Add parcelizeModels CLI option

[absimas]

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Description of the PR

With cli option parcelizeModels (false by default) allow the use of kotlin's parcelize feature which generates all boilerplate automatically. Currently, the user will require to manually set

androidExtensions {
    experimental = true
}

but it's a small price to pay IMO.

@jimschubert @dr4ke616

[wing328]

@absimas Thanks for the PR. Java client generator already supports this option as follows:

    public static final String PARCELABLE_MODEL = "parcelableModel";
    ......
    cliOptions.add(CliOption.newBoolean(PARCELABLE_MODEL, "Whether to generate models for Android that implement Parcelable with the okhttp-gson library."));

Shall we name it consistently using parcelableModel instead?

Ref: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java#L64

[absimas]

I would disagree because parcelize is just an annotation that internally generates parcelable implementation for models.
parcelableModel generates the implementation itself which is not the same.

[wing328]

Understood there's a slight difference. My intention is to have one single "Parcelable" option to make our life easier (we want to avoid adding too many options if possible)

Let's see if @jimschubert @dr4ke616 have opinions on this.

[absimas]

I understand the need but I think it's important to make the distinction here.
Since they're different there may be a need for parcelableModel in kotlin too.

[wing328]

@absimas I ran some tests and got errors doing gradle test using the option --additional-properties parcelizeModels=true:

➜  kotlin_client gradle build

> Task :compileKotlin
Using kotlin incremental compilation

e: /private/tmp/kotlin_client/src/main/kotlin/org/openapitools/client/models/Pet.kt: (15, 8): Unresolved reference: android
e: /private/tmp/kotlin_client/src/main/kotlin/org/openapitools/client/models/Pet.kt: (16, 8): Unresolved reference: kotlinx
e: /private/tmp/kotlin_client/src/main/kotlin/org/openapitools/client/models/Pet.kt: (24, 2): Unresolved reference: Parcelize
e: /private/tmp/kotlin_client/src/main/kotlin/org/openapitools/client/models/Pet.kt: (29, 5): Unresolved reference: Parcelable

Spec: https://github.com/OAI/OpenAPI-Specification/blob/master/examples/v2.0/yaml/petstore-minimal.yaml

Do I need to update build.gradle to make it work?

[absimas]

@wing328 as I've said in the PRs description, you need to allow experimental features by adding the following lines to your build.gradle file:

androidExtensions {
    experimental = true
}

[wing328]

@absimas actually I did try that (and other "solutions" I found in SO) earlier but no luck:

➜  kotlin_client3 gradle build

FAILURE: Build failed with an exception.

* Where:
Build file '/private/tmp/kotlin_client3/build.gradle' line: 22

* What went wrong:
A problem occurred evaluating root project 'kotlin-client'.
> Could not find method androidExtensions() for arguments [build_et5ydjjkf5wdkoo2a980cxo4s$_run_closure2@42fc727a] on root project 'kotlin-client' of type org.gradle.api.Project.

* 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

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0.
See https://docs.gradle.org/4.8/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 1s

Do I need to use a newer version of Gradle in order to recognize androidExtensions()?

I'm using Gradle 4.8.

[absimas]

For future reference: the problem is that the kotlin client doesn't depend on the android's framework which provides the base Parcelable that's required by the kotlin-android-extensions Parcelize.

[wing328]

@absimas when you've time, please have a look at the compile issue reported by the CI below:

$ mvn --quiet clean install
[ERROR] COMPILATION ERROR : 
[ERROR] /home/travis/build/OpenAPITools/openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java:[364,14] ';' expected
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.5.1:compile (default-compile) on project openapi-generator: Compilation failure
[ERROR] /home/travis/build/OpenAPITools/openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java:[364,14] ';' expected
[ERROR] 

[wing328]

@absimas can you please also run ./bin/utils/export_docs_generators.sh to ensure the documentation is up-to-date?

[wing328]

If no further feedback/question on this PR, I'll merge it on coming Friday.

[wing328]

The CircleCI failure is due to outdated generator doc and I'll update after merging this PR into master.

[wing328]

@absimas thanks for the PR, which has been included in the v3.3.3 release: https://twitter.com/oas_generator/status/1062929948191510528