lib.strings: fix negative number handling for toInt and toIntBase10

The previous version would be unstable due to an input validation regex
not expecting a '-' in front of the number.

lib/strings.nix

@@ -807,9 +807,9 @@ rec {
   */
   toInt = str:
     let
-      # RegEx: Match any leading whitespace, then any digits, and finally match any trailing
+      # RegEx: Match any leading whitespace, possibly a '-', one or more digits,
-      # whitespace.
+      # and finally match any trailing whitespace.
-      strippedInput = match "[[:space:]]*([[:digit:]]+)[[:space:]]*" str;
+      strippedInput = match "[[:space:]]*(-?[[:digit:]]+)[[:space:]]*" str;
 
       # RegEx: Match a leading '0' then one or more digits.
       isLeadingZero = match "0[[:digit:]]+" (head strippedInput) == [];
@@ -858,9 +858,10 @@ rec {
   */
   toIntBase10 = str:
     let
-      # RegEx: Match any leading whitespace, then match any zero padding, capture any remaining
+      # RegEx: Match any leading whitespace, then match any zero padding,
-      # digits after that, and finally match any trailing whitespace.
+      # capture possibly a '-' followed by one or more digits,
-      strippedInput = match "[[:space:]]*0*([[:digit:]]+)[[:space:]]*" str;
+      # and finally match any trailing whitespace.
+      strippedInput = match "[[:space:]]*0*(-?[[:digit:]]+)[[:space:]]*" str;
 
       # RegEx: Match at least one '0'.
       isZero = match "0+" (head strippedInput) == [];

lib/tests/misc.nix

@@ -339,6 +339,8 @@ runTests {
     (0 == toInt " 0")
     (0 == toInt "0 ")
     (0 == toInt " 0 ")
+    (-1 == toInt "-1")
+    (-1 == toInt " -1 ")
   ];
 
   testToIntFails = testAllTrue [
@@ -383,6 +385,8 @@ runTests {
     (0 == toIntBase10 " 000000")
     (0 == toIntBase10 "000000 ")
     (0 == toIntBase10 " 000000 ")
+    (-1 == toIntBase10 "-1")
+    (-1 == toIntBase10 " -1 ")
   ];
 
   testToIntBase10Fails = testAllTrue [