Model and render elements

src/check.rs

@@ -0,0 +1,78 @@
+/// <https://infra.spec.whatwg.org/#ascii-alpha>
+pub fn is_ascii_alpha(c: char) -> bool {
+    c.is_ascii_alphabetic()
+}
+
+/// <https://infra.spec.whatwg.org/#ascii-alphanumeric>
+pub fn is_ascii_alphanumeric(c: char) -> bool {
+    c.is_ascii_alphanumeric()
+}
+
+/// <https://html.spec.whatwg.org/multipage/syntax.html#syntax-tag-name>
+///
+/// The rules around what is a valid tag name are complicated. The standard
+/// doesn't give an easy answer. Because of this, we're conservative in what we
+/// allow. This way, the output we produce should parse correctly in a wide
+/// range of circumstances while following the standard.
+pub fn is_valid_tag_name(name: &str) -> bool {
+    !name.is_empty()
+        && name.chars().take(1).all(is_ascii_alpha)
+        && name.chars().all(is_ascii_alphanumeric)
+}
+
+/// <https://html.spec.whatwg.org/multipage/syntax.html#syntax-attribute-name>
+///
+/// The rules around what is a valid attribute name are complicated. The
+/// standard doesn't give an easy answer. Because of this, we're conservative in
+/// what we allow. This way, the output we produce should parse correctly in a
+/// wide range of circumstances while following the standard.
+pub fn is_valid_attribute_name(name: &str) -> bool {
+    !name.is_empty()
+        && name.chars().take(1).all(is_ascii_alpha)
+        && name
+            .chars()
+            .all(|c| is_ascii_alphanumeric(c) || c == '-' || c == '_')
+}
+
+/// https://html.spec.whatwg.org/multipage/syntax.html#cdata-rcdata-restrictions
+///
+/// The tag name must be ascii-only.
+pub fn is_valid_raw_text(tag_name: &str, text: &str) -> bool {
+    // In case we ever decide to relax tag name ascii requirements.
+    assert!(tag_name.is_ascii());
+
+    // "The text in raw text and escapable raw text elements must not contain
+    // any occurrences of the string "</" (U+003C LESS-THAN SIGN, U+002F
+    // SOLIDUS) [...]"
+    for (i, _) in text.match_indices("</") {
+        let start = i + "</".len();
+
+        let potential_tag_name = text[start..]
+            .chars()
+            .take(tag_name.chars().count())
+            .collect::<String>();
+
+        // "[...] followed by characters that case-insensitively match the tag
+        // name of the element [...]"
+        //
+        // Note: Since we know that tag names are ascii-only, we can convert
+        // both to lowercase for a case-insensitive comparison without weird
+        // unicode shenanigans.
+        if potential_tag_name.to_ascii_lowercase() != tag_name.to_ascii_lowercase() {
+            continue;
+        }
+
+        // "[...] followed by [...]"
+        let Some(trailing) = text[start + potential_tag_name.len()..].chars().next() else {
+            continue;
+        };
+
+        // "[...] one of U+0009 CHARACTER TABULATION (tab), U+000A LINE FEED
+        // (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), U+0020
+        // SPACE, U+003E GREATER-THAN SIGN (>), or U+002F SOLIDUS (/)."
+        if matches!(trailing, '\t' | '\n' | '\x0C' | '\r' | ' ' | '>' | '/') {
+            return false;
+        }
+    }
+    true
+}