easy way to customize the diagnostic severity of all lint rules

[DetachHead]

i originally raised Dart-Code/Dart-Code#5058, @DanTup suggested that i raise it here instead:

Is your feature request related to a problem? Please describe. i have my CI set up to fail on all analyzer diagnostics, but many of them are displayed in vscode as "information":

"information" implies that it's not a problem, but since the CI will fail if this code is committed, i want it to show as a warning or an error.

also, information diagnostics do not show up on the file name, but warnings and errors do:

Describe the solution you'd like an option to change the severity of diagnostics

as discussed there, the solution ended up being to duplicate the list of rules i have enabled in my project, like so:

analysis_options.yaml

linter:
  rules:
    prefer_single_quotes: true 
    avoid_unused_constructor_parameters: true
    avoid_dynamic_calls: true
    avoid_annotating_with_dynamic: false 
    literal_only_boolean_expressions: true
    prefer_final_locals: true
    prefer_final_parameters: true
    prefer_foreach: true
    prefer_if_elements_to_conditional_expressions: true
    prefer_interpolation_to_compose_strings: true
    prefer_mixin: true
    public_member_api_docs: false
    require_trailing_commas: true
    sized_box_shrink_expand: true
    sort_child_properties_last: true
    sort_constructors_first: false 
    sort_unnamed_constructors_first: true
    tighten_type_of_initializing_formals: true
    unawaited_futures: true
    unnecessary_await_in_return: true
    unnecessary_constructor_name: true
    unnecessary_lambdas: true
    unnecessary_late: true
    unnecessary_null_aware_assignments: true
    unnecessary_null_checks: true
    unnecessary_nullable_for_final_variable_declarations: true
    unnecessary_parenthesis: true
    unnecessary_raw_strings: true
    use_colored_box: true
    use_decorated_box: true
    use_enums: true
    use_if_null_to_convert_nulls_to_bools: true
    use_is_even_rather_than_modulo: true
    use_late_for_private_fields_and_variables: true
    use_named_constants: true
    use_raw_strings: true
    use_setters_to_change_properties: true
    use_string_buffers: true
    use_super_parameters: true
    use_test_throws_matchers: true
    use_to_and_as_if_applicable: true
    depend_on_referenced_packages: true
    secure_pubspec_urls: true
    sort_pub_dependencies: true
    avoid_void_async: true

analyzer:
  errors:
    prefer_single_quotes: warning
    avoid_unused_constructor_parameters: warning
    avoid_dynamic_calls: warning
    literal_only_boolean_expressions: warning
    prefer_final_locals: warning
    prefer_final_parameters: warning
    prefer_foreach: warning
    prefer_if_elements_to_conditional_expressions: warning
    prefer_interpolation_to_compose_strings: warning
    prefer_mixin: warning
    require_trailing_commas: warning
    sized_box_shrink_expand: warning
    sort_child_properties_last: warning
    sort_constructors_first: false 
    sort_unnamed_constructors_first: warning
    tighten_type_of_initializing_formals: warning
    unawaited_futures: warning
    unnecessary_await_in_return: warning
    unnecessary_constructor_name: warning
    unnecessary_lambdas: warning
    unnecessary_late: warning
    unnecessary_null_aware_assignments: warning
    unnecessary_null_checks: warning
    unnecessary_nullable_for_final_variable_declarations: warning
    unnecessary_parenthesis: warning
    unnecessary_raw_strings: warning
    use_colored_box: warning
    use_decorated_box: warning
    use_enums: warning
    use_if_null_to_convert_nulls_to_bools: warning
    use_is_even_rather_than_modulo: warning
    use_late_for_private_fields_and_variables: warning
    use_named_constants: warning
    use_raw_strings: warning
    use_setters_to_change_properties: warning
    use_string_buffers: warning
    use_super_parameters: warning
    use_test_throws_matchers: warning
    use_to_and_as_if_applicable: warning
    depend_on_referenced_packages: warning
    secure_pubspec_urls: warning
    sort_pub_dependencies: warning
    avoid_void_async: warning

this isn't ideal because enabling a new rule requires specifying it twice. it would be nice if there was an option to set the diagnostic severity for all lint rules.

[bwilkerson]

While this would be a useful feature to add, it's fairly low on our priority list at the moment so I don't know whether we'll be able to get to it.