[10.x] Improve decimal shape validation

[timacdonald]

The decimal rules checks that a value is numeric and then checks the value against a regex.

The current decimal validation regex is expecting:

[+-]? an optional positive / negative symbol

\d* zero or more digits

. any character, except new lines

\d* zero of more digits

All of the following values would pass this regex:

+
-
123
+123
-123
123@
123.
+123@
-123@
+123.
-123.
123@456
123.456
+123@456
-123@456
+123.456
-123.456

However, we first check that the value is numeric in PHP's eyes, so that reduces the values that get checked against the regex to the following set:

123
+123
-123
123.
+123.
-123.
123.456
+123.456
-123.456

but scientific notation will also pass the is_numeric check. So we add the following to the possible values. You will note, however, that these do not match the regex:

1.2e3
7E-10

When the preg_match happens, it has 0 results in $matches, and the rule interprets this as the number having 0 decimal places.

I believe this is a bug and the decimal rule should in fact check that the string matches the expected pattern, i.e., the decimal rule fails for scientific notation.

[timacdonald]

The "dot" has been escaped here. I believe this was a mistake in the original PR.

The dot allows 1 of any character. I believe it should only be a literal ..