Testing only code (ie: matchers) should be exported through a specific library

[jakemac53]

See https://github.com/dart-lang/code_builder/blob/master/lib/src/matchers.dart#L5.

This causes problems internally because it prevents matcher from being a testonly target, which it should be. It also means matcher is a transitive dep of anything that depends on code_builder, which should not be the case.

This would probably have to be a breaking change though.

[devoncarew]

To follow up on this, of the top 200 packages that depend on this package from pub, here are the ones that reference the symbol equalsDart:

references to equalsDart:

• package:ngcompiler
• package:json_parse_model
• package:widgetbook_generator
• package:figmage
• package:nitrite_generator

references to equalsDart:

• package:ngcompiler/test/v1/angular_compiler/emitter/injector_test.dart
• package:ngcompiler/test/v1/angular_compiler/integration/generate_injector_test.dart
• package:json_parse_model/test/class_extension_test.dart
• package:widgetbook_generator/test/helpers/code.dart
• package:figmage/test/src/data/generators/theme_extension_generators/text_style_theme_extension_generator_test.dart
• package:figmage/test/src/data/generators/theme_extension_generators/color_theme_extension_generator_test.dart
• package:figmage/test/src/data/generators/theme_extension_generators/number_theme_extension_generator_test.dart
• package:figmage/test/src/data/generators/file_generators/base_file_generator_test.dart
• package:figmage/test/src/data/generators/file_generators/color_file_generator_test.dart
• package:figmage/test/src/data/generators/reference_generators/spacer_generator_test.dart
• package:figmage/test/src/data/generators/reference_generators/padding_generator_test.dart
• package:nitrite_generator/test/entity_writer_test.dart