Muitilile error during generation openapi client from swagger

Decomprimi test-github-api.zip, entra nella directory test-github-api ed esegui mvn clean install per riprodurre gli errori di compilazione del client generato. Esamina i file generati RepositoryCreatedAt.java, RepositoryPushedAt.java, JSON.java e i file dei modelli budget, insieme allo schema OpenAPI che li ha prodotti. Il lavoro è completato quando i sorgenti Java generati segnalati vengono compilati senza gli errori relativi ai metodi mancanti e alla classe ContentDirectory.

Hi
I am generating client using openapi toolkit base on your swagger schema. I and during compilation getting multiple errors

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.11.0:compile (default-compile) on project test-github-api: Compilation failure: Compilation failure:
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryCreatedAt.java:[118,39] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryCreatedAt.java:[242,27] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryPushedAt.java:[118,39] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryPushedAt.java:[247,27] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/JSON.java:[79,94] cannot find symbol
[ERROR] symbol: class ContentDirectory
[ERROR] location: package api.github.com.generated.model
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/BillingUpdateBudgetOrg200ResponseBudget.java:[461,15] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/Budget.java:[397,13] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/GetBudget.java:[464,13] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/BillingUpdateBudgetOrgRequest.java:[432,15] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] -> [Help 1]

How to reproduce:

1. open zip file test-github-api.zip
2. cd test-github-api
3. mvn clean install

Thanks
Arseniy Isakov

test-github-api.zip