Add a system test to check the mk and ninja files generated by incremental build.

Bug: 358428180
Test: Run the test locally.
Change-Id: If1862ee44976216f3c5a5c62d50c6d688d38023b

android/init.go

@@ -18,5 +18,6 @@ import "encoding/gob"
 
 func init() {
 	gob.Register(ModuleOutPath{})
+	gob.Register(PhonyPath{})
 	gob.Register(unstableInfo{})
 }

cmd/soong_build/main.go

@@ -212,7 +212,14 @@ func writeDepFile(outputFile string, eventHandler *metrics.EventHandler, ninjaDe
 }
 
 // Check if there are changes to the environment file, product variable file and
-// soong_build binary, in which case no incremental will be performed.
+// soong_build binary, in which case no incremental will be performed. For env
+// variables we check the used env file, which will be removed in soong ui if
+// there is any changes to the env variables used last time, in which case the
+// check below will fail and a full build will be attempted. If any new env
+// variables are added in the new run, soong ui won't be able to detect it, the
+// used env file check below will pass. But unless there is a soong build code
+// change, in which case the soong build binary check will fail, otherwise the
+// new env variables shouldn't have any affect.
 func incrementalValid(config android.Config, configCacheFile string) (*ConfigCache, bool) {
 	var newConfigCache ConfigCache
 	data, err := os.ReadFile(shared.JoinPath(topDir, usedEnvFile))

tests/build_action_caching_test.sh

@@ -0,0 +1,110 @@
+#!/bin/bash -u
+
+set -o pipefail
+
+# Test that the mk and ninja files generated by Soong don't change if some
+# incremental modules are restored from cache.
+
+OUTPUT_DIR="$(mktemp -d tmp.XXXXXX)"
+echo ${OUTPUT_DIR}
+
+function cleanup {
+  rm -rf "${OUTPUT_DIR}"
+}
+trap cleanup EXIT
+
+function run_soong_build {
+  USE_RBE=false TARGET_PRODUCT=aosp_arm TARGET_RELEASE=trunk_staging TARGET_BUILD_VARIANT=userdebug build/soong/soong_ui.bash --make-mode --incremental-build-actions nothing
+}
+
+function run_soong_clean {
+  build/soong/soong_ui.bash --make-mode clean
+}
+
+function assert_files_equal {
+  if [ $# -ne 2 ]; then
+    echo "Usage: assert_files_equal file1 file2"
+    exit 1
+  fi
+
+  if ! cmp -s "$1" "$2"; then
+    echo "Files are different: $1 $2"
+    exit 1
+  fi
+}
+
+function compare_mtimes() {
+  if [ $# -ne 2 ]; then
+    echo "Usage: compare_mtimes file1 file2"
+    exit 1
+  fi
+
+  file1_mtime=$(stat -c '%Y' $1)
+  file2_mtime=$(stat -c '%Y' $2)
+
+  if [ "$file1_mtime" -eq "$file2_mtime" ]; then
+      return 1
+  else
+      return 0
+  fi
+}
+
+function test_build_action_restoring() {
+  run_soong_clean
+  cat > ${OUTPUT_DIR}/Android.bp <<'EOF'
+python_binary_host {
+  name: "my_little_binary_host",
+  srcs: ["my_little_binary_host.py"],
+}
+EOF
+  touch ${OUTPUT_DIR}/my_little_binary_host.py
+  run_soong_build
+  mkdir -p "${OUTPUT_DIR}/before"
+  cp -pr out/soong/build_aosp_arm_ninja_incremental out/soong/*.mk out/soong/build.aosp_arm.*.ninja ${OUTPUT_DIR}/before
+  # add a comment to the bp file, this should force a new analysis but no module
+  # should be really impacted, so all the incremental modules should be skipped.
+  cat >> ${OUTPUT_DIR}/Android.bp <<'EOF'
+// new comments
+EOF
+  run_soong_build
+  mkdir -p "${OUTPUT_DIR}/after"
+  cp -pr out/soong/build_aosp_arm_ninja_incremental out/soong/*.mk out/soong/build.aosp_arm.*.ninja ${OUTPUT_DIR}/after
+
+  compare_files
+}
+
+function compare_files() {
+  for file_before in ${OUTPUT_DIR}/before/*.ninja; do
+    file_after="${OUTPUT_DIR}/after/$(basename "$file_before")"
+    assert_files_equal $file_before $file_after
+    compare_mtimes $file_before $file_after
+    if [ $? -ne 0 ]; then
+      echo "Files have identical mtime: $file_before $file_after"
+      exit 1
+    fi
+  done
+
+  for file_before in ${OUTPUT_DIR}/before/*.mk; do
+    file_after="${OUTPUT_DIR}/after/$(basename "$file_before")"
+    assert_files_equal $file_before $file_after
+    compare_mtimes $file_before $file_after
+    # mk files shouldn't be regenerated
+    if [ $? -ne 1 ]; then
+      echo "Files have different mtimes: $file_before $file_after"
+      exit 1
+    fi
+  done
+
+  for file_before in ${OUTPUT_DIR}/before/build_aosp_arm_ninja_incremental/*.ninja; do
+    file_after="${OUTPUT_DIR}/after/build_aosp_arm_ninja_incremental/$(basename "$file_before")"
+    assert_files_equal $file_before $file_after
+    compare_mtimes $file_before $file_after
+    # ninja files of skipped modules shouldn't be regenerated
+    if [ $? -ne 1 ]; then
+      echo "Files have different mtimes: $file_before $file_after"
+      exit 1
+    fi
+  done
+}
+
+test_build_action_restoring