[10.x] Replace Deprecated DBAL Comparator creation with schema aware Comparator

[liamh101]

Reference to change in DBAL and why this needs to be done: doctrine/dbal#4746

This is currently causing this bug in Laravel where certain migration changes are ignored: #46492

Not sure if this is affecting other database types.

An example project of the existing bug can be found here: https://github.com/liamh101/laravel-column-bug

[liamh101]

I'll get those failing integration tests fixed this evening, just need to pop out for a few hours.

[hafezdivandari]

@liamh101 What about TableDiff on this function, do we have to replace that too?

framework/src/Illuminate/Database/Schema/Grammars/Grammar.php

Lines 324 to 331 in 7d15f7e

	public function getDoctrineTableDiff(Blueprint $blueprint, SchemaManager $schema)
	{
	$table = $this->getTablePrefix().$blueprint->getTable();
	return tap(new TableDiff($table), function ($tableDiff) use ($schema, $table) {
	$tableDiff->fromTable = $schema->introspectTable($table);
	});
	}

[liamh101]

@hafezdivandari Just need to do the introspectTable before creating the TableDiff class, and I believe the tap function call is now redundant. I'll get that changed and see if there are any side effects.

[hafezdivandari]

@liamh101 isn't it better to change this function and use it on ChangeColumn class too if possible?

[liamh101]

@hafezdivandari can I do some further cleaning as a follow-up PR? I don't want to change too much and introduce additional bugs.

My feeling is that this bug can go under the radar on many projects and have massive consequences, partially multi-tenant projects where fresh database migrations can happen regularly.

[hafezdivandari]

@liamh101 sure, it was just a suggestion. But it seems that RenameColumn class has the same issue (using getDoctrineTableDiff()), I think we should not use TableDiff directly and use $schema->createComparator()->compareTables(). Does renaming a mediumText column using DBAL works right now?

[liamh101]

Renaming a column will work. However, changing a text type using the default Comparator won't work.

[driesvints]

Thanks for digging more into this @liamh101. I feel like we should give this a shot.

[taylorotwell]

Can someone summarize all behavior changes / features / breaking changes / things we are not confident about for this PR in a single bullet point list? Please mark as ready for review when that is done.

[liamh101]

Sure!

• Replace deprecated DBAL Comparator creation for a Schema Aware Comparator. ( ChangeColumn.php) Reasoning why DBAL deprecated this can be found here: Platform-aware schema comparison  doctrine/dbal#4746
• Clean up the additional deprecated function call to DBAL in Grammar.php however does not affect any behaviour.
• Changes in DatabaseSchemaBlueprintIntegrationTest.php to account for SQL changes present between stable and lowest versions of DBAL 3.x .
• Add schema builder test to validate text types change in MYSQL. The current version of Laravel is bugged with existing and new migrations. A project demonstrating this issue can be found here: https://github.com/liamh101/laravel-column-bug

No breaking changes were introduced in this PR, just a bug fix.

Once this has been reviewed and merged, I will investigate other places Laravel might use deprecated DBAL functionality and replace them. This PR is to fix the migration issues introduced when upgrading DBAL from 2.x to 3.x.

[taylorotwell]

Thanks