Merging upstream version 125.0.1.

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

9 files changed, 1135 insertions, 0 deletions

diff --git a/third_party/rust/document-features/.cargo-checksum.json b/third_party/rust/document-features/.cargo-checksum.json
new file mode 100644
index 0000000000..0b9d0b431c
--- /dev/null
+++ b/third_party/rust/document-features/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"CHANGELOG.md":"c1ccf4587ca168b3baa54580469c5dcc776decac0d996d3bb31d2341b47efa11","Cargo.toml":"390d32c2b791a6745c075c474e6d57c65d5f77f0e7190ff8a8c5342fbb40722a","LICENSE-APACHE":"074e6e32c86a4c0ef8b3ed25b721ca23aca83df277cd88106ef7177c354615ff","LICENSE-MIT":"aa893340d14b9844625be6a50ac644169a01b52f0211cbf81b09e1874c8cd81d","README.md":"89a83c4acc6891e5651772fc78a1d6362070774eaa6c5b5d4bfbe9e57a957be9","lib.rs":"2f4ede9d0619d85449891d9055605188db681d57b405e40e529831266e014ee5","rustfmt.toml":"f74204a6f92aa7422a16ecb2ffe2d5bae0f123b778d08b5db1a398a3c9ca4306","tests/self-doc.rs":"24bbda93f3b323c0b7c543c1df3bf45522b8026283103211805f070de66abadc"},"package":"ef5282ad69563b5fc40319526ba27e0e7363d552a896f0297d54f767717f9b95"}
\ No newline at end of file
diff --git a/third_party/rust/document-features/CHANGELOG.md b/third_party/rust/document-features/CHANGELOG.md
new file mode 100644
index 0000000000..f94ee19ead
--- /dev/null
+++ b/third_party/rust/document-features/CHANGELOG.md
@@ -0,0 +1,44 @@
+# Changelog
+
+
+## 0.2.7 - 2023-12-29
+
+* Remove `\n` between features (#17)
+* Don't throw an error when there is no features in Cargo.toml (#20)
+
+## 0.2.7 - 2022-12-21
+
+* Fix parsing of Cargo.toml with multi-line array of array (#16)
+
+## 0.2.6 - 2022-09-24
+
+* Fix parsing of escaped string literal in the macro arguments
+
+## 0.2.5 - 2022-09-17
+
+* Allow customization of the output with the `feature_label=` parameter
+
+## 0.2.4 - 2022-09-14
+
+* Fix dependencies or features written with quotes
+
+## 0.2.3 - 2022-08-15
+
+* Fix parsing of table with `#` within strings (#10)
+
+## 0.2.2 - 2022-07-25
+
+* Fix parsing of dependencies or feature spanning multiple lines (#9)
+
+## 0.2.1 - 2022-02-12
+
+* Fix indentation of multi-lines feature comments (#5)
+
+## 0.2.0 - 2022-02-11
+
+* Added ability to document optional features. (This is a breaking change in the
+  sense that previously ignored comments may now result in errors)
+
+## 0.1.0 - 2022-02-01
+
+Initial release
diff --git a/third_party/rust/document-features/Cargo.toml b/third_party/rust/document-features/Cargo.toml
new file mode 100644
index 0000000000..bae5ff2a3b
--- /dev/null
+++ b/third_party/rust/document-features/Cargo.toml
@@ -0,0 +1,40 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "document-features"
+version = "0.2.8"
+authors = ["Slint Developers <info@slint-ui.com>"]
+description = "Extract documentation for the feature flags from comments in Cargo.toml"
+homepage = "https://slint-ui.com"
+readme = "README.md"
+keywords = [
+    "documentation",
+    "features",
+    "rustdoc",
+    "macro",
+]
+categories = ["development-tools"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/slint-ui/document-features"
+
+[lib]
+path = "lib.rs"
+proc-macro = true
+
+[dependencies.litrs]
+version = "0.4.1"
+default-features = false
+
+[features]
+default = []
+self-test = []
diff --git a/third_party/rust/document-features/LICENSE-APACHE b/third_party/rust/document-features/LICENSE-APACHE
new file mode 100644
index 0000000000..137069b823
--- /dev/null
+++ b/third_party/rust/document-features/LICENSE-APACHE
@@ -0,0 +1,73 @@
+Apache License
+Version 2.0, January 2004
+http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
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+you may not use this file except in compliance with the License.
