Avoid bogus rebuilds due to the parser generator when nothing changed

Author: timfel

graalpython/com.oracle.graal.python.pegparser.generator/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.10)
 project(pegparser)
 
 set(PEGPARSER_SRC_PATH "${CMAKE_CURRENT_LIST_DIR}/../com.oracle.graal.python.pegparser/src")
@@ -14,7 +14,6 @@ else()
     set(PYTHON_EXE "python3")
 endif()
 
-set(PARSER_OUTPUT "Parser.java")
 set(PARSER_TARGET "${PARSER_PATH}/Parser.java")
 
 set(GRAMMAR "${INPUT_PATH}/python.gram")
@@ -33,17 +32,17 @@ file(GLOB_RECURSE ASDL_FILES
 
 set(ASDL_STAMP "Python.asdl.stamp")
 
-add_custom_target(grammar ALL 
-    DEPENDS "${PARSER_OUTPUT}")
 add_custom_command(
-    OUTPUT "${PARSER_OUTPUT}"
+    OUTPUT "${PARSER_TARGET}"
     COMMAND ${PYTHON_EXE} "${CMAKE_CURRENT_LIST_DIR}/main_parser_gen.py" "${GRAMMAR}" "${TOKENS}" "${PARSER_TARGET}"
-    DEPENDS "${CMAKE_CURRENT_LIST_DIR}/main_parser_gen.py" "${GRAMMAR}" "${TOKENS}" "${PARSER_TARGET}" ${PEGEN_FILES} ${PEGJAVA_FILES})
+    DEPENDS "${CMAKE_CURRENT_LIST_DIR}/main_parser_gen.py" "${GRAMMAR}" "${TOKENS}" ${PEGEN_FILES} ${PEGJAVA_FILES})
 
-add_custom_target(asdl ALL 
-    DEPENDS "${ASDL_STAMP}")
 add_custom_command(
     OUTPUT "${ASDL_STAMP}"
-    COMMAND ${PYTHON_EXE} "${CMAKE_CURRENT_LIST_DIR}/main_asdl_gen.py" "${ASDL}" --sst-path "${PEGPARSER_SRC_PATH}" --ast-path "${GRAALPY_SRC_PATH}"
-    COMMAND ${CMAKE_COMMAND} -E touch "${ASDL_STAMP}"
+    COMMAND ${PYTHON_EXE} "${CMAKE_CURRENT_LIST_DIR}/main_asdl_gen.py" "${ASDL}" --sst-path "${PEGPARSER_SRC_PATH}" --ast-path "${GRAALPY_SRC_PATH}" --stamp "${ASDL_STAMP}"
     DEPENDS "${CMAKE_CURRENT_LIST_DIR}/main_asdl_gen.py" "${ASDL}" ${ASDL_FILES})
+
+add_custom_target(
+    Parser
+    ALL
+    DEPENDS "${PARSER_TARGET}" "${ASDL_STAMP}")

graalpython/com.oracle.graal.python.pegparser.generator/main_asdl_gen.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# Copyright (c) 2022, 2022, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # The Universal Permissive License (UPL), Version 1.0
@@ -43,14 +43,32 @@
 from asdl.asdl_java import generate
 
 
+def stamp(sst_path: pathlib.Path, ast_path: pathlib.Path):
+    if sst_path.is_dir() and ast_path.is_dir():
+        return [
+            p.read_text() for p in sorted(sst_path.rglob("*")) if p.is_file()
+        ] + [
+            p.read_text() for p in sorted(ast_path.rglob("*")) if p.is_file()
+        ]
+    else:
+        return []
+
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("input_file", type=pathlib.Path)
     parser.add_argument("-S", "--sst-path", type=pathlib.Path, required=True)
     parser.add_argument("-A", "--ast-path", type=pathlib.Path, required=True)
+    parser.add_argument("--stamp", type=pathlib.Path, required=True)
 
     args = parser.parse_args()
+
+    old_contents = stamp(args.sst_path, args.ast_path)
     generate(args.input_file, args.sst_path, args.ast_path)
+    if old_contents != stamp(args.sst_path, args.ast_path):
+        args.stamp.touch()
+    else:
+        print(f"{args.sst_path} and {args.ast_path} not modified")
 
 
 if __name__ == '__main__':