[pigeon] Allows swift generator to skip error class generation

[wamynobe]

Since the Kotlin generator allows skipping error class generation, it makes sense for the Swift generator to have the same option.

Related to: #6183 https://github.com/flutter/flutter/issues/142099

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[wamynobe]

Hi @tarrinneal, In your previous PR #6183 , there are a few parts that I don't really understand (mostly about how to generate test files), for example the code kotlinIncludeErrorClass: input != 'core_tests', in packages/pigeon/tool/shared/generation.dart. Could you please guide me through these test cases?

[wamynobe]

looks like the test cases using the default error class name in Swift have failed.

[wamynobe]

How can I run those custom_package_tests test cases on my local machine?

[tarrinneal]

if you navigate to the pigeon directory you can run dart run tool/test.dart -f -t ios_swift_integration_tests

[tarrinneal]

This code

    final bool kotlinErrorClassGenerationTestFiles =
        input == 'core_tests' || input == 'background_platform_channels';

    final String kotlinErrorName = kotlinErrorClassGenerationTestFiles
        ? 'FlutterError'
        : '${pascalCaseName}Error';

and the corresponding usage of kotlinErrorName ensures that there are two files with the same error class name. You'll need to do that for swift as well.

[wamynobe]

if you navigate to the pigeon directory you can run dart run tool/test.dart -f -t ios_swift_integration_tests

Thanks @tarrinneal I am now able to run those test cases.

and the corresponding usage of kotlinErrorName ensures that there are two files with the same error class name. You'll need to do that for swift as well.

I saw swiftErrorUseDefaultErrorName which has the same purpose as kotlinErrorClassGenerationTestFiles. Updated!

[tarrinneal]

@stuartmorgan for 2nd review