made logging work even if no log-config was passed

.gitignore

@@ -1,6 +1,7 @@
 src/legenddataflowscripts/_version.py
 
 # New additions go at the top!
+.vscode
 *.c
 .DS_Store
 *.npz

src/legenddataflowscripts/utils/log.py

@@ -26,7 +26,7 @@ def flush(self):
 
 
 def build_log(
-    config_dict: dict, log_file: str | None = None, fallback: str = "prod"
+    config_dict: dict | str, log_file: str | None = None, fallback: str = "prod"
 ) -> logging.Logger:
     """Build a logger from a configuration dictionary.
 
@@ -39,18 +39,52 @@ def build_log(
     log_file
         The path to the log file.
     """
-    if isinstance(config_dict, str | dict):
+    # Accept either:
+    # - a str pointing to a logging properties file
+    # - a plain logging dict (handlers/formatters/etc.)
+    # - a dict already containing "options" -> {"logging": ...}
+    # If a dict is provided and it already contains an "options" key, assume
+    # caller set options explicitly (so we must not wrap it).
+    if isinstance(config_dict, str) or (
+        isinstance(config_dict, dict) and "options" not in config_dict
+    ):
         config_dict = {"options": {"logging": config_dict}}
 
-    if "logging" in config_dict["options"]:
+    if (
+        isinstance(config_dict, dict)
+        and "options" in config_dict
+        and "logging" in config_dict["options"]
+    ):
         log_config = config_dict["options"]["logging"]
         # if it's a str, interpret it as a path to a file
         if isinstance(log_config, str):
             log_config = Props.read_from(log_config)
 
         if log_file is not None:
             Path(log_file).parent.mkdir(parents=True, exist_ok=True)
-            log_config["handlers"]["dataflow"]["filename"] = log_file
+            # Ensure the logging config has a handlers->dataflow entry; create
+            # minimal structure if needed so we can set the filename.
+            if isinstance(log_config, dict):
+                handlers = log_config.setdefault("handlers", {})
+                dataflow = handlers.setdefault("dataflow", {})
+                # Set the filename for the dataflow handler
+                dataflow["filename"] = log_file
+                dataflow.setdefault("class", "logging.FileHandler")
+                dataflow.setdefault("level", "INFO")
+                log_config.setdefault("version", 1)
+                if (
+                    "handlers" in log_config
+                    and "dataflow" in log_config["handlers"]
+                    and "root" not in log_config
+                    and "loggers" not in log_config
+                ):
+                    dataflow_level = log_config["handlers"]["dataflow"].get(
+                        "level", "INFO"
+                    )
+                    log_config["root"] = {
+                        "level": dataflow_level,
+                        "handlers": ["dataflow"],
+                    }
 
         dictConfig(log_config)
         log = logging.getLogger(config_dict["options"].get("logger", "prod"))