2 files changed, 137 insertions, 0 deletions
diff --git a/src/tools/html-checker/Cargo.toml b/src/tools/html-checker/Cargo.toml
new file mode 100644
index 000000000..72d61d9bd
--- /dev/null
+++ b/src/tools/html-checker/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "html-checker"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "html-checker"
+path = "main.rs"
+
+[dependencies]
+walkdir = "2"
+rayon = "1.5"
diff --git a/src/tools/html-checker/main.rs b/src/tools/html-checker/main.rs
new file mode 100644
index 000000000..9b4d2c525
--- /dev/null
+++ b/src/tools/html-checker/main.rs
@@ -0,0 +1,125 @@
+use rayon::iter::{ParallelBridge, ParallelIterator};
+use std::env;
+use std::path::Path;
+use std::process::{Command, Output};
+
+fn check_html_file(file: &Path) -> usize {
+    let to_mute = &[
+        // "disabled" on <link> or "autocomplete" on <select> emit this warning
+        "PROPRIETARY_ATTRIBUTE",
+        // It complains when multiple in the same page link to the same anchor for some reason...
+        "ANCHOR_NOT_UNIQUE",
+        // If a <span> contains only HTML elements and no text, it complains about it.
+        "TRIM_EMPTY_ELEMENT",
+        // FIXME: the three next warnings are about <pre> elements which are not supposed to
+        //        contain HTML. The solution here would be to replace them with a <div>
+        "MISSING_ENDTAG_BEFORE",
+        "INSERTING_TAG",
+        "DISCARDING_UNEXPECTED",
+        // This error is caused by nesting the Notable Traits tooltip within an <h4> tag.
+        // The solution is to avoid doing that, but we need to have the <h4> tags for accessibility
+        // reasons, and we need the Notable Traits tooltip to help everyone understand the Iterator
+        // combinators
+        "TAG_NOT_ALLOWED_IN",
+    ];
+    let to_mute_s = to_mute.join(",");
+    let mut command = Command::new("tidy");
+    command
+        .arg("-errors")
+        .arg("-quiet")
+        .arg("--mute-id") // this option is useful in case we want to mute more warnings
+        .arg("yes")
+        .arg("--mute")
+        .arg(&to_mute_s)
+        .arg(file);
+
+    let Output { status, stderr, .. } = command.output().expect("failed to run tidy command");
+    if status.success() {
+        0
+    } else {
+        let stderr = String::from_utf8(stderr).expect("String::from_utf8 failed...");
+        if stderr.is_empty() && status.code() != Some(2) {
+            0
+        } else {
+            eprintln!(
+                "=> Errors for `{}` (error code: {}) <=",
+                file.display(),
+                status.code().unwrap_or(-1)
+            );
+            eprintln!("{}", stderr);
+            stderr.lines().count()
+        }
+    }
+}
+
+const DOCS_TO_CHECK: &[&str] =
+    &["alloc", "core", "proc_macro", "implementors", "src", "std", "test"];
+
+// Returns the number of files read and the number of errors.
+fn find_all_html_files(dir: &Path) -> (usize, usize) {
+    walkdir::WalkDir::new(dir)
+        .into_iter()
+        .filter_entry(|e| {
+            e.depth() != 1
+                || e.file_name()
+                    .to_str()
+                    .map(|s| DOCS_TO_CHECK.into_iter().any(|d| *d == s))
+                    .unwrap_or(false)
+        })
+        .par_bridge()
+        .map(|entry| {
+            let entry = entry.expect("failed to read file");
+            if !entry.file_type().is_file() {
+                return (0, 0);
+            }
+            let entry = entry.path();
+            // (Number of files processed, number of errors)
+            if entry.extension().and_then(|s| s.to_str()) == Some("html") {
+                (1, check_html_file(&entry))
+            } else {
+                (0, 0)
+            }
+        })
+        .reduce(|| (0, 0), |a, b| (a.0 + b.0, a.1 + b.1))
+}
+
+/// Default `tidy` command for macOS is too old that it does not have `mute-id` and `mute` options.
+/// `tidy` on macOS Monterey was released on 31 October 2006, and the same date can be seen seven
+/// years ago at <https://stackoverflow.com/questions/22283382/overwrite-osx-tidy>. Accordingly,
+/// the macOS environment using pre-installed `tidy` should immediately suspend HTML checker process
+/// and show a hint to install a newer one.
+#[cfg(target_os = "macos")]
+fn check_tidy_version() -> Result<(), String> {
+    let output = Command::new("tidy").arg("-v").output().expect("failed to run tidy command");
+    let version = String::from_utf8(output.stdout).expect("failed to read version of tidy command");
+    if version.contains("HTML Tidy for Mac OS X released on 31 October 2006") {
+        eprintln!("The pre-installed HTML Tidy for macOS is not supported.");
+        eprintln!("Consider installing a newer one and re-running.");
+        eprintln!("If you're using Homebrew, you can install it by the following command:");
+        eprintln!("    brew install tidy-html5");
+        eprintln!();
+        Err("HTML check failed: 1 error".to_string())
+    } else {
+        Ok(())
+    }
+}
+
+fn main() -> Result<(), String> {
+    let args = env::args().collect::<Vec<_>>();
+    if args.len() != 2 {
+        return Err(format!("Usage: {} <doc folder>", args[0]));
+    }
+    #[cfg(target_os = "macos")]
+    check_tidy_version()?;
+
+    println!("Running HTML checker...");
+
+    let (files_read, errors) = find_all_html_files(&Path::new(&args[1]));
+    println!("Done! Read {} files...", files_read);
+    if errors > 0 {
+        Err(format!("HTML check failed: {} errors", errors))
+    } else {
+        println!("No error found!");
+        Ok(())
+    }
+}