Merge pull request #172 from ElectreAAS/parsing-message-fail-test

Added failing test on parsing failure

CHANGES.md

@@ -8,6 +8,10 @@
 
 ### Fixed
 
+- Fix the error location reported in the exception. Regression in 2.1.1
+  (reported by @johnridesabike, regression test by @ElectreAAS, fix by
+  @Leonidas-from-XIV, #171, #172)
+
 ### Removed
 
 ### Security

lib/lexer_utils.mll

@@ -7,3 +7,10 @@ rule read_junk buf n = parse
        read_junk buf (n - 1) lexbuf
      end
      }
+
+{
+let read_junk_without_positions buf n (lexbuf : Lexing.lexbuf) =
+  let junk_start_pos = lexbuf.lex_start_pos in
+  read_junk buf n lexbuf;
+  lexbuf.lex_start_pos <- junk_start_pos + 1
+}

lib/read.mll

@@ -71,8 +71,9 @@
 
   let long_error descr v lexbuf =
     let junk = Lexing.lexeme lexbuf in
-    let buf = Buffer.create 32 in
-    let () = Lexer_utils.read_junk buf 32 lexbuf in
+    let buf_size = 32 in
+    let buf = Buffer.create buf_size in
+    let () = Lexer_utils.read_junk_without_positions buf buf_size lexbuf in
     let extra_junk = Buffer.contents buf in
     custom_error
       (sprintf "%s '%s%s'" descr junk extra_junk)

test/test_read.ml

@@ -3,6 +3,11 @@ let from_string () =
     __LOC__ Fixtures.json_value
     (Yojson.Safe.from_string Fixtures.json_string)
 
+let from_string_fail () =
+  Alcotest.check_raises "Location of parsing failure is correct"
+    (Yojson.Json_error "Line 1, bytes 0-5:\nInvalid token 'hello'") (fun () ->
+      Yojson.Safe.from_string "hello" |> ignore)
+
 let from_file () =
   let input_file = Filename.temp_file "test_yojson_from_file" ".json" in
   let oc = open_out input_file in
@@ -51,6 +56,7 @@ let map_ident_and_string () =
 let single_json =
   [
     ("from_string", `Quick, from_string);
+    ("from_string_fail", `Quick, from_string_fail);
     ("from_file", `Quick, from_file);
     ("unquoted_from_string", `Quick, unquoted_from_string);
     ("map_ident/map_string", `Quick, map_ident_and_string);