initial commit

.gitignore

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+/_build
+/result

dune-project

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+(lang dune 3.15)
+
+(name ppx_unicode)
+
+(generate_opam_files true)
+
+(source
+ (github username/reponame))
+
+(authors "Author Name")
+
+(maintainers "Maintainer Name")
+
+(license LICENSE)
+
+(documentation https://url/to/documentation)
+
+(package
+ (name ppx_unicode)
+ (synopsis "A short synopsis")
+ (description "A longer description")
+ (depends ocaml dune)
+ (tags
+  (topics "to describe" your project)))
+
+; See the complete stanza docs at https://dune.readthedocs.io/en/stable/dune-files.html#dune-project

ppx/dune

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+(library
+ (name ppx_unicode)
+ (public_name ppx_unicode)
+ (synopsis "ppx rewriters for unicode normalization")
+ (preprocess
+  (pps ppxlib.metaquot))
+ (libraries ppxlib uunf)
+ (kind ppx_deriver))

ppx/ppx_unicode.ml

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+open Ppxlib
+
+let has_attr name attrs =
+  List.find_opt (fun attr -> attr.attr_name.txt = name) attrs
+  |> Option.is_some
+
+let decode_single_uchar_opt str =
+  if String.is_valid_utf_8 str then
+    let res = String.get_utf_8_uchar str 0 in
+    if (Uchar.utf_decode_is_valid res) && (Uchar.utf_decode_length res == String.length str) then
+      Some (Uchar.utf_decode_uchar res |> Uchar.to_int)
+    else
+      None
+  else
+    None
+
+let nfc_mapper = object
+  inherit Ast_traverse.map as super
+
+  method! expression =
+    fun { pexp_desc; pexp_loc; pexp_loc_stack; pexp_attributes } ->
+      if has_attr "uchar" pexp_attributes then
+        let pexp_attributes =
+          List.filter (fun attr -> attr.attr_name.txt <> "uchar") pexp_attributes in
+        match pexp_desc with
+        | Pexp_constant (Pconst_string (value, loc, _)) ->
+          begin match decode_single_uchar_opt value with
+          | Some cp ->
+            let cp = Pconst_integer (Int.to_string cp, None) in
+            let cp = {
+              pexp_desc = Pexp_constant cp;
+              pexp_loc; pexp_loc_stack; pexp_attributes
+            } in
+            [%expr Uchar.of_int [%e cp]]
+          | None ->
+            let err_ext =
+              Pexp_extension begin Location.error_extensionf ~loc:loc
+                "[@uchar] string must consist of a single valid utf-8 codepoint" end
+            in { pexp_desc = err_ext; pexp_loc; pexp_loc_stack; pexp_attributes }
+          end
+        | _ ->
+          let err_ext =
+            Pexp_extension begin Location.error_extensionf ~loc:pexp_loc
+              "[@uchar] attribute must be on a string constant" end
+          in { pexp_desc = err_ext; pexp_loc; pexp_loc_stack; pexp_attributes }
+      else
+        super#expression { pexp_desc; pexp_loc; pexp_loc_stack; pexp_attributes }
+
+  method! constant = function
+    | Pconst_string (value, loc, delim) ->
+      if String.is_valid_utf_8 value then
+        Pconst_string ((Uunf_string.normalize_utf_8 `NFC value), loc, delim)
+      else
+        Location.raise_errorf ~loc "invalid utf-8 in string literal"
+    | const -> super#constant const
+end
+
+let () =
+  Driver.register_transformation
+    ~impl:nfc_mapper#structure
+    "ppx_unicode"

ppx_unicode.opam

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+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "A short synopsis"
+description: "A longer description"
+maintainer: ["Maintainer Name"]
+authors: ["Author Name"]
+license: "LICENSE"
+tags: ["topics" "to describe" "your" "project"]
+homepage: "https://github.com/username/reponame"
+doc: "https://url/to/documentation"
+bug-reports: "https://github.com/username/reponame/issues"
+depends: [
+  "ocaml"
+  "dune" {>= "3.15"}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/username/reponame.git"

test/dune

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+(test
+ (name test_ppx_unicode)
+ (preprocess (pps ppx_unicode)))

test/test_ppx_unicode.ml

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+let () =
+  let a = "å"[@uchar] in
+  ignore a