add tests for runtime decode errors

2 files changed, 76 insertions, 4 deletions

diff --git a/src/gleam_json_ffi.mjs b/src/gleam_json_ffi.mjs
index 115c503..b60d848 100644
--- a/src/gleam_json_ffi.mjs
+++ b/src/gleam_json_ffi.mjs
@@ -36,7 +36,7 @@ export function decode(string) {
   }
 }
 
-function getJsonDecodeError(stdErr, json) {
+export function getJsonDecodeError(stdErr, json) {
   if (isUnexpectedEndOfInput(stdErr)) return new UnexpectedEndOfInput()
   const unexpectedByteRuntime = getUnexpectedByteRuntime(stdErr)
   if (unexpectedByteRuntime) return toUnexpectedByteError(unexpectedByteRuntime, stdErr, json)
@@ -88,7 +88,7 @@ const chromiumUnexpectedByteRegex = /unexpected token (.) in JSON at position (\
  * 
  * JavascriptCore only reports what the character is and not its position.
  */
-const jsCoreUnexpectedByteRegex = /unexpected identifier "(.)"/i
+const jsCoreUnexpectedByteRegex = /unexpected (identifier|token) "(.)"/i
 
 /**
  * Matches unexpected byte messages in:
@@ -96,7 +96,7 @@ const jsCoreUnexpectedByteRegex = /unexpected identifier "(.)"/i
  * 
  * Matches the position in a 2d grid only and not the character.
  */
-const spidermonkeyUnexpectedByteRegex = /(unexpected character|expected double-quoted property name) at line (\d+) column (\d+)/i
+const spidermonkeyUnexpectedByteRegex = /(unexpected character|expected .*) at line (\d+) column (\d+)/i
 
 function getUnexpectedByteRuntime(err) {
   if (chromiumUnexpectedByteRegex.test(err.message)) return Runtime.chromium
@@ -151,7 +151,7 @@ function toSpidermonkeyUnexpectedByteError(err, json) {
 
 function toJsCoreUnexpectedByteError(err) {
   const match = jsCoreUnexpectedByteRegex.exec(err.message)
-  const byte = toHex(match[1])
+  const byte = toHex(match[2])
   return new UnexpectedByte(byte, 0)
 }
 
diff --git a/test/gleam_json_js_ffi_test.gleam b/test/gleam_json_js_ffi_test.gleam
new file mode 100644
index 0000000..74d1867
--- /dev/null
+++ b/test/gleam_json_js_ffi_test.gleam
@@ -0,0 +1,72 @@
+import gleeunit
+import gleam/json.{DecodeError, UnexpectedByte, UnexpectedEndOfInput}
+import gleeunit/should
+
+if javascript {
+  pub fn main() {
+    gleeunit.main()
+  }
+}
+
+type StandardError {
+  StandardError(message: String)
+}
+
+// === End of input tests === //
+pub fn chromium_end_of_input_test() {
+  "Unexpected end of JSON input"
+  |> StandardError
+  |> get_json_decode_error("")
+  |> should.equal(UnexpectedEndOfInput)
+}
+
+pub fn spidermonkey_end_of_input_test() {
+  "JSON.parse: unexpected end of data at line 1 column 1 of the JSON data"
+  |> StandardError
+  |> get_json_decode_error("")
+  |> should.equal(UnexpectedEndOfInput)
+}
+
+pub fn javascript_core_end_of_input_test() {
+  "JSON Parse error: Unexpected EOF"
+  |> StandardError
+  |> get_json_decode_error("")
+  |> should.equal(UnexpectedEndOfInput)
+}
+
+// === Unexpected byte tests === //
+pub fn chromium_unexpected_byte_test() {
+  "Unexpected token a in JSON at position 5"
+  |> StandardError
+  |> get_json_decode_error("{\"b\":a}")
+  |> should.equal(UnexpectedByte(byte: "0x61", position: 5))
+}
+
+pub fn spidermonkey_unexpected_byte_test() {
+  "JSON.parse: expected property name or '}' at line 1 column 6 of the JSON data"
+  |> StandardError
+  |> get_json_decode_error("{\"b\":a}")
+  |> should.equal(UnexpectedByte(byte: "0x61", position: 5))
+}
+
+pub fn javascript_core_unexpected_byte_test() {
+  "JSON Parse error: Unexpected identifier \"a\""
+  |> StandardError
+  |> get_json_decode_error("{\"b\":a}")
+  |> should.equal(UnexpectedByte(byte: "0x61", position: 0))
+}
+
+pub fn spidermonkey_multiline_unexpected_byte_test() {
+  "JSON.parse: expected property name or '}' at line 2 column 6 of the JSON data"
+  |> StandardError
+  |> get_json_decode_error("{\n\"b\": a\n}")
+  |> should.equal(UnexpectedByte(byte: "0x61", position: 7))
+
+  "JSON.parse: expected double-quoted property name at line 3 column 1 of the JSON data"
+  |> StandardError
+  |> get_json_decode_error("{\n\"b\": \"x\",\na\n}")
+  |> should.equal(UnexpectedByte(byte: "0x61", position: 12))
+}
+
+external fn get_json_decode_error(StandardError, String) -> DecodeError =
+  "./gleam_json_ffi.mjs" "getJsonDecodeError"