Flutter的強制自我審查

在《如何做好 Code Review》中我論述過程式碼審查對於保證程式碼品質的重要性，最近開始採用Git Hooks的方式為Flutter專案增加提交前的強制自我審查。這樣做的好處在於將機械化檢查交給電腦，把思考的部分留給大腦。

我認為程式碼提交前需要做的最基本檢查包括格式和程式碼規範。前者交給Prettier，後者由Analyze負責。

Lefthook

我採用Lefthook實現Git鉤子，如果你有更好的選擇，歡迎推薦分享。

# Mac
brew install lefthook && lefthook install

安裝Lefthook後，在專案根目錄下執行lefthook install命令來生成lefthook.yml檔案，並在其中的pre-commit > commands節點下新增兩項配置：

prettier:
  glob: "*.dart"
  run: flutter format {staged_files} && git add {staged_files}
linter:
  run: flutter analyze

Analyze

flutter analyze通過flutter_lints外掛對Dart程式碼進行靜態語言檢查，檢查規則配置在analysis_options.yaml檔案中。但是開啟該檔案可以看到，Flutter 並沒有為我們配置任何預設規則。我把我正在採用的規則配置放在文末，歡迎酌情采納。

接下來我們可以測試一下配置能否正常工作。比如，將main()替換為：

void main() {
  const title=    'Flutter';
  runApp(const MyApp());}

aa()         {}

然後執行命令：

git add .&&git commit -m 'Commit for analysis.'

接下來你會發現，Prettier 將程式碼格式化為：

void main() {
  const title = 'Flutter';
  runApp(const MyApp());
}

aa() {}

但是靜態檢查沒有通過，因為title變數沒有被使用、函式aa沒有返回型別等：

EXECUTE > linter
 Analyzing demo_lint_flutter...

   info • The value of the local variable 'title' isn't used • lib/main.dart:4:9 • unused_local_variable
   info • The function 'aa' should have a return type but doesn't • lib/main.dart:8:1 • always_declare_return_types
   info • Type annotate public APIs • lib/main.dart:8:1 • type_annotate_public_apis

3 issues found. (ran in 2.0s)

強烈建議你在接下來的每一個Flutter專案裡都堅持這樣做，不要提交Smelling Code。

analysis_options.yaml

include: package:flutter_lints/flutter.yaml

analyzer:
  strong-mode:
    implicit-casts: false
  errors:
    missing_required_param: warning
    missing_return: warning
    todo: ignore

linter:
  rules:
    always_declare_return_types: true
    always_require_non_null_named_parameters: true
    annotate_overrides: true
    avoid_bool_literals_in_conditional_expressions: true
    avoid_catching_errors: true
    avoid_classes_with_only_static_members: true
    avoid_empty_else: true
    avoid_escaping_inner_quotes: true
    avoid_field_initializers_in_const_classes: true
    avoid_function_literals_in_foreach_calls: true
    avoid_implementing_value_types: true
    avoid_init_to_null: true
    avoid_multiple_declarations_per_line: true
    avoid_null_checks_in_equality_operators: true
    avoid_positional_boolean_parameters: true
    avoid_print: true
    avoid_private_typedef_functions: true
    avoid_redundant_argument_values: true
    avoid_relative_lib_imports: true
    avoid_return_types_on_setters: true
    avoid_returning_null_for_future: true
    avoid_returning_null_for_void: true
    avoid_setters_without_getters: true
    avoid_shadowing_type_parameters: true
    avoid_single_cascade_in_expression_statements: true
    avoid_type_to_string: true
    avoid_types_as_parameter_names: true
    avoid_unnecessary_containers: true
    avoid_unused_constructor_parameters: true
    avoid_void_async: true
    avoid_web_libraries_in_flutter: true
    await_only_futures: true
    camel_case_extensions: true
    camel_case_types: true
    cancel_subscriptions: true
    cast_nullable_to_non_nullable: true
    constant_identifier_names: true
    control_flow_in_finally: true
    curly_braces_in_flow_control_structures: true
    depend_on_referenced_packages: true
    deprecated_consistency: true
    empty_catches: true
    empty_constructor_bodies: true
    empty_statements: true
    eol_at_end_of_file: true
    exhaustive_cases: true
    file_names: true
    hash_and_equals: true
    implementation_imports: true
    invariant_booleans: true
    iterable_contains_unrelated_type: true
    join_return_with_assignment: true
    leading_newlines_in_multiline_strings: true
    library_names: true
    library_prefixes: true
    list_remove_unrelated_type: true
    missing_whitespace_between_adjacent_strings: true
    no_adjacent_strings_in_list: true
    no_duplicate_case_values: true
    no_logic_in_create_state: true
    no_runtimeType_toString: true
    non_constant_identifier_names: true
    noop_primitive_operations: true
    null_check_on_nullable_type_parameter: true
    null_closures: true
    overridden_fields: true
    package_names: true
    package_prefixed_library_names: true
    parameter_assignments: true
    prefer_asserts_in_initializer_lists: true
    prefer_collection_literals: true
    prefer_conditional_assignment: true
    prefer_const_constructors: true
    prefer_const_constructors_in_immutables: true
    prefer_const_declarations: true
    prefer_const_literals_to_create_immutables: true
    prefer_constructors_over_static_methods: true
    prefer_contains: true
    prefer_equal_for_default_values: true
    prefer_final_fields: true
    prefer_final_in_for_each: true
    prefer_final_locals: true
    prefer_for_elements_to_map_fromIterable: true
    prefer_function_declarations_over_variables: true
    prefer_generic_function_type_aliases: true
    prefer_if_elements_to_conditional_expressions: true
    prefer_if_null_operators: true
    prefer_initializing_formals: true
    prefer_inlined_adds: true
    prefer_interpolation_to_compose_strings: true
    prefer_is_empty: true
    prefer_is_not_empty: true
    prefer_is_not_operator: true
    prefer_iterable_whereType: true
    prefer_null_aware_method_calls: true
    prefer_spread_collections: true
    prefer_typing_uninitialized_variables: true
    prefer_void_to_null: true
    provide_deprecation_message: true
    recursive_getters: true
    require_trailing_commas: true
    sized_box_for_whitespace: true
    slash_for_doc_comments: true
    sort_child_properties_last: true
    sort_unnamed_constructors_first: true
    test_types_in_equals: true
    throw_in_finally: true
    tighten_type_of_initializing_formals: true
    type_annotate_public_apis: true
    type_init_formals: true
    unnecessary_await_in_return: true
    unnecessary_brace_in_string_interps: true
    unnecessary_const: true
    unnecessary_getters_setters: true
    unnecessary_new: true
    unnecessary_null_aware_assignments: true
    unnecessary_null_checks: true
    unnecessary_null_in_if_null_operators: true
    unnecessary_nullable_for_final_variable_declarations: true
    unnecessary_overrides: true
    unnecessary_parenthesis: true
    unnecessary_raw_strings: true
    unnecessary_statements: true
    unnecessary_string_escapes: true
    unnecessary_string_interpolations: true
    unnecessary_this: true
    unrelated_type_equality_checks: true
    unsafe_html: true
    use_build_context_synchronously: true
    use_full_hex_values_for_flutter_colors: true
    use_function_type_syntax_for_parameters: true
    use_named_constants: true
    use_late_for_private_fields_and_variables: true
    use_rethrow_when_possible: true
    use_setters_to_change_properties: true
    use_string_buffers: true
    use_test_throws_matchers: true
    valid_regexps: true
    void_checks: true