generator: accept multiple .py files as input

The types.py file in the Subiquity tree is getting difficult to maintain
and it would be ideal to split it into multiple files going forward.

Ensure that the generator script can parse content from multiple files.

NOTE: Previously the syntax `./generator.py file1 file2` would parse
"file1" and output to "file2". Now, this syntax would parse "file1" and
"file2" ; and would output to the standard output. The generator will
look for specific file extensions when reading (i.e., *.py) and writing
(i.e., *.dart) so there should be no risk of overwriting important files
if using the generator incorrectly.

Signed-off-by: Olivier Gayot <[email protected]>

packages/subiquity_client/generator/Makefile

@@ -2,7 +2,7 @@ types_py = ../subiquity/subiquity/common/types.py
 types_dart = ../lib/src/types.dart
 
 generate:
-	python3 generator.py $(types_py) $(types_dart)
+	python3 generator.py $(types_py) --output $(types_dart)
 	dart format $(types_dart)
 
 check:

packages/subiquity_client/generator/generator.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 
+import argparse
 import ast
 import fileinput
 import os
@@ -355,17 +356,43 @@ def __str__(self):
 }}
 """
 
+class PythonInputFile(argparse.FileType):
+    def __init__(self):
+        super().__init__("r", encoding="utf-8")
+
+    def __call__(self, path: str):
+        if path != "-" and not path.endswith(".py"):
+            raise argparse.ArgumentTypeError(f"{path} does not have the .py extension")
+
+        return super().__call__(path)
+
+
+def DartOutputFile(path: str | None) -> str | None:
+    if path is None or path == "-":
+        return None
+
+    if not path.endswith(".dart"):
+        raise argparse.ArgumentTypeError(f"{path} does not have a .dart extension")
+    return path
+
 
 def main():
-    input = sys.argv[1] if len(sys.argv) > 1 else ""
-    output = sys.argv[2] if len(sys.argv) == 3 else None
+    parser = argparse.ArgumentParser()
+
+    # FileType is supposed to work with default="-" but it does not when used
+    # with positional arguments.
+    parser.add_argument("python-input-files", nargs="+",
+                        type=PythonInputFile(), metavar="input.py")
+    parser.add_argument("--output", default="-", metavar="output.dart",
+                        type=DartOutputFile)
+
+    args = vars(parser.parse_args())
 
-    if not input.endswith(".py") or (output is not None and not output.endswith(".dart")):
-        print("usage: generator <input.py> (<output.dart>)")
-        return
+    input_files = args["python-input-files"]
+    output = args["output"]
 
     generator = Generator()
-    with open(sys.argv[1], "r") as file:
+    for file in input_files:
         generator.parse(file.read())
 
     data = generator.to_dart()