fix(csharp): make generichost oneOf constructors public

[wing328]

based on #24341

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---

Summary by cubic

Limit C# oneOf constructors to operation inputs to reduce public surface and prevent misuse. Previously all generated oneOf constructors were public; now constructors are public only for models used in request bodies or parameters, and internal for response-only models.

• Adds x-model-is-operation-input and marks models by scanning operations’ request bodies and parameter schemas in AbstractCSharpCodegen.postProcessAllModels; the C# generichost modelGeneric.mustache uses this to set constructor visibility.
• Adds issue_23046.yaml and CSharpClientCodegenTest#testGenericHostOneOfConstructorsRespectApiVisibility to verify public vs internal constructors; regenerates samples accordingly.

Migration

• If you were directly instantiating response-only oneOf models, update code to rely on deserialization results or use input model types. No config changes are required for typical client usage.

^{Written for commit e5e3bb2. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 191 files

Prompt for AI agents (unresolved 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="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java:624">
P3: `postProcessAllModels` here lives in AbstractCSharpCodegen, the base for every C# generator (csharp, csharp-netcore, csharp-dotnet2, ...). `getOperationInputModels()` walks every path, parameter, and the whole reachable schema graph and mutates each model's vendor extensions, but the new `x-model-is-operation-input` vendor extension is consumed only by the generichost `modelGeneric.mustache`. All non-generichost C# generators now pay this traversal cost for a result they never use. Consider gating the call (and the per-model extension writes) on the generichost library to avoid the wasted work elsewhere.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P3: postProcessAllModels here lives in AbstractCSharpCodegen, the base for every C# generator (csharp, csharp-netcore, csharp-dotnet2, ...). getOperationInputModels() walks every path, parameter, and the whole reachable schema graph and mutates each model's vendor extensions, but the new x-model-is-operation-input vendor extension is consumed only by the generichost modelGeneric.mustache. All non-generichost C# generators now pay this traversal cost for a result they never use. Consider gating the call (and the per-model extension writes) on the generichost library to avoid the wasted work elsewhere.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java, line 624:

<comment>`postProcessAllModels` here lives in AbstractCSharpCodegen, the base for every C# generator (csharp, csharp-netcore, csharp-dotnet2, ...). `getOperationInputModels()` walks every path, parameter, and the whole reachable schema graph and mutates each model's vendor extensions, but the new `x-model-is-operation-input` vendor extension is consumed only by the generichost `modelGeneric.mustache`. All non-generichost C# generators now pay this traversal cost for a result they never use. Consider gating the call (and the per-model extension writes) on the generichost library to avoid the wasted work elsewhere.</comment>

<file context>
@@ -616,6 +621,7 @@ public ModelsMap postProcessModels(ModelsMap objs) {
     @Override
     public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs) {
         final Map<String, ModelsMap> processed = super.postProcessAllModels(objs);
+        final Set<String> operationInputModels = getOperationInputModels();
 
         Map<String, CodegenModel> enumRefs = new HashMap<>();
</file context>