[BUG] [gradle] Tasks that inherit ValidateTask will fail if recommend is not assigned.

[doyasu24]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

I am using the openapi-generator-gradle-plugin.
I've noticed that the default value doesn't work well with ValidateTask.
I tried the samples in this repository and the problem was reproduced.

Although recommend has a default value, tasks that inherit ValidateTask will fail if recommend is not assigned.
https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator-gradle-plugin#openapivalidate

task validateGoodSpec(type: org.openapitools.generator.gradle.plugin.tasks.ValidateTask){
    inputSpec = "$rootDir/petstore-v3.0.yaml".toString()
//	recommend = true
//      recommend = false
}

openapi-generator version

I have tried with 4.3.0 and 4.3.1.

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-gradle-plugin/samples/local-spec/petstore-v3.0.yaml

Command line used for generation

./gradlew validateGoodSpec
./gradlew -PopenApiGeneratorVersion=4.3.0 validateGoodSpec
./gradlew -PopenApiGeneratorVersion=4.3.1 validateGoodSpec

Steps to reproduce

I clone this repository and exec validateGoodSpec.

git clone git@github.com:OpenAPITools/openapi-generator.git
cd openapi-generator/modules/openapi-generator-gradle-plugin/samples/local-spec
./gradlew validateGoodSpec

> Task :validateGoodSpec FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':validateGoodSpec'.
> No value has been specified for this provider.

* 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 895ms
1 actionable task: 1 executed

I have explicitly assigned true or false to recommend.
Then the task was successful.

> Task :validateGoodSpec
Validating spec /****/openapi-generator/modules/openapi-generator-gradle-plugin/samples/local-spec/petstore-v3.0.yaml
Spec is valid.

BUILD SUCCESSFUL in 1s
1 actionable task: 1 executed

Related issues/PRs

#4643
#5183

Suggest a fix

I think it should be set default value before get is called at

openapi-generator/modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/tasks/ValidateTask.kt

Line 72 in 5fe34fb

val recommendations = recommend.get()

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[mrworkman]

Just ran into this too. Would be nice if the docs said recommend is required in this case.

[doyasu24]

This issue was fixed by the following commit.
e4c858c
#6716

[doyasu24]

still reproduced in v7.0.0