JSON config support for cmd_conf utility (#3227)

Summary:
Pull Request resolved: #3227

Added a support for JSON file configuration of cmd_conf decorator for benchmark parameters parsing. This feature makes easier to reproduce complex configurations without the need to pass CLI arguments.

Example .json file should look like:
```
{
    "RunOptions": {
        "world_size": 1,
        "num_batches": 3
    },
    "PipelineConfig": {
        "pipeline": "sparse"
    }
}
```
Also, configs can be listed in a 'flat' way as well:
```
{
    "world_size": 2,
    "num_batches": 3,
    "pipeline": "base"
}

```
To run, add `--json_config` flag with the .json file path. JSON configs will override YAML configs if both are given.

Reviewed By: aliafzal

Differential Revision: D78833153

fbshipit-source-id: 9be6b0e8945497f4f4e9f5c3cf96bd79ff03ea9d

Author: SSYernar

torchrec/distributed/benchmark/benchmark_utils.py

@@ -536,6 +536,20 @@ def set_embedding_config(
 # pyre-ignore [24]
 def cmd_conf(func: Callable) -> Callable:
 
+    def _load_config_file(config_path: str, is_json: bool = False) -> Dict[str, Any]:
+        if not config_path:
+            return {}
+
+        try:
+            with open(config_path, "r") as f:
+                if is_json:
+                    return json.load(f) or {}
+                else:
+                    return yaml.safe_load(f) or {}
+        except Exception as e:
+            logger.warning(f"Failed to load config because {e}. Proceeding without it.")
+            return {}
+
     # pyre-ignore [3]
     def wrapper() -> Any:
         sig = inspect.signature(func)
@@ -548,6 +562,13 @@ def wrapper() -> Any:
             help="YAML config file for benchmarking",
         )
 
+        parser.add_argument(
+            "--json_config",
+            type=str,
+            default=None,
+            help="JSON config file for benchmarking",
+        )
+
         # Add loglevel argument with current logger level as default
         parser.add_argument(
             "--loglevel",
@@ -558,18 +579,18 @@ def wrapper() -> Any:
 
         pre_args, _ = parser.parse_known_args()
 
-        yaml_defaults: Dict[str, Any] = {}
-        if pre_args.yaml_config:
-            try:
-                with open(pre_args.yaml_config, "r") as f:
-                    yaml_defaults = yaml.safe_load(f) or {}
-                logger.info(
-                    f"Loaded YAML config from {pre_args.yaml_config}: {yaml_defaults}"
-                )
-            except Exception as e:
-                logger.warning(
-                    f"Failed to load YAML config because {e}. Proceeding without it."
-                )
+        yaml_defaults: Dict[str, Any] = (
+            _load_config_file(pre_args.yaml_config, is_json=False)
+            if pre_args.yaml_config
+            else {}
+        )
+        json_defaults: Dict[str, Any] = (
+            _load_config_file(pre_args.json_config, is_json=True)
+            if pre_args.json_config
+            else {}
+        )
+        # Merge the two dictionaries, JSON overrides YAML
+        merged_defaults = {**yaml_defaults, **json_defaults}
 
         seen_args = set()  # track all --<name> we've added
 
@@ -595,10 +616,10 @@ def wrapper() -> Any:
                         ftype = non_none[0]
                         origin = get_origin(ftype)
 
-                # Handle default_factory value and allow YAML config to override it
-                default_value = yaml_defaults.get(
+                # Handle default_factory value and allow config to override
+                default_value = merged_defaults.get(
                     arg_name,  # flat lookup
-                    yaml_defaults.get(cls.__name__, {}).get(  # hierarchy lookup
+                    merged_defaults.get(cls.__name__, {}).get(  # hierarchy lookup
                         arg_name,
                         (
                             f.default_factory()  # pyre-ignore [29]