Swift: cleanup and some docstrings for codegen

Also added code generation and clang formatting to the pre-commit
configuration.

swift/codegen/lib/options.py

@@ -0,0 +1,48 @@
+""" generator options, categorized by tags """
+
+import argparse
+import collections
+import pathlib
+from typing import Tuple
+
+from . import paths
+
+
+def _init_options():
+    Option("--check", "-c", action="store_true")
+    Option("--verbose", "-v", action="store_true")
+    Option("--schema", tags=["schema"], type=pathlib.Path, default=paths.swift_dir / "codegen/schema.yml")
+    Option("--dbscheme", tags=["dbscheme"], type=pathlib.Path, default=paths.swift_dir / "ql/lib/swift.dbscheme")
+
+
+_options = collections.defaultdict(list)
+
+
+class Option:
+    def __init__(self, *args, tags=None, **kwargs):
+        tags = tags or []
+        self.args = args
+        self.kwargs = kwargs
+        if tags:
+            for t in tags:
+                _options[t].append(self)
+        else:
+            _options["*"].append(self)
+
+    def add_to(self, parser: argparse.ArgumentParser):
+        parser.add_argument(*self.args, **self.kwargs)
+
+
+_init_options()
+
+
+def get(tags: Tuple[str]):
+    """ get options marked by `tags`
+
+    Return all options if tags is falsy. Options tagged by wildcard '*' are always returned
+    """
+    if not tags:
+        return (o for tagged_opts in _options.values() for o in tagged_opts)
+    else:
+        # use specifically tagged options + those tagged with wildcard *
+        return (o for tag in ('*',) + tags for o in _options[tag])