fix: error with leading zero after sign

src/parsers/integer.rs

@@ -44,10 +44,15 @@ pub fn parse<R: Read, W: Writer>(
             ExpectingState::DigitOrSign => {
                 if char.is_ascii_digit() {
                     writer.write_byte(byte)?;
-                    first_digit_is_zero = true;
+
+                    if char == '0' {
+                        first_digit_is_zero = true;
+                    }
+
                     ExpectingState::DigitOrEnd
                 } else if char == '-' {
                     writer.write_byte(byte)?;
+
                     ExpectingState::DigitAfterSign
                 } else {
                     return Err(Error::UnexpectedByteParsingInteger(byte, byte as char));
@@ -56,18 +61,24 @@ pub fn parse<R: Read, W: Writer>(
             ExpectingState::DigitAfterSign => {
                 if char.is_ascii_digit() {
                     writer.write_byte(byte)?;
+
+                    if char == '0' {
+                        first_digit_is_zero = true;
+                    }
+
                     ExpectingState::DigitOrEnd
                 } else {
                     return Err(Error::UnexpectedByteParsingInteger(byte, byte as char));
                 }
             }
             ExpectingState::DigitOrEnd => {
                 if char.is_ascii_digit() {
+                    writer.write_byte(byte)?;
+
                     if char == '0' && first_digit_is_zero {
                         return Err(Error::LeadingZerosInIntegersNotAllowed);
                     }
 
-                    writer.write_byte(byte)?;
                     ExpectingState::DigitOrEnd
                 } else if byte == BENCODE_END_INTEGER {
                     return Ok(());
@@ -178,4 +189,18 @@ mod tests {
             Err(Error::LeadingZerosInIntegersNotAllowed)
         ));
     }
+
+    #[test]
+    fn it_should_fail_when_it_finds_leading_zeros_in_a_negative_integer() {
+        // Leading zeros are not allowed.Only the zero integer can start with zero.
+
+        let int_with_invalid_byte = b"i-00e";
+
+        let result = try_bencode_to_json(int_with_invalid_byte);
+
+        assert!(matches!(
+            result,
+            Err(Error::LeadingZerosInIntegersNotAllowed)
+        ));
+    }
 }