[Java, java8,resttemplate] Generated code doesn't compile when System property 'supportingFiles' is set to 'false'

Description

I integrate swagger-codegen-maven-plugin's goal 'generate' into my Maven build and use following configuration:

                          <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/swagger.json</inputSpec>
                            <language>java</language>
                            <generateApiTests>false</generateApiTests>
                            <generateModelTests>false</generateModelTests>
                            <generateSupportingFiles>false</generateSupportingFiles>
                            <configOptions>
                                <library>resttemplate</library>
                                <dateLibrary>java8</dateLibrary>
                            </configOptions>
                        </configuration>

Calling mvn clean package produces a failing build with following output

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.685 s
[INFO] Finished at: 2019-01-07T15:13:51+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project swagger-playground: Compilation failure: Compilation failure: 
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[3,25] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: package io.swagger.client
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[29,13] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.StoreApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[36,21] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.StoreApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[40,12] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.StoreApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[44,30] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.StoreApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[3,25] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: package io.swagger.client
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[31,13] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.PetApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[38,19] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.PetApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[42,12] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.PetApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[46,30] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.PetApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[3,25] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: package io.swagger.client
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[29,13] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.UserApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[36,20] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.UserApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[40,12] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.UserApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[44,30] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.UserApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/StoreApi.java:[32,18] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.StoreApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[34,18] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.PetApi
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[149,72] package ApiClient does not exist
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/PetApi.java:[186,72] package ApiClient does not exist
[ERROR] /home/sparsick/dev/workspace_github/swagger-playground/target/generated-sources/swagger/src/main/java/io/swagger/client/api/UserApi.java:[32,18] cannot find symbol
[ERROR]   symbol:   class ApiClient
[ERROR]   location: class io.swagger.client.api.UserApi
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

When I change the property 'generateSupportingFiles' to true, the build is successful.

In case <generateSupportingFiles>false</generateSupportingFiles> following Java Classes are not generated:

• io.swagger.client.ApiClient.java
• io.swagger.client.RFC3339DateFormat.java
• io.swagger.client.auth.ApiKeyAuth.java
• io.swagger.client.auth.Authentication.java
• io.swagger.client.auth.HttpBasicAuth.java
• io.swagger.client.auth.OAuth.java
• io.swagger.client.auth.OAuthFlow.java

Swagger-codegen version

<groupId>io.swagger</groupId>
<artifactId>swagger-codegen-maven-plugin</artifactId>
<version>2.3.1</version>

Swagger declaration file content or url

https://petstore.swagger.io/v2/swagger.json

Command line used for generation

git clone  https://github.com/sparsick/swagger-playground
cd swagger-playground
mvn clean package

Steps to reproduce

see above

Related issues/PRs

Suggest a fix/enhancement

If you confirm that this is a bug, I could try to fix it.

Start by reproducing the failure with the swagger-playground repository and the Maven command described in the issue, using the petstore Swagger definition and generateSupportingFiles=false. Inspect the generated StoreApi.java, PetApi.java, and UserApi.java references to ApiClient and compare generation with supporting files enabled. Done means the generated client compiles without generating supporting files.