Flutter code formatting on auto save

Overview

Flutter/Dart supports automatic code formatting on save through IDE settings and the

dart format

VS Code — Format on Save

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// .vscode/settings.json (project-specific) or User Settings
{
  "editor.formatOnSave": true,
  "[dart]": {
    "editor.defaultFormatter": "Dart-Code.dart-code",
    "editor.formatOnSave": true
  }
}

Or via VS Code settings UI:

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1. Ctrl+Shift+P → Open Settings (JSON)
2. Add the settings above
3. File → Preferences → Settings → search "format on save" → Enable

Android Studio — Format on Save

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Preferences → Tools → Actions on Save
→ Check "Reformat code"
→ Check "Optimize imports" (optional)
→ Apply

Or: Preferences → Editor → Code Style → Dart → Set line length

dart format CLI

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# Format a single file
dart format lib/main.dart

# Format entire lib/ directory
dart format lib/

# Check formatting (exit 1 if not formatted)
dart format --output=none --set-exit-if-changed lib/

# Format with custom line length (default: 80)
dart format --line-length 120 lib/

In pubspec / analysis_options

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# analysis_options.yaml
analyzer:
  errors:
    lines_longer_than_80_chars: ignore  # Relax line length rule

linter:
  rules:
    - always_declare_return_types  # Enforce return types
    - prefer_const_constructors    # Prefer const
    - sort_child_properties_last   # style rule

Pre-commit Hook (Format Before Commit)

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# .git/hooks/pre-commit
#!/bin/sh
dart format --output=none --set-exit-if-changed lib/
if [ $? -ne 0 ]; then
  echo "❌ Code not formatted. Run: dart format lib/"
  exit 1
fi

CI/CD Check (GitHub Actions)

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- name: Check formatting
  run: dart format --output=none --set-exit-if-changed .

Best Practice: Enable format-on-save in your IDE, set line length to 80 (Dart default), and add

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dart format

as a CI check. This ensures all team members write consistently formatted code.