Add support for generate-swagger to generate in YAML format

[segevfiner]

Prerequisites

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🚀 Feature Proposal

The fastify.swagger() API also supports a { yaml: true } argument to get a YAML string. It would be nice to expose this from generate-swagger.

I would have implemented this myself, maybe even with an -o file.txt output file support. But I'm not sure how to add custom arguments for just this command with the way parseArgs works.

Motivation

OpenAPI schemas are often represented in YAML for readability, and its already supported by fastify.swagger() just need to expose this in the CLI.

Example

fastify generate-swagger --yaml -o openapi.yaml dist/app.js

[mcollina]

Thanks for reporting! Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[segevfiner]

Yeah. Just what should I use to parse the arguments?

[mcollina]

yargs-parser