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I am just today wrestling with the OpenAPI-generated libraries for Java and, summarising: I hate it. I even went as far as trying to set up my own code generat

I am just today wrestling with the OpenAPI-generated libraries for Java and, summarising: I hate it. I even went as far as trying to set up my own code generator using the OpenAPI generator toolkit. It is not my favourite code. Everything is deeply nested inheritance hierarchies with humptyjillion methods that do oddly specific stuff. I eventually gave up on it. Now I am at the point where, to map the generated types to the same types described in the original OpenAPI YAML, I have about 50 goofy lines of string juggling and chasing data structures through 4 or 5 levels of nullable references. I don't know how we wound up here but I wish we hadn't.

DmitryOlshansky 7y ago
Actually I’ve been through this but since we use Scala and our HTTP client wasn’t accounted for in default generators I went straight to writing a plugin for the ehm code-generator toolkit. Mostly same observations, but I actually made that plugin work. In retrospect writing complete generator from scratch would take far less time and effort. I believe original authors have never written a compiler nor considered a code-generator to be a compiler (which it is). Hence the funky architectural style - whatever was the conceptual model behind it fits poorly to the problem at hand and likely was patched multiple times to cover niche corner cases.
eropple 7y ago
IME that's more of a problem between Java and the generator than it is OpenAPI. Expressing things feels clunky when generating Java code in general. Which, I stress, is not to say it's not a problem, and it super sucks when you hit it. The languages I tend to consume OpenAPI in the most are TypeScript (great), Ruby (pretty good), and on-demand JavaScript (really flexible and comfortable) via openapi-js. I've had some luck with the Kotlin generator on the JVM, too.
- jacques_chester 7y ago
  As it happens, my main code is in Kotlin. I found myself thinking "maybe I could do a better generator" and then my fingers and toes began to tingle ominously.
  - eropple 7y ago
    You very well may. The generators are, right now, the worst part of the entire OpenAPI experience. But they're getting steadily better.
jrockway 7y ago
Interacting with generated code is never going to be as nice as hand-written code. It is a tradeoff to express semantics that exist in the interface definition language and the n- languages that the generator targets. Go and "oneof" in protos is always fun: https://github.com/jrockway/ekglue/blob/master/pkg/glue/glue.go#L150 https://github.com/jrockway/ekglue/blob/master/pkg/glue/glue... But it's better than saying "welp, that program is written in c++, so you have to write your tools that interface with it in c++ as well."

DmitryOlshansky 7y ago

Actually I’ve been through this but since we use Scala and our HTTP client wasn’t accounted for in default generators I went straight to writing a plugin for the ehm code-generator toolkit. Mostly same observations, but I actually made that plugin work. In retrospect writing complete generator from scratch would take far less time and effort. I believe original authors have never written a compiler nor considered a code-generator to be a compiler (which it is). Hence the funky architectural style - whatever was the conceptual model behind it fits poorly to the problem at hand and likely was patched multiple times to cover niche corner cases.

eropple 7y ago

IME that's more of a problem between Java and the generator than it is OpenAPI. Expressing things feels clunky when generating Java code in general. Which, I stress, is not to say it's not a problem, and it super sucks when you hit it. The languages I tend to consume OpenAPI in the most are TypeScript (great), Ruby (pretty good), and on-demand JavaScript (really flexible and comfortable) via openapi-js. I've had some luck with the Kotlin generator on the JVM, too.

jacques_chester 7y ago
As it happens, my main code is in Kotlin. I found myself thinking "maybe I could do a better generator" and then my fingers and toes began to tingle ominously.
- eropple 7y ago
  You very well may. The generators are, right now, the worst part of the entire OpenAPI experience. But they're getting steadily better.

jrockway 7y ago

Interacting with generated code is never going to be as nice as hand-written code. It is a tradeoff to express semantics that exist in the interface definition language and the n- languages that the generator targets. Go and "oneof" in protos is always fun: https://github.com/jrockway/ekglue/blob/master/pkg/glue/glue.go#L150 https://github.com/jrockway/ekglue/blob/master/pkg/glue/glue... But it's better than saying "welp, that program is written in c++, so you have to write your tools that interface with it in c++ as well."