[CMake] Merge Clang's features file with Swift's

lib/Option/CMakeLists.txt

@@ -6,16 +6,20 @@ add_dependencies(swiftOption
 target_link_libraries(swiftOption PRIVATE
   swiftBasic)
 
-set(features_file_src "${CMAKE_CURRENT_SOURCE_DIR}/features.json")
+set(features_merger "${SWIFT_SOURCE_DIR}/utils/merge-features.py")
+set(features_file_swift_src "${CMAKE_CURRENT_SOURCE_DIR}/features.json")
+set(features_file_clang_src "${LLVM_MAIN_SRC_DIR}/../clang/tools/driver/features.json")
 set(features_file_dest "${CMAKE_BINARY_DIR}/share/swift/features.json")
 
 add_custom_command(
   OUTPUT
     ${features_file_dest}
   COMMAND
-    ${CMAKE_COMMAND} -E copy ${features_file_src} ${features_file_dest}
+    ${features_merger} -f ${features_file_swift_src} -p \"\" -f ${features_file_clang_src} -p clang- ${features_file_dest}
   DEPENDS
-    ${features_file_src}
+    ${features_merger}
+    ${features_file_swift_src}
+    ${features_file_clang_src}
 )
 
 add_custom_target(swift-features-file DEPENDS ${features_file_dest})

utils/merge-features.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+
+import argparse
+import json
+import sys
+
+
+def error(message):
+    sys.stderr.write(message)
+    sys.stderr.write("\n")
+    sys.exit(1)
+
+
+def invalid_file(features_file, message):
+    error(f"Invalid features file '{features_file}': {message}")
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description="""
+        Merges the given feature files together into DEST (or stdout if DEST
+        is not given). Each file FILE must be given a corresponding PREFIX to
+        prefix the name of each entry in its features list, though these could
+        be empty if no prefix is required.
+
+        Note that the files and prefixes are treated as an ordered list, ie.
+        the first FILE corresponds to the first PREFIX.
+        """)
+
+    parser.add_argument(
+        "--file", "-f", action="append", dest="files",
+        help="path of a file to merge"
+    )
+    parser.add_argument(
+        "--prefix", "-p", action="append", dest="prefixes",
+        help="prefix to prepend to the name of each feature"
+    )
+    parser.add_argument(
+        "dest", nargs="?",
+        help="path to store the merged file"
+    )
+
+    return parser.parse_known_args()
+
+
+def read_features(from_file, add_prefix):
+    with open(from_file, "r") as f:
+        features_dict = json.load(f)
+
+    if "features" not in features_dict:
+        invalid_file(from_file, "missing 'features' key")
+
+    features = []
+    for feature in features_dict["features"]:
+        if "name" not in feature:
+            invalid_file(from_file, "missing name in features list")
+
+        features.append({"name": add_prefix + feature["name"]})
+    return features
+
+
+def main():
+    (args, _) = parse_args()
+
+    if not args.files:
+        error("No files to merge were provided")
+
+    if len(args.files) != len(args.prefixes):
+        error("Must supply the same number of files and prefixes")
+
+    features = []
+    for i, (f, prefix) in enumerate(zip(args.files, args.prefixes)):
+        features.extend(read_features(f, prefix))
+
+    data = {
+        "features": features
+    }
+
+    if args.dest:
+        with open(args.dest, "w") as f:
+            json.dump(data, f, indent=2)
+    else:
+        sys.stdout.write(json.dumps(data, indent=2))
+
+
+if __name__ == '__main__':
+    main()