Flutter プロジェクト新規作成直後の analysis_options.yaml は下記になっています。実質 include: package:flutter_lints/flutter.yaml しているだけの状態です。

# This file configures the analyzer, which statically analyzes Dart code to
# check for errors, warnings, and lints.
#
# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
# invoked from the command line by running `flutter analyze`.

# The following line activates a set of recommended lints for Flutter apps,
# packages, and plugins designed to encourage good coding practices.
include: package:flutter_lints/flutter.yaml

linter:
  # The lint rules applied to this project can be customized in the
  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
  # included above or to enable additional rules. A list of all available lints
  # and their documentation is published at
  # https://dart-lang.github.io/linter/lints/index.html.
  #
  # Instead of disabling a lint rule for the entire project in the
  # section below, it can also be suppressed for a single line of code
  # or a specific dart file by using the `// ignore: name_of_lint` and
  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
  # producing the lint.
  rules:
    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
#
# Additional information about this file can be found at
# https://dart.dev/guides/language/analysis-options

そして package:flutter_lints/flutter.yaml は内部で package:lints/recommended.yamlimport し、さらにそれが package:lints/core.yamlimport しています。

つまり、下記3ファイルの設定が有効になっている状態です。

  1. package:flutter_lints/flutter.yaml
  2. package:lints/recommended.yaml
  3. package:lints/core.yaml

これがデフォルトの設定ですが、特に複数人で開発をする場合、ルールはできる限り厳しくしておきたいです。

analyzer の設定を厳しくする

linter の話に入る前にまずは analyzer から取り掛かります。

analyzer には language のオプションがあり、ここで Dart の型システムよりも厳しい型チェック制約を設けることができます。

ルールは3つしかなく、設定はシンプルです。

analyzer:
  language:
    strict-casts: true
    strict-inference: true
    strict-raw-types: true

linter の設定を厳しくする

さて linter についてです。なにか良いパッケージはないかと探していたところ、次の記事に行き当たりました。

この記事を読んで、まずはすべてのリントルールを有効化した後で不要なものだけを除いていけば、最大限の厳しいルールを設定できそうだと思い至りました。

詳細は上記記事に譲るとして、私の最終的な結果を以下に貼り付けておきます。

設定ファイル例

analysis_options.yaml

# https://dart.dev/guides/language/analysis-options

include: all_lint_rules.yaml

analyzer:
  language:
    strict-casts: true
    strict-inference: true
    strict-raw-types: true
  errors:
    fixme: ignore
    invalid_annotation_target: ignore
  exclude:
    - '**/*.freezed.dart'
    - '**/*.g.dart'

linter:
  rules:

errorsexclude は Freezed、json_serializable やその他の兼ね合いで設定しているものですので読み飛ばしてください。

all_lint_rules.yaml

# All rules
#   - https://dart-lang.github.io/linter/lints/options/options.html
# Rule explanation
#   - https://dart-lang.github.io/linter/lints/index.html
#   - https://dart.dev/tools/linter-rules

