[java-client][okhttp-gson] fixes for interceptors in ApiClient.java

[lostiniceland]

ApiClient for Okhttp3 must not copy the interceptors when setting the HttpClient.

fixes #3497

[jmini]

CircleCI reports that this change gets overridden when the samples are updated:

diff --git a/samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/ApiClientTest.java b/samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/ApiClientTest.java
index 3675d8645a..6181e8afa2 100644
--- a/samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/ApiClientTest.java
+++ b/samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/ApiClientTest.java
@@ -335,7 +335,7 @@ public class ApiClientTest {
         OkHttpClient oldClient = apiClient.getHttpClient();
         assertEquals(1, oldClient.networkInterceptors().size());
 
-        OkHttpClient newClient = apiClient.getHttpClient().newBuilder().build();
+        OkHttpClient newClient = new OkHttpClient();
         apiClient.setHttpClient(newClient);
         assertEquals(1, apiClient.getHttpClient().networkInterceptors().size());
         apiClient.setHttpClient(newClient);

This is because the source for this file is in the CI/samples.ci folder. Can you update this file:

openapi-generator/CI/samples.ci/client/petstore/java/test-manual/okhttp-gson/ApiClientTest.java

Line 338 in 6824bd8

OkHttpClient newClient = new OkHttpClient();

[jmini]

@lostiniceland: Thank you a lot for this PR. It looks great.

Can you also change the mentioned file?

[lostiniceland]

Updated as requested by review.

I would argue though that the Tests I've fixed are not very usefull at all. They might have been with the old "logic" but now the tested method is a plain setter, except the check for equality, which could also be removed.
A usefull invariant would be that the passed client must not be null, because the ApiClient cannot function without a httpClient.

[lostiniceland]

@jmini I've added another commit which contains the mentioned invariant and removed the unnecessary tests

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[lostiniceland]

@wing328 thanks for pointing that out. I've added my work-email to Github so it should match now.

[jmini]

LGTM. Thank you for the change.

[wing328]

@lostiniceland thanks for the PR, which has been included in the 4.1.0 release: https://twitter.com/oas_generator/status/1160000504455319553