Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 1004 insertions, 0 deletions

diff --git a/dom/webgpu/tests/cts/vendor/src/fs.rs b/dom/webgpu/tests/cts/vendor/src/fs.rs
new file mode 100644
index 0000000000..31697f9758
--- /dev/null
+++ b/dom/webgpu/tests/cts/vendor/src/fs.rs
@@ -0,0 +1,331 @@
+use std::{
+    ffi::OsStr,
+    fmt::{self, Display},
+    fs,
+    ops::Deref,
+    path::{Path, PathBuf, StripPrefixError},
+};
+
+use miette::{ensure, Context, IntoDiagnostic};
+
+#[derive(Debug)]
+pub(crate) struct FileRoot {
+    nickname: &'static str,
+    path: PathBuf,
+}
+
+impl Eq for FileRoot {}
+
+impl PartialEq for FileRoot {
+    fn eq(&self, other: &Self) -> bool {
+        self.path == other.path
+    }
+}
+
+impl Ord for FileRoot {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.path.cmp(&other.path)
+    }
+}
+
+impl PartialOrd for FileRoot {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl FileRoot {
+    pub(crate) fn new<P>(nickname: &'static str, path: P) -> miette::Result<Self>
+    where
+        P: AsRef<Path>,
+    {
+        let path = path.as_ref();
+        Ok(Self {
+            nickname,
+            path: dunce::canonicalize(path)
+                .map_err(miette::Report::msg)
+                .wrap_err_with(|| format!("failed to canonicalize {path:?}"))?,
+        })
+    }
+
+    pub(crate) fn nickname(&self) -> &str {
+        self.nickname
+    }
+
+    pub(crate) fn try_child<P>(&self, path: P) -> Result<Child<'_>, StripPrefixError>
+    where
+        P: AsRef<Path>,
+    {
+        let path = path.as_ref();
+        if path.is_absolute() {
+            path.strip_prefix(&self.path)?;
+        }
+        Ok(Child {
+            root: self,
+            path: self.path.join(path),
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn child<P>(&self, path: P) -> Child<'_>
+    where
+        P: AsRef<Path>,
+    {
+        self.try_child(path)
+            .into_diagnostic()
+            .wrap_err("invariant violation: `path` is absolute and not a child of this file root")
+            .unwrap()
+    }
+
+    fn removed_dir<P>(&self, path: P) -> miette::Result<Child<'_>>
+    where
+        P: AsRef<Path>,
+    {
+        let path = path.as_ref();
+        let child = self.child(path);
+        if child.exists() {
+            log::info!("removing old contents of {child}…",);
+            log::trace!("removing directory {:?}", &*child);
+            fs::remove_dir_all(&*child)
+                .map_err(miette::Report::msg)
+                .wrap_err_with(|| format!("failed to remove old contents of {child}"))?;
+        }
+        Ok(child)
+    }
+
+    fn removed_file<P>(&self, path: P) -> miette::Result<Child<'_>>
+    where
+        P: AsRef<Path>,
+    {
+        let path = path.as_ref();
+        let child = self.child(path);
+        if child.exists() {
+            log::info!("removing old copy of {child}…",);
+            fs::remove_file(&*child)
+                .map_err(miette::Report::msg)
+                .wrap_err_with(|| format!("failed to remove old copy of {child}"))?;
+        }
+        Ok(child)
+    }
+
+    pub(crate) fn regen_dir<P>(
+        &self,
+        path: P,
+        gen: impl FnOnce(&Child<'_>) -> miette::Result<()>,
+    ) -> miette::Result<Child<'_>>
+    where
+        P: AsRef<Path>,
+    {
+        let child = self.removed_dir(path)?;
+        gen(&child)?;
+        ensure!(
+            child.is_dir(),
+            "{} was not regenerated for an unknown reason",
+            child,
+        );
+        Ok(child)
+    }
+
+    pub(crate) fn regen_file<P>(
+        &self,
+        path: P,
+        gen: impl FnOnce(&Child<'_>) -> miette::Result<()>,
+    ) -> miette::Result<Child<'_>>
+    where
+        P: AsRef<Path>,
+    {
+        let child = self.removed_file(path)?;
+        gen(&child)?;
+        ensure!(
+            child.is_file(),
+            "{} was not regenerated for an unknown reason",
+            child,
+        );
+        Ok(child)
+    }
+}
+
+impl Deref for FileRoot {
+    type Target = Path;
+
+    fn deref(&self) -> &Self::Target {
+        &self.path
+    }
+}
+
+impl AsRef<Path> for FileRoot {
+    fn as_ref(&self) -> &Path {
+        &self.path
+    }
+}
+
+impl AsRef<OsStr> for FileRoot {
+    fn as_ref(&self) -> &OsStr {
+        self.path.as_os_str()
+    }
+}
+
+impl Display for FileRoot {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self { nickname, path } = self;
+        write!(f, "`{}` (AKA `<{nickname}>`)", path.display())
+    }
+}
+
+#[derive(Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub(crate) struct Child<'a> {
+    root: &'a FileRoot,
+    /// NOTE: This is always an absolute path that is a child of the `root`.
