Flutter Analyzer Setup for Code Quality Checking

Setting Up Flutter Analyzer for Code Quality

Flutter Analyzer is a built-in static analyzer for Dart/Flutter based on dart analyze. Without configuration it already works in IDE, but in CI it's often ignored or run without proper flags. Result: code with dynamic instead of typed variables, unused imports, deprecated API — all accumulates and migrates to production.

analysis_options.yaml

All analyzer settings are in analysis_options.yaml in project root:

include: package:flutter_lints/flutter.yaml

analyzer:
  exclude:
    - "**/*.g.dart"
    - "**/*.freezed.dart"
    - "lib/generated/**"
  errors:
    invalid_annotation_target: ignore  # for freezed
  language:
    strict-casts: true
    strict-inference: true
    strict-raw-types: true

linter:
  rules:
    # Include in addition to flutter_lints
    - always_use_package_imports
    - avoid_dynamic_calls
    - avoid_empty_else
    - avoid_print
    - avoid_relative_lib_imports
    - avoid_slow_async_io
    - avoid_type_to_string
    - cancel_subscriptions
    - close_sinks
    - comment_references
    - invariant_booleans
    - literal_only_boolean_expressions
    - no_adjacent_strings_in_list
    - prefer_const_constructors
    - prefer_const_declarations
    - prefer_final_fields
    - prefer_final_locals
    - prefer_void_to_null
    - unnecessary_await_in_return
    - unnecessary_statements
    - use_build_context_synchronously

strict-casts: true, strict-inference: true, strict-raw-types: true — three strict mode flags. strict-inference is especially important: forbids implicit dynamic where type can't be inferred.

Running in CI

- name: Analyze
  run: flutter analyze --fatal-infos --fatal-warnings

- name: Check formatting
  run: dart format --output=none --set-exit-if-changed lib/ test/

--fatal-infos turns info messages into errors. Harsh, but effective: forces developers not to ignore minor remarks.

dart format --set-exit-if-changed checks formatting without modifying files — if formatting doesn't match dart format, CI fails.

Custom Lint Rules via dart_code_linter

For deeper analysis — dart_code_linter (formerly dart_code_metrics):

# pubspec.yaml
dev_dependencies:
  dart_code_linter: ^1.1.0

# analysis_options.yaml
dart_code_linter:
  metrics:
    cyclomatic-complexity: 20
    lines-of-code: 100
    number-of-parameters: 4
    maximum-nesting-level: 5
  metrics-exclude:
    - test/**
  rules:
    - avoid-unnecessary-setstate
    - prefer-extracting-callbacks
    - avoid-returning-widgets
    - check-for-equals-in-render-methods

avoid-returning-widgets and prefer-extracting-callbacks — Flutter-specific rules that standard analyzer doesn't cover, and they directly impact rebuild performance.

Pre-commit Integration

# .pre-commit-config.yaml
repos:
  - repo: local
    hooks:
      - id: flutter-analyze
        name: Flutter Analyze
        language: system
        entry: flutter analyze
        types: [dart]
        pass_filenames: false
      - id: dart-format
        name: Dart Format
        language: system
        entry: dart format --set-exit-if-changed
        types: [dart]

Timeline: 1 day. Cost is calculated individually.