[BUG][java][spring] Non-compiling models generated with allOf

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 a model declares a property with type object AND it includes the allOf keyword the generated java code doesn't compile

openapi-generator version

This issue occurs with version 6.x and 7.x. But wasn't present in 5.4.0.
The issue occurs when using OAS2 and OAS3.

OpenAPI declaration file content or url

FlatUser:
  type: object
  properties:
    broken:
      type: object
      properties:
        field1:
          type: string
        field2:
          type: string
  allOf:
    - $ref: '#/definitions/Names'
    - $ref: '#/definitions/Address'

Complete document

Generation Details

generation details

Steps to reproduce

See https://github.com/peter-janssen/openapi-bug/tree/allOf-bug (run .mvnw compile results in a compilation error)

[ERROR] ...demo/target/generated-sources/openapi/src/main/java/com/example/FlatUser.java:[86,56] <identifier> expected
[ERROR] ...demo/target/generated-sources/openapi/src/main/java/com/example/FlatUser.java:[88,21] illegal start of expression

This is due to the fact the generated code is incorrect:

public FlatUser putBrokenItem(String key,  brokenItem) {
  if (this.broken == null) {
    this.broken = ;
  }
  this.broken.put(key, brokenItem);
  return this;
}

This is due to the fact the broken property is now marked as a map ("isMap": true) by the generator:

 "vars" : [ {
      "openApiType" : "object",
      "baseName" : "broken",
      "getter" : "getBroken",
      "setter" : "setBroken",
      "dataType" : "Object",
      "datatypeWithEnum" : "Object",
      "name" : "broken",
      "defaultValueWithParam" : " = data.broken;",
      "baseType" : "Object",
      "jsonSchema" : "{\n  \"type\" : \"object\",\n  \"properties\" : {\n    \"field1\" : {\n      \"type\" : \"string\"\n    },\n    \"field2\" : {\n      \"type\" : \"string\"\n    }\n  }\n}",
      "exclusiveMinimum" : false,
      "exclusiveMaximum" : false,
      "required" : false,
      "deprecated" : false,
      "hasMoreNonReadOnly" : false,
      "isPrimitiveType" : true,
      "isModel" : true,
      "isContainer" : false,
      "isString" : false,
      "isNumeric" : false,
      "isInteger" : false,
      "isShort" : false,
      "isLong" : false,
      "isUnboundedInteger" : false,
      "isNumber" : false,
      "isFloat" : false,
      "isDouble" : false,
      "isDecimal" : false,
      "isByteArray" : false,
      "isBinary" : false,
      "isFile" : false,
      "isBoolean" : false,
      "isDate" : false,
      "isDateTime" : false,
      "isUuid" : false,
      "isUri" : false,
      "isEmail" : false,
      "isNull" : false,
      "isFreeFormObject" : false,
      "isAnyType" : false,
      "isArray" : false,
      "isMap" : true,
      "isEnum" : false,
      "isReadOnly" : false,
      "isWriteOnly" : false,
      "isNullable" : false,
      "isSelfReference" : false,
      "isCircularReference" : false,
      "isDiscriminator" : false,
      "vars" : [ {

This triggers this part of the pojo.mustache of the template:

  {{#isMap}}

  public {{classname}} put{{nameInCamelCase}}Item(String key, {{{items.datatypeWithEnum}}} {{name}}Item) {
    {{#vendorExtensions.x-is-jackson-optional-nullable}}
    if (this.{{name}} == null || !this.{{name}}.isPresent()) {
      this.{{name}} = JsonNullable.<{{{datatypeWithEnum}}}>of({{{defaultValue}}});
    }
    try {
      this.{{name}}.get().put(key, {{name}}Item);
    } catch (java.util.NoSuchElementException e) {
      // this can never happen, as we make sure above that the value is present
    }
    return this;
    {{/vendorExtensions.x-is-jackson-optional-nullable}}
    {{^vendorExtensions.x-is-jackson-optional-nullable}}
    {{^required}}
    if (this.{{name}} == null) {
      this.{{name}} = {{{defaultValue}}};
    }
    {{/required}}
    this.{{name}}.put(key, {{name}}Item);
    return this;
    {{/vendorExtensions.x-is-jackson-optional-nullable}}
  }
  {{/isMap}}

Related issues/PRs

#13551 could be the same bug but triggered in a slightly different manner.
#11696 again very similar (but I already wrote the whole issue 😢

This might be just a duplicate. If so please close this issue.

Workaround

If the object is moved to a model the issue does not occur:

FlatUser:
  type: object
  properties:
    broken:
      $ref: '#/definitions/Broken'
  allOf:
    - $ref: '#/definitions/Names'
    - $ref: '#/definitions/Address'
...
Broken:
  type: object
  properties:
    field1:
      type: string
    field2:
      type: string

Start with the example.yaml reproduction and run .mvnw compile to confirm the generated FlatUser.java errors. Read the Java native pojo.mustache map-handling section and inspect how the inline object property is represented in the generator metadata. Done means the allOf model with an inline object generates valid Java and compiles without the reported errors.