Rules / Style / provide-deprecation-message

provide-deprecation-message

lint/style/provide-deprecation-message

recommended

Same as provide_deprecation_message · Dart lints

Flags @deprecated and @Deprecated() annotations that carry no message.

A deprecation is only useful if it tells callers what to do instead — which replacement to adopt, or since when the API is going away. The bare @deprecated constant can never carry that guidance, and @Deprecated() with no argument (or an empty/whitespace-only string) is just as unhelpful, so both should be replaced with @Deprecated("message"). A @Deprecated whose positional argument is any non-empty expression is accepted. The rule also inspects field-level annotations, which the generic AST walk would otherwise skip.

Invalid

example.dartdart

class Api {
  @deprecated
  void oldMethod() {}

  @Deprecated('')
  void emptyMessage() {}

  @Deprecated('   ')
  void whitespaceMessage() {}

  @deprecated
  int oldField = 0;
}

@deprecated
void oldTopLevel() {}

Provide a deprecation message, via @Deprecated("message").

1class Api {

2 @deprecated

∙

Provide a deprecation message, via @Deprecated("message").

4

5 @Deprecated('')

∙

Provide a deprecation message, via @Deprecated("message").

7

8 @Deprecated(' ')

∙

Provide a deprecation message, via @Deprecated("message").

10

11 @deprecated

∙

Provide a deprecation message, via @Deprecated("message").

14

15@deprecated

∙

Valid

example.dartdart

class Api {
  @Deprecated('Use newMethod instead.')
  void oldMethod() {}

  @Deprecated('Removed in version 2.0.')
  int oldField = 0;

  @override
  String toString() => 'Api';
}

@Deprecated('No longer supported; use Service.')
void oldTopLevel() {}

@Deprecated('Use the replacement class.')
class OldClass {}

How to configure

Set the severity of provide-deprecation-message in your falcon.json:

falcon.jsonjson

{
  "linter": {
    "rules": {
      "style": {
        "provide-deprecation-message": "error"
      }
    }
  }
}