add gradle repository for using gralde dependency in plugin

[fujigon]

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Description of the PR

org.gradle:gradle-tooling-api is on Gradle Releases repository (cf. https://mvnrepository.com/artifact/org.gradle/gradle-tooling-api/4.10.2)

So, we need to add this repository to pluginManagement.

Without this setting, following error will occur in some environment.

[INFO] --- gradle-maven-plugin:1.0.8:invoke (default) @ openapi-generator-gradle-plugin-mvn-wrapper ---
[WARNING] The POM for org.gradle:gradle-tooling-api:jar:4.10.2 is missing, no dependency information available
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] openapi-generator-project .......................... SUCCESS [  3.859 s]
[INFO] openapi-generator-core ............................. SUCCESS [  3.680 s]
[INFO] openapi-generator (core library) ................... SUCCESS [ 50.943 s]
[INFO] openapi-generator (executable) ..................... SUCCESS [ 17.679 s]
[INFO] openapi-generator (maven-plugin) ................... SUCCESS [  6.745 s]
[INFO] openapi-generator-gradle-plugin (maven wrapper) .... FAILURE [  0.061 s]
[INFO] openapi-generator-online ........................... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 01:23 min
[INFO] Finished at: 2019-09-10T05:05:53+00:00
[INFO] Final Memory: 69M/1395M
[INFO] ------------------------------------------------------------------------

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

[jimschubert]

@fujigon what are the conditions that might cause this? Do you have a modified Maven settings.xml? And what version of Maven?

We don't really build the Gradle plugin via Maven, so it might be better to remove it and just rely on CI to report build issues in the plugin.

@wing328 any thoughts? If no concerns, we may want to merge after 4.1.2 is released. Workaround for whatever environment conditions cause this would be for the user to manually add the above configuration locally.

[fujigon]

I'm still gathering the facts, please give me a moment.

[fujigon]

can reproduce the error in some environments, cannot do in other environments.

Following command will reproduce the error though I found the issue while I run my complicated mvn commands for my internal package release to my private maven repository.

mvn install

I confirmed that all my trial invoke gradle-maven-plugin:1.0.8:invoke, and the error is produced by it (if error occurs).
But results varies in environments.

When succeeds, I get

[INFO] --- gradle-maven-plugin:1.0.8:invoke (default) @ openapi-generator-gradle-plugin-mvn-wrapper ---
[INFO] jvmArgs: [Ljava.lang.String;@1841d013
[INFO] gradleProjectDirectory: /mnt/c/publicgithub/openapi-generator/modules/openapi-generator-gradle-plugin
[INFO] Build
[INFO] Connecting to Gradle Daemon
...
[INFO] Task :publishPluginMavenPublicationToMavenLocal
> Task :publishMavenJavaPublicationToMavenLocal
> Task :generatePomFileForOpenApiGeneratorPluginMarkerMavenPublication[INFO] Run tasks

> Task :publishOpenApiGeneratorPluginMarkerMavenPublicationToMavenLocal
> Task :generatePomFileForPluginMavenPublication
[INFO] Task :publishToMavenLocal
[INFO] Run tasks
[INFO] Run build
[INFO] Build
[INFO] Deleting unused version-specific caches in /mnt/c/publicgithub/openapi-generator/modules/openapi-generator-gradle-plugin/.gradle
[INFO] Build
> Task :publishPluginMavenPublicationToMavenLocal
> Task :publishToMavenLocal

BUILD SUCCESSFUL in 6s
14 actionable tasks: 14 executed
[INFO]
[INFO] gradle execution complete

When fails, I get

[INFO] --- gradle-maven-plugin:1.0.8:invoke (default) @ openapi-generator-gradle-plugin-mvn-wrapper ---
[WARNING] The POM for org.gradle:gradle-tooling-api:jar:4.10.2 is missing, no dependency information available

environment 1 error occurs

(I challenged all combination, i.e. 8 patterns)

• CentOS 6.6
• maven 3.3.3 / maven 3.5.3
• java 1.8.0_66, oracle / java 1.8.0_22 openjdk
• with my local settings.xml / with no settings.xml

environment 2 error occurs

• CentOS 6.10
• maven 3.3.9
• java 1.8.0_212, amazon correto
• with my local settings.xml

environment 3 no error

• Windows Subsystem for Linux Ubuntu 1804 on Windows 10
• maven 3.6.0
• java 1.8.0_222 openjdk
• with my local settings.xml / with no settings.xml

environment 4 no error

• Windows 10
• maven 3.3.9 (IntelliJ build-in)
• java 1.8.0_212, amazon correto
• with my local settings.xml
• command executed via IntelliJ GUI

[fujigon]

@jimschubert could you please check my error environment report please? thanks! :)

[fujigon]

confirmed this PR will

• environment 1 succeeds (only limited patterns checked)
  • maven 3.5.3
  • java 1.8.0_66 oracle / java 1.8.0_222 openjdk
  • with my local settings.xml / with no settings.xml
• environment 2 succeeds
• environment 3 still succeeds
• environment 4 still succeeds

[jmini]

This pom file:

        <groupId>org.openapitools</groupId>
        <artifactId>openapi-generator-gradle-plugin-mvn-wrapper</artifactId>
        <version>4.1.2-SNAPSHOT</version>

Is not something we release. It is only here to trigger gradle as part of the maven build.

It does not seems to hurt to give maven an additional way to fetch the dependencies requested for one of the plugins used in this pom.

[wing328]

@fujigon thanks for the PR, which has been included in the v4.1.3 release: https://twitter.com/oas_generator/status/1180123829626003456