JSON5 Support

CHANGES.md

@@ -2,6 +2,8 @@
 
 ### Added
 
+- Added support for JSON5 (@dhilst, @gorm-issuu, @gertsonderby, #152)
+
 ### Changed
 
 ### Deprecated

dune-project

@@ -35,3 +35,14 @@ meant for developers that are worried about performance changes in Yojson.")
     (core (>= v0.14.0))
     (core_unix (>= v0.14.0))
     (sexplib (>= v0.9.0))))
+
+(package
+  (name yojson-json5)
+  (synopsis "Yojson_json5 is a parsing and printing library for the JSON5 format")
+  (description "Yojson_json5 is a parsing and printing library for the JSON5 format.
+It supports parsing JSON5 to Yojson.Basic.t and Yojson.Safe.t types.")
+  (depends
+    (ocaml (>= 4.08))
+    (sedlex (>= 2.5))
+    (alcotest (and :with-test (>= 0.8.5)))))
+

lib/json5/ast.ml

@@ -0,0 +1,27 @@
+type t =
+  | Assoc of (string * t) list
+  | List of t list
+  | StringLit of string
+  | IntLit of string
+  | FloatLit of string
+  | Bool of bool
+  | Null
+
+let rec to_basic = function
+  | Assoc l -> `Assoc (List.map (fun (name, obj) -> (name, to_basic obj)) l)
+  | List l -> `List (List.map to_basic l)
+  | StringLit s -> `String s
+  | FloatLit s -> `Float (float_of_string s)
+  | IntLit s -> `Int (int_of_string s)
+  | Bool b -> `Bool b
+  | Null -> `Null
+
+let rec to_safe = function
+  | Assoc l -> `Assoc (List.map (fun (name, obj) -> (name, to_safe obj)) l)
+  | List l -> `List (List.map to_safe l)
+  | StringLit s -> `String s
+  | FloatLit s -> `Float (float_of_string s)
+  | IntLit s -> (
+      match int_of_string_opt s with Some i -> `Int i | None -> `Intlit s)
+  | Bool b -> `Bool b
+  | Null -> `Null

lib/json5/basic.ml

@@ -0,0 +1,7 @@
+include Yojson.Basic
+
+include Read.Make (struct
+  type t = Yojson.Basic.t
+
+  let convert = Ast.to_basic
+end)

lib/json5/dune

@@ -0,0 +1,6 @@
+(library
+ (name yojson_json5)
+ (public_name yojson-json5)
+ (libraries yojson sedlex)
+ (preprocess
+  (pps sedlex.ppx)))

lib/json5/let_syntax.ml

@@ -0,0 +1,4 @@
+module Result = struct
+  let ( let* ) = Result.bind
+  let ( let+ ) v f = Result.map f v
+end

