[OCaml][Fix] Unreferenced enum + Direct recursive types

[sir4ur0n]

• Add support for directly recursive types (e.g., A -> A)
  • Mutually recursive types are not supported because this is MUCH more complex to implement in OCaml and I don't have the time to do the huge refactor needed for them
• Fix a bug where empty string enums broke generation
• Fix a bug where enums inside anyOf/oneOf/allOf were not correctly detected

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
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  ./mvnw clean package || exit
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  Commit all changed files.
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@cgensoul @wing328

CI fails for seemingly unrelated reasons but I can't manually restart it.

---

Summary by cubic

Fixes crashes in the OCaml client generator when enums appear in anyOf/allOf/oneOf, and adds robust support for direct self-recursive models across properties, arrays, and maps. Adds targeted tests and samples, and updates CI to OCaml 5.3.

• Bug Fixes

  • Recursively collect enums in composed schemas (anyOf/allOf/oneOf), including direct branch enums and nested $ref; prefix composed enum types with Enums.
  • Make enum hashing order-independent with Set, fixing “unreferenced enum” and supporting empty-string enum values.

• New Features

  • Support direct recursive models by normalizing self-references to t across fields and container items; handle required recursive fields and multiple recursive properties.
  • Add 3.0 test specs and samples for composed-schema enums and recursion; update OCaml generator help text.

^{Written for commit f3e7e8d. Summary will update on new commits.}

[sir4ur0n]

@cgensoul @wing328 this is ready for review 🙏

[cubic-dev-ai]

3 issues found across 49 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="samples/client/petstore/ocaml-recursion-test/README.md">

<violation number="1" location="samples/client/petstore/ocaml-recursion-test/README.md:1">
P2: Malformed Markdown header - title text should be on the same line as the `#` marker</violation>
</file>

<file name="samples/client/petstore/ocaml-recursion-test/src/models/required_recursion.ml">

<violation number="1" location="samples/client/petstore/ocaml-recursion-test/src/models/required_recursion.ml:18">
P1: Syntax error in generated OCaml record: `[@key]` attributes are misplaced after field separators (`;`). Attributes must be placed after the field type and BEFORE the semicolon, e.g., `value: string [@key "value"];`. The current placement will cause compilation failure and break JSON serialization.</violation>
</file>

<file name="samples/client/petstore/ocaml-enum-in-composed-schema/src/models/test_model.ml">

<violation number="1" location="samples/client/petstore/ocaml-enum-in-composed-schema/src/models/test_model.ml:17">
P0: Incorrect placement of `[@key]` attributes breaks JSON serialization mappings</violation>
</file>

---

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[cubic-dev-ai]

P0: Incorrect placement of [@key] attributes breaks JSON serialization mappings

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/ocaml-enum-in-composed-schema/src/models/test_model.ml, line 17:

<comment>Incorrect placement of `[@key]` attributes breaks JSON serialization mappings</comment>

<file context>
@@ -0,0 +1,38 @@
+                   option [@default None]
+                
+                
+                ; [@key "name"]
+                                              config: Test_model_config.t
+                  
</file context>

[sir4ur0n]

What? How does that break JSON serialization mappings?
This is exactly the same as all the existing code and it works fine.
See e.g. https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/ocaml/src/models/pet.ml#L18

It works perfectly fine as far as OCaml compilation is concerned.

You have to consider with proper formatting, the line is

name : string option; [@default None] [@key "name"]

which works.

[cubic-dev-ai]

P1: Syntax error in generated OCaml record: [@key] attributes are misplaced after field separators (;). Attributes must be placed after the field type and BEFORE the semicolon, e.g., value: string [@key "value"];. The current placement will cause compilation failure and break JSON serialization.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/ocaml-recursion-test/src/models/required_recursion.ml, line 18:

<comment>Syntax error in generated OCaml record: `[@key]` attributes are misplaced after field separators (`;`). Attributes must be placed after the field type and BEFORE the semicolon, e.g., `value: string [@key "value"];`. The current placement will cause compilation failure and break JSON serialization.</comment>

<file context>
@@ -0,0 +1,33 @@
+                  
+                
+                
+                ; [@key "value"]
+                                              parent: t
+                  
</file context>

[sir4ur0n]

Same response as #23005 (comment)

[cubic-dev-ai]

P2: Malformed Markdown header - title text should be on the same line as the # marker

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/ocaml-recursion-test/README.md, line 1:

<comment>Malformed Markdown header - title text should be on the same line as the `#` marker</comment>

<file context>
@@ -0,0 +1,44 @@
+# 
+Test for direct recursive types in OCaml generator.
+
</file context>