fix(framework:skip) Support overriding run config from a TOML (#4080)

src/py/flwr/common/config.py

@@ -185,23 +185,26 @@ def parse_config_args(
     if config is None:
         return overrides
 
+    # Handle if .toml file is passed
+    if len(config) == 1 and config[0].endswith(".toml"):
+        with Path(config[0]).open("rb") as config_file:
+            overrides = flatten_dict(tomli.load(config_file))
+        return overrides
+
     # Regular expression to capture key-value pairs with possible quoted values
     pattern = re.compile(r"(\S+?)=(\'[^\']*\'|\"[^\"]*\"|\S+)")
 
     for config_line in config:
         if config_line:
-            matches = pattern.findall(config_line)
+            # .toml files aren't allowed alongside other configs
+            if config_line.endswith(".toml"):
+                raise ValueError(
+                    "TOML files cannot be passed alongside key-value pairs."
+                )
 
-            if (
-                len(matches) == 1
-                and "=" not in matches[0][0]
-                and matches[0][0].endswith(".toml")
-            ):
-                with Path(matches[0][0]).open("rb") as config_file:
-                    overrides = flatten_dict(tomli.load(config_file))
-            else:
-                toml_str = "\n".join(f"{k} = {v}" for k, v in matches)
-                overrides.update(tomli.loads(toml_str))
+            matches = pattern.findall(config_line)
+            toml_str = "\n".join(f"{k} = {v}" for k, v in matches)
+            overrides.update(tomli.loads(toml_str))
 
     return overrides
 

src/py/flwr/common/config_test.py

@@ -15,6 +15,7 @@
 """Test util functions handling Flower config."""
 
 import os
+import tempfile
 import textwrap
 from pathlib import Path
 from unittest.mock import patch
@@ -254,3 +255,50 @@ def test_parse_config_args_overrides() -> None:
         "key5": True,
         "key6": "value6",
     }
+
+
+def test_parse_config_args_from_toml_file() -> None:
+    """Test if a toml passed to --run-config it is loaded and fused correctly."""
+    # Will be saved as a temp .toml file
+    toml_config = """
+        num-server-rounds = 10
+        momentum = 0.1
+        verbose = true
+    """
+    # This is the UserConfig that would be extracted from pyproject.toml
+    initial_run_config: UserConfig = {
+        "num-server-rounds": 5,
+        "momentum": 0.2,
+        "dataset": "my-fancy-dataset",
+        "verbose": False,
+    }
+    expected_config = {
+        "num-server-rounds": 10,
+        "momentum": 0.1,
+        "dataset": "my-fancy-dataset",
+        "verbose": True,
+    }
+
+    # Create a temporary directory using a context manager
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Create a temporary TOML file within that directory
+        toml_config_file = os.path.join(temp_dir, "extra_config.toml")
+
+        # Write the data to the TOML file
+        with open(toml_config_file, "w", encoding="utf-8") as toml_file:
+            toml_file.write(textwrap.dedent(toml_config))
+
+        # Parse config (this mimics what `--run-config path/to/config.toml` does)
+        config_from_toml = parse_config_args([toml_config_file])
+        # Fuse
+        config = fuse_dicts(initial_run_config, config_from_toml)
+
+        # Assert
+        assert config == expected_config
+
+
+def test_parse_config_args_passing_toml_and_key_value() -> None:
+    """Test that passing a toml and key-value configs aren't allowed."""
+    config = ["my-other-config.toml", "lr=0.1", "epochs=99"]
+    with pytest.raises(ValueError):
+        parse_config_args(config)