[gen_ast_dump_json_test.py] Copy to binary directory to omit --clang argument

The script will now check if a clang binary exists in the same directory
and default to that instead of requiring a --clang argument. The script
is copied to the clang build directory using CMake configure_file() with
COPYONLY. This ensures that the version in the build directory is updated
any time the source version changes.

See https://reviews.llvm.org/D70119

clang/test/AST/gen_ast_dump_json_test.py

@@ -56,10 +56,18 @@ def filter_json(dict_var, filters, out):
                 if isinstance(e, OrderedDict):
                     filter_json(e, filters, out)
 
+
+def default_clang_path():
+    guessed_clang = os.path.join(os.path.dirname(__file__), "clang")
+    if os.path.isfile(guessed_clang):
+        return guessed_clang
+    return None
+
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("--clang", help="The clang binary (could be a relative or absolute path)",
-                        action="store", required=True)
+                        action="store", default=default_clang_path())
     parser.add_argument("--source", help="the source file. Command used to generate the json will be of the format <clang> -cc1 -ast-dump=json <opts> <source>",
                         action="store", required=True)
     parser.add_argument("--filters", help="comma separated list of AST filters. Ex: --filters=TypedefDecl,BuiltinType",

clang/test/CMakeLists.txt

@@ -136,6 +136,10 @@ if (CLANG_ENABLE_STATIC_ANALYZER)
   endif()
 endif()
 
+# Copy gen_ast_dump_json_test.py to the clang build dir. This allows invoking
+# it without having to pass the --clang= argument
+configure_file(AST/gen_ast_dump_json_test.py ${LLVM_TOOLS_BINARY_DIR}/gen_ast_dump_json_test.py COPYONLY)
+
 add_custom_target(clang-test-depends DEPENDS ${CLANG_TEST_DEPS})
 set_target_properties(clang-test-depends PROPERTIES FOLDER "Clang tests")