+    path: PathBuf,
+}
+
+impl Child<'_> {
+    pub(crate) fn relative_path(&self) -> &Path {
+        let Self { root, path } = self;
+        path.strip_prefix(root).unwrap()
+    }
+
+    pub(crate) fn try_child<P>(&self, path: P) -> Result<Self, StripPrefixError>
+    where
+        P: AsRef<Path>,
+    {
+        let child_path = path.as_ref();
+        let Self { root, path } = self;
+
+        if child_path.is_absolute() {
+            child_path.strip_prefix(path)?;
+        }
+        Ok(Child {
+            root,
+            path: path.join(child_path),
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn child<P>(&self, path: P) -> Self
+    where
+        P: AsRef<Path>,
+    {
+        self.try_child(path)
+            .into_diagnostic()
+            .wrap_err("invariant violation: `path` is absolute and not a child of this child")
+            .unwrap()
+    }
+}
+
+impl Deref for Child<'_> {
+    type Target = Path;
+
+    fn deref(&self) -> &Self::Target {
+        &self.path
+    }
+}
+
+impl AsRef<Path> for Child<'_> {
+    fn as_ref(&self) -> &Path {
+        &self.path
+    }
+}
+
+impl AsRef<OsStr> for Child<'_> {
+    fn as_ref(&self) -> &OsStr {
+        self.path.as_os_str()
+    }
+}
+
+impl Display for Child<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "`<{}>{}{}`",
+            self.root.nickname(),
+            std::path::MAIN_SEPARATOR,
+            self.relative_path().display()
+        )
+    }
+}
+
+pub(crate) fn existing_file<P>(path: P) -> P
+where
+    P: AsRef<Path>,
+{
+    let p = path.as_ref();
+    assert!(p.is_file(), "{p:?} does not exist as a file");
+    path
+}
+
+pub(crate) fn copy_dir<P, Q>(source: P, dest: Q) -> miette::Result<()>
+where
+    P: Display + AsRef<Path>,
+    Q: Display + AsRef<Path>,
+{
+    log::debug!(
+        "copy-merging directories from {} into {}",
+        source.as_ref().display(),
+        dest.as_ref().display(),
+    );
+    ::dircpy::copy_dir(&source, &dest)
+        .into_diagnostic()
+        .wrap_err_with(|| format!("failed to copy files from {source} to {dest}"))
+}
+
+pub(crate) fn read_to_string<P>(path: P) -> miette::Result<String>
+where
+    P: AsRef<Path>,
+{
+    fs::read_to_string(&path)
+        .into_diagnostic()
+        .wrap_err_with(|| {
+            format!(
+                "failed to read UTF-8 string from path {}",
+                path.as_ref().display()
+            )
+        })
+}
+
+pub(crate) fn copy<P1, P2>(from: P1, to: P2) -> miette::Result<u64>
+where
+    P1: AsRef<Path>,
+    P2: AsRef<Path>,
+{
+    fs::copy(&from, &to).into_diagnostic().wrap_err_with(|| {
+        format!(
+            "failed to copy {} to {}",
+            from.as_ref().display(),
+            to.as_ref().display()
+        )
+    })
+}
+
+pub(crate) fn create_dir_all<P>(path: P) -> miette::Result<()>
+where
+    P: AsRef<Path>,
+{
+    fs::create_dir_all(&path)
+        .into_diagnostic()
+        .wrap_err_with(|| {
+            format!(
+                "failed to create directories leading up to {}",
+                path.as_ref().display()
+            )
+        })
+}
+
+pub(crate) fn remove_file<P>(path: P) -> miette::Result<()>
+where
+    P: AsRef<Path>,
+{
+    fs::remove_file(&path)
+        .into_diagnostic()
+        .wrap_err_with(|| format!("failed to remove file at path {}", path.as_ref().display()))
+}
+
+pub(crate) fn write<P, C>(path: P, contents: C) -> miette::Result<()>
+where
+    P: AsRef<Path>,
+    C: AsRef<[u8]>,
+{
+    fs::write(&path, &contents)
+        .into_diagnostic()
+        .wrap_err_with(|| format!("failed to write to path {}", path.as_ref().display()))
+}
