ABI export: output unnamed arguments as null

src/abi_export.jl

@@ -162,7 +162,9 @@ function emit_method_info!(ctx::TypeEmitter, method::Core.Method; indent::Int =
         for i in 2:length(sig.parameters)
             print(ctx.io, " " ^ (indent + 4))
             print(ctx.io, "{")
-            print(ctx.io, " \"name\": ", escape_string_json(argnames[i]), ",")
+            argname = argnames[i]
+            name_json = argname == "#unused#" ? "null" : escape_string_json(argname)
+            print(ctx.io, " \"name\": ", name_json, ",")
             print(ctx.io, " \"type_id\": ", ctx.type_ids[sig.parameters[i]])
             println(ctx.io, i == length(sig.parameters) ? " }" : " },")
         end

test/cli.jl

@@ -113,6 +113,10 @@ end
     # `Ptr{CTree{Float64}}` should refer (recursively) back to the original type id
     Ptr_CTree_Float64 = abi["types"][CVector_CTree_Float64["fields"][2]["type_id"]]
     @test Ptr_CTree_Float64["pointee_type_id"] == CTree_Float64_id
+
+    # Unnamed argument names should be exported as empty strings
+    unnamed = abi["functions"][findfirst(x -> x["symbol"] == "unnamed_arguments", abi["functions"])::Int]
+    @test all(isnothing, arg["name"] for arg in unnamed["arguments"])
 end
 
 @testset "CLI library privatize end-to-end" begin

test/libsimple.jl

@@ -45,6 +45,10 @@ Base.@ccallable function countsame(list::Ptr{MyTwoVec}, n::Int32)::Int32
     return count
 end
 
+Base.@ccallable function unnamed_arguments(::Int32, _::Int32)::Int32
+    return 0
+end
+
 export countsame, copyto_and_sum
 
 # FIXME? varargs