OCaml: Add support for direct recursive types

sir4ur0n · sir4ur0n · commit 067bd6b89306 · 2026-02-18T14:30:28.000+01:00
diff --git a/.github/workflows/samples-ocaml.yaml b/.github/workflows/samples-ocaml.yaml
@@ -8,13 +8,15 @@ on:
       - 'samples/client/petstore/ocaml-oneOf-primitive/**'
       - 'samples/client/petstore/ocaml-additional-properties/**'
       - 'samples/client/petstore/ocaml-enum-in-composed-schema/**'
+      - 'samples/client/petstore/ocaml-recursion-test/**'
   pull_request:
     paths:
       - 'samples/client/petstore/ocaml/**'
       - 'samples/client/petstore/ocaml-fake-petstore/**'
       - 'samples/client/petstore/ocaml-oneOf-primitive/**'
       - 'samples/client/petstore/ocaml-additional-properties/**'
       - 'samples/client/petstore/ocaml-enum-in-composed-schema/**'
+      - 'samples/client/petstore/ocaml-recursion-test/**'
 
 jobs:
   build:
@@ -29,6 +31,7 @@ jobs:
           - 'samples/client/petstore/ocaml-oneOf-primitive/'
           - 'samples/client/petstore/ocaml-additional-properties/'
           - 'samples/client/petstore/ocaml-enum-in-composed-schema/'
+          - 'samples/client/petstore/ocaml-recursion-test/'
     steps:
       - uses: actions/checkout@v5
       - name: Set-up OCaml
diff --git a/.gitignore b/.gitignore
@@ -305,6 +305,7 @@ samples/client/petstore/ocaml-fake-petstore/_build/
 samples/client/petstore/ocaml-oneOf-primitive/_build/
 samples/client/petstore/ocaml-additional-properties/_build/
 samples/client/petstore/ocaml-enum-in-composed-schema/_build/
+samples/client/petstore/ocaml-recursion-test/_build/
 
 # jetbrain http client
 samples/client/jetbrains/adyen/checkout71/http/client/Apis/http-client.private.env.json
diff --git a/bin/configs/ocaml-recursion-test.yaml b/bin/configs/ocaml-recursion-test.yaml
@@ -0,0 +1,6 @@
+generatorName: ocaml
+outputDir: samples/client/petstore/ocaml-recursion-test
+inputSpec: modules/openapi-generator/src/test/resources/3_0/recursion.yaml
+templateDir: modules/openapi-generator/src/main/resources/ocaml
+additionalProperties:
+  packageName: recursion_test
diff --git a/docs/generators/ocaml.md b/docs/generators/ocaml.md
@@ -11,7 +11,7 @@ title: Documentation for the ocaml Generator
 | generator type | CLIENT | |
 | generator language | OCaml | |
 | generator default templating engine | mustache | |
-| helpTxt | Generates an OCaml client library (beta). | |
+| helpTxt | Generates an OCaml client library. | |
 
 ## CONFIG OPTIONS
 These options may be applied as additional-properties (cli) or configOptions (plugins). Refer to [configuration docs](https://openapi-generator.tech/docs/configuration) for more details.
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java
@@ -51,8 +51,10 @@ public class OCamlClientCodegen extends DefaultCodegen implements CodegenConfig
 
     static final String X_MODEL_MODULE = "x-model-module";
 
-    @Setter protected String packageName = "openapi";
-    @Setter protected String packageVersion = "1.0.0";
+    @Setter
+    protected String packageName = "openapi";
+    @Setter
+    protected String packageVersion = "1.0.0";
     protected String apiDocPath = "docs/";
     protected String modelDocPath = "docs/";
     protected String apiFolder = "src/apis";
@@ -74,7 +76,7 @@ public String getName() {
 
     @Override
     public String getHelp() {
-        return "Generates an OCaml client library (beta).";
+        return "Generates an OCaml client library.";
     }
 
     public OCamlClientCodegen() {
@@ -233,6 +235,71 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> supero
 