diff --git a/dom/webgpu/tests/cts/vendor/src/main.rs b/dom/webgpu/tests/cts/vendor/src/main.rs
new file mode 100644
index 0000000000..750b65c62e
--- /dev/null
+++ b/dom/webgpu/tests/cts/vendor/src/main.rs
@@ -0,0 +1,565 @@
+use std::{
+    collections::{BTreeMap, BTreeSet},
+    env::{current_dir, set_current_dir},
+    path::{Path, PathBuf},
+    process::ExitCode,
+};
+
+use clap::Parser;
+use lets_find_up::{find_up_with, FindUpKind, FindUpOptions};
+use miette::{bail, ensure, miette, Context, Diagnostic, IntoDiagnostic, Report, SourceSpan};
+use regex::Regex;
+
+use crate::{
+    fs::{copy_dir, create_dir_all, existing_file, remove_file, FileRoot},
+    path::join_path,
+    process::{which, EasyCommand},
+};
+
+mod fs;
+mod path;
+mod process;
+
+/// Vendor WebGPU CTS tests from a local Git checkout of [our `gpuweb/cts` fork].
+///
+/// WPT tests are generated into `testing/web-platform/mozilla/tests/webgpu/`. If the set of tests
+/// changes upstream, make sure that the generated output still matches up with test expectation
+/// metadata in `testing/web-platform/mozilla/meta/webgpu/`.
+///
+/// [our `gpuweb/cts` fork]: https://github.com/mozilla/gpuweb-cts
+#[derive(Debug, Parser)]
+struct CliArgs {
+    /// A path to the top-level directory of your WebGPU CTS checkout.
+    cts_checkout_path: PathBuf,
+}
+
+fn main() -> ExitCode {
+    env_logger::builder()
+        .filter_level(log::LevelFilter::Info)
+        .parse_default_env()
+        .init();
+
+    let args = CliArgs::parse();
+
+    match run(args) {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(e) => {
+            log::error!("{e:?}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn run(args: CliArgs) -> miette::Result<()> {
+    let CliArgs { cts_checkout_path } = args;
+
+    let orig_working_dir = current_dir().unwrap();
+
+    let cts_dir = join_path(["dom", "webgpu", "tests", "cts"]);
+    let cts_vendor_dir = join_path([&*cts_dir, "vendor".as_ref()]);
+    let gecko_ckt = {
+        let find_up_opts = || FindUpOptions {
+            cwd: Path::new("."),
+            kind: FindUpKind::Dir,
+        };
+        let find_up = |root_dir_name| {
+            let err = || {
+                miette!(
+                    concat!(
+                        "failed to find a Mercurial repository ({:?}) in any of current ",
+                        "working directory and its parent directories",
+                    ),
+                    root_dir_name
+                )
+            };
+            find_up_with(root_dir_name, find_up_opts())
+                .map_err(Report::msg)
+                .wrap_err_with(err)
+                .and_then(|loc_opt| loc_opt.ok_or_else(err))
+                .map(|mut dir| {
+                    dir.pop();
+                    dir
+                })
+        };
+        let gecko_source_root = find_up(".hg").or_else(|e| match find_up(".git") {
+            Ok(path) => {
+                log::debug!("{e:?}");
+                Ok(path)
+            }
+            Err(e2) => {
+                log::warn!("{e:?}");
+                log::warn!("{e2:?}");
+                bail!("failed to find a Gecko repository root")
+            }
+        })?;
+
+        let root = FileRoot::new("gecko", &gecko_source_root)?;
+        log::info!("detected Gecko repository root at {root}");
+
+        ensure!(
+            root.try_child(&orig_working_dir)
+                .map_or(false, |c| c.relative_path() == cts_vendor_dir),
+            concat!(
+                "It is expected to run this tool from the root of its Cargo project, ",
+                "but this does not appear to have been done. Bailing."
