[BUG] [JAVA] Invalid default assignments for complex object properties

[mtraynham]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When an OpenAPI spec supplies complex default objects, the Java generator is assigning invalid defaults.

The issue relates to these lines, https://github.com/OpenAPITools/openapi-generator/blob/v7.12.0/modules/openapi-generator/src/main/resources/Java/pojo.mustache#L72-L87

A simple OpenAPI spec could look like the following:

components:
  schemas:
    Test:
      type: object
      properties:
        testEmptyInlineObject:
          type: object
          default: {}

And this generates the following invalid Java default assignment:

private Object testEmptyInlineObject = {};

A full example with other various scenarios, such as references with defaults, can be tested with https://github.com/mtraynham/openapi-generator-java-defaults-bug

I will note that it's not really denoted in the OpenAPI documentation if this is entirely valid - but I haven't seen anything suggesting it's not.

openapi-generator version

• 7.12.0
• main

OpenAPI declaration file content or url

https://github.com/mtraynham/openapi-generator-java-defaults-bug/blob/main/openapi.yaml

Generation Details

• Java

Steps to reproduce

1. Clone https://github.com/mtraynham/openapi-generator-java-defaults-bug
2. Run make .generated

Related issues/PRs

Suggest a fix

I suppose the defaults can be removed in these cases, or proper Java objects should be created
from the JSON.

For now, I've opted to provide my own pojo.mustache template which removes default assignments.

74c74
<   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} JsonNullable<{{{datatypeWithEnum}}}> {{name}} = JsonNullable.<{{{datatypeWithEnum}}}>undefined();
---
>   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} JsonNullable<{{{datatypeWithEnum}}}> {{name}};
77c77
<   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} JsonNullable<{{{datatypeWithEnum}}}> {{name}} = JsonNullable.<{{{datatypeWithEnum}}}>{{#defaultValue}}of({{{.}}}){{/defaultValue}}{{^defaultValue}}undefined(){{/defaultValue}};
---
>   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} JsonNullable<{{{datatypeWithEnum}}}> {{name}};
82c82
<   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
---
>   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} {{{datatypeWithEnum}}} {{name}};
85c85
<   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
---
>   {{#hasChildren}}protected{{/hasChildren}}{{^hasChildren}}private{{/hasChildren}} {{{datatypeWithEnum}}} {{name}};

[DavidGrath]

@mtraynham , hey! I've looked into this and found something interesting.
There's actually a global property that seems to indirectly address this, because it would create classes rather than Objects:

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java

Line 28 in d6c4634

public static final String GENERATE_RECURSIVE_DEPENDENT_MODELS = "generateRecursiveDependentModels";

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java

Line 528 in d6c4634

if (generateRecursiveDependentModels) {

But for some reason I can't find it in the documentation, and it's off by default
Here's what it looks like when I add

 generateRecursiveDependentModels: 'true'

to the globalProperties of your config file

public class TestTestNullableComplexInlineObject {
  public static final String SERIALIZED_NAME_FOO = "foo";
  @SerializedName(SERIALIZED_NAME_FOO)
  @javax.annotation.Nullable
  private String foo;

  public TestTestNullableComplexInlineObject() {
  }

  public TestTestNullableComplexInlineObject foo(@javax.annotation.Nullable String foo) {
    this.foo = foo;
    return this;
  }

  /**
   * Get foo
   * @return foo
   */
  @javax.annotation.Nullable
  public String getFoo() {
    return foo;
  }

  public void setFoo(@javax.annotation.Nullable String foo) {
    this.foo = foo;
  }



  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    TestTestNullableComplexInlineObject testTestNullableComplexInlineObject = (TestTestNullableComplexInlineObject) o;
    return Objects.equals(this.foo, testTestNullableComplexInlineObject.foo);
  }

  @Override
  public int hashCode() {
    return Objects.hash(foo);
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("class TestTestNullableComplexInlineObject {\n");
    sb.append("    foo: ").append(toIndentedString(foo)).append("\n");
    sb.append("}");
    return sb.toString();
  }

  /**
   * Convert the given object to string with each line indented by 4 spaces
   * (except the first line).
   */
  private String toIndentedString(Object o) {
    if (o == null) {
      return "null";
    }
    return o.toString().replace("\n", "\n    ");
  }
...

[DavidGrath]

Sorry, I see the issue still persists, I overlooked Test.java. I'll look into it more

[DavidGrath]

@mtraynham , my initial assessment was wrong, but now I've fixed it and made a PR

[mtraynham]

Awesome sauce. Thanks @DavidGrath!