Migrate public to private metakey

[tijmenbruggeman]

Will migrate the tiny_compress_images to _tiny_compress_images marking it as a private key. This will ensure that the field will not be editable through custom fields.

Changed

• Added Tiny_Migrate class to contain migrations.
  • It has a method run which runs before the plugin does (see tiny-compress-images.php)
  • The method will compare a const DB_VERSION_NR to the stored version
    • If the stored version number is higher than the constant, it will exit and not run migrations.
    • If the stored version does not exist or is lower it will run down the path to check migrations
  • For standards, each migration:
    • will have a associated version number.
    • is a private static in the migration class

Considerations

• Why a seperate version number for the database and not follow plugin versions? It will be easier to follow on which version you are on. 1 -> 2 -> 3 is easier to follow than 3.7.0 -> 4.2.0 -> 5.6.0.
• When comparing to Utm tracking to links, add meta key prefix #34, what are the differences? The other version uses a N+1 loop to do a separate db query which might end up with a ton of queries. PR 34 also does a update and then delete which is two queries. Straight update (https://developer.wordpress.org/reference/classes/wpdb/update/) is considerably more stable and reliable.

After merging, we can close:

• Utm tracking to links, add meta key prefix #34
• Prefix meta key with underscore to keep private #33

[Copilot]

Pull request overview

This PR makes the plugin's post meta key private by renaming tiny_compress_images → _tiny_compress_images (so it no longer appears in WordPress's Custom Fields UI), and introduces a lightweight, version-tracked migration framework that rewrites existing meta rows in a single $wpdb->update call. A Tiny_Migrate::run() invocation is added to the main plugin bootstrap so the rename is applied automatically on upgrade.

Changes:

• Change Tiny_Config::META_KEY to _tiny_compress_images and update the meta-key invariant test hash.
• Add Tiny_Migrate class with a DB_VERSION / tinypng_db_version option to gate one-shot migrations, plus a first migration that renames the existing meta keys.
• Extend the WordPress test stubs to support $wpdb->update, non-callable stub values, and a postmeta table name; add unit tests for Tiny_Migrate.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
tiny-compress-images.php	Loads new migration class and runs migrations at plugin bootstrap.
src/class-tiny-migrate.php	New migration runner with DB_VERSION tracking and the meta-key rename migration.
src/config/class-tiny-config.php	Prefixes META_KEY with an underscore to make it private.
readme.txt	Adds a = 3.7.0 = changelog entry for the meta-key migration.
test/helpers/wordpress.php	Exposes postmeta, registers an update method, and permits non-callable stub return values.
test/unit/TinyMigrateTest.php	New unit tests for the migration's run / skip / option-update behaviours.
test/unit/TinyImageTest.php	Updates the SHA-1 invariant test for the new meta-key value.

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