+            )
+        );
+
+        root
+    };
+
+    let cts_vendor_dir = gecko_ckt.child(orig_working_dir.parent().unwrap());
+
+    let wpt_tests_dir = {
+        let child = gecko_ckt.child(join_path(["testing", "web-platform", "mozilla", "tests"]));
+        ensure!(
+            child.is_dir(),
+            "WPT tests dir ({child}) does not appear to exist"
+        );
+        child
+    };
+
+    let (cts_ckt_git_dir, cts_ckt) = {
+        let failed_find_git_err = || {
+            miette!(concat!(
+                "failed to find a Git repository (`.git` directory) in the provided path ",
+                "and all of its parent directories"
+            ))
+        };
+        let git_dir = find_up_with(
+            ".git",
+            FindUpOptions {
+                cwd: &cts_checkout_path,
+                kind: FindUpKind::Dir,
+            },
+        )
+        .map_err(Report::msg)
+        .wrap_err_with(failed_find_git_err)?
+        .ok_or_else(failed_find_git_err)?;
+
+        let ckt = FileRoot::new("cts", git_dir.parent().unwrap())?;
+        log::debug!("detected CTS checkout root at {ckt}");
+        (git_dir, ckt)
+    };
+
+    let git_bin = which("git", "Git binary")?;
+    let npm_bin = which("npm", "NPM binary")?;
+
+    // XXX: It'd be nice to expose separate operations for copying in source and generating WPT
+    // cases from the vendored copy. Checks like these really only matter when updating source.
+    let ensure_no_child = |p1: &FileRoot, p2| {
+        ensure!(
+            p1.try_child(p2).is_err(),
+            "{p1} is a child path of {p2}, which is not supported"
+        );
+        Ok(())
+    };
+    ensure_no_child(&cts_ckt, &gecko_ckt)?;
+    ensure_no_child(&gecko_ckt, &cts_ckt)?;
+
+    log::info!("making a vendored copy of checked-in files from {cts_ckt}…",);
+    gecko_ckt.regen_file(
+        join_path([&*cts_dir, "checkout_commit.txt".as_ref()]),
+        |checkout_commit_file| {
+            let mut git_status_porcelain_cmd = EasyCommand::new(&git_bin, |cmd| {
+                cmd.args(["status", "--porcelain"])
+                    .envs([("GIT_DIR", &*cts_ckt_git_dir), ("GIT_WORK_TREE", &*cts_ckt)])
+            });
+            log::info!(
+                "  …ensuring the working tree and index are clean with {}…",
+                git_status_porcelain_cmd
+            );
+            let git_status_porcelain_output = git_status_porcelain_cmd.just_stdout_utf8()?;
+            ensure!(
+                git_status_porcelain_output.is_empty(),
+                concat!(
+                    "expected a clean CTS working tree and index, ",
+                    "but {}'s output was not empty; ",
+                    "for reference, it was:\n\n{}",
+                ),
+                git_status_porcelain_cmd,
+                git_status_porcelain_output,
+            );
+
+            gecko_ckt.regen_dir(&cts_vendor_dir.join("checkout"), |vendored_ckt_dir| {
+                log::info!("  …copying files tracked by Git to {vendored_ckt_dir}…");
+                let files_to_vendor = {
+                    let mut git_ls_files_cmd = EasyCommand::new(&git_bin, |cmd| {
+                        cmd.arg("ls-files").env("GIT_DIR", &cts_ckt_git_dir)
+                    });
+                    log::debug!("  …getting files to vendor from {git_ls_files_cmd}…");
+                    let output = git_ls_files_cmd.just_stdout_utf8()?;
+                    let mut files = output
+                        .split_terminator('\n')
+                        .map(PathBuf::from)
+                        .collect::<BTreeSet<_>>();
+                    log::trace!("  …files from {git_ls_files_cmd}: {files:#?}");
+
+                    log::trace!("  …validating that files from Git repo still exist…");
+                    let files_not_found = files
+                        .iter()
+                        .filter(|p| !cts_ckt.child(p).exists())
+                        .collect::<Vec<_>>();
+                    ensure!(
+                        files_not_found.is_empty(),
+                        concat!(
+                            "the following files were returned by `git ls-files`, ",
+                            "but do not exist on disk: {:#?}",
+                        ),
+                        files_not_found,
+                    );
+
+                    log::trace!("  …stripping files we actually don't want to vendor…");
+                    let files_to_actually_not_vendor = [
+                        // There's no reason to bring this over, and lots of reasons to not bring in
+                        // security-sensitive content unless we have to.
