Refactor Mastodon import to use arrays, add tests

[pfefferle]

Refactored Mastodon import logic to consistently use associative arrays instead of stdClass objects, improving compatibility and reliability. Updated Blocks and Mastodon classes, adjusted related docblocks, and added comprehensive PHPUnit tests for the Mastodon import process, including edge cases for public/private posts, hashtags, summaries, duplicates, and filter hooks.

Fixes #2405

Proposed changes:

• Modified json_decode() to use associative flag, ensuring all decoded JSON is in array format
• Updated all references to use array syntax ['key'] instead of object syntax ->key
• Added comprehensive test coverage for the import functionality

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

• Go to '..'

Changelog entry

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Changelog Entry Details

Significance

• Patch
• Minor
• Major

Type

• Added - for new features
• Changed - for changes in existing functionality
• Deprecated - for soon-to-be removed features
• Removed - for now removed features
• Fixed - for any bug fixes
• Security - in case of vulnerabilities

Message

Refactored Mastodon import handling to use consistent array-based data, improving reliability and compatibility across all import scenarios.

[Copilot]

Pull Request Overview

This PR fixes a critical bug in the Mastodon importer where json_decode() was creating stdClass objects instead of arrays, causing fatal errors when the code tried to use array syntax on nested objects. The fix changes json_decode() to use the associative flag (true) to return arrays consistently throughout the import process.

Key Changes:

• Modified json_decode() to use associative flag, ensuring all decoded JSON is in array format
• Updated all references to use array syntax ['key'] instead of object syntax ->key
• Added comprehensive test coverage for the import functionality

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
includes/wp-admin/import/class-mastodon.php	Changed json_decode() to return arrays and updated all object property accesses to array syntax
includes/class-blocks.php	Updated filter function to accept arrays instead of objects and use null coalescing operator for safer access
tests/phpunit/tests/includes/wp-admin/import/class-test-mastodon.php	Added comprehensive test suite covering various import scenarios including the stdClass bug
tests/phpunit/tests/includes/class-test-blocks.php	Updated existing tests to use array syntax and added new test cases for the filter function

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[obenland]

I've not thought this through yet, but I wonder if we should create a fixture with a "full" export, including attachments, that we could re-use. Not sure how much sense that makes?

[pfefferle]

I like the idea, but can we have that a different PR?

[Jiwoon-Kim]

I’ve been thinking about why post migration is so difficult in ActivityPub, and I believe the biggest reason is the immutability of IDs.
While other properties can be changed, the id must remain constant.

The second issue is visibility — particularly when posts are set to followers-only.
You can migrate your followings, but followers cannot be migrated, which means the visibility scope can change after migration.
The complication deepens with the inReplyTo object, since its visibility should inherit from the parent post — and this dependency can make post-level migration nearly impossible to handle correctly.

The third reason is that what we usually call “migration” is actually actor-level migration, not object-level migration.
A post object may appear to belong to its actor, but in essence, both the actor and the post are independent entities.

And most importantly — we’re not migrating the full set of activities, inbox, and outbox data, right?
That’s why followers can’t be transferred when an account is migrated.