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+Unless required by applicable law or agreed to in writing, software
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+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/third_party/rust/document-features/LICENSE-MIT b/third_party/rust/document-features/LICENSE-MIT
new file mode 100644
index 0000000000..13a82b270c
--- /dev/null
+++ b/third_party/rust/document-features/LICENSE-MIT
@@ -0,0 +1,19 @@
+Copyright (c) 2020 Olivier Goffart <ogoffart@sixtyfps.io>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/third_party/rust/document-features/README.md b/third_party/rust/document-features/README.md
new file mode 100644
index 0000000000..81fccc0f44
--- /dev/null
+++ b/third_party/rust/document-features/README.md
@@ -0,0 +1,43 @@
+# Document your crate's feature flags
+
+[![Crates.io](https://img.shields.io/crates/v/document-features)](https://crates.io/crates/document-features)
+[![Documentation](https://docs.rs/document-features/badge.svg)](https://docs.rs/document-features/)
+
+This crate provides a macro that extracts documentation comments from Cargo.toml
+
+To use this crate, add `#![doc = document_features::document_features!()]` in your crate documentation.
+The `document_features!()` macro reads your `Cargo.toml` file, extracts feature comments and generates
+a markdown string for your documentation.
+
+Use `## ` and `#! ` comments in your Cargo.toml to document features, for example:
+
+```toml
+[dependencies]
+document-features = "0.2"
+## ...
+
+[features]
+## The foo feature enables the `foo` functions
+foo = []
+## The bar feature enables the [`bar`] module
+bar = []
+
+#! ### Experimental features
+#! The following features are experimental
+
+## Activate the fusion reactor
+fusion = []
+```
+
+These comments keep the feature definition and documentation next to each other, and they are then
+rendered into your crate documentation.
+
+Check out the [documentation](https://docs.rs/document-features/) for more details.
+
+## Contributions
+
+Contributions are welcome. We accept pull requests and bug reports.
+
+## License
+
+MIT OR Apache-2.0
diff --git a/third_party/rust/document-features/lib.rs b/third_party/rust/document-features/lib.rs
new file mode 100644
index 0000000000..b30ebe7f42
--- /dev/null
+++ b/third_party/rust/document-features/lib.rs
@@ -0,0 +1,877 @@
+// Copyright © SixtyFPS GmbH <info@sixtyfps.io>
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+/*!
+Document your crate's feature flags.
+
+This crates provides a macro that extracts "documentation" comments from Cargo.toml
+
+To use this crate, add `#![doc = document_features::document_features!()]` in your crate documentation.
+The `document_features!()` macro reads your `Cargo.toml` file, extracts feature comments and generates
+a markdown string for your documentation.
+
+Basic example:
+
+```rust
+//! Normal crate documentation goes here.
+//!
+//! ## Feature flags
+#![doc = document_features::document_features!()]
+
+// rest of the crate goes here.
+```
+
+## Documentation format:
+
+The documentation of your crate features goes into `Cargo.toml`, where they are defined.
+
+The `document_features!()` macro analyzes the contents of `Cargo.toml`.
+Similar to Rust's documentation comments `///` and `//!`, the macro understands
+comments that start with `## ` and `#! `. Note the required trailing space.
+Lines starting with `###` will not be understood as doc comment.
+
+`## ` comments are meant to be *above* the feature they document.
+There can be several `## ` comments, but they must always be followed by a
+feature name or an optional dependency.
+There should not be `#! ` comments between the comment and the feature they document.
+
+`#! ` comments are not associated with a particular feature, and will be printed
+in where they occur. Use them to group features, for example.
+
+## Examples:
+
+*/
+// Note: because rustdoc escapes the first `#` of a line starting with `#`,
+// these docs comments have one more `#` ,
+#![doc = self_test!(/**
+[package]
+name = "..."
+## ...
+
+[features]
+default = ["foo"]
+##! This comments goes on top
+
+### The foo feature enables the `foo` functions
+foo = []
+
+### The bar feature enables the bar module
+bar = []
+
+##! ### Experimental features
+##! The following features are experimental
+
+### Enable the fusion reactor
+###
+### ⚠️ Can lead to explosions
+fusion = []
+
+[dependencies]
+document-features = "0.2"
+
+##! ### Optional dependencies
+
+### Enable this feature to implement the trait for the types from the genial crate
+genial = { version = "0.2", optional = true }
+
+### This awesome dependency is specified in its own table
+[dependencies.awesome]
+version = "1.3.5"
+optional = true
+*/
+=>
+    /**
+This comments goes on top
+* **`foo`** *(enabled by default)* —  The foo feature enables the `foo` functions
+* **`bar`** —  The bar feature enables the bar module
+
+#### Experimental features
+The following features are experimental
+* **`fusion`** —  Enable the fusion reactor
+
+  ⚠️ Can lead to explosions
+
+#### Optional dependencies
+* **`genial`** —  Enable this feature to implement the trait for the types from the genial crate
+* **`awesome`** —  This awesome dependency is specified in its own table
+*/
+)]
+/*!