+                        "deploy_key.enc",
+                    ]
+                    .map(Path::new);
+                    log::trace!("    …files we don't want: {files_to_actually_not_vendor:?}");
+                    for path in files_to_actually_not_vendor {
+                        ensure!(
+                            files.remove(path),
+                            concat!(
+                                "failed to remove {} from list of files to vendor; ",
+                                "does it still exist?"
+                            ),
+                            cts_ckt.child(path)
+                        );
+                    }
+                    files
+                };
+
+                log::debug!("  …now doing the copying…");
+                for path in files_to_vendor {
+                    let vendor_from_path = cts_ckt.child(&path);
+                    let vendor_to_path = vendored_ckt_dir.child(&path);
+                    if let Some(parent) = vendor_to_path.parent() {
+                        create_dir_all(vendored_ckt_dir.child(parent))?;
+                    }
+                    log::trace!("    …copying {vendor_from_path} to {vendor_to_path}…");
+                    fs::copy(&vendor_from_path, &vendor_to_path)?;
+                }
+
+                Ok(())
+            })?;
+
+            log::info!("  …writing commit ref pointed to by `HEAD` to {checkout_commit_file}…");
+            let mut git_rev_parse_head_cmd = EasyCommand::new(&git_bin, |cmd| {
+                cmd.args(["rev-parse", "HEAD"])
+                    .env("GIT_DIR", &cts_ckt_git_dir)
+            });
+            log::trace!("    …getting output of {git_rev_parse_head_cmd}…");
+            fs::write(
+                checkout_commit_file,
+                git_rev_parse_head_cmd.just_stdout_utf8()?,
+            )
+            .wrap_err_with(|| format!("failed to write HEAD ref to {checkout_commit_file}"))
+        },
+    )?;
+
+    set_current_dir(&*cts_ckt)
+        .into_diagnostic()
+        .wrap_err("failed to change working directory to CTS checkout")?;
+    log::debug!("changed CWD to {cts_ckt}");
+
+    let mut npm_ci_cmd = EasyCommand::new(&npm_bin, |cmd| cmd.arg("ci"));
+    log::info!(
+        "ensuring a clean {} directory with {npm_ci_cmd}…",
+        cts_ckt.child("node_modules"),
+    );
+    npm_ci_cmd.spawn()?;
+
+    let out_wpt_dir = cts_ckt.regen_dir("out-wpt", |out_wpt_dir| {
+        let mut npm_run_wpt_cmd = EasyCommand::new(&npm_bin, |cmd| cmd.args(["run", "wpt"]));
+        log::info!("generating WPT test cases into {out_wpt_dir} with {npm_run_wpt_cmd}…");
+        npm_run_wpt_cmd.spawn()
+    })?;
+
+    let cts_https_html_path = out_wpt_dir.child("cts.https.html");
+    log::info!("refining the output of {cts_https_html_path} with `npm run gen_wpt_cts_html …`…");
+    EasyCommand::new(&npm_bin, |cmd| {
+        cmd.args(["run", "gen_wpt_cts_html"]).arg(existing_file(
+            &cts_ckt.child("tools/gen_wpt_cfg_unchunked.json"),
+        ))
+    })
+    .spawn()?;
+
+    {
+        let extra_cts_https_html_path = out_wpt_dir.child("cts-chunked2sec.https.html");
+        log::info!("removing extraneous {extra_cts_https_html_path}…");
+        remove_file(&*extra_cts_https_html_path)?;
+    }
+
+    log::info!("analyzing {cts_https_html_path}…");
+    let cts_https_html_content = fs::read_to_string(&*cts_https_html_path)?;
+    let cts_boilerplate_short_timeout;
+    let cts_boilerplate_long_timeout;
+    let cts_cases;
+    {
+        {
+            let (boilerplate, cases_start) = {
+                let cases_start_idx = cts_https_html_content
+                    .find("<meta name=variant")
+                    .ok_or_else(|| miette!("no test cases found; this is unexpected!"))?;
+                cts_https_html_content.split_at(cases_start_idx)
+            };
+
+            {
+                if !boilerplate.is_empty() {
+                    #[derive(Debug, Diagnostic, thiserror::Error)]
+                    #[error("last character before test cases was not a newline; bug, or weird?")]
