Language docs for previous Kotlin versions

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The Kotlin documentation for the language and the standard library are really awesome and one of the easiest to reference, period.

However, it looks like at least on the language docs side of things, the second a new version of Kotlin is released as stable, there’s no way to access the documentation for the older versions of the language. This is really unfortunate, as not every project can (or indeed will) be migrated to the latest Kotlin version.

I see there’s a version picker for the standard library API docs (see screenshot below).

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But there’s not similar picker (or even a more convoluted way) to get to older version of the “prose” documentation for the main language concepts (there’s a small tag in the title, but that only points to the release on GitHub).

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Furthermore, language additions (e.g. data objects are not clearly labeled with the version they were introduced in. It makes sense when documenting a version that already has them, but if I want to know if e.g. my Kotlin 1.7 codebase supports a certain feature, there’s no clear easy way to figure it out from the docs.

So, am I missing something obvious? Is there an easy way to “go back in time” and access the language docs for a specific Kotlin version?

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Is there an easy way to “go back in time” and access the language docs for a specific Kotlin version?

This is a frustrating gap indeed.

I was just looking at docs for Json.decodeFromJsonElement, and puzzled by why it wasn’t working.

The docs are for 1.7.3, but due to other dependencies I cannot yet use anything newer than 1.6.3… and this method was renamed from fromJson in a commit prior to 1.7.3.

Very frustrating not to be able to see earlier versions’ docs online.

Unlike Kotlin, Python’s documentation site gets this effortlessly right:

  • Latest 3.x: https://docs.python.org/3/library/json.html
  • Specific version: https://docs.python.org/3.9/library/json.html
  • Version picker dropdown for docs:
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