[REQ] Better support for openapi document inline/nested schemas

[spacether]

Is your feature request related to a problem? Please describe.

Please add better support for inline/nested schemas

Describe the solution you'd like

These json schema keywords:

• additionalProperties
• allOf
• anyOf
• items
• not
• oneOf
• properties

Allow inline schema definitions.
Many generators do not support deep levels of inlining/nesting.
If those schemas are traversed with post order traversal, then accumulated into a list, they can be generated in an order where the root schema that uses the dependencies comes last. Naming should be done in a pre order traversal (reverse the class writing order) to ensure that the root schema has a highest priority name.

This would allow inline schemas to be supported in many more generators.
I wrote a PR that does this in my similar-to python generator project here:
openapi-json-schema-tools/openapi-json-schema-generator#177
Your project could add a similar feature

Example:

schemas:
- SchemaA:
    type: object
    allOf:
    - type: object
       minProperties: 2

Becomes a list of schemas when examining SchemaA

- AllOf1:
    type: object
    minProperties: 2
- SchemaA:
    type: object
    allOf:
    - CodegenProperty AllOf1

Describe alternatives you've considered

• build nested schema support into other generators
  • many languages would not support this

Additional context

Related issues:

• [BUG] [R] Nested anyOf/oneOf cause the R client to generate unusable code #14664
• [BUG][C++][cpp-restsdk] cpp-restsdk not able to handle maps with nested schemas ("additionalProperties") #12737
• [BUG] [aspnetcore] Nullable annotations work incorrectly with nested objects #11028
• [BUG][Generator] Missing field for nested allOf when defined in intermediate properties #10219
• [BUG] [scala-sttp][java-client]Models not generated properly with nested oneOf #10191
• [BUG] Nested fields can result in name conflict resulting in invalid code #9899
• [BUG] Typescript fetch URLEncoding for nested JSON object #9070
• [Java] Bug - Doesn't generate correct classes for models with same nested properties #8948
• [BUG] Nested arrays containing objects have no type #5667
• [BUG][JAVA][Typescript] Nested additionalProperties not working #5532
• [BUG] Nested containers in response not supported #2284
• [BUG] Generator is merging nested models #2178
• [typescript] Prevent nested models/interfaces #2220
• [BUG] Nested components are generated with no type #1889
• JSR 303 – Nested validation #1769
• "Could not process model" with nested schema #583
• [BUG][Go] Generator results in missing objects when defining inline anyOf, or oneOf #14801
• [BUG] [DART] Invalid dart file generated for inline schema models (ValidationError/LocationInner) #13302
• [BUG][typescript-angular] [5.4.0] Array with inline object not generated correctly #11528
• [BUG] Code gen for inline response schemata #9947
• [BUG][SCALA-AKKA] Doesn't generate models when defined inline (reproduced for java & scala-akka) #8966
• [REQ]config flag for inline model generation #8005
• [BUG][Go] Inline enums not generated #2360

[spacether]

I am no longer a contributor to this repo. Please open a new issue if you plan on adding this feature.