fix(datastore): sync pending mutation events with latest synced metadata

[5d]

Issue #

#1308

Description

• This patch aligns with the existing amplify-android logic:
  • Apply metadata (version) from incoming mutation events when there is an pending mutation.
  • When syncing with AppSync, retrieve the latest synchronized metadata (version) and submit it along with the pending mutation event.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (459aaed) 68.16% compared to head (29cea64) 68.12%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
...eAndLocalSave/ReconcileAndLocalSaveOperation.swift	88.52%	7 Missing ⚠️
...ngMutationQueue/SyncMutationToCloudOperation.swift	60.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3377      +/-   ##
==========================================
- Coverage   68.16%   68.12%   -0.05%     
==========================================
  Files        1079     1078       -1     
  Lines       36033    35987      -46     
==========================================
- Hits        24563    24517      -46     
  Misses      11470    11470              

Flag	Coverage Δ
API_plugin_unit_test	67.07% <ø> (ø)
AWSPluginsCore	64.45% <ø> (ø)
Amplify	47.83% <ø> (ø)
Analytics_plugin_unit_test	81.16% <ø> (ø)
Auth_plugin_unit_test	79.37% <ø> (-0.13%)	⬇️
CoreMLPredictions_plugin_unit_test	59.44% <ø> (ø)
DataStore_plugin_unit_test	80.84% <88.31%> (+0.06%)	⬆️
Geo_plugin_unit_test	70.75% <ø> (ø)
Logging_plugin_unit_test	63.09% <ø> (ø)
Predictions_plugin_unit_test	37.29% <ø> (ø)
PushNotifications_plugin_unit_test	87.03% <ø> (ø)
Storage_plugin_unit_test	78.10% <ø> (ø)
unit_tests	68.12% <88.31%> (-0.05%)	⬇️

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[lawmicha]

Some follow up questions, first and formost would be: Should MutationEvent's version property be deprecated?

Exploring if we removed version from MutationEvent:

• OutgoingMutationQueue processes existing pending mutations by reconciling the version from the incoming mutation response through MutationEvent.reconcilePendingMutationEventsVersion. Is this still needed if we always get the latest sync metadata from storage?
• ReconcileAndLocalSaveOperation will call notify(savedModel:mutationType) and the hub payload is a MutationEvent. if the answer to the first question is that version is deprecated, then this will impact customers listening to hub events with MutationEvent payloads.
• Similar question to above, MutationEvent is also the event for DataStore.observe API. Asking the deprecated question in another way: Are other platform's observe API returning data that contains the version as well?
• Some other areas of interest is AWSMutationDatabaseAdapter

[5d]

Some follow up questions, first and formost would be: Should MutationEvent's version property be deprecated?

Exploring if we removed version from MutationEvent:

• OutgoingMutationQueue processes existing pending mutations by reconciling the version from the incoming mutation response through MutationEvent.reconcilePendingMutationEventsVersion. Is this still needed if we always get the latest sync metadata from storage?
• ReconcileAndLocalSaveOperation will call notify(savedModel:mutationType) and the hub payload is a MutationEvent. if the answer to the first question is that version is deprecated, then this will impact customers listening to hub events with MutationEvent payloads.
• Similar question to above, MutationEvent is also the event for DataStore.observe API. Asking the deprecated question in another way: Are other platform's observe API returning data that contains the version as well?
• Some other areas of interest is AWSMutationDatabaseAdapter

I think for now, the safest way to do is mark it as deprecated field. If we remove the version field, shouldn't it be a major version change? For those customer who still using the mutation event version, the version will have the same value and meaning as before.

[lawmicha]

We can test passing in a closure that returns non-nil as well and assert the API call is made with the version

[5d]

will update the test!