use_gap

v0.2.0WarningFixConfigurableWidget Best Practices

This rule suggests replacing SizedBox and Padding spacers inside multi-child widgets (Column, Row, etc.) with the Gap widget from the gap package. Gap automatically picks the right axis based on its parent, so you never accidentally use width in a Column or height in a Row.

Why use this rule

Using SizedBox(height: 16) for spacing works, but it is error-prone in Row (where you need width instead) and verbose in either case. Gap(16) is axis-aware, shorter, and makes the intent clearer: this is a spacer, not a box with specific dimensions. It also reduces bugs when refactoring a Column to a Row or vice versa.

See also: gap package

Don’t

final widgets = <Widget>[
  Column(
    children: const [
      Text('First'),
      SizedBox(height: 16),
      Text('Second'),
    ],
  ),
  Row(
    children: const [
      Text('Left'),
      SizedBox(width: 8),
      Text('Right'),
    ],
  ),
];

Do

final widgets = <Widget>[
  Column(
    children: const [Text('First'), Gap(16), Text('Second')],
  ),
  Row(
    children: const [Text('Left'), Gap(8), Text('Right')],
  ),
];

Turning this rule off

This rule is in no preset, so it is off unless you enable it by name:

many_lints.yaml

rules:
  use_gap: true

To turn it off again:

many_lints.yaml

rules:
  use_gap: false

To keep the rule on but skip certain paths, use per-rule exclude.

Options

analysis_options.yaml

analysis_options.yaml

many_lints:
  rules:
    use_gap:
      min_children: 3

many_lints.yaml

many_lints.yaml

rules:
  use_gap:
    min_children: 3

Option	Type	Default	Description
min_children	int	1	Minimum number of children in the list before spacers are reported

Related rules

• prefer_spacing — Opposing convention. Use the spacing argument on Row/Column instead of SizedBox spacers.
• avoid_expanded_as_spacer — Use Spacer instead of Expanded with an empty child.
• always_pass_global_key — Don’t create a GlobalKey inside build.
• avoid_conditional_hooks — Never call hooks inside conditionals, loops, or ternaries.