+                    #[diagnostic(severity("warning"))]
+                    struct Oops {
+                        #[label(
+                            "this character ({:?}) was expected to be a newline, so that {}",
+                            source_code.chars().last().unwrap(),
+                            "the test spec. following it is on its own line"
+                        )]
+                        span: SourceSpan,
+                        #[source_code]
+                        source_code: String,
+                    }
+                    ensure!(
+                        boilerplate.ends_with('\n'),
+                        Oops {
+                            span: SourceSpan::from(0..boilerplate.len()),
+                            source_code: cts_https_html_content,
+                        }
+                    );
+                }
+
+                // NOTE: Adding `_mozilla` is necessary because [that's how it's mounted][source].
+                //
+                // [source]: https://searchfox.org/mozilla-central/rev/cd2121e7d83af1b421c95e8c923db70e692dab5f/testing/web-platform/mozilla/README#1-4]
+                log::info!(concat!(
+                    "  …fixing `script` paths in WPT boilerplate ",
+                    "so they work as Mozilla-private WPT tests…"
+                ));
+                let expected_wpt_script_tag =
+                    "<script type=module src=/webgpu/common/runtime/wpt.js></script>";
+                ensure!(
+                    boilerplate.contains(expected_wpt_script_tag),
+                    concat!(
+                        "failed to find expected `script` tag for `wpt.js` ",
+                        "({:?}); did something change upstream?",
+                    ),
+                    expected_wpt_script_tag
+                );
+                let mut boilerplate = boilerplate.replacen(
+                    expected_wpt_script_tag,
+                    "<script type=module src=/_mozilla/webgpu/common/runtime/wpt.js></script>",
+                    1,
+                );
+
+                cts_boilerplate_short_timeout = boilerplate.clone();
+
+                let timeout_insert_idx = {
+                    let meta_charset_utf8 = "\n<meta charset=utf-8>\n";
+                    let meta_charset_utf8_idx =
+                        boilerplate.find(meta_charset_utf8).ok_or_else(|| {
+                            miette!(
+                                "could not find {:?} in document; did something change upstream?",
+                                meta_charset_utf8
+                            )
+                        })?;
+                    meta_charset_utf8_idx + meta_charset_utf8.len()
+                };
+                boilerplate.insert_str(
+                    timeout_insert_idx,
+                    concat!(
+                        r#"<meta name="timeout" content="long">"#,
+                        " <!-- TODO: narrow to only where it's needed, see ",
+                        "https://bugzilla.mozilla.org/show_bug.cgi?id=1850537",
+                        " -->\n"
+                    ),
+                );
+                cts_boilerplate_long_timeout = boilerplate
+            };
+
+            log::info!("  …parsing test variants in {cts_https_html_path}…");
+            let mut parsing_failed = false;
+            let meta_variant_regex = Regex::new(concat!(
+                "^",
+                "<meta name=variant content='\\?q=([^']*?):\\*'>",
+                "$"
+            ))
+            .unwrap();
+            cts_cases = cases_start
+                .split_terminator('\n')
+                .filter_map(|line| {
+                    let path_and_meta = meta_variant_regex
+                        .captures(line)
+                        .map(|caps| (caps[1].to_owned(), line));
+                    if path_and_meta.is_none() {
+                        parsing_failed = true;
+                        log::error!("line is not a test case: {line:?}");
+                    }
+                    path_and_meta
+                })
+                .collect::<Vec<_>>();
+            ensure!(
+                !parsing_failed,
+                "one or more test case lines failed to parse, fix it and try again"
+            );
+        };
+        log::trace!("\"original\" HTML boilerplate:\n\n{cts_boilerplate_short_timeout}");
+
+        ensure!(
+            !cts_cases.is_empty(),
+            "no test cases found; this is unexpected!"
+        );
+        log::info!("  …found {} test cases", cts_cases.len());
+    }
+
+    cts_ckt.regen_dir(out_wpt_dir.join("cts"), |cts_tests_dir| {
+        log::info!("re-distributing tests into single file per test path…");
+        let mut failed_writing = false;
+        let mut cts_cases_by_spec_file_dir = BTreeMap::<_, BTreeSet<_>>::new();
+        for (path, meta) in cts_cases {
+            let case_dir = {
+                // Context: We want to mirror CTS upstream's `src/webgpu/**/*.spec.ts` paths as
+                // entire WPT tests, with each subtest being a WPT variant. Here's a diagram of
+                // a CTS path to explain why the logic below is correct:
+                //
+                // ```sh
+                // webgpu:this,is,the,spec.ts,file,path:subtest_in_file:…
+                // \____/ \___________________________/^\_____________/
+                //  test      `*.spec.ts` file path    |       |
+                // \__________________________________/|       |
+                //                   |                 |       |
+                //              We want this…          | …but not this. CTS upstream generates
+                //                                     | this too, but we don't want to divide
+                //         second ':' character here---/ here (yet).
