Internal: Used beforeChange instead of change to force command read-only mode.

[oskarwrobel]

Suggested merge commit message (convention)

Internal: Used beforeChange instead of change to force Command read-only mode. Closes https://github.com/ckeditor/ckeditor5-utils/issues/171.

---

Requires

• Feature: Added beforeChange event to ObservableMixin. ckeditor5-utils#241

[coveralls]

Coverage remained the same at 100.0% when pulling db2d2af on t/ckeditor5-util/171 into 6f55c20 on master.

[oleq]

The change requires tests ;-)

[oskarwrobel]

This functionality is tested

ckeditor5-core/tests/command.js

Lines 69 to 100 in 6f55c20

	it( 'is always falsy when the editor is in read-only mode', () => {
	editor.isReadOnly = false;
	command.isEnabled = true;
	editor.isReadOnly = true;
	// Is false.
	expect( command.isEnabled ).to.false;
	command.refresh();
	// Still false.
	expect( command.isEnabled ).to.false;
	editor.isReadOnly = false;
	// And is back to true.
	expect( command.isEnabled ).to.true;
	} );
	it( 'is observable when is overridden', () => {
	editor.isReadOnly = false;
	command.isEnabled = true;
	editor.bind( 'something' ).to( command, 'isEnabled' );
	expect( editor.something ).to.true;
	editor.isReadOnly = true;
	expect( editor.something ).to.false;
	} );

.

[Reinmar]

So why is this change needed? If everything is fine here, then there's no need for a PR. But we know that something is wrong. So let's test it.

[oskarwrobel]

Ok, test is added.