Auto merge of #25447 - teapotd:form-validation, r=jdm

Form constraint validation

It's almost done, there are few things remaining:

- ~Range underflow, range overflow and step mismatch implementation require #25405~
- ~There are some test failures due to missing DOM parts (#25003)~
- ~`pattern` attribute uses JS regexp syntax. Currently I used regex crate, but it's probably incompatible. Should we use SpiderMonkey's regexp via jsapi?~
- Currently validation errors are reported using `println!`. Are there any better options?
- ~["While the user interface is representing input that the user agent cannot convert to punycode, the control is suffering from bad input."](https://html.spec.whatwg.org/multipage/#e-mail-state-(type%3Demail)%3Asuffering-from-bad-input)~

r? @jdm

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #11444
- [x] There are tests for these changes

1 files changed, 22 insertions, 0 deletions

diff --git a/components/script/dom/bindings/str.rs b/components/script/dom/bindings/str.rs
index 986554206b6..0905c157143 100644
--- a/components/script/dom/bindings/str.rs
+++ b/components/script/dom/bindings/str.rs
@@ -519,6 +519,28 @@ impl DOMString {
         // Step 7, 8, 9
         Ok((date_tuple, time_tuple))
     }
+
+    /// https://html.spec.whatwg.org/multipage/#valid-e-mail-address
+    pub fn is_valid_email_address_string(&self) -> bool {
+        lazy_static! {
+            static ref RE: Regex = Regex::new(concat!(
+                r"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?",
+                r"(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$"
+            ))
+            .unwrap();
+        }
+        RE.is_match(&self.0)
+    }
+
+    /// https://html.spec.whatwg.org/multipage/#valid-simple-colour
+    pub fn is_valid_simple_color_string(&self) -> bool {
+        let mut chars = self.0.chars();
+        if self.0.len() == 7 && chars.next() == Some('#') {
+            chars.all(|c| c.is_digit(16))
+        } else {
+            false
+        }
+    }
 }
 
 impl Borrow<str> for DOMString {