task: add get arg and env getting

derivermodule/scandata.py

@@ -7,7 +7,7 @@ from pathlib import Path
 import xmltodict
 
 from .const import PB_ITEM, PB_TMP
-from . import logger
+from .logger import logger
 
 def get_scandata_xml(identifier, source_file):
     """

derivermodule/task.py

 from json import load, dump
 from os.path import join
+from os import environ
 
 from .const import PB_TASK
 
@@ -40,4 +41,37 @@ def get_task_args(task_info):
     Returns:
     dict of task arguments
     """
-    return task['task']['args']
+    if 'task' in task_info and 'args' in task_info['task']:
+        return task_info['task']['args']
+    return {}
+
+
+def get_task_arg_or_environ_arg(task_args, name):
+    """
+    Returns the value of a task argument if it is present in task_args or in
+    the environment.
+
+    The naming of task arguments is using lowercase and hypens, whereas the
+    enviroment variables are upper cased and use underscores. The functions
+    applies the task argument to environment variable to the `name` argument.
+
+    So if the task argument is 'ocr-perform-foo', pass that as `name`, and the
+    function will also check the environment variables for 'OCR_PERFORM_FOO'.
+
+    Environment arguments are preferred over task arguments.
+
+    Args:
+
+    * task_args: As returned by get_task_args
+    * name: Custom task argument name, implementation defined.
+
+    Returns the value of the argument, if present, and None otherwise.
+    """
+    environ_name = name.replace('-', '_').upper()
+    if environ_name in environ:
+        return environ.get(environ_name)
+
+    if name is task_args:
+        return task_args.get(name)
+
+    return None