uucore: parser: num_parser: Ignore empty exponents

Numbers like 123.15e or 123.15e- should return PartialMatch.

Numbers like `e`, `.e` are not valid.

Fixes #7685.

src/uucore/src/lib/features/parser/num_parser.rs

@@ -458,7 +458,7 @@ pub(crate) fn parse<'a>(
     let mut chars = rest.chars().enumerate().fuse().peekable();
     let mut digits: Option<BigUint> = None;
     let mut scale = 0u64;
-    let mut exponent = BigInt::zero();
+    let mut exponent: Option<BigInt> = None;
     while let Some(d) = chars.peek().and_then(|&(_, c)| base.digit(c)) {
         chars.next();
         digits = Some(digits.unwrap_or_default() * base as u8 + d);
@@ -487,6 +487,8 @@ pub(crate) fn parse<'a>(
             .peek()
             .is_some_and(|&(_, c)| c.to_ascii_lowercase() == exp_char)
         {
+            // Save the iterator position in case we do not parse any exponent.
+            let save_chars = chars.clone();
             chars.next();
             let exp_negative = match chars.peek() {
                 Some((_, '-')) => {
@@ -501,10 +503,15 @@ pub(crate) fn parse<'a>(
             };
             while let Some(d) = chars.peek().and_then(|&(_, c)| Base::Decimal.digit(c)) {
                 chars.next();
-                exponent = exponent * 10 + d as i64;
+                exponent = Some(exponent.unwrap_or_default() * 10 + d as i64);
             }
-            if exp_negative {
+            if let Some(exp) = &exponent {
-                exponent = -exponent;
+                if exp_negative {
+                    exponent = Some(-exp);
+                }
+            } else {
+                // No exponent actually parsed, reset iterator to return partial match.
+                chars = save_chars;
             }
         }
     }
@@ -532,7 +539,7 @@ pub(crate) fn parse<'a>(
     }
 
     let ebd_result =
-        construct_extended_big_decimal(digits, negative, base, scale, exponent);
+        construct_extended_big_decimal(digits, negative, base, scale, exponent.unwrap_or_default());
 
     // Return what has been parsed so far. If there are extra characters, mark the
     // parsing as a partial match.
@@ -671,6 +678,16 @@ mod tests {
             Ok(0.15),
             f64::extended_parse(".150000000000000000000000000231313")
         );
+        assert!(matches!(f64::extended_parse("123.15e"),
+                         Err(ExtendedParserError::PartialMatch(f, "e")) if f == 123.15));
+        assert!(matches!(f64::extended_parse("123.15E"),
+                         Err(ExtendedParserError::PartialMatch(f, "E")) if f == 123.15));
+        assert!(matches!(f64::extended_parse("123.15e-"),
+                         Err(ExtendedParserError::PartialMatch(f, "e-")) if f == 123.15));
+        assert!(matches!(f64::extended_parse("123.15e+"),
+                         Err(ExtendedParserError::PartialMatch(f, "e+")) if f == 123.15));
+        assert!(matches!(f64::extended_parse("123.15e."),
+                         Err(ExtendedParserError::PartialMatch(f, "e.")) if f == 123.15));
         assert!(matches!(f64::extended_parse("1.2.3"),
                          Err(ExtendedParserError::PartialMatch(f, ".3")) if f == 1.2));
         assert!(matches!(f64::extended_parse("123.15p5"),
@@ -833,6 +850,38 @@ mod tests {
             Err(ExtendedParserError::NotNumeric),
             ExtendedBigDecimal::extended_parse(".")
         );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("e")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse(".e")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("-e")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("+.e")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("e10")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("e-10")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("-e10")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("+e10")
+        );
     }
 
     #[test]
@@ -853,6 +902,15 @@ mod tests {
         // but we can check that the number still gets parsed properly: 0x0.8e5 is 0x8e5 / 16**3
         assert_eq!(Ok(0.555908203125), f64::extended_parse("0x0.8e5"));
 
+        assert!(matches!(f64::extended_parse("0x0.1p"),
+                        Err(ExtendedParserError::PartialMatch(f, "p")) if f == 0.0625));
+        assert!(matches!(f64::extended_parse("0x0.1p-"),
+                        Err(ExtendedParserError::PartialMatch(f, "p-")) if f == 0.0625));
+        assert!(matches!(f64::extended_parse("0x.1p+"),
+                        Err(ExtendedParserError::PartialMatch(f, "p+")) if f == 0.0625));
+        assert!(matches!(f64::extended_parse("0x.1p."),
+                        Err(ExtendedParserError::PartialMatch(f, "p.")) if f == 0.0625));
+
         assert_eq!(
             Ok(ExtendedBigDecimal::BigDecimal(
                 BigDecimal::from_str("0.0625").unwrap()
@@ -910,7 +968,7 @@ mod tests {
             ))
         ));
 
-        // TODO: GNU coreutils treats these 2 as partial match.
+        // TODO: GNU coreutils treats these as partial matches.
         assert_eq!(
             Err(ExtendedParserError::NotNumeric),
             ExtendedBigDecimal::extended_parse("0x")
@@ -919,6 +977,14 @@ mod tests {
             Err(ExtendedParserError::NotNumeric),
             ExtendedBigDecimal::extended_parse("0x.")
         );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("0xp")
+        );
+        assert_eq!(
+            Err(ExtendedParserError::NotNumeric),
+            ExtendedBigDecimal::extended_parse("0xp-2")
+        );
     }
 
     #[test]