+
+## Customization
+
+You can customize the formatting of the features in the generated documentation by setting
+the key **`feature_label=`** to a given format string. This format string must be either
+a [string literal](https://doc.rust-lang.org/reference/tokens.html#string-literals) or
+a [raw string literal](https://doc.rust-lang.org/reference/tokens.html#raw-string-literals).
+Every occurrence of `{feature}` inside the format string will be substituted with the name of the feature.
+
+For instance, to emulate the HTML formatting used by `rustdoc` one can use the following:
+
+```rust
+#![doc = document_features::document_features!(feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#)]
+```
+
+The default formatting is equivalent to:
+
+```rust
+#![doc = document_features::document_features!(feature_label = "**`{feature}`**")]
+```
+
+## Compatibility
+
+The minimum Rust version required to use this crate is Rust 1.54 because of the
+feature to have macro in doc comments. You can make this crate optional and use
+`#[cfg_attr()]` statements to enable it only when building the documentation:
+You need to have two levels of `cfg_attr` because Rust < 1.54 doesn't parse the attribute
+otherwise.
+
+```rust,ignore
+#![cfg_attr(
+    feature = "document-features",
+    cfg_attr(doc, doc = ::document_features::document_features!())
+)]
+```
+
+In your Cargo.toml, enable this feature while generating the documentation on docs.rs:
+
+```toml
+[dependencies]
+document-features = { version = "0.2", optional = true }
+
+[package.metadata.docs.rs]
+features = ["document-features"]
+## Alternative: enable all features so they are all documented
+## all-features = true
+```
+ */
+
+#[cfg(not(feature = "default"))]
+compile_error!(
+    "The feature `default` must be enabled to ensure \
+    forward compatibility with future version of this crate"
+);
+
+extern crate proc_macro;
+
+use proc_macro::{TokenStream, TokenTree};
+use std::borrow::Cow;
+use std::collections::HashSet;
+use std::convert::TryFrom;
+use std::fmt::Write;
+use std::path::Path;
+use std::str::FromStr;
+
+fn error(e: &str) -> TokenStream {
+    TokenStream::from_str(&format!("::core::compile_error!{{\"{}\"}}", e.escape_default())).unwrap()
+}
+
+fn compile_error(msg: &str, tt: Option<TokenTree>) -> TokenStream {
+    let span = tt.as_ref().map_or_else(proc_macro::Span::call_site, TokenTree::span);
+    use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing};
+    use std::iter::FromIterator;
+    TokenStream::from_iter(vec![
+        TokenTree::Ident(Ident::new("compile_error", span)),
+        TokenTree::Punct({
+            let mut punct = Punct::new('!', Spacing::Alone);
+            punct.set_span(span);
+            punct
+        }),
+        TokenTree::Group({
+            let mut group = Group::new(Delimiter::Brace, {
+                TokenStream::from_iter([TokenTree::Literal({
+                    let mut string = Literal::string(msg);
+                    string.set_span(span);
+                    string
+                })])
+            });
+            group.set_span(span);
+            group
+        }),
+    ])
+}
+
+#[derive(Default)]
+struct Args {
+    feature_label: Option<String>,
+}
+
+fn parse_args(input: TokenStream) -> Result<Args, TokenStream> {
+    let mut token_trees = input.into_iter().fuse();
+
+    // parse the key, ensuring that it is the identifier `feature_label`
+    match token_trees.next() {
+        None => return Ok(Args::default()),
+        Some(TokenTree::Ident(ident)) if ident.to_string() == "feature_label" => (),
+        tt => return Err(compile_error("expected `feature_label`", tt)),
+    }
+
+    // parse a single equal sign `=`
+    match token_trees.next() {
+        Some(TokenTree::Punct(p)) if p.as_char() == '=' => (),
+        tt => return Err(compile_error("expected `=`", tt)),
+    }
+
+    // parse the value, ensuring that it is a string literal containing the substring `"{feature}"`
+    let feature_label;
+    if let Some(tt) = token_trees.next() {
+        match litrs::StringLit::<String>::try_from(&tt) {
+            Ok(string_lit) if string_lit.value().contains("{feature}") => {
+                feature_label = string_lit.value().to_string()
+            }
+            _ => {
+                return Err(compile_error(
+                    "expected a string literal containing the substring \"{feature}\"",
+                    Some(tt),
+                ))
+            }
+        }
