chore(rule): add html lang validation

RULES.md

@@ -10,6 +10,7 @@ List of techniques we want to have and whether we have it handled or not for WCA
 | -------------------------------------------------- | -------------------------- | -------- |
 | [H25](https://www.w3.org/TR/WCAG20-TECHS/H25.html) | empty titles               | ✅       |
 | [H32](https://www.w3.org/TR/WCAG20-TECHS/H32.html) | missing form submit button | ✅       |
+| [H57](https://www.w3.org/TR/WCAG20-TECHS/H57.html) | html contains valid lang   | ✅       |
 
 ### WCAGAA
 

accessibility-rs/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "accessibility-rs"
-version = "0.0.5"
+version = "0.0.6"
 authors = ["The A11yWatch Project Developers", "Jeff Mendez <[email protected]>"]
 edition = "2021"
 license = "MIT OR Apache-2.0"
@@ -26,6 +26,8 @@ accessibility-tree = { version = "0.0.1", path = "../accessibility-tree/victor"
 markup5ever = "0.11.0"
 cssparser = { workspace = true }
 slotmap = "1.0.6"
+strum = "0.25"
+strum_macros = "0.25"
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3.37"

accessibility-rs/src/engine/issue.rs

@@ -18,6 +18,10 @@ pub struct Clip {
 pub struct RunnerExtras {
     /// the url to get more information on the issue
     pub help_url: &'static str,
+    /// a detailed description of the issue
+    pub description: &'static str,
+    /// the impact level criteria
+    pub impact: &'static str,
 }
 
 /// issue details

accessibility-rs/src/engine/rules/ids.rs

@@ -1,27 +1,29 @@
 use std::vec;
+use strum_macros::IntoStaticStr;
 
-#[derive(PartialOrd, Ord, std::cmp::Eq, PartialEq, Hash, Debug)]
+#[derive(PartialOrd, Ord, std::cmp::Eq, PartialEq, Hash, Debug, IntoStaticStr)]
 /// techniques for WCAG <https://www.w3.org/TR/WCAG20-TECHS/>
 pub enum Techniques {
     /// <https://www.w3.org/TR/WCAG20-TECHS/H25.html>
     H25,
     /// <https://www.w3.org/TR/WCAG20-TECHS/H32.html>
     H32,
+    /// <https://www.w3.org/TR/WCAG20-TECHS/H57>
+    H57
 }
 
 impl Techniques {
     /// get rule id to string
     pub fn as_str(&self) -> &'static str {
-        match self {
-            Techniques::H25 => "H25",
-            Techniques::H32 => "H32",
-        }
+        // todo: make macro
+       self.into()
     }
     /// get pairs for a rule
     pub fn pairs(&self) -> Vec<&'static str> {
         match self {
             Techniques::H25 => vec!["H25.1.NoTitleEl", "H25.1.EmptyTitle"],
             Techniques::H32 => vec!["H32.2"],
+            Techniques::H57 => vec!["H57.2", "H57.3.Lang", "H57.3.XmlLang"],
         }
     }
 }

accessibility-rs/src/engine/rules/wcag_base.rs

@@ -47,6 +47,8 @@ impl Principle {
 pub enum Guideline {
     /// Provide ways to help users navigate, find content, and determine where they are.
     Navigable,
+    /// Make text content readable and understandable.
+    Readable,
     /// Make Web pages appear and operate in predictable ways.
     Predictable,
 }
@@ -55,6 +57,7 @@ impl Guideline {
     pub fn as_str(&self) -> &'static str {
         match self {
             Guideline::Navigable => "Guideline2_4",
+            Guideline::Readable => "Guideline3_1",
             Guideline::Predictable => "Guideline3_2",
         }
     }

accessibility-rs/src/engine/rules/wcag_rule_map.rs

@@ -9,6 +9,16 @@ lazy_static! {
     /// a list of rules that should be applied for WCAG1
     pub static ref RULES_A: BTreeMap<&'static str, Vec<Rule>> =
         vec![
+            ("html", Vec::from([
+                Rule::new(Techniques::H57, Criteria::Error, Principle::Understandable, Guideline::Readable, |_rule, nodes| {
+                    (!nodes[0].0.attr("lang").unwrap_or_default().is_empty(), "2", Default::default())
+                }),
+                Rule::new(Techniques::H57, Criteria::Error, Principle::Understandable, Guideline::Readable, |_rule, nodes| {
+                    let lang = nodes[0].0.attr("lang").unwrap_or_default();
+                    // <https://www.rfc-editor.org/rfc/bcp/bcp47.txt>
+                    (lang.chars().all(|x| x.is_alphanumeric()) && !lang.contains("_") && lang.len() < 12, "3.Lang", Default::default())
+                }),
+            ])),
             // empty titles
             ("title", Vec::from([
                 Rule::new(Techniques::H25, Criteria::Error, Principle::Operable, Guideline::Navigable, |_rule, nodes| {

accessibility-rs/src/i18n/locales.rs

@@ -101,7 +101,10 @@ lazy_static! {
         BTreeMap::from([
             (Techniques::H25.pairs()[0], Messages::new(&"A title should be provided for the document, using a non-empty title element in the head section.", "", "")),
             (Techniques::H25.pairs()[1], Messages::new(&"The title element in the head section should be non-empty.", "", "")),
-            (Techniques::H32.pairs()[0], Messages::new(&r###"Form does not contain a submit button (input type="submit", input type="image", or button type="submit")."###, "", ""))
+            (Techniques::H32.pairs()[0], Messages::new(&r###"Form does not contain a submit button (input type="submit", input type="image", or button type="submit")."###, "", "")),
+            (Techniques::H57.pairs()[0], Messages::new(&"The html element should have a lang or xml:lang attribute which describes the language of the document.", "", "")),
+            (Techniques::H57.pairs()[1], Messages::new(&"The language specified in the lang attribute of the document element does not appear to be well-formed.", "", "")),
+            (Techniques::H57.pairs()[2], Messages::new(&"The language specified in the xml:lang attribute of the document element does not appear to be well-formed.", "", "")),
         ])
     };
 }