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avoid-negated-conditions

Group: Suspicious
Path: lint/suspicious/avoid-negated-conditions
Default: Off, opt in
Origin: Falcon
Rule: 96 of 512

Prefer positive conditions when both branches can be swapped. Checks if statements, conditional expressions, and collection/map if/else elements. ignore-null-checks (default false) exempts comparisons with null.

Invalid

example.dartdart

void f(bool flag, dynamic value) {
  if (!flag) {} else {}
  if (value != 1) {} else {}
  if (value is! String) {} else {}
  final a = !flag ? 1 : 2;
  final b = value != null ? 1 : 2;
  final c = value is! int ? 1 : 2;
  final list = [if (!flag) 1 else 2];
  final set = {if (value != 1) 1 else 2};
  final map = {if (value is! int) 1: 2 else 3: 4};
  final chained = [if (!flag) 1 else if (value != 1) 2 else 3];
}

Prefer a positive condition and swap the branches.

1void f(bool flag, dynamic value) {

2 if (!flag) {} else {}

∙

Prefer a positive condition and swap the branches.

2 if (!flag) {} else {}

3 if (value != 1) {} else {}

∙

Prefer a positive condition and swap the branches.

3 if (value != 1) {} else {}

4 if (value is! String) {} else {}

∙

Prefer a positive condition and swap the branches.

4 if (value is! String) {} else {}

5 final a = !flag ? 1 : 2;

∙

Prefer a positive condition and swap the branches.

5 final a = !flag ? 1 : 2;

6 final b = value != null ? 1 : 2;

∙

Prefer a positive condition and swap the branches.

6 final b = value != null ? 1 : 2;

7 final c = value is! int ? 1 : 2;

∙

Prefer a positive condition and swap the branches.

7 final c = value is! int ? 1 : 2;

8 final list = [if (!flag) 1 else 2];

∙

Prefer a positive condition and swap the branches.

8 final list = [if (!flag) 1 else 2];

9 final set = {if (value != 1) 1 else 2};

∙

Prefer a positive condition and swap the branches.

9 final set = {if (value != 1) 1 else 2};

10 final map = {if (value is! int) 1: 2 else 3: 4};

∙

Prefer a positive condition and swap the branches.

10 final map = {if (value is! int) 1: 2 else 3: 4};

11 final chained = [if (!flag) 1 else if (value != 1) 2 else 3];

∙

Valid

example.dartdart

void f(bool flag, dynamic value) {
  if (flag) {} else {}
  if (!flag) return;
  if (value == 1) {} else {}
  if (value is String) {} else {}
  final a = flag ? 1 : 2;
  if (!flag) {} else if (value == 1) {}
  final list = [if (flag) 1 else 2];
  final set = {if (!flag) 1};
  final map = {if (flag) 1: 2 else 3: 4};
  final mapWithoutElse = {if (value != 1) 1: 2};
  final chained = [if (!flag) 1 else if (value == 1) 2];
  final chainedMap = {if (!flag) 1: 2 else if (value == 1) 3: 4};
}

Configure avoid-negated-conditions

Set its severity in falcon.json. See the configuration guide.

falcon.jsonjson

{
  "linter": {
    "rules": {
      "suspicious": {
        "avoid-negated-conditions": "error"
      }
    }
  }
}

Or silence one occurrence with a suppression comment; the reason is required.

example.dartdart

// falcon-ignore lint/suspicious/avoid-negated-conditions: <reason>

avoid-nested-assignments
Require assignments to be standalone statements, arrow bodies or loop operations.
avoid-non-final-exception-class-fields
Exception and Error payloads should not change after construction.
avoid-passing-async-when-sync-expectedavoid-passing-async-when-sync-expectedrecommended
Flags an async closure passed to a proven synchronous callback parameter.
avoid-passing-bloc-to-blocbloc
Rejects direct Bloc and Cubit arguments to other blocs.
avoid-passing-bloc-to-widgetbloc
Rejects direct Bloc and Cubit arguments to Flutter widget constructors.
avoid-passing-build-context-to-blocsbloc
Keeps Flutter BuildContext arguments outside Bloc and Cubit APIs.
avoid-printavoid_printrecommendedflutter
Flags calls and callback arguments resolving to dart:core's print.
avoid-referencing-subclasses
Keeps base classes independent from their transitive subclasses.