Add test to verify SourceKit is used or diabled (#6440)

.github/workflows/build.yml

@@ -21,6 +21,8 @@ jobs:
         name: Build SwiftLint with Bazel
         env:
           CI_BAZELRC_FILE_CONTENT: ${{ secrets.CI_BAZELRC_FILE_CONTENT }}
+      - name: Verify SourceKit dynamic loading behavior
+        run: bash tools/verify-sourcekit-loading.sh bazel-bin/swiftlint .
 
   plugins_linux:
     name: SPM plugins, Linux, Swift ${{ matrix.version }}

tools/verify-sourcekit-loading.sh

@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+bin="${1:-bazel-bin/swiftlint}"
+paths_to_lint="${2:-.}"
+
+if [[ "$(uname -s)" != "Linux" ]]; then
+  echo "This script is Linux-only (requires /proc/<pid>/maps)."
+  exit 0
+fi
+
+if [[ ! -d /proc ]]; then
+  echo "Expected /proc to be available."
+  exit 1
+fi
+
+if [[ ! -x "$bin" ]]; then
+  echo "Expected SwiftLint binary at '$bin'"
+  exit 1
+fi
+
+sourcekit_regex="${SOURCEKIT_REGEX:-sourcekit|libsourcekitd|libsourcekitdInProc}"
+
+run_and_assert_sourcekit() {
+  local label="$1"; shift
+  local expect_loaded="$1"; shift
+
+  echo "::group::${label}"
+  echo "Running: $*"
+
+  "$@" &
+  local pid=$!
+
+  local seen=0
+  local matched_lines=""
+
+  # Poll until the process exits. The lint run should be long enough to observe mappings.
+  while kill -0 "$pid" 2>/dev/null; do
+    if [[ -r "/proc/$pid/maps" ]]; then
+      matched_lines="$(grep -iE "$sourcekit_regex" "/proc/$pid/maps" || true)"
+      if [[ -n "$matched_lines" ]]; then
+        seen=1
+        if [[ "$expect_loaded" == "loaded" ]]; then
+          break
+        fi
+      fi
+    fi
+    sleep 0.05
+  done
+
+  wait "$pid"
+  local rc=$?
+
+  if [[ $rc -ne 0 ]]; then
+    echo "Command failed (exit code $rc)"
+    exit $rc
+  fi
+
+  case "$expect_loaded" in
+    loaded)
+      if [[ $seen -ne 1 ]]; then
+        echo "Expected SourceKit to be loaded but it was not observed in /proc/<pid>/maps"
+        exit 1
+      fi
+      ;;
+    not-loaded)
+      if [[ $seen -ne 0 ]]; then
+        echo "Expected SourceKit NOT to be loaded but it was observed in /proc/<pid>/maps"
+        echo "$matched_lines" || true
+        exit 1
+      fi
+      ;;
+    *)
+      echo "Invalid expect_loaded='$expect_loaded'"
+      exit 1
+      ;;
+  esac
+
+  echo "OK: SourceKit '$expect_loaded'"
+  echo "::endgroup::"
+}
+
+# Use a SourceKit-dependent rule to make the "normal" case deterministic.
+common_lint_args=(--quiet --no-cache --only-rule statement_position "$paths_to_lint")
+
+run_and_assert_sourcekit "normal" "loaded" \
+  "$bin" lint "${common_lint_args[@]}"
+
+run_and_assert_sourcekit "flag" "not-loaded" \
+  "$bin" lint --disable-sourcekit "${common_lint_args[@]}"
+
+run_and_assert_sourcekit "env" "not-loaded" \
+  env SWIFTLINT_DISABLE_SOURCEKIT=1 "$bin" lint "${common_lint_args[@]}"