+                // ```
+                let subtest_and_later_start_idx =
+                    match path.match_indices(':').nth(1).map(|(idx, _s)| idx) {
+                        Some(some) => some,
+                        None => {
+                            failed_writing = true;
+                            log::error!(
+                                concat!(
+                                    "failed to split suite and test path segments ",
+                                    "from CTS path `{}`"
+                                ),
+                                path
+                            );
+                            continue;
+                        }
+                    };
+                let slashed =
+                    path[..subtest_and_later_start_idx].replace(|c| matches!(c, ':' | ','), "/");
+                cts_tests_dir.child(slashed)
+            };
+            if !cts_cases_by_spec_file_dir
+                .entry(case_dir)
+                .or_default()
+                .insert(meta)
+            {
+                log::warn!("duplicate entry {meta:?} detected")
+            }
+        }
+
+        struct WptEntry<'a> {
+            cases: BTreeSet<&'a str>,
+            timeout_length: TimeoutLength,
+        }
+        enum TimeoutLength {
+            Short,
+            Long,
+        }
+        let split_cases = {
+            let mut split_cases = BTreeMap::new();
+            fn insert_with_default_name<'a>(
+                split_cases: &mut BTreeMap<fs::Child<'a>, WptEntry<'a>>,
+                spec_file_dir: fs::Child<'a>,
+                cases: WptEntry<'a>,
+            ) {
+                let path = spec_file_dir.child("cts.https.html");
+                assert!(split_cases.insert(path, cases).is_none());
+            }
+            {
+                let dld_path =
+                    &cts_tests_dir.child("webgpu/api/validation/state/device_lost/destroy");
+                let (spec_file_dir, cases) = cts_cases_by_spec_file_dir
+                    .remove_entry(dld_path)
+                    .expect("no `device_lost/destroy` tests found; did they move?");
+                insert_with_default_name(
+                    &mut split_cases,
+                    spec_file_dir,
+                    WptEntry {
+                        cases,
+                        timeout_length: TimeoutLength::Short,
+                    },
+                );
+            }
+            for (spec_file_dir, cases) in cts_cases_by_spec_file_dir {
+                insert_with_default_name(
+                    &mut split_cases,
+                    spec_file_dir,
+                    WptEntry {
+                        cases,
+                        timeout_length: TimeoutLength::Long,
+                    },
+                );
+            }
+            split_cases
+        };
+
+        for (path, entry) in split_cases {
+            let dir = path.parent().expect("no parent found for ");
+            match create_dir_all(&dir) {
+                Ok(()) => log::trace!("made directory {}", dir.display()),
+                Err(e) => {
+                    failed_writing = true;
+                    log::error!("{e:#}");
+                    continue;
+                }
+            }
+            let file_contents = {
+                let WptEntry {
+                    cases,
+                    timeout_length,
+                } = entry;
+                let content = match timeout_length {
+                    TimeoutLength::Short => &cts_boilerplate_short_timeout,
+                    TimeoutLength::Long => &cts_boilerplate_long_timeout,
+                };
+                let mut content = content.as_bytes().to_vec();
+                for meta in cases {
+                    content.extend(meta.as_bytes());
+                    content.extend(b"\n");
+                }
+                content
+            };
+            match fs::write(&path, &file_contents)
+                .wrap_err_with(|| miette!("failed to write output to path {path:?}"))
+            {
+                Ok(()) => log::debug!("  …wrote {path}"),
+                Err(e) => {
+                    failed_writing = true;
+                    log::error!("{e:#}");
+                }
+            }
+        }
+        ensure!(
+            !failed_writing,
+            "failed to write one or more WPT test files; see above output for more details"
+        );
+        log::debug!("  …finished writing new WPT test files!");
+
+        log::info!("  …removing {cts_https_html_path}, now that it's been divided up…");
+        remove_file(&cts_https_html_path)?;
+
+        Ok(())
+    })?;
+
+    gecko_ckt.regen_dir(wpt_tests_dir.join("webgpu"), |wpt_webgpu_tests_dir| {
+        log::info!("copying contents of {out_wpt_dir} to {wpt_webgpu_tests_dir}…");
+        copy_dir(&out_wpt_dir, wpt_webgpu_tests_dir)
+    })?;
+
+    log::info!("All done! Now get your CTS _ON_! :)");
+
+    Ok(())
+}
diff --git a/dom/webgpu/tests/cts/vendor/src/path.rs b/dom/webgpu/tests/cts/vendor/src/path.rs
new file mode 100644
index 0000000000..aa5bae2e6d
--- /dev/null
+++ b/dom/webgpu/tests/cts/vendor/src/path.rs
@@ -0,0 +1,23 @@
+use std::path::{Path, PathBuf};
+
+/// Construct a [`PathBuf`] from individual [`Path`] components.
