $$dirs; do \
+			nested=0; walk="$$dir"; \
+			while test "$$walk" != "." && test "$$walk" != "/"; do \
+				if test -f "$$walk/go.mod"; then nested=1; break; fi; \
+				walk="$$(dirname "$$walk")"; \
+			done; \
+			if test "$$nested" = 1; then continue; fi; \
 			if ls "$$dir"/*.go >/dev/null 2>&1; then pkgs="$$pkgs ./$$dir"; fi; \
 		done; \
 	fi; \

docs/changes/unreleased/1332-touched-packages-skip-nested-modules.md

@@ -0,0 +1,15 @@
+---
+kind: fixed
+title: a changed directory in a nested module is not a package of the root module
+pr: 1332
+surface: [build]
+invalidates:
+  - "The `touched packages` job derived its test set as every directory holding a changed `.go` file, with no test for which module that directory belongs to. A change that edits a bench fixture under `bench/bashloop/fixtures/` fed `go test` a directory under its own `go.mod`, which answers `main module (github.com/Agent-Field/codeaf) does not contain package …` and failed the job as a setup error while every real package passed. The job now walks up from each directory to the first `go.mod` and keeps the directory only when that `go.mod` is the root's."
+  - "`.github/workflows/ci.yml` and the Makefile's `test-touched` target derived the touched set separately, and only one of them was ever fixed. They now carry the same walk, so `make pr-ready` predicts the gate again."
+---
+
+The bench fixtures are small programs the task door edits during a bench run, and
+each carries a `go.mod` of its own so a worker can build and test it in place.
+That makes them modules, not packages of this one, and `go test ./that/dir` from
+the root has always refused them. Nothing had touched one in the same change as a
+Go file before, so the gap was latent until a branch that edits both.