Add Option for Initializing Document

[window9u]

What this PR does / why we need it:

• Provides an option for initializing a document during creation.
• When a client attempts to attach to a document created with this option, and there is no existing document, the changes will be applied.
• If there is an existing document, the operations in the changes will be removed, and the server will always return a snapshot.
• This approach eliminates the need for the client to rollback; instead, they can simply apply the snapshot.
• This change is not applied to every attaching document with changes. it doesn't conflict with this test code Code reference
• It is valid only when the first change has the "initialDoc" message and an existing document already exists.

Which issue(s) this PR fixes:

Fixes #669

Special notes for your reviewer:

Handling Client Rollback with Snapshot

To handle failures, we need to implement Client's Rollback.

In the current implementation, there is no rollback for invalid changes. If the initial document fails during attachment, we can roll back the changes by resetting the root, as there was no document initially.

However, we need to consider the following situation:

• Resetting the client's root directly could cause errors and be difficult to manage.
• If a client detaches and then re-attaches a document after normal interaction, resetting the root alone is insufficient for rollback.

Solution: Always applying a Snapshot from the server. By applying a snapshot, we can handle rollbacks without changing the Client code, allowing the existing logic to proceed as intended.

Handling Failure Change

Possible Solutions:

1. Marking Invalid Changes: Add a special marker to the change message, such as invalid_init.

   • Advantage: Makes debugging easier.
   • Disadvantage: Every component that applies and evaluates changes must handle invalid_init on both the server and client sides.

2. Server Deletion of Invalid Changes: The server can remove operations related to invalid changes.

   • Advantage: Eliminates the need for additional logic to check for invalid changes.
   • Disadvantage: Causes the server to mutate the changes.

I chose option 2 for simpler implementation. We could mitigate this by adding a bool valid field to the Change, but I'm not certain this approach is correct. Additionally, if there are no plans to check for invalid changes, adding a field for this feature may be excessive.

Does this PR introduce a user-facing change?:

Users can use this option to initialize a document, but changes will not be applied if a document already exists.

Additional documentation:

Checklist:

• [x] Added relevant tests or not required
• [ ] Didn't break anything

Summary by CodeRabbit

• New Features

  • Introduced a method to clear operations from the Change struct, enhancing its functionality.
  • Added an InitialDoc field to the Options struct for more flexible document initialization.

• Bug Fixes

  • Enhanced error handling during document instantiation across various tests and functions, improving robustness and reliability.

• Documentation

  • Improved clarity by capturing errors during document creation in multiple test cases.

• Refactor

  • Updated test cases to ensure document creation errors are handled before proceeding with assertions.

[coderabbitai[bot]]

Walkthrough

The recent updates significantly enhance error handling and introduce new features for document management in the system. Key changes include capturing errors during document instantiation and providing a method to set an initial document value at creation. These improvements increase the robustness and flexibility of document handling, ensuring that errors are caught early and improving overall usability.

Changes

Files	Change Summary
api/converter/converter_test.go	Improved error handling in test cases by capturing errors from document creation.
pkg/document/change/change.go	Added RemoveOperations method to clear operations in the Change struct.
pkg/document/document.go	Updated Options struct to include InitialDoc field and modified New function for error handling.
pkg/document/document_test.go	Enhanced error handling in test cases for document creation.
pkg/document/gc_test.go	Added error handling during document instantiation in garbage collection tests.
server/packs/packs.go	Updated PushPull function to improve synchronization of client-server states.

Assessment against linked issues

Objective	Addressed	Explanation
Provide an interface to set the initial value when creating a document (#669)	✅

🐇 Hop along, my friend, so spry and bright,
With new features and checks, we’ll code with delight.
Documents now stand tall, no errors in sight,
In our garden of code, all blooms look just right! 🌼✨

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[window9u]

This PR addresses a simple issue of adding an initializing interface. However, considering scenarios where a document needs to be initialized and attached while an existing document is already present, this PR has expanded in scope.

1. Add Interface for Initializing Documents
   • Commit 07f2658
   • Commit ea43263
2. Server Handling for Failed initialDoc
   • Commit 1ab2040
   • Commit d3e077a
   • 2.1. Handling Failure Change
   • 2.2. Handling Client Rollback with Snapshot

Therefore, I suggest applying only the first part of this issue (#669) in this PR and addressing the second part after resolving issue #805. It is better to consider this approach when dealing with this issue.

[window9u]

Closing this PR in favor of a new approach.

This work will be continued in PR #986, which implements a more refined strategy for applying the InitialRoot option during Document attachment.