+///
+/// This is a simple and legible way to construct `PathBuf`s that use the system's native path
+/// separator character. (It's ugly to see paths mixing `\` and `/`.)
+///
+/// # Examples
+///
+/// ```rust
+/// # use std::path::Path;
+/// # use vendor_webgpu_cts::path::join_path;
+/// assert_eq!(&*join_path(["foo", "bar", "baz"]), Path::new("foo/bar/baz"));
+/// ```
+pub(crate) fn join_path<I, P>(iter: I) -> PathBuf
+where
+    I: IntoIterator<Item = P>,
+    P: AsRef<Path>,
+{
+    let mut path = PathBuf::new();
+    path.extend(iter);
+    path
+}
diff --git a/dom/webgpu/tests/cts/vendor/src/process.rs b/dom/webgpu/tests/cts/vendor/src/process.rs
new file mode 100644
index 0000000000..b36c3b953d
--- /dev/null
+++ b/dom/webgpu/tests/cts/vendor/src/process.rs
@@ -0,0 +1,85 @@
+use std::{
+    ffi::{OsStr, OsString},
+    fmt::{self, Display},
+    iter::once,
+    process::{Command, Output},
+};
+
+use format::lazy_format;
+use miette::{ensure, Context, IntoDiagnostic};
+
+pub(crate) fn which(name: &'static str, desc: &str) -> miette::Result<OsString> {
+    let found = ::which::which(name)
+        .into_diagnostic()
+        .wrap_err(lazy_format!("failed to find `{name}` executable"))?;
+    log::debug!("using {desc} from {}", found.display());
+    Ok(found.file_name().unwrap().to_owned())
+}
+
+pub(crate) struct EasyCommand {
+    inner: Command,
+}
+
+impl EasyCommand {
+    pub(crate) fn new<C>(cmd: C, f: impl FnOnce(&mut Command) -> &mut Command) -> Self
+    where
+        C: AsRef<OsStr>,
+    {
+        let mut cmd = Command::new(cmd);
+        f(&mut cmd);
+        Self { inner: cmd }
+    }
+
+    pub(crate) fn spawn(&mut self) -> miette::Result<()> {
+        log::debug!("spawning {self}…");
+        let status = self
+            .inner
+            .spawn()
+            .into_diagnostic()
+            .wrap_err_with(|| format!("failed to spawn {self}"))?
+            .wait()
+            .into_diagnostic()
+            .wrap_err_with(|| format!("failed to wait for exit code from {self}"))?;
+        log::debug!("{self} returned {:?}", status.code());
+        ensure!(status.success(), "{self} returned {:?}", status.code());
+        Ok(())
+    }
+
+    fn just_stdout(&mut self) -> miette::Result<Vec<u8>> {
+        log::debug!("getting `stdout` output of {self}");
+        let output = self
+            .inner
+            .output()
+            .into_diagnostic()
+            .wrap_err_with(|| format!("failed to execute `{self}`"))?;
+        let Output {
+            status,
+            stdout: _,
+            stderr,
+        } = &output;
+        log::debug!("{self} returned {:?}", status.code());
+        ensure!(
+            status.success(),
+            "{self} returned {:?}; full output: {output:#?}",
+            status.code(),
+        );
+        assert!(stderr.is_empty());
+        Ok(output.stdout)
+    }
+
+    pub(crate) fn just_stdout_utf8(&mut self) -> miette::Result<String> {
+        String::from_utf8(self.just_stdout()?)
+            .into_diagnostic()
+            .wrap_err_with(|| format!("output of {self} was not UTF-8 (!?)"))
+    }
+}
+
+impl Display for EasyCommand {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self { inner } = self;
+        let prog = inner.get_program().to_string_lossy();
+        let args = inner.get_args().map(|a| a.to_string_lossy());
+        let shell_words = ::shell_words::join(once(prog).chain(args));
+        write!(f, "`{shell_words}`")
+    }
+}