+    } else {
+        return Err(compile_error(
+            "expected a string literal containing the substring \"{feature}\"",
+            None,
+        ));
+    }
+
+    // ensure there is nothing left after the format string
+    if let tt @ Some(_) = token_trees.next() {
+        return Err(compile_error("unexpected token after the format string", tt));
+    }
+
+    Ok(Args { feature_label: Some(feature_label) })
+}
+
+/// Produce a literal string containing documentation extracted from Cargo.toml
+///
+/// See the [crate] documentation for details
+#[proc_macro]
+pub fn document_features(tokens: TokenStream) -> TokenStream {
+    parse_args(tokens)
+        .and_then(|args| document_features_impl(&args))
+        .unwrap_or_else(std::convert::identity)
+}
+
+fn document_features_impl(args: &Args) -> Result<TokenStream, TokenStream> {
+    let path = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    let mut cargo_toml = std::fs::read_to_string(Path::new(&path).join("Cargo.toml"))
+        .map_err(|e| error(&format!("Can't open Cargo.toml: {:?}", e)))?;
+
+    if !cargo_toml.contains("\n##") && !cargo_toml.contains("\n#!") {
+        // On crates.io, Cargo.toml is usually "normalized" and stripped of all comments.
+        // The original Cargo.toml has been renamed Cargo.toml.orig
+        if let Ok(orig) = std::fs::read_to_string(Path::new(&path).join("Cargo.toml.orig")) {
+            if orig.contains("##") || orig.contains("#!") {
+                cargo_toml = orig;
+            }
+        }
+    }
+
+    let result = process_toml(&cargo_toml, args).map_err(|e| error(&e))?;
+    Ok(std::iter::once(proc_macro::TokenTree::from(proc_macro::Literal::string(&result))).collect())
+}
+
+fn process_toml(cargo_toml: &str, args: &Args) -> Result<String, String> {
+    // Get all lines between the "[features]" and the next block
+    let mut lines = cargo_toml
+        .lines()
+        .map(str::trim)
+        // and skip empty lines and comments that are not docs comments
+        .filter(|l| {
+            !l.is_empty() && (!l.starts_with('#') || l.starts_with("##") || l.starts_with("#!"))
+        });
+    let mut top_comment = String::new();
+    let mut current_comment = String::new();
+    let mut features = vec![];
+    let mut default_features = HashSet::new();
+    let mut current_table = "";
+    while let Some(line) = lines.next() {
+        if let Some(x) = line.strip_prefix("#!") {
+            if !x.is_empty() && !x.starts_with(' ') {
+                continue; // it's not a doc comment
+            }
+            if !current_comment.is_empty() {
+                return Err("Cannot mix ## and #! comments between features.".into());
+            }
+            if top_comment.is_empty() && !features.is_empty() {
+                top_comment = "\n".into();
+            }
+            writeln!(top_comment, "{}", x).unwrap();
+        } else if let Some(x) = line.strip_prefix("##") {
+            if !x.is_empty() && !x.starts_with(' ') {
+                continue; // it's not a doc comment
+            }
+            writeln!(current_comment, " {}", x).unwrap();
+        } else if let Some(table) = line.strip_prefix('[') {
+            current_table = table
+                .split_once(']')
+                .map(|(t, _)| t.trim())
+                .ok_or_else(|| format!("Parse error while parsing line: {}", line))?;
+            if !current_comment.is_empty() {
+                let dep = current_table
+                    .rsplit_once('.')
+                    .and_then(|(table, dep)| table.trim().ends_with("dependencies").then(|| dep))
+                    .ok_or_else(|| format!("Not a feature: `{}`", line))?;
+                features.push((
+                    dep.trim(),
+                    std::mem::take(&mut top_comment),
+                    std::mem::take(&mut current_comment),
+                ));
+            }
+        } else if let Some((dep, rest)) = line.split_once('=') {
+            let dep = dep.trim().trim_matches('"');
+            let rest = get_balanced(rest, &mut lines)
+                .map_err(|e| format!("Parse error while parsing value {}: {}", dep, e))?;
+            if current_table == "features" && dep == "default" {
+                let defaults = rest
+                    .trim()
+                    .strip_prefix('[')
+                    .and_then(|r| r.strip_suffix(']'))
+                    .ok_or_else(|| format!("Parse error while parsing dependency {}", dep))?
