dart-long-lines

--- name: dart-long-lines description: |- Guidelines for handling long lines in Dart code to adhere to the 80-column rule. The `lines_longer_than_80_chars` lint. license: Apache-2.0 key_features: - 80-column rule compliance - Line length refactoring - Linter rule enforcement ---

# Dart Long Lines

## 1. When to use this skill

Use this skill when: - Writing Dart code that might exceed the 80-column limit. - Refactoring code to comply with the `lines_longer_than_80_chars` lint. Reference: https://dart.dev/tools/linter-rules/lines_longer_than_80_chars

## Discovery

To find lines that exceed the limit:

### Automated Analysis The most reliable way to find long lines is to use the Dart analyzer: - **Command**: `dart analyze` - **Lint**: `lines_longer_than_80_chars`

### Manual Search To search for long lines using regex: - **Regex**: `^.{81,}$` (Matches any line with 81 or more characters).

## 2. Guidelines

### Format First Always run `dart format` before manually breaking long lines. The formatter often automatically fixes long lines, especially in generated code, and applies standard Dart styling rules.

### Code Comments Break long code comments (`//`) cleanly at word boundaries to ensure lines do not exceed 80 characters. Maintain tight formatting and avoid unnecessary vertical space.

### Documentation Comments (`///`) - Apply the same line-breaking rules as for code comments. - Avoid breaking markdown link blocks like `[name]` or `[text](http://example.com)` across lines. Place them on their own line if they exceed the limit. - Start doc comments with a single summary sentence, followed by a blank line before the rest of the comment. It is okay to break this first sentence across multiple lines to fit the 80-column limit. - Avoid unresolved references or dangling sentences.

### Long Strings - Use adjacent string literals (e.g., `'part 1 ' 'part 2'`) to break long strings. Break at word boundaries. - If a single-line string contains newline characters (`\n`) or if there are consecutive `print` statements, consider migrating to a multi-line string literal (`'''`).

### Format and Analyze After Changes - Run `dart format` and `dart analyze` after making changes. - Be aware that splitting strings may trigger new lints (e.g., `prefer_single_quotes` if a double-quoted string is split into parts that no longer contain single quotes).

## 3. Examples

### Documentation Comment Link **Avoid:** ```dart /// This is a long doc comment that contains a link to [a very long /// URL](http://example.com/very/long/url/that/exceeds/eighty/chars). ```

**Prefer:** ```dart /// This is a long doc comment that contains a link to [a very long URL][ref]. /// /// [ref]: http://example.com/very/long/url/that/exceeds/eighty/chars ```

### Adjacent String Literals **Prefer:** ```dart final longString = 'This is a very long string that needs to be broken ' 'across multiple lines to stay under the limit.'; ```

### Multi-line String Migration **Avoid:** ```dart print('This is line 1\nThis is line 2 that is also quite long\nThis is line 3 which makes the whole thing exceed eighty characters'); ```

**Prefer:** ```dart print('''This is line 1 This is line 2 that is also quite long This is line 3 which makes the whole thing exceed eighty characters'''); ```