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Analyzing and Fixing Dart Code

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Analysis Configuration

Configure the Dart analyzer using the analysis_options.yaml file located at the package root.

  • Base Configuration: Always include a standard rule set (e.g., package:lints/recommended.yaml or package:flutter_lints/flutter.yaml) using the include: directive.
  • Strict Type Checks: Enable strict type checks under the analyzer: language: node to prevent implicit downcasts and dynamic inferences. Set strict-casts: true, strict-inference: true, and strict-raw-types: true.
  • Linter Rules: Explicitly enable or disable specific rules under the linter: rules: node. Use a key-value map (rule_name: true/false) when overriding included rules, or a list (- rule_name) when defining a fresh set. Do not mix list and map syntax in the same rules block.
  • Formatter Configuration: Configure dart format behavior under the formatter: node. Set page_width (default 80) and trailing_commas (automate or preserve).
  • Analyzer Plugins: Enable custom diagnostics by adding plugins under the analyzer: plugins: node. Ensure the plugin package is added as a dev_dependency in pubspec.yaml.

Diagnostic Suppression

When a diagnostic (lint or warning) yields a false positive or applies to generated code, suppress it explicitly.

  • File-level Exclusion: Use the analyzer: exclude: node in analysis_options.yaml to exclude entire files or directories (e.g., **/*.g.dart) using glob patterns.
  • File-level Suppression: Add // ignore_for_file: <diagnostic_code> at the top of a Dart file to suppress specific diagnostics for the entire file. Use // ignore_for_file: type=lint to suppress all linter rules.
  • Line-level Suppression: Add // ignore: <diagnostic_code> on the line directly above the offending code, or appended to the end of the offending line.
  • Pubspec Suppression: Add # ignore: <diagnostic_code> above the offending line in pubspec.yaml files (e.g., # ignore: sort_pub_dependencies).
  • Plugin Diagnostics: Prefix the diagnostic code with the plugin name when suppressing plugin-specific issues (e.g., // ignore: some_plugin/some_code).

Workflow: Executing Static Analysis

Use this workflow to identify type-related bugs, style violations, and potential runtime errors.

Task Progress: - [ ] 1. Verify analysis_options.yaml exists at the project root. - [ ] 2. Run the analyzer using the analyze_files MCP tool (if available) or the CLI command dart analyze <target_directory>. - [ ] 3. Review the diagnostic output. - [ ] 4. If info-level issues must be treated as failures, append the --fatal-infos flag. - [ ] 5. Resolve reported errors manually or proceed to the Automated Fixes workflow.

Workflow: Applying Automated Fixes

Use this workflow to resolve outdated API usages, apply quick fixes, and migrate code (e.g., Dart 3 migrations).

Task Progress: - [ ] 1. Execute a dry run to preview proposed changes using the dart_fix MCP tool or CLI command dart fix --dry-run. - [ ] 2. Review the proposed fixes to ensure they align with the intended architecture. - [ ] 3. If additional fixes are required, verify that the corresponding linter rules are enabled in analysis_options.yaml. - [ ] 4. Apply the fixes using the dart_fix MCP tool or CLI command dart fix --apply. - [ ] 5. Format the modified code using the dart_format MCP tool or CLI command dart format .. - [ ] 6. Run the static analysis workflow to verify all diagnostics are resolved.

Examples

Comprehensive analysis_options.yaml

include: package:flutter_lints/recommended.yaml

analyzer:
  exclude:
    - "**/*.g.dart"
    - "lib/generated/**"
  language:
    strict-casts: true
    strict-inference: true
    strict-raw-types: true
  errors:
    todo: ignore
    invalid_assignment: warning
    missing_return: error

linter:
  rules:
    avoid_shadowing_type_parameters: false
    await_only_futures: true
    use_super_parameters: true

formatter:
  page_width: 100
  trailing_commas: preserve

Inline Diagnostic Suppression

// Suppress for the entire file
// ignore_for_file: unused_local_variable, dead_code

void processData() {
  // Suppress for a specific line
  // ignore: invalid_assignment
  int x = '';

  const y = 10; // ignore: constant_identifier_names
}