Generate shorthand throwing APIs for providing inputs and handling outputs

[simonjbeaumont]

Motivation

The review period for SOAR-0007 (Shorthand APIs for inputs and outputs) has now concluded. This pull request adds the required SPIs to the runtime library to throw a runtime error when the response and/or body does not match that of the shorthand API being used.

For further context, please review the proposal itself.¹

Modifications

• Add support for computed properties with effects (e.g. throwing getters).
• Generate a protocol extension to APIProtocol with an overload for each operation that lifts each of the parameters of Input.init as function parameters.
• Generate a throwing computed property for each enum case related to a documented outcome, which will return the associated value for the expected case, or throw a runtime error if the value is a different enum case.

Result

Code that used to be written like this

// before
switch try await client.getGreeting(.init()) {
case .ok(let response):
    switch response.body {
    case .json(let body):
        print(body.message)
    }
case .undocumented(statusCode: _, _):
    throw UnexpectedResponseError()
}

// after
print(try await client.getGreeting().ok.body.json.message)
//                     ^          ^  ^       ^
//                     |          |  |       `- (New) Throws if body did not conform to documented JSON.
//                     |          |  |
//                     |          |  `- (New) Throws if HTTP response is not 200 (OK).
//                     |          |
//                     |          `- (New) No need to wrap parameters in input value.
//                     |
//                     `- (Existing) Throws if there is an error making the API call.

Test Plan

This PR includes updates to the various tests:

• SnippetBasedReferenceTests
• FileBasedReferenceTests
• PetstoreConsumerTests

Related Issues

• Resolves Generate convenience initializers that flatten some nested scopes #22
• Resolves Improve ergonomics when switching over Outputs #104
• Resolves Wrap operation methods in specialized methods (1 success response, 1 content type) #145

Footnotes

1. https://github.com/apple/swift-openapi-generator/pull/291 ↩

[czechboy0]

A few suggestions, but no blockers so I'll let you make the final call on these.

[simonjbeaumont]

@swift-server-bot test this please

[simonjbeaumont]

@swift-server-bot test this please

[simonjbeaumont]

@swift-server-bot test this please

[simonjbeaumont]

@swift-server-bot test this please

[simonjbeaumont]

@swift-server-bot test this please