handle snake-case and camel-case data attributes more consistently

jsx/tyxml_jsx.ml

@@ -23,16 +23,22 @@ let lowercase_lead s =
   String.mapi (fun i c -> if i = 0 then Char.lowercase_ascii c else c) s
 
 let to_kebab_case name =
-  let length = String.length name in
-  if length > 5 then
-    let first = String.sub name 0 4 in
-    match first with
-    | "aria"
-    | "data" ->
-      first ^ "-" ^ lowercase_lead (String.sub name 4 (length - 4))
-    | _ -> name
-  else
-    name
+  let open Re in
+  let kebab string =
+    replace (Posix.compile_pat "[A-Z]") ~f:(fun g -> "-" ^ Group.get g 0) string
+    |> String.lowercase_ascii
+    |> replace_string (compile @@ char '_') ~by:"-" in
+  match exec_opt (Perl.compile_pat {|^(data_?|aria_?)(.+)|}) name with
+  | None -> 
+    if name.[0] == '_'
+    (* need to keep the leading underscore, as that's what the syntax support keys
+       off of to know to use Unsafe.string_attrib *)
+    then "_" ^ kebab @@ String.sub name 1 (String.length name - 1)
+    else name
+  | Some g ->
+    let prefix = String.sub name 0 4 in
+    let suffix = kebab @@ Group.get g 2 in
+    prefix ^ (if suffix.[0] == '-' then "" else "-") ^ suffix
 
 let make_attr_name name =
   let name =

test/test_jsx.re

@@ -158,7 +158,22 @@ let attribs = (
         [<script type_="text/javascript" />],
         [script(~a=[a_script_type(`Mime("text/javascript"))], txt(""))],
       ),
-    ],
+      ( "camel-case data attribs",
+        [<div dataFooBar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+      ( "kebab-case data attribs",
+        [<div data_foo_bar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+      ( "kebab-case data attribs, again",
+        [<div datafoo_bar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+    ]
   ),
 );