alt Hacker NewsThat's a great question!
Adding new features is usually not a problem because you can always add optional fields and extend open unions. So, you just change `media: Link | Picture | unknown` to `media: Link | Picture | Video | unknown`.
You can't remove things true, so records do get some deprecated fields.
Re: updating safely, the rule is that you can't change which records it would consider valid after it gets used in the wild. So you can't change whether some field is optional or required, you can only add new optional fields. The https://github.com/bluesky-social/goat tool has a linting command that instantly checks whether your changes pass the rules. In general it would be nice if lexicon tooling matures a bit, but I think with time it should get really good because there's explicit information the tooling can use.
If you have to make a breaking change, you can make a new Lexicon. It doesn't have to cause tech debt because you can make all your code deal with a new version, and convert it during ingestion.
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Are these just guidelines or is this enforced in some way? I guess readers could validate and skip anything that doesn't match their schema.
That's true if you define the problem as "does my parser crash" and not whether the app is perceived as working correctly. If some platform adds support for video posts, then the next thing that happens is people start making posts that are only video. Meaning that in every other client, users see what appears to be an entirely empty post. Which will be considered a bug.
This is the core argument of Moxie's seminal essay, The Ecosystem Is Moving:
https://signal.org/blog/the-ecosystem-is-moving/
One of the controversial things we did with Signal early on was to build it as an unfederated service. Nothing about any of the protocols we’ve developed requires centralization; it’s entirely possible to build a federated Signal Protocol-based messenger, but I no longer believe that it is possible to build a competitive federated messenger at all.
That was written in 2016 but it was true then and continues to be true today. Users reject federated open platforms because the coordination costs mean they don't move as fast as proprietary centralized platforms, and they often appear broken even if technically working as designed.
Nothing about that analysis is unique to social media. It is also true of file formats. OpenOffice never took off because new features got added to Office first, so files that used those features would open in semi-corrupted ways in OpenOffice. The fact that OO represented things internally using open unions didn't matter at all.