[Java] Fixing subClassed types so that they can use enums

[who]

This fixes #1050 .

The bug repros if your models use inheritance and enums together. In this event, swagger-codegen output is invalid Java code and will not compile. This is due to a type conflict with the properties copied from the parent class. The solution proposed in this PR is to remove any enums from child classes that already exist in the parent class.

[fehguy]

I don't quite get this yet. Could you please add a test to verify the results of this?

[who]

@fehguy

Here's a repro:

me@box:/tmp/tmp.SUB54PNhX$ cd `mktemp -d /tmp/tmp.XXXXXXXXX`
me@box:/tmp/tmp.SUB54PNhX$ git clone https://github.com/swagger-api/swagger-codegen.git -q .
me@box:/tmp/tmp.SUB54PNhX$ git checkout develop_2.0
me@box:/tmp/tmp.SUB54PNhX$ sed -ie 's/1.0.9-SNAPSHOT/1.0.9/g' pom.xml 
me@box:/tmp/tmp.SUB54PNhX$ mvn clean install 
me@box:/tmp/tmp.SUB54PNhX$ java -jar ./modules/swagger-codegen-cli/target/swagger-codegen-cli.jar generate -i https://gist.githubusercontent.com/who/2ad48a523ce91b646ba7/raw/e9cda73c4bd523fa04bfb59484d6fbfebf75baa2/repro_1051.json -l java -o output
me@box:/tmp/tmp.SUB54PNhX$ cd output; mvn compile;

Repro output:

[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for io.swagger:swagger-java-client:jar:1.0.0
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:build-helper-maven-plugin is missing. @ line 68, column 15
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING] 
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building swagger-java-client 1.0.0
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- build-helper-maven-plugin:1.9.1:add-source (add_sources) @ swagger-java-client ---
[INFO] Source directory: /tmp/tmp.SUB54PNhX/output/src/main/java added.
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ swagger-java-client ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /tmp/tmp.SUB54PNhX/output/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:2.3.2:compile (default-compile) @ swagger-java-client ---
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 2 source files to /tmp/tmp.SUB54PNhX/output/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /tmp/tmp.SUB54PNhX/output/src/main/java/io/swagger/client/model/SubObject.java:[35,23] error: getThingType() in SubObject cannot override getThingType() in SuperObject
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.321 s
[INFO] Finished at: 2015-08-05T21:29:17-07:00
[INFO] Final Memory: 12M/107M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project swagger-java-client: Compilation failure
[ERROR] /tmp/tmp.SUB54PNhX/output/src/main/java/io/swagger/client/model/SubObject.java:[35,23] error: getThingType() in SubObject cannot override getThingType() in SuperObject
[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

[who]

@fehguy I'll put some tests together.

[who]

Ping @fehguy - I added a test for this

[who]

Hey @xhh, could I get your opinion on this PR?

The same bug probably exists in the Android (and maybe Scala) generators.

[who]

@wing328 @fehguy Could this please be merged? It's blocking my team from using swagger codegen in some cases because the output doesn't compile.

[fehguy]

@wing328 what do you think on this one?

[wing328]

Tested and was able to repeat the compile error, which's addressed by this PR. Compared with the prevention approach, this approach (post-processing) is preferable in my opinion.

[who]

Thank you, @wing328 !