Patch ActiveRecord::ConnectionNotEstablished snag

[jbaxendale-ut]

Updated data_migrate’s db:prepare:with_data initialization check so it inspects the schema_migrations table through the temporary pool connection for the database currently being prepared.

This avoids the nested connection checkout path that can raise ActiveRecord::ConnectionNotEstablished on newer Rails immediately after a database is created.

We needed this because db:prepare was working, but db:prepare:with_data was failing during the “is this database already initialized?” check.

The fix keeps the existing Rails-compatible behavior intact: missing databases are still created, and databases that already exist but have not been initialized still have schema restored before migrations run.

[Copilot]

Pull request overview

Updates DataMigrate::DatabaseTasks.database_initialized? to check for the schema migrations table using the temporary pool’s checked-out connection (instead of implicitly using the global ActiveRecord connection), avoiding ActiveRecord::ConnectionNotEstablished during db:prepare:with_data right after database creation on newer Rails.

Changes:

• Switch initialization detection to pool.with_connection { |conn| conn.data_source_exists?(schema_migration.table_name) }.
• Add specs asserting initialization checks are performed via the temporary pool connection and correctly handle missing schema_migrations.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/data_migrate/database_tasks.rb	Fixes initialization check to query schema_migrations via the temporary pool’s connection to avoid nested checkout/connection establishment issues.
spec/data_migrate/database_tasks_spec.rb	Adds focused tests for the new database_initialized? behavior using a temporary pool + connection double.

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[jbaxendale-ut]

What changed:

• 8b88eb9 tightened the earlier patch shape.
• 2b68131 changed database_initialized? to use Rails’ own
  ActiveRecord::Tasks::DatabaseTasks.migration_connection_pool.schema_migration.table_exists? on newer Rails, instead
  of checking through the temporary pool.
• 928b15f added a version-safe fallback for older Rails that do not implement migration_connection_pool, using the
  pre-existing DataMigrate::RailsHelper.schema_migration.table_exists?.
• 8c0a2f8 removed the now-unused pool argument from database_initialized? and cleaned up the specs accordingly.

Why we needed it:

• The original problem was specific to db:prepare:with_data on newer Rails: after creating a database, the temporary-
  pool-based initialization check could hit a stale connection path and raise ActiveRecord::ConnectionNotEstablished.
• Mirroring Rails’ own db:prepare initialization check fixed that on newer Rails.
• That Rails API does not exist on 6.1, 7.0, or 7.1, so the fallback was necessary to keep older versions working.
• The “created but not initialized database” behavior was intentionally preserved the whole way: if the database
  exists but lacks schema_migrations, schema still gets loaded before migrations run.

What did not change:

• We did not change the overall prepare_all_with_data control flow.
• We did not change create/retry semantics for missing databases.
• We did not broaden the patch into schema loading, migration ordering, or seed behavior.