src/vs/workbench/contrib/customEditor/common/customEditor.ts/CustomEditorInfoCollection/defaultEditor
class CustomEditorInfoCollection:	public get defaultEditor(): CustomEditorInfo | undefined {
		return this.allEditors.find(editor => {
			switch (editor.priority) {
				case RegisteredEditorPriority.default:
				case RegisteredEditorPriority.builtin:
					// A default editor must have higher priority than all other contributed editors.
					return this.allEditors.every(otherEditor =>
						otherEditor === editor || isLowerPriority(otherEditor, editor));

				default:
					return false;
			}
		});
	}