feat: add KeyValueAction argparse action

src/byteb4rb1e/utils/argparse/actions.py

@@ -0,0 +1,33 @@
+"""Custom argparse actions."""
+
+from __future__ import annotations
+
+import argparse
+from typing import Any
+
+
+class KeyValueAction(argparse.Action):
+    """Argparse action that accumulates ``KEY=VALUE`` pairs into a dict.
+
+    Usage::
+
+        parser.add_argument("--config", action=KeyValueAction,
+                            default={}, metavar="KEY=VALUE",
+                            help="Set a config option (can be repeated)")
+
+    Then ``args.config`` is a ``dict[str, str]``.
+    """
+
+    def __call__(
+        self,
+        parser: argparse.ArgumentParser,
+        namespace: argparse.Namespace,
+        values: Any,
+        option_string: str | None = None,
+    ) -> None:
+        d = getattr(namespace, self.dest, None) or {}
+        if "=" not in values:
+            parser.error(f"Invalid format: {values!r} (expected KEY=VALUE)")
+        key, _, value = values.partition("=")
+        d[key.strip()] = value.strip()
+        setattr(namespace, self.dest, d)