fix zero-arg documented function formatting

src/fennel-ls/formatter.fnl

@@ -29,9 +29,11 @@ user code. Fennel-ls doesn't support user-code formatting as of now."
   "formats a special using its builtin metadata magic"
   (..
     (code-block
-      (if metadata.fnl/arglist
-        (.. "(" (tostring binding) " " (table.concat metadata.fnl/arglist " ") ")")
-        (tostring binding)))
+      (if (not metadata.fnl/arglist)
+        (tostring binding)
+        (= 0 (length metadata.fnl/arglist))
+        (.. "(" (tostring binding) ")")
+        (.. "(" (tostring binding) " " (table.concat metadata.fnl/arglist " ") ")")))
     "\n"
     metadata.fnl/docstring))
 

test/completion.fnl

@@ -233,6 +233,10 @@
           (t.i"
     ["insert"]
     [{:documentation #(= nil $)}])
+  (check "debug.deb|"
+    [{:label "debug"
+      :documentation #(and $.value ($.value:find "```fnl\n(debug.debug)\n```" 1 true))}]
+    [])
   nil)
 
 (local eglot {:params {:capabilities {:general {:positionEncodings [:utf-8]}}