lib/json5/lexer.ml

@@ -0,0 +1,251 @@
+open Let_syntax.Result
+
+type token =
+  | OPEN_PAREN
+  | CLOSE_PAREN
+  | OPEN_BRACE
+  | CLOSE_BRACE
+  | OPEN_BRACKET
+  | CLOSE_BRACKET
+  | COLON
+  | COMMA
+  | COMMENT of string
+  | TRUE
+  | FALSE
+  | NULL
+  | FLOAT of string
+  | INT_OR_FLOAT of string
+  | INT of string
+  | STRING of string
+  | IDENTIFIER_NAME of string
+
+let pp_token ppf = function
+  | OPEN_PAREN -> Format.fprintf ppf "'('"
+  | CLOSE_PAREN -> Format.fprintf ppf "')'"
+  | OPEN_BRACE -> Format.fprintf ppf "'{'"
+  | CLOSE_BRACE -> Format.fprintf ppf "'}'"
+  | OPEN_BRACKET -> Format.fprintf ppf "'['"
+  | CLOSE_BRACKET -> Format.fprintf ppf "']'"
+  | COLON -> Format.fprintf ppf "':'"
+  | COMMA -> Format.fprintf ppf "','"
+  | COMMENT s -> Format.fprintf ppf "COMMENT '%s'" s
+  | TRUE -> Format.fprintf ppf "'true'"
+  | FALSE -> Format.fprintf ppf "'false'"
+  | NULL -> Format.fprintf ppf "'null'"
+  | FLOAT s -> Format.fprintf ppf "FLOAT '%s'" s
+  | INT_OR_FLOAT s -> Format.fprintf ppf "INT_OR_FLOAT '%s'" s
+  | INT s -> Format.fprintf ppf "INT '%s'" s
+  | STRING s -> Format.fprintf ppf "STRING '%s'" s
+  | IDENTIFIER_NAME s -> Format.fprintf ppf "IDENTIFIER_NAME '%s'" s
+
+let source_character = [%sedlex.regexp? any]
+let line_terminator = [%sedlex.regexp? 0x000A | 0x000D | 0x2028 | 0x2029]
+
+let line_terminator_sequence =
+  [%sedlex.regexp? 0x000A | 0x000D, Opt 0x000A | 0x2028 | 0x2029]
+
+(* NUMBERS, 7.8.3 *)
+let non_zero_digit = [%sedlex.regexp? '1' .. '9']
+let decimal_digit = [%sedlex.regexp? '0' .. '9']
+let decimal_digits = [%sedlex.regexp? Plus decimal_digit]
+let hex_digit = [%sedlex.regexp? '0' .. '9' | 'a' .. 'f' | 'A' .. 'F']
+let exponent_indicator = [%sedlex.regexp? 'e' | 'E']
+
+let signed_integer =
+  [%sedlex.regexp? decimal_digits | '+', decimal_digits | '-', decimal_digits]
+
+let exponent_part = [%sedlex.regexp? exponent_indicator, signed_integer]
+
+let decimal_integer_literal =
+  [%sedlex.regexp? '0' | non_zero_digit, Opt decimal_digits]
+
+let hex_integer_literal =
+  [%sedlex.regexp? "0x", Plus hex_digit | "0X", Plus hex_digit]
+
+(* float *)
+let float_literal =
+  [%sedlex.regexp?
+    ( decimal_integer_literal, '.', Opt decimal_digits, Opt exponent_part
+    | '.', decimal_digits, Opt exponent_part )]
+
+let json5_float =
+  [%sedlex.regexp? float_literal | '+', float_literal | '-', float_literal]
+
+(* int_or_float *)
+let int_or_float_literal =
+  [%sedlex.regexp? decimal_integer_literal, Opt exponent_part]
+
+let json5_int_or_float =
+  [%sedlex.regexp?
+    int_or_float_literal | '+', int_or_float_literal | '-', int_or_float_literal]
+
+(* int/hex *)
+let int_literal =
+  [%sedlex.regexp? decimal_digits | '+', decimal_digits | '-', decimal_digits]
+
+let json5_int =
+  [%sedlex.regexp?
+    ( hex_integer_literal
+    | '+', hex_integer_literal
+    | '-', hex_integer_literal
+    | int_literal )]
+
+(* STRING LITERALS, 7.8.4 *)
+let unicode_escape_sequence =
+  [%sedlex.regexp? 'u', hex_digit, hex_digit, hex_digit, hex_digit]
+
+let single_escape_character = [%sedlex.regexp? Chars {|'"\\bfnrtv|}]
+
+let escape_character =
+  [%sedlex.regexp? single_escape_character | decimal_digit | 'x' | 'u']
+
+let non_escape_character =
+  [%sedlex.regexp? Sub (source_character, (escape_character | line_terminator))]
+
+let character_escape_sequence =
+  [%sedlex.regexp? single_escape_character | non_escape_character]
+
+let line_continuation = [%sedlex.regexp? '\\', line_terminator_sequence]
+let hex_escape_sequence = [%sedlex.regexp? 'x', hex_digit, hex_digit]
+
+let escape_sequence =
+  [%sedlex.regexp?
+    ( character_escape_sequence
+    | '0', Opt (decimal_digit, decimal_digit)
+    | hex_escape_sequence | unicode_escape_sequence )]
+
+let single_string_character =
+  [%sedlex.regexp?
+    ( Sub (source_character, ('\'' | '\\' | line_terminator))
+    | '\\', escape_sequence
+    | line_continuation )]
+
+let double_string_character =
+  [%sedlex.regexp?
+    ( Sub (source_character, ('"' | '\\' | line_terminator))
+    | '\\', escape_sequence
+    | line_continuation )]
+
+let string_literal =
+  [%sedlex.regexp?
+    ( '"', Star double_string_character, '"'
+    | '\'', Star single_string_character, '\'' )]
+