     }
 
+    /**
+     * Add support for direct recursive types (e.g., A -> A).
+     * This does *not* support mutually recursive types (e.g., A -> B -> A), as this is a much more complex beast in OCaml (since mutually recursive types must live in the same file).
+     */
+    @Override
+    public ModelsMap postProcessModels(ModelsMap objs) {
+        objs = super.postProcessModels(objs);
+
+        for (ModelMap mo : objs.getModels()) {
+            CodegenModel cm = mo.getModel();
+
+            // Check if any property is a self-reference
+            boolean hasSelfRef = cm.allVars.stream()
+                    .anyMatch(prop -> prop.isSelfReference);
+
+            if (hasSelfRef) {
+                // Add vendor extension for template
+                cm.getVendorExtensions().put("x-ocaml-has-self-reference", true);
+
+                // Collect names of self-referencing properties
+                Set<String> selfRefPropNames = cm.allVars.stream()
+                        .filter(p -> p.isSelfReference)
+                        .map(p -> p.name)
+                        .collect(Collectors.toSet());
+
+                // The property lists (vars, allVars, etc.) contain DIFFERENT objects
+                // Match by name since isSelfReference might only be set in allVars
+                List<List<CodegenProperty>> allPropertyLists = Arrays.asList(
+                        cm.allVars, cm.vars, cm.requiredVars, cm.optionalVars,
+                        cm.readOnlyVars, cm.readWriteVars, cm.parentVars
+                );
+
+                for (List<CodegenProperty> propList : allPropertyLists) {
+                    for (CodegenProperty prop : propList) {
+                        if (selfRefPropNames.contains(prop.name)) {
+                            // Replace "ModelName.t" with just "t" in all relevant fields
+                            prop.dataType = "t";
+                            prop.datatypeWithEnum = "t";
+                            if (prop.baseType != null) {
+                                prop.baseType = "t";
+                            }
+                            if (prop.complexType != null) {
+                                prop.complexType = "t";
+                            }
+
+                            // If it's a container type (e.g., array), update items as well
+                            if (prop.isContainer && prop.items != null) {
+                                prop.items.dataType = "t";
+                                prop.items.datatypeWithEnum = "t";
+                                if (prop.items.baseType != null) {
+                                    prop.items.baseType = "t";
+                                }
+                                if (prop.items.complexType != null) {
+                                    prop.items.complexType = "t";
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        return objs;
+    }
+
     private void enrichPropertiesWithEnumDefaultValues(List<CodegenProperty> properties) {
         for (CodegenProperty property : properties) {
             if (property.get_enum() != null && property.get_enum().size() == 1) {
diff --git a/modules/openapi-generator/src/main/resources/ocaml/model-record.mustache b/modules/openapi-generator/src/main/resources/ocaml/model-record.mustache
@@ -1,4 +1,4 @@
-type t = {
+type {{#vendorExtensions.x-ocaml-has-self-reference}}rec {{/vendorExtensions.x-ocaml-has-self-reference}}t = {
 {{#vars}}
     {{#isEnum}}
       {{{name}}}: {{^isMap}}Enums.{{/isMap}}{{{datatypeWithEnum}}}
diff --git a/samples/client/petstore/ocaml-recursion-test/.ocamlformat b/samples/client/petstore/ocaml-recursion-test/.ocamlformat
@@ -0,0 +1,2 @@
+version=0.27.0
+ocaml-version=4.14.0
diff --git a/samples/client/petstore/ocaml-recursion-test/.openapi-generator-ignore b/samples/client/petstore/ocaml-recursion-test/.openapi-generator-ignore
@@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md
diff --git a/samples/client/petstore/ocaml-recursion-test/.openapi-generator/FILES b/samples/client/petstore/ocaml-recursion-test/.openapi-generator/FILES
@@ -0,0 +1,13 @@
+.ocamlformat
+README.md
+dune
+dune-project
+recursion_test.opam
+src/apis/default_api.ml
+src/apis/default_api.mli
+src/models/bar.ml
+src/models/baz.ml
+src/models/foo.ml
+src/support/enums.ml
+src/support/jsonSupport.ml
+src/support/request.ml
diff --git a/samples/client/petstore/ocaml-recursion-test/.openapi-generator/VERSION b/samples/client/petstore/ocaml-recursion-test/.openapi-generator/VERSION
@@ -0,0 +1 @@
+7.21.0-SNAPSHOT
diff --git a/samples/client/petstore/ocaml-recursion-test/README.md b/samples/client/petstore/ocaml-recursion-test/README.md
@@ -0,0 +1,33 @@
+# 
+Test
+
+This OCaml package is automatically generated by the [OpenAPI Generator](https://openapi-generator.tech) project:
+
+- API version: 1.0.0
+- Package version: 1.0.0
+- Generator version: 7.21.0-SNAPSHOT
+- Build package: org.openapitools.codegen.languages.OCamlClientCodegen
+
+## Requirements.
+
+OCaml 5.x
+
+## Installation
+
+Please run the following commands to build the package `recursion_test`:
+
+```sh
+opam install . --deps-only --with-test
+eval $(opam env)
