Fix pickle compatibility by using HIGHEST_PROTOCOL

[andreaturchet]

This commit addresses two primary issues encountered when running the project on macOS: an OSError during EPUB loading and a PicklingError during data serialization.

Summary by CodeRabbit

• Chores
  • Enhanced data serialization efficiency during file storage operations.

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[coderabbitai]

Walkthrough

The PR modifies reader3.py by disabling the dynamic reassignment of public class module attributes and explicitly configuring pickle to use the highest protocol version with an added comment.

Changes

Cohort / File(s)	Summary
Module and Serialization Updates reader3.py	Commented out the loop that reassigned __module__ to "reader3" for public classes (ChapterContent, TOCEntry, BookMetadata, Book); updated save_to_pickle() to explicitly use pickle.HIGHEST_PROTOCOL instead of default with a clarifying comment.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Minimal scope: Single file with two straightforward, independent changes
• No logic changes: Both modifications are configuration/documentation updates without altering control flow
• Low cognitive load: The commented-out code and protocol parameter change are self-explanatory

Poem

🐇 A rabbit's whisker'd wisdom true:
When modules rest where nature grew,
And pickle jars hold protocol high,
Our data flows with clearer eye! 🥒✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Fix pickle compatibility by using HIGHEST_PROTOCOL' directly reflects the main change: using pickle.HIGHEST_PROTOCOL in save_to_pickle for improved pickle compatibility.

✨ Finishing touches

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between f327fb8 and b5a041a.

📒 Files selected for processing (1)

• reader3.py (2 hunks)

🔇 Additional comments (1)

reader3.py (1)

76-78: Correct the misleading comment about pickle protocol compatibility.

Line 355 comment states "Use protocol 4 or higher for better compatibility," but this is inaccurate. Higher pickle protocols require more recent Python versions to read, making them less compatible with older Python releases. Using HIGHEST_PROTOCOL can break compatibility: pickles created with Python 3.8 (which uses protocol 5) fail to load in Python 3.6-3.7 (which use protocol 4).

Change the comment to reflect the actual tradeoff: "Use HIGHEST_PROTOCOL for best performance and compression (requires Python 3.4+)" or consider if an explicit lower protocol (e.g., protocol=4) would better match your deployment environment.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Clarify the protocol comment: higher protocols reduce backward compatibility.

The comment states "for better compatibility," but pickle.HIGHEST_PROTOCOL actually reduces compatibility with older Python versions. Higher protocols improve efficiency and support more data types, but cannot be unpickled by older Python versions.

Apply this diff to clarify the comment:

-        # Use protocol 4 or higher for better compatibility
+        # Use highest protocol for efficiency and full data type support
         pickle.dump(book, f, protocol=pickle.HIGHEST_PROTOCOL)

If backward compatibility with Python < 3.8 is required, use protocol=4 instead of HIGHEST_PROTOCOL.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	# Use protocol 4 or higher for better compatibility
	pickle.dump(book, f, protocol=pickle.HIGHEST_PROTOCOL)
	# Use highest protocol for efficiency and full data type support
	pickle.dump(book, f, protocol=pickle.HIGHEST_PROTOCOL)

🤖 Prompt for AI Agents

In reader3.py around lines 355-356, the comment "Use protocol 4 or higher for
better compatibility" is misleading because higher pickle protocols reduce
backward compatibility with older Python versions; update the comment to state
that higher protocols improve efficiency and support more types but may not be
unpicklable on older Python interpreters, and if compatibility with Python <3.8
is required, change the call to use protocol=4 instead of
pickle.HIGHEST_PROTOCOL (or explicitly document the chosen protocol and
compatibility target).