fix: mypy default target + kubeconform empty-batch graceful exit

- mypy: detect when caller's args contain no path target and default to `.`,
  so a bare `id: mypy` no longer fails with "Missing target module, package,
  files, or command." Consumers can still pass an explicit target via args.
- kubeconform: when every input file gets filtered out (e.g. a batch of only
  Helm values.yaml + Chart.yaml — neither manifests nor chart templates),
  exit 0 instead of falling through to a no-arg kubeconform call that blocks
  reading from stdin and emits "failing to read data from stdin".

Author: Goldziher

hooks/kubeconform/run.sh

@@ -121,8 +121,11 @@ if ((${#plain_files[@]} > 0)); then
   fi
 fi
 
+# All inputs were filtered out (e.g. values.yaml + Chart.yaml only — no manifests
+# and no chart templates). Nothing to validate; exit 0 instead of falling
+# through to a kubeconform invocation that would block reading from stdin.
 if ((${#chart_roots[@]} == 0 && ${#plain_files[@]} == 0)); then
-  exec "${bin_path}" "${flags[@]}"
+  exit 0
 fi
 
 exit "${status}"

hooks/mypy/run.sh

@@ -2,17 +2,34 @@
 # mypy — Python static type checker (category: toolchain wrapper).
 # Prefers `uv run mypy` when uv is available; falls back to `python -m mypy`.
 # If neither is on PATH, prints a skip warning and exits 0.
+#
+# pre-commit / prek invoke this with `pass_filenames: false`, so $@ is just the
+# `args:` from .pre-commit-hooks.yaml. If the caller's args don't include any
+# target path, mypy refuses to run with "Missing target module, package, files,
+# or command." We default to `.` so a bare `id: mypy` works out of the box.
 set -euo pipefail
 
-if command -v uv >/dev/null 2>&1; then
+# Detect whether $@ contains a path-like target (anything that isn't a flag).
+has_target=0
+for arg in "$@"; do
+  case "${arg}" in
+    -*) ;;
+    *) has_target=1; break ;;
+  esac
+done
+if ((has_target == 0)); then
+  set -- "$@" "."
+fi
+
+if command -v uv > /dev/null 2>&1; then
   exec uv run mypy "$@"
 fi
 
-if command -v python >/dev/null 2>&1; then
+if command -v python > /dev/null 2>&1; then
   exec python -m mypy "$@"
 fi
 
-if command -v python3 >/dev/null 2>&1; then
+if command -v python3 > /dev/null 2>&1; then
   exec python3 -m mypy "$@"
 fi