dart-best-practices

SKILL.md

Dart Best Practices

1. When to use this skill

Use this skill when:

Writing or reviewing Dart code.

Looking for guidance on idiomatic Dart usage.

2. Best Practices

Multi-line Strings

Prefer using multi-line strings (''') over concatenating strings with + and
\n, especially for large blocks of text like SQL queries, HTML, or
PEM-encoded keys. This improves readability and avoids
lines_longer_than_80_chars lint errors by allowing natural line breaks.
Avoid:

final pem = '-----BEGIN RSA PRIVATE KEY-----\n' +
    base64Encode(fullBytes) +
    '\n-----END RSA PRIVATE KEY-----';

Prefer:

final pem = '''
-----BEGIN RSA PRIVATE KEY-----
${base64Encode(fullBytes)}
-----END RSA PRIVATE KEY-----''';

Line Length

Avoid lines longer than 80 characters, even in Markdown files and comments.
This ensures code is readable in split-screen views and on smaller screens
without horizontal scrolling.

Prefer:
Target 80 characters for wrapping text. Exceptions are allowed for long URLs
or identifiers that cannot be broken.

Discovery

Multi-line Strings

To find candidates for multi-line strings, search for string concatenation
with + involving newlines:

Regex: ['"]\s*\+\s*['"]

Regex: \+\s*['"].*\\n

Line Length

Rely on the lines_longer_than_80_chars lint from the analyzer.

Related Skills

dart-modern-features: For idiomatic
usage of modern Dart features like Pattern Matching (useful for deep JSON
extraction), Records, and Switch Expressions.