fix: [SQLite3][Postgres][SQLSRV][OCI8] Forge::modifyColumn() changes NULL constraint incorrectly

[kenjis]

Description
See #7302

• The $forge->modifyColumn() has been fixed. Due to a bug, in previous versions, SQLite3/Postgres/SQLSRV might change NULL/NOT NULL unpredictably.
• In previous versions, the OCI8 driver did not change NULL/NOT NULL when you don’t specify null value.
• Now in all database drivers $forge->modifyColumn() always sets NULL when you don’t specify null value.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[kenjis]

Because sanity-tests fail, we cannot run database-live-tests...

[kenjis]

Okay. SQLite3 database-live-tests passed.
https://github.com/codeigniter4/CodeIgniter4/actions/runs/4497811722

[kenjis]

@codeigniter4/database-team Should this be false? What do you think?

Maybe different databases have different defaults when not specifying null or not null?

[kenjis]

I have also changed the behavior of other drivers to match the behavior of MySQL.

[kenjis]

I didn't know but the following test passes on MySQL.

        $this->forge->dropTable('forge_test_modify', true);

        $this->forge->addField([
            'col1' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => false],
            'col2' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => false],
            'col3' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => false],
        ]);
        $this->forge->createTable('forge_test_modify');

        $this->forge->modifyColumn('forge_test_modify', [
            'col1' => ['name' => 'new_name', 'type' => 'VARCHAR', 'constraint' => 1],
            'col2' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => true],
            'col3' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => false],
        ]);

        $this->db->resetDataCache();

        $col1 = $this->getMetaData('new_name', 'forge_test_modify');
        $this->assertTrue($col1->nullable); // Nullable if not specified.
        $col2 = $this->getMetaData('col2', 'forge_test_modify');
        $this->assertTrue($col2->nullable);
        $col3 = $this->getMetaData('col3', 'forge_test_modify');
        $this->assertFalse($col3->nullable);

Added notes in the docs: 3b8a428

[kenjis]

Rebased and add upgrade note.

[kenjis]

@codeigniter4/database-team Please review.

[kenjis]

Any comment?

[MGatner]

I would prefer someone DB to take a look too but the code makes sense and tests look good so I trust this is appropriate.

[kenjis]

I believe this code is okay. The issue is that this behavior is okay.

[michalsn]

I think that using:

null value

Could be a bit misleading, and some users may think they should define their table fields as null (at least for me). So, we could use something more specific.

[kenjis]

@michalsn Exactly! Applied your suggestions.