linter:
  rules:
    - always_declare_return_types
    - always_put_control_body_on_new_line
    - always_put_required_named_parameters_first
    - always_require_non_null_named_parameters
    - always_specify_types
    # - always_use_package_imports # This is the opposite of 'prefer_relative_imports'.
    - annotate_overrides
    - avoid_annotating_with_dynamic
    - avoid_bool_literals_in_conditional_expressions
    - avoid_catches_without_on_clauses
    - avoid_catching_errors
    # - avoid_classes_with_only_static_members # NO NEED
    - avoid_double_and_int_checks
    - avoid_dynamic_calls
    - avoid_empty_else
    - avoid_equals_and_hash_code_on_mutable_classes
    - avoid_escaping_inner_quotes
    - avoid_field_initializers_in_const_classes
    - avoid_final_parameters
    - avoid_function_literals_in_foreach_calls
    - avoid_implementing_value_types
    - avoid_init_to_null
    - avoid_js_rounded_ints
    - avoid_multiple_declarations_per_line
    - avoid_null_checks_in_equality_operators
    - avoid_positional_boolean_parameters
    - avoid_print
    - avoid_private_typedef_functions
    # - avoid_redundant_argument_values # NO NEED
    - avoid_relative_lib_imports
    - avoid_renaming_method_parameters
    - avoid_return_types_on_setters
    - avoid_returning_null
    - avoid_returning_null_for_future
    - avoid_returning_null_for_void
    - avoid_returning_this
    - avoid_setters_without_getters
    - avoid_shadowing_type_parameters
    - avoid_single_cascade_in_expression_statements
    - avoid_slow_async_io
    - avoid_type_to_string
    - avoid_types_as_parameter_names
    # - avoid_types_on_closure_parameters # Incompatible with: always_specify_types.
    - avoid_unnecessary_containers
    - avoid_unused_constructor_parameters
    - avoid_void_async
    - avoid_web_libraries_in_flutter
    - await_only_futures
    - camel_case_extensions
    - camel_case_types
    - cancel_subscriptions
    - cascade_invocations
    - cast_nullable_to_non_nullable
    - close_sinks
    - comment_references
    - conditional_uri_does_not_exist
    - constant_identifier_names
    - control_flow_in_finally
    - curly_braces_in_flow_control_structures
    - depend_on_referenced_packages
    - deprecated_consistency
    # - diagnostic_describe_all_properties # NO NEED
    - directives_ordering
    - discarded_futures
    - do_not_use_environment
    - empty_catches
    - empty_constructor_bodies
    - empty_statements
    - eol_at_end_of_file
    - exhaustive_cases
    - file_names
    - flutter_style_todos
    - hash_and_equals
    - implementation_imports
    - iterable_contains_unrelated_type
    - join_return_with_assignment
    - leading_newlines_in_multiline_strings
    - library_names
    - library_prefixes
    - library_private_types_in_public_api
    - lines_longer_than_80_chars
    - list_remove_unrelated_type
    - literal_only_boolean_expressions
    - missing_whitespace_between_adjacent_strings
    - no_adjacent_strings_in_list
    # - no_default_cases # experimental
    - no_duplicate_case_values
    - no_leading_underscores_for_library_prefixes
    - no_leading_underscores_for_local_identifiers
    - no_logic_in_create_state
    - no_runtimeType_toString
    - non_constant_identifier_names
    - noop_primitive_operations
    - null_check_on_nullable_type_parameter
    - null_closures
    # - omit_local_variable_types # Incompatible with: always_specify_types.
    - one_member_abstracts
    - only_throw_errors
    - overridden_fields
    - package_api_docs
    - package_names
    - package_prefixed_library_names
    - parameter_assignments
    - prefer_adjacent_string_concatenation
    - prefer_asserts_in_initializer_lists
    - prefer_asserts_with_message
    - prefer_collection_literals
    - prefer_conditional_assignment
    - prefer_const_constructors
    - prefer_const_constructors_in_immutables
    - prefer_const_declarations
    - prefer_const_literals_to_create_immutables
    - prefer_constructors_over_static_methods
    - prefer_contains
    # - prefer_double_quotes # Incompatible with: prefer_single_quotes.
    - prefer_equal_for_default_values
    # - prefer_expression_function_bodies # NO NEED
    - prefer_final_fields
    - prefer_final_in_for_each
    - prefer_final_locals
    # - prefer_final_parameters # Incompatible with: unnecessary_final, avoid_final_parameters.
    - prefer_for_elements_to_map_fromIterable
    - prefer_foreach
    - prefer_function_declarations_over_variables
    - prefer_generic_function_type_aliases
    - prefer_if_elements_to_conditional_expressions
    - prefer_if_null_operators
    - prefer_initializing_formals
    - prefer_inlined_adds
    - prefer_int_literals
    - prefer_interpolation_to_compose_strings
    - prefer_is_empty
    - prefer_is_not_empty
    - prefer_is_not_operator
    - prefer_iterable_whereType
    - prefer_mixin
    - prefer_null_aware_method_calls
    - prefer_null_aware_operators
    - prefer_relative_imports
    - prefer_single_quotes
    - prefer_spread_collections
    - prefer_typing_uninitialized_variables
    - prefer_void_to_null
    - provide_deprecation_message
    # - public_member_api_docs # NO NEED
    - recursive_getters
    - require_trailing_commas
    - secure_pubspec_urls
    - sized_box_for_whitespace
    - sized_box_shrink_expand
    - slash_for_doc_comments
    - sort_child_properties_last
    - sort_constructors_first
    - sort_pub_dependencies
    - sort_unnamed_constructors_first
    - test_types_in_equals
    - throw_in_finally
    - tighten_type_of_initializing_formals
    - type_annotate_public_apis
    - type_init_formals
    - unawaited_futures
    - unnecessary_await_in_return
    - unnecessary_brace_in_string_interps
    - unnecessary_const
    - unnecessary_constructor_name
    # - unnecessary_final # Incompatible with: prefer_final_locals, prefer_final_parameters.
    - unnecessary_getters_setters
    - unnecessary_lambdas
    - unnecessary_late
    - unnecessary_new
    - unnecessary_null_aware_assignments
    - unnecessary_null_aware_operator_on_extension_on_nullable
    - unnecessary_null_checks
    - unnecessary_null_in_if_null_operators
    - unnecessary_nullable_for_final_variable_declarations
    - unnecessary_overrides
    - unnecessary_parenthesis
    - unnecessary_raw_strings
    - unnecessary_statements
    - unnecessary_string_escapes
    - unnecessary_string_interpolations
    - unnecessary_this
    - unnecessary_to_list_in_spreads
    - unrelated_type_equality_checks
    - unsafe_html
    - use_build_context_synchronously
    - use_colored_box
    - use_decorated_box
    - use_enums
    - use_full_hex_values_for_flutter_colors
    - use_function_type_syntax_for_parameters
    - use_if_null_to_convert_nulls_to_bools
    - use_is_even_rather_than_modulo
    - use_key_in_widget_constructors
    - use_late_for_private_fields_and_variables
    - use_named_constants
    - use_raw_strings
    - use_rethrow_when_possible
    - use_setters_to_change_properties
    - use_string_buffers
    # - use_super_parameters # experimental
    - use_test_throws_matchers
    - use_to_and_as_if_applicable
    - valid_regexps
    - void_checks

FYI:その他参考になりそうな記事

analyzerlinter の設定の概要が知りたいなら

linter のルールに関する公式ドキュメント

他の人はどのようなルール設定にしているかの参考に