Fix crash on params array parameter types in API doc generation

When a C# method has a `params` array parameter (e.g. `params object[] args`),
the array type is represented in FCS as an entity named `[]'1` whose `FullName`
property throws because array types have no qualified name in the F# type system.

Replace the single-expression type-name formatter in `getXmlDocSigForMember` with
a small recursive helper (`formatParamType`) that:
- handles generic parameters as before (via typeArgsMap),
- detects array-type entities (`IsArrayType = true`) and builds the name as
  `<element-type-name><DisplayName>` (e.g. `System.Object[]`), and
- falls back to `BasicQualifiedName` for types without a type definition.

Also adds `ParamsMethod(params object[] args)` to the C# test fixture and a
corresponding assertion in the existing csharp-support test to prevent regression.

Fixes #439

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 2 people

RELEASE_NOTES.md

@@ -14,6 +14,7 @@
 * Strip `#if SYMBOL` / `#endif // SYMBOL` marker lines from `LiterateCode` source before syntax-highlighting so they do not appear in formatted output. [#693](https://github.com/fsprojects/FSharp.Formatting/issues/693)
 * Fix incorrect column ranges for inline spans (links, images, inline code) in the Markdown parser — spans and subsequent literals now report correct `StartColumn`/`EndColumn` values. [#744](https://github.com/fsprojects/FSharp.Formatting/issues/744)
 * Normalize `--projects` paths to absolute paths before passing to the project cracker, fixing failures when relative paths are supplied. [#793](https://github.com/fsprojects/FSharp.Formatting/issues/793)
+* Fix crash when generating API docs for C# methods with `params` array parameters — the array type `[]`1` now resolves correctly instead of throwing "does not have a qualified name". [#439](https://github.com/fsprojects/FSharp.Formatting/issues/439)
 
 ### Changed
 * Update FCS to 43.10.100. [#935](https://github.com/fsprojects/FSharp.Formatting/pull/966)

src/FSharp.Formatting.ApiDocs/GenerateModel.fs

@@ -750,20 +750,30 @@ module internal CrossReferences =
                         else
                             ""
 
+                    let rec formatParamType (typ: FSharpType) =
+                        if typ.IsGenericParameter then
+                            typeArgsMap.[typ.GenericParameter.Name]
+                        elif typ.HasTypeDefinition then
+                            let td = typ.TypeDefinition
+
+                            if td.IsArrayType then
+                                // Array types (e.g. params object[]) have no FullName in FCS.
+                                // Build it from the element type and the display-name suffix ("[]", "[,]" etc.)
+                                let elementTypeName = formatParamType typ.GenericArguments.[0]
+                                elementTypeName + td.DisplayName
+                            else
+                                td.FullName
+                        else
+                            typ.BasicQualifiedName
+
                     let paramList =
                         if
                             memb.CurriedParameterGroups.Count > 0
                             && memb.CurriedParameterGroups.[0].Count > 0
                         then
                             let head = memb.CurriedParameterGroups.[0]
 
-                            let paramTypeList =
-                                head
-                                |> Seq.map (fun param ->
-                                    if param.Type.IsGenericParameter then
-                                        typeArgsMap.[param.Type.GenericParameter.Name]
-                                    else
-                                        param.Type.TypeDefinition.FullName)
+                            let paramTypeList = head |> Seq.map (fun param -> formatParamType param.Type)
 
                             "(" + System.String.Join(", ", paramTypeList) + ")"
                         else

tests/FSharp.ApiDocs.Tests/ApiDocsTests.fs

@@ -810,6 +810,9 @@ let ``ApiDocs test that csharp (publiconly) support works`` (format: OutputForma
     files.[(sprintf "csharpsupport-sampleclass.%s" format.Extension)]
     |> shouldContainText "My_Method"
 
+    files.[(sprintf "csharpsupport-sampleclass.%s" format.Extension)]
+    |> shouldContainText "My_Params_Method"
+
     files.[(sprintf "csharpsupport-sampleclass.%s" format.Extension)]
     |> shouldContainText "My_Property"
 

tests/FSharp.ApiDocs.Tests/files/csharpSupport/SampleClass.cs

@@ -93,6 +93,11 @@ public SampleClass() { }
         /// </summary>
         public void Method() { }
 
+        /// <summary>
+        /// My_Params_Method
+        /// </summary>
+        public void ParamsMethod(params object[] args) { }
+
 
         /// <summary>
         /// My_Property