mvn swagger-codegen:generate throws out of memory error for query parameter with allOff in OpenAPI spec file.

mvn swagger-codegen:generate throws out of memory error for the following OpenAPI spec file.

{
  "x-generator": "NSwag v14.3.0.0 (NJsonSchema v11.2.0.0 (Newtonsoft.Json v13.0.0.0))",
  "openapi": "3.0.0",
  "info": {
    "title": "test API",
    "version": "1.0.0"
  },
  "paths": {
    "/data": {
      "get": {
        "summary": "Retrieves data",
        "operationId": "GetData",
        "parameters": [
          {
            "name": "dataType",
            "in": "query",
            "required": true,
            "schema": {
              "allOf": [
                {
                  "$ref": "#/components/schemas/DataType"
                }
              ]
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Success"
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "DataType": {
        "type": "string",
        "description": "",
        "x-enumNames": [
          "String",
          "Number"
        ],
        "enum": [
          "String",
          "Number"
        ]
      }
    }
  }
}

Logs

[ERROR] Java heap space -> [Help 1]
java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf (Arrays.java:3689)
    at java.util.ArrayList.grow (ArrayList.java:238)
    at java.util.ArrayList.grow (ArrayList.java:243)
    at java.util.ArrayList.add (ArrayList.java:486)
    at java.util.ArrayList.add (ArrayList.java:499)
    at io.swagger.codegen.v3.generators.DefaultCodegenConfig.fixUpParentAndInterfaces (DefaultCodegenConfig.java:303)
    at io.swagger.codegen.v3.generators.java.AbstractJavaCodegen.fixUpParentAndInterfaces (AbstractJavaCodegen.java:1061)
    at io.swagger.codegen.v3.generators.DefaultCodegenConfig.postProcessAllCodegenModels (DefaultCodegenConfig.java:274)
    at io.swagger.codegen.v3.generators.DefaultCodegenConfig.postProcessAllModels (DefaultCodegenConfig.java:266)
    at io.swagger.codegen.v3.generators.java.JavaClientCodegen.postProcessAllModels (JavaClientCodegen.java:481)
    at io.swagger.codegen.v3.DefaultGenerator.generateModels (DefaultGenerator.java:416)
    at io.swagger.codegen.v3.DefaultGenerator.generate (DefaultGenerator.java:852)
    at io.swagger.codegen.v3.maven.plugin.CodeGenMojo.execute_ (CodeGenMojo.java:567)
    at io.swagger.codegen.v3.maven.plugin.CodeGenMojo.execute (CodeGenMojo.java:326)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
[ERROR]
[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/OutOfMemoryError

It seems to be happening because of the dataType query parameter that extends from DataType schema. The code builds a ComposedSchema (don't remember exact name seen during debug) identified by dataType with parent DataType. Because the names are similar without case sensitivity, it processes the same object again when it loops on the parent essentially creating an infinite loop.

If the dataType name is changed to say dataType1 it completes. It does create another model class DataType1.

The spec was generated by NSwag. I have no control over why it chose allOff for that query parameter when something simpler could have been used I suppose. Anyway the openapi-generator seems to be working fine with this - it doesn't create the DataType1 either.

Start with the supplied OpenAPI document and reproduce it with mvn swagger-codegen:generate. Inspect DefaultCodegenConfig.fixUpParentAndInterfaces and the Java generator call chain shown in the stack trace, focusing on the case-insensitive dataType/DataType parent relationship. Done means generation completes without exhausting the heap and does not repeatedly process the same model.