+dune build
+```
+
+## Getting Started
+
+The generated directory structure is:
+- `src/apis`: contains several modules, each with several functions. Each function is an API endpoint.
+- `src/models`: contains several modules. Each module contains:
+  - a type `t` representing an input and/or output schema of the OpenAPI spec
+  - a smart constructor `create` for this type
+- `src/support`: various modules used by the generated APIs and Models
+
diff --git a/samples/client/petstore/ocaml-recursion-test/dune b/samples/client/petstore/ocaml-recursion-test/dune
@@ -0,0 +1,9 @@
+(include_subdirs unqualified)
+(library
+   (name recursion_test)
+   (public_name recursion_test)
+   (flags (:standard -w -27))
+   (libraries str cohttp-lwt-unix lwt yojson ppx_deriving_yojson.runtime)
+   (preprocess (pps ppx_deriving_yojson ppx_deriving.std))
+   (wrapped true)
+)
diff --git a/samples/client/petstore/ocaml-recursion-test/dune-project b/samples/client/petstore/ocaml-recursion-test/dune-project
@@ -0,0 +1,2 @@
+(lang dune 2.0)
+(name recursion_test)
diff --git a/samples/client/petstore/ocaml-recursion-test/recursion_test.opam b/samples/client/petstore/ocaml-recursion-test/recursion_test.opam
@@ -0,0 +1,25 @@
+opam-version: "2.0"
+name: "recursion_test"
+version: "1.0.0"
+synopsis: ""
+description: """
+Longer description
+"""
+maintainer: "Name <email>"
+authors: "Name <email>"
+license: ""
+homepage: ""
+bug-reports: ""
+dev-repo: ""
+depends: [
+  "ocaml"
+  "ocamlfind"
+  "ocamlformat" {= "0.27.0"}
+  "dune"
+  "ppx_deriving_yojson"
+  "conf-libev"
+  "lwt"
+  "cohttp-lwt-unix" {< "6.0.0"}
+  "cohttp-async" {< "6.0.0"}
+]
+build: ["dune" "build" "-p" name]
diff --git a/samples/client/petstore/ocaml-recursion-test/src/apis/default_api.ml b/samples/client/petstore/ocaml-recursion-test/src/apis/default_api.ml
@@ -0,0 +1,14 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
+
+let foo_post () =
+    let open Lwt.Infix in
+    let uri = Request.build_uri "/foo" in
+    let headers = Request.default_headers in
+    Cohttp_lwt_unix.Client.call `POST uri ~headers >>= fun (resp, body) ->
+    Request.read_json_body_as (JsonSupport.unwrap Foo.of_yojson) resp body
+
diff --git a/samples/client/petstore/ocaml-recursion-test/src/apis/default_api.mli b/samples/client/petstore/ocaml-recursion-test/src/apis/default_api.mli
@@ -0,0 +1,8 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
+
+val foo_post : unit -> Foo.t Lwt.t
diff --git a/samples/client/petstore/ocaml-recursion-test/src/models/bar.ml b/samples/client/petstore/ocaml-recursion-test/src/models/bar.ml
@@ -0,0 +1,24 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
+
+
+
+    
+        type t = {
+                              baz: Baz.t
+                  
+                   option [@default None]
+                
+                
+                ; [@key "baz"]
+                        } [@@deriving yojson { strict = false }, show, eq ];;
+        
+        let create () : t = {
+            baz = None;
+        }
+    
+
diff --git a/samples/client/petstore/ocaml-recursion-test/src/models/baz.ml b/samples/client/petstore/ocaml-recursion-test/src/models/baz.ml
@@ -0,0 +1,24 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
+
+
+
+    
+        type t = {
+                              bar: Bar.t
+                  
+                   option [@default None]
+                
+                
+                ; [@key "bar"]
+                        } [@@deriving yojson { strict = false }, show, eq ];;
+        
+        let create () : t = {
+            bar = None;
+        }
+    
+
diff --git a/samples/client/petstore/ocaml-recursion-test/src/models/foo.ml b/samples/client/petstore/ocaml-recursion-test/src/models/foo.ml
@@ -0,0 +1,24 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
+
+
+
+    
+        type rec t = {
+                              foo: t
+                  
+                   option [@default None]
+                
+                
+                ; [@key "foo"]
+                        } [@@deriving yojson { strict = false }, show, eq ];;
+        
+        let create () : t = {
+            foo = None;
+        }
+    
+
diff --git a/samples/client/petstore/ocaml-recursion-test/src/support/enums.ml b/samples/client/petstore/ocaml-recursion-test/src/support/enums.ml
@@ -0,0 +1,6 @@
+(*
+ * This file has been generated by the OCamlClientCodegen generator for openapi-generator.
+ *
+ * Generated by: https://openapi-generator.tech
+ *
+ *)
diff --git a/samples/client/petstore/ocaml-recursion-test/src/support/jsonSupport.ml b/samples/client/petstore/ocaml-recursion-test/src/support/jsonSupport.ml
diff --git a/samples/client/petstore/ocaml-recursion-test/src/support/request.ml b/samples/client/petstore/ocaml-recursion-test/src/support/request.ml

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-type t = {`
	`1`	`+type {{#vendorExtensions.x-ocaml-has-self-reference}}rec {{/vendorExtensions.x-ocaml-has-self-reference}}t = {`
`2`	`2`	`{{#vars}}`
`3`	`3`	`{{#isEnum}}`
`4`	`4`	`{{{name}}}: {{^isMap}}Enums.{{/isMap}}{{{datatypeWithEnum}}}`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+version=0.27.0`
	`2`	`+ocaml-version=4.14.0`