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no-leading-underscores-for-library-prefixes

Same as no_leading_underscores_for_library_prefixes in Dart lints

Group: Style
Path: lint/style/no-leading-underscores-for-library-prefixes
Default: On (recommended)
Origin: Dart lints
Rule: 288 of 512

recommended

Flags import prefixes that begin with an underscore.

In Dart a leading underscore signals library privacy, but an import prefix is only a local alias — it is never exported and cannot be made private, so the underscore is meaningless noise that only muddies the privacy convention. Rename the prefix without the leading underscore. A wildcard prefix composed solely of underscores (e.g. _) is exempt, since it is an intentional throwaway name rather than a misapplied privacy marker.

Invalid

example.dartdart

// Import prefixes must not start with an underscore.

import 'dart:math' as _math;
import 'dart:async' as _async;
import 'dart:convert' as _convert;
import 'dart:io' as _io;
import 'dart:collection' as _collection;
import 'dart:typed_data' as _typed_data;

Avoid leading underscores for library prefixes.

2

3import 'dart:math' as _math;

∙

Avoid leading underscores for library prefixes.

3import 'dart:math' as _math;

4import 'dart:async' as _async;

∙

Avoid leading underscores for library prefixes.

4import 'dart:async' as _async;

5import 'dart:convert' as _convert;

∙

Avoid leading underscores for library prefixes.

5import 'dart:convert' as _convert;

6import 'dart:io' as _io;

∙

Avoid leading underscores for library prefixes.

6import 'dart:io' as _io;

7import 'dart:collection' as _collection;

∙

Avoid leading underscores for library prefixes.

7import 'dart:collection' as _collection;

8import 'dart:typed_data' as _typed_data;

∙

Valid

example.dartdart

// Import prefixes without leading underscores (all-underscore wildcard is fine).

import 'dart:math' as math;
import 'dart:async' as async_lib;
import 'dart:convert' as convert;
import 'dart:io' as io;
import 'dart:collection' as collection;
import 'dart:typed_data' as _;

Configure no-leading-underscores-for-library-prefixes

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

falcon.jsonjson

{
  "linter": {
    "rules": {
      "style": {
        "no-leading-underscores-for-library-prefixes": "error"
      }
    }
  }
}

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

example.dartdart

// falcon-ignore lint/style/no-leading-underscores-for-library-prefixes: <reason>

no-leading-underscores-for-local-identifiersno_leading_underscores_for_local_identifiersrecommended
Flags local variables and parameters whose names begin with an underscore.
no-literal-bool-comparisonsno_literal_bool_comparisons
Flags boolean literals compared or combined with a non-nullable bool.
no-magic-numberno-magic-number
Flags unnamed numeric literals (magic numbers) used inline in expressions.
no-object-declarationno-object-declaration
Flags class members declared with the type Object (or Object?).
no-runtime-type-to-stringno_runtimeType_toString
Avoid calling toString() on runtimeType.
non-constant-identifier-namesnon_constant_identifier_namesrecommended
Flags non-constant identifiers that are not written in lowerCamelCase.
omit-local-variable-typesomit_local_variable_types
Flags local variable type annotations that repeat the initializer's type.
only-throw-errorsonly_throw_errorsrecommended
Only throw instances of classes that extend Exception or Error.