Swagger code-gen (doc -> code) is a huge project which generates client/server stub for different programming langauges and frameworks. In the same way, there should be a project "swagger scanner"; which would work for different programming languages and framework. It will scan code and generate swagger document in YAML/json file.
Requriments for swagger-scanner
Wrapper for all open-source tools to generate swagger doc. It would look inside code and generate swagger doc for different programming language.
User would be able to run swagger-scanner.jar (just like swagger-codegen). Users would not have to depend on build tools to generate swagger doc.
Honestly, I would happy if there is some tool which satisfies second requriement.
Swagger inspector is not an open source tool. Also swagger-core only works with Maven/Gradle. It would have been great if there was a dedicated Java class that can scan for annotations and generate swagger document without depending on Maven/Gradle.
Also, swagger-codegen is an open-source and it supports many programming languages. In the same way, swagger-scanner would be a wrapper would generate swagger docs and it would support multiple programming languages. Also, it would not depend on a specific build tool.
Many of the open-sourced swagger projects do not have good document. A document should clearly lay out input, output and procedure to get output.