okhttp:5.0.0-alpha.10 can run into java.lang.ClassNotFoundException: kotlin.time.DurationUnit

[staktrace]

See previous discussions in #7267, #7329, and #7343. This is a continuation of that thread of problems, trying to iron out issues when using okhttp in a gradle plugin where the runtime kotlin version is restricted to 1.5.

Now I have put together a minimal standalone reproduction of the problem. It can be found at https://github.com/staktrace/20220627-okhttp-durationunit/tree/57afefa7bbe4f1cf1ae0b1dd8b6d4e01c4b738ff. To reproduce, clone the repo and run the ./reproduce.sh script. The setup is that there are two separate gradle projects - one is a plugin that uses okhttp, and the other is a consumer that uses the plugin.

Some things I discovered along the way of creating this reproducer:

• If the plugin lives in the buildSrc folder of the consumer project, the problem doesn't reproduce
• The kotlin-dsl plugin being applied is important since it seems to be the thing that actually pins the gradle version to 1.5.31.

[staktrace]

For the cases I care about, I was able to work around this issue by doing this - adding the kotlin 1.6 jvm plugin to the consumer repo made the DurationUnit class available and everything worked fine. In a bunch of cases the consumer already had the kotlin-dsl plugin which I had to replace with kotlin("jvm") instead, but this effectively solved all the problems I was seeing in downstream projects.

[yschimke]

@staktrace do you still have that repro repo?

[staktrace]

The repro is linked in the top comment - https://github.com/staktrace/20220627-okhttp-durationunit (main branch)

[yschimke]

@staktrace is it private?

[staktrace]

Ah sorry! Yes, it was private. Made it public now.

[yschimke]

I'm a bi confused, so want to kick off the discussion of whether this is still needed?

I think this gradle/gradle#19539

and this gradle/gradle#16345, discussed here https://twitter.com/martinbonnin/status/1550035276604522498

Mean that we can revert this. So suggest that we do, I'll put a PR up and compile against 1.6.21.

[yschimke]

Or is this the issue? gradle/gradle#19568

Gradle 7.5 will ship with Kotlin 1.6.21 but still target language/api 1/4 for backwards compatibility reasons. This can only be changed in a major version, next one being Gradle 8.0.

[yschimke]

Your test PR, with 7.6 works. So going to revert this!

Can you try gradle 7.6 snapshot, or 7.5 release with an older version that you previously had problems with?

I tried your reproducer with the following and it appears to work

implementation("com.squareup.okhttp3:okhttp:5.0.0-alpha.8")

[yschimke]

from https://downloads.gradle-dn.com/distributions-snapshots/gradle-7.6-20220719081901+0000-bin.zip

[martinbonnin]

If the plugin lives in the buildSrc folder of the consumer project, the problem doesn't reproduce

Got curious and made a small test there https://github.com/martinbonnin/classloaders. Looks like the dependencies of buildSrc are also put in the classpath albeit with a lower precedence than the embedded Kotlin jar. This way, you effectively end up with 2 versions of kotlin-stdlib on the classpath. So kotlin-stdlib symbols will resolve to the 1.5.31 version, except those that are not present that will fallback and load from the 1.6.10 jar. Gradle classloaders never cease to amaze 🙃 .

In all cases, Gradle 7.5 will fix the issue as it will put 1.6.something by default and this one has DurationUnit available.

[yschimke]

@martinbonnin sounds like you agree we can revert the existing attempts and ask people to upgrade to 7.5?

[martinbonnin]

Yep, users that want to use OkHttp in Gradle plugin should be able to do so with Gradle 7.5. Maybe you could add a runtime check when building a new client to point to this issue or give an actionable error message?

[yschimke]

I know OkHttp already understands Android vs JVM platforms, but doing so for a build system seems a step too far.

[martinbonnin]

Yup, that's fair 👍

[staktrace]

I also confirmed that the original problem I was seeing goes away with gradle 7.5. So 👍 from me for reverting all the things.