TaskWithState.process_get_state(), any changes to process_data now ig…

…nored

#14

And docs: #13

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+## Changed
+
+- In `TaskWithState.process_get_state()` any changes to `process_data` are now ignored. https://github.com/OpenDataServices/lib-cove-web-2/issues/14
+
 ## [0.3.0] - 2023-09-14
 
 When upgrading to this version, `ALLOWED_UNKNOWN_CONTENT_TYPES` must be set in the Django settings file, ideally from the settings file included with this library.

libcoveweb2/process/common_tasks/task_with_state.py

@@ -10,12 +10,18 @@
 class TaskWithState(ProcessDataTask):
     """An abstract task that helps you save state from
     the processing step and add it to the context.
+
+    It will cache one JSON blob for you, and add
+    it to the view context when a user is looking at the results.
+    (So make sure you choose keys in the JSON blob carefully
+    so as not to clash with other view context variables!)
+
     Extend and provide your own state_filename and process_get_state.
     """
 
     #: Set state_filename to a unique name for each task.
     #:
-    #: If you change this name the task will be rerun, so this is is a good way to
+    #: If you change this name the task will be rerun, so this is a good way to
     #: make sure all underlying data changes if a new version of this bit of cove
     #: is released.
     state_filename: str = "task_with_state.json"
@@ -28,14 +34,19 @@ def process_get_state(self, process_data: dict):
 
         Should return a tuple.
         The first item is the results to save, as a dictionary.
-        The second item is process_data, as a dictionary."""
+        The second item is process_data, as a dictionary.
+
+        Do NOT change process_data in this function!
+        The fact it's returned is a mistake:
+        https://github.com/OpenDataServices/lib-cove-web-2/issues/14
+        """
         return {}, process_data
 
     def process(self, process_data: dict) -> dict:
         if self.does_state_exist():
             return process_data
 
-        state, process_data = self.process_get_state(process_data)
+        state, process_data_throw_away = self.process_get_state(process_data)
 
         default_storage.save(
             os.path.join(self.supplied_data.storage_dir(), self.state_filename),