[META] Requirements for tagging Drupal 9.0.0-beta1

Problem/Motivation

Must-haves prior to tagging Drupal 9.0.0-beta1

8.9.x and 9.0.x will enter beta at the same time and will have the same beta stability requirements as a normal minor release. Additionally:

1. There must be no outstanding issues to update PHP and JavaScript dependencies (i.e. they should be on the latest release of the latest branch we intend to ship with). Also unused dependencies should be removed prior to beta.
   • PHP: All must have parts done for Drupal 9: #3009213: [META] Update / reconsider PHP dependencies for Drupal 9
   • JavaScript and CSS: #3094468: [plan] Update core JavaScript (and CSS) dependencies prior to 9.0.0-beta1
     Remaining:
     • #2550717: [JS] Replace jQuery.cookie with JS-cookie and provide a BC layer
     • #2821525: Update normalize.css to the most recent version

    

2. ALL BETA SCOPE DONE: All deprecated code usages and backwards compatibility layers must be removed and deprecations properly documented - we can't remove deprecated code that is called by Drupal core. (see the @deprecated tag). This includes deprecated JavaScript libraries etc.
   See:
   • #2716163: [META] Remove deprecated classes, methods, procedural functions and code paths outside of deprecated modules on the Drupal 9 branch
   • Done: #2959269: [meta] Core should not trigger deprecated code except in tests and during updates

    

3. Any critical Drupal 8 upgrade path bugsmust be triaged / resolved in 8.x so that sites are not stranded on pre-8.9.x versions due to known core bugs.
   Remaining:
   • #2917600: update_fix_compatibility() puts sites into unrecoverable state
   • #3056543: taxonomy_post_update_make_taxonomy_term_revisionable() fails when terms have no default translation
   • #3052318: Update from 8.6.15 to 8.7 fails due to corrupt "menu_link_content" entity data

    

4. Also in 9.0.x, updates from versions prior to Drupal 8.8.x must be removed and hook_update_last_removed() implementations added: #3108254: [META] Drupal 8-9 upgrade path clean-up This is to minimise the surface area for 8-9 upgrade path bugs.
   Remaining:
   • #3066801: Add hook_removed_post_updates()
   • #3106666: [pp-1] Remove post updates added prior to 8.8.0
   • (nice to have for beta) #3095333: Extend filled database dump with new stable modules and content for them

    

5. There must be a Drupal 9-specific version of the Stable theme, so that contributed and custom themes are able to port to it. #3050374: Create Drupal 9 stable theme
    
6. NO OUTSTANDING ISSUES: Any known 9.0.x-only security or data integrity criticals must be resolved.
    
7. ALL BETA SCOPE DONE: Simpletest module must be either successfully moved to contrib, or retained in core and undeprecated #3110983: Verify that simpletest tests can be run in contrib, or add simpletest back to core. (done)

Should-haves

These issues are not hard blockers to releasing Drupal 9, but there would be significant negative consequences of them not being completed in time for Drupal 9's release. Outstanding should-haves may cause 9.0.0 to be deferred from the June release window to the August window.

1. NO OUTSTANDING ISSUES: Any critical API changes, API additions, or data model changes should be completed, as these changes will no longer be allowed during the beta.
    

2. All Drupal 6 and Drupal 7 -> Drupal 8/9 core content migrations should be stable. In practice this mostly means multilingual migrations #2208401: [META] Stabilise Migrate Drupal Multilingual module , and #2746541: Migrate D6 and D7 node revision translations to D8 is the final beta-blocking issue for those. If we don't do this, we can't expect people to migrate from Drupal 6 and Drupal 7.

There may be minor configuration translation migrations or contrib -> core migrations still outstanding which would be great to clean up but should not actually block release.
 

3. ALL BETA SCOPE DONE: We should have adopted a policy for PHP 7.x version support, as this needs to be announced as far as possible before the LTS and 9.0.0 release so hosts have time to upgrade. #2917655: [policy] Decide whether and how to drop PHP 7.3 support in Drupal 9 during its lifetime.
    
4. We should have MySQL, PostgreSQL and SQLite requirements implemented.
   • Policies:
     • #3107113: [policy] Decide on MySQL/MariaDB/Percona Server version support status for Drupal 9
     • #3106077: [policy] Decide on PostgreSQL 9.x/10.x support status
     • #3107155: Raise SQLite version requirement to 3.26 in Drupal 9 (was the policy)
   • Implementation:
     • #3109534: Raise the minimum MySQL version to 5.7 and MariaDB version to 10.2 in Drupal 9
     • #2846994: Increase minimum version requirement for Postgres to 9.6.x
     • #3107155: Raise SQLite version requirement to 3.26 in Drupal 9

    

5. ALL BETA SCOPE DONE: We should provide accurate update recommendations (9.0, not a non-existent minor version of Drupal 8) on the Status Report (/admin/reports/status). #2991207: Drupal core should inform the user of the security coverage for the site's installed minor version including final 8.x LTS releases#3111929: If no recommended update is found, Update Status recommends the latest release, even if it is unsupported.
    
6. ALL BETA SCOPE DONE: We should have a proper policy for CSS and markup changes.
    
7. ALL BETA SCOPE DONE: Drupal.org should be able to fully handle contributed projects that are compatible with both 8.x and 9.x and not assume core compatibility based on version/branch name: #3054433: Support multiple core branch functionality for contributed projects on drupal.org This spans multiple projects and areas such as project listing, composer façade, update.xml from drupal.org and localization files.

   &snbp;

8. We should have dropped support for Node.js 8 since it's EOL. #3107918: [PP-1] Drop support for Node.js 8

Nice to haves

1. #3111409: [META] Add new default Olivero frontend theme to Drupal 9 core only if done enough in time, otherwise moves to Drupal 9.1.0 earliest.

Must have and should have issues (and their children) have been tagged "Drupal 9.0.0-beta1 requirement" on a best effort basis for an easier cut-through view of all issues regardless of their hierarchy or project affected.