+(* IDENTIFIER_NAME (keys in objects) *)
+let unicode_combining_mark = [%sedlex.regexp? mn | mc]
+let unicode_digit = [%sedlex.regexp? nd]
+let unicode_connector_punctuation = [%sedlex.regexp? pc]
+let unicode_letter = [%sedlex.regexp? lu | ll | lt | lm | lo | nl]
+let zwnj = [%sedlex.regexp? 0x200C]
+let zwj = [%sedlex.regexp? 0x200D]
+
+let identifier_start =
+  [%sedlex.regexp? unicode_letter | '$' | '_' | '\\', unicode_escape_sequence]
+
+let identifier_part =
+  [%sedlex.regexp?
+    ( identifier_start | unicode_combining_mark | unicode_digit
+    | unicode_connector_punctuation | zwnj | zwj )]
+
+let identifier_name = [%sedlex.regexp? identifier_start, Star identifier_part]
+
+(* COMMENTS 7.4 *)
+let single_line_comment_char =
+  [%sedlex.regexp? Sub (source_character, line_terminator)]
+
+let single_line_comment = [%sedlex.regexp? "//", Star single_line_comment_char]
+let multi_line_not_asterisk_char = [%sedlex.regexp? Sub (source_character, '*')]
+let multi_line_not_slash_char = [%sedlex.regexp? Sub (source_character, '/')]
+
+let multi_line_comment_char =
+  [%sedlex.regexp?
+    multi_line_not_asterisk_char | '*', Plus multi_line_not_slash_char]
+
+let multi_line_comment =
+  [%sedlex.regexp? "/*", Star multi_line_comment_char, Opt '*', "*/"]
+
+let comment = [%sedlex.regexp? multi_line_comment | single_line_comment]
+
+let white_space =
+  [%sedlex.regexp? 0x0009 | 0x000B | 0x000C | 0x0020 | 0x00A0 | 0xFEFF | zs]
+
+let string_lex_single lexbuf strbuf =
+  let lexeme = Sedlexing.Utf8.lexeme in
+  let rec lex lexbuf strbuf =
+    match%sedlex lexbuf with
+    | '\'' -> Ok (Buffer.contents strbuf)
+    | '\\', escape_sequence ->
+        let* s = Unescape.unescape (lexeme lexbuf) in
+        Buffer.add_string strbuf s;
+        lex lexbuf strbuf
+    | line_continuation -> lex lexbuf strbuf
+    | Sub (source_character, ('\'' | line_terminator)) ->
+        Buffer.add_string strbuf (lexeme lexbuf);
+        lex lexbuf strbuf
+    | _ ->
+        lexeme lexbuf
+        |> Format.sprintf "Unexpected character: %s"
+        |> Result.error
+  in
+  lex lexbuf strbuf
+
+let string_lex_double lexbuf strbuf =
+  let lexeme = Sedlexing.Utf8.lexeme in
+  let rec lex lexbuf strbuf =
+    match%sedlex lexbuf with
+    | '"' -> Ok (Buffer.contents strbuf)
+    | '\\', escape_sequence ->
+        let* s = Unescape.unescape (lexeme lexbuf) in
+        Buffer.add_string strbuf s;
+        lex lexbuf strbuf
+    | line_continuation -> lex lexbuf strbuf
+    | Sub (source_character, ('"' | line_terminator)) ->
+        Buffer.add_string strbuf (lexeme lexbuf);
+        lex lexbuf strbuf
+    | _ ->
+        lexeme lexbuf
+        |> Format.sprintf "Unexpected character: %s"
+        |> Result.error
+  in
+  lex lexbuf strbuf
+
+let string_lex lexbuf quote =
+  let strbuf = Buffer.create 200 in
+  if quote = "'" then string_lex_single lexbuf strbuf
+  else if quote = {|"|} then string_lex_double lexbuf strbuf
+  else Error (Format.sprintf "Invalid string quote %S" quote)
+
+let rec lex tokens buf =
+  let lexeme = Sedlexing.Utf8.lexeme in
+  match%sedlex buf with
+  | '(' -> lex (OPEN_PAREN :: tokens) buf
+  | ')' -> lex (CLOSE_PAREN :: tokens) buf
+  | '{' -> lex (OPEN_BRACE :: tokens) buf
+  | '}' -> lex (CLOSE_BRACE :: tokens) buf
+  | '[' -> lex (OPEN_BRACKET :: tokens) buf
+  | ']' -> lex (CLOSE_BRACKET :: tokens) buf
+  | ':' -> lex (COLON :: tokens) buf
+  | ',' -> lex (COMMA :: tokens) buf
+  | Chars {|"'|} ->
+      let* s = string_lex buf (lexeme buf) in
+      lex (STRING s :: tokens) buf
+  | multi_line_comment | single_line_comment | white_space | line_terminator ->
+      lex tokens buf
+  | "true" -> lex (TRUE :: tokens) buf
+  | "false" -> lex (FALSE :: tokens) buf
+  | "null" -> lex (NULL :: tokens) buf
+  | json5_float ->
+      let s = lexeme buf in
+      lex (FLOAT s :: tokens) buf
+  | json5_int ->
+      let s = lexeme buf in
+      lex (INT s :: tokens) buf
+  | json5_int_or_float ->
+      let s = lexeme buf in
+      lex (INT_OR_FLOAT s :: tokens) buf
+  | identifier_name ->
+      let s = lexeme buf in
+      lex (IDENTIFIER_NAME s :: tokens) buf
+  | eof -> Ok (List.rev tokens)
+  | _ ->
+      lexeme buf |> Format.asprintf "Unexpected character: '%s'" |> Result.error