Crash on startup with 1.3.3 for kotlin app not using kotlinx-coroutines-reactor

[gotson]

Describe the bug
After upgrading from 1.3.2 to 1.3.3 the application crashes at startup.

java.lang.IllegalStateException: Unable to load cache item
	at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:79) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:134) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:319) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:569) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:416) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassEnhancer.createClass(ConfigurationClassEnhancer.java:137) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassEnhancer.enhance(ConfigurationClassEnhancer.java:109) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:423) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanFactory(ConfigurationClassPostProcessor.java:257) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:286) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:130) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:706) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.gotson.komga.ApplicationKt.main(Application.kt:17) [main/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.2.6.RELEASE.jar:2.2.6.RELEASE]
Caused by: java.lang.NoClassDefFoundError: kotlinx/coroutines/flow/Flow
	at org.springdoc.kotlin.SpringDocKotlinConfiguration.<clinit>(SpringDocKotlinConfiguration.java:41) ~[springdoc-openapi-kotlin-1.3.3.jar:1.3.3]
	at java.lang.Class.forName0(Native Method) ~[na:1.8.0_222]
	at java.lang.Class.forName(Class.java:348) ~[na:1.8.0_222]
	at org.springframework.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:571) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:363) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:582) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:110) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:108) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_222]
	at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	... 25 common frames omitted
Caused by: java.lang.ClassNotFoundException: kotlinx.coroutines.flow.Flow
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382) ~[na:1.8.0_222]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_222]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_222]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_222]
	... 36 common frames omitted

It seems to be related to the fix for #560

Steps to reproduce the behavior:

• What version of spring-boot you are using? 2.2.6.RELEASE
• What modules and versions of springdoc-openapi are you using?

org.springdoc:springdoc-openapi-ui:1.3.3
org.springdoc:springdoc-openapi-data-rest:1.3.3
org.springdoc:springdoc-openapi-security:1.3.3
org.springdoc:springdoc-openapi-kotlin:1.3.3

[gotson]

Removing org.springdoc:springdoc-openapi-kotlin:1.3.3 seems to solve the problem.

My project is in Kotlin, but i don't use coroutines.

I think it's mostly a documentation issue. The website mentions this about the kotlin module:

For a project that uses Kotlin, you should add the following dependency, together with the springdoc-openapi-ui dependency: This dependency improves the support of Kotlin types:

Which is slightly incorrect, because the project requires a dependency on org.jetbrains.kotlinx:kotlinx-coroutines-reactor, and you can definitely use Kotlin without that.

I would suggest clarifying the content and requirements of the Kotlin module.

[bnasslahsen]

The issue you are facing is linked to kotlinx-coroutines-reactor, which exists in different packages from kotlin.coroutines.

You app, doesn't depend on reactor and the springdoc-kotlin module should support both apps using reactor or not.
This issue will be fixed today on v1.3.4.