+                    .split(',')
+                    .map(|d| d.trim().trim_matches(|c| c == '"' || c == '\'').trim().to_string())
+                    .filter(|d| !d.is_empty());
+                default_features.extend(defaults);
+            }
+            if !current_comment.is_empty() {
+                if current_table.ends_with("dependencies") {
+                    if !rest
+                        .split_once("optional")
+                        .and_then(|(_, r)| r.trim().strip_prefix('='))
+                        .map_or(false, |r| r.trim().starts_with("true"))
+                    {
+                        return Err(format!("Dependency {} is not an optional dependency", dep));
+                    }
+                } else if current_table != "features" {
+                    return Err(format!(
+                        r#"Comment cannot be associated with a feature: "{}""#,
+                        current_comment.trim()
+                    ));
+                }
+                features.push((
+                    dep,
+                    std::mem::take(&mut top_comment),
+                    std::mem::take(&mut current_comment),
+                ));
+            }
+        }
+    }
+    if !current_comment.is_empty() {
+        return Err("Found comment not associated with a feature".into());
+    }
+    if features.is_empty() {
+        return Ok("*No documented features in Cargo.toml*".into());
+    }
+    let mut result = String::new();
+    for (f, top, comment) in features {
+        let default = if default_features.contains(f) { " *(enabled by default)*" } else { "" };
+        if !comment.trim().is_empty() {
+            if let Some(feature_label) = &args.feature_label {
+                writeln!(
+                    result,
+                    "{}* {}{} —{}",
+                    top,
+                    feature_label.replace("{feature}", f),
+                    default,
+                    comment.trim_end(),
+                )
+                .unwrap();
+            } else {
+                writeln!(result, "{}* **`{}`**{} —{}", top, f, default, comment.trim_end())
+                    .unwrap();
+            }
+        } else if let Some(feature_label) = &args.feature_label {
+            writeln!(result, "{}* {}{}", top, feature_label.replace("{feature}", f), default,)
+                .unwrap();
+        } else {
+            writeln!(result, "{}* **`{}`**{}", top, f, default).unwrap();
+        }
+    }
+    result += &top_comment;
+    Ok(result)
+}
+
+fn get_balanced<'a>(
+    first_line: &'a str,
+    lines: &mut impl Iterator<Item = &'a str>,
+) -> Result<Cow<'a, str>, String> {
+    let mut line = first_line;
+    let mut result = Cow::from("");
+
+    let mut in_quote = false;
+    let mut level = 0;
+    loop {
+        let mut last_slash = false;
+        for (idx, b) in line.as_bytes().iter().enumerate() {
+            if last_slash {
+                last_slash = false
+            } else if in_quote {
+                match b {
+                    b'\\' => last_slash = true,
+                    b'"' | b'\'' => in_quote = false,
+                    _ => (),
+                }
+            } else {
+                match b {
+                    b'\\' => last_slash = true,
+                    b'"' => in_quote = true,
+                    b'{' | b'[' => level += 1,
+                    b'}' | b']' if level == 0 => return Err("unbalanced source".into()),
+                    b'}' | b']' => level -= 1,
+                    b'#' => {
+                        line = &line[..idx];
+                        break;
+                    }
+                    _ => (),
+                }
+            }
+        }
+        if result.len() == 0 {
+            result = Cow::from(line);
+        } else {
+            *result.to_mut() += line;
+        }
+        if level == 0 {
+            return Ok(result);
+        }
+        line = if let Some(l) = lines.next() {
+            l
+        } else {
+            return Err("unbalanced source".into());
+        };
+    }
+}
+
+#[test]
+fn test_get_balanced() {
+    assert_eq!(
+        get_balanced(
+            "{",
+            &mut IntoIterator::into_iter(["a", "{ abc[], #ignore", " def }", "}", "xxx"])
+        ),
+        Ok("{a{ abc[],  def }}".into())
+    );
+    assert_eq!(
+        get_balanced("{ foo = \"{#\" } #ignore", &mut IntoIterator::into_iter(["xxx"])),
+        Ok("{ foo = \"{#\" } ".into())
+    );
+    assert_eq!(
+        get_balanced("]", &mut IntoIterator::into_iter(["["])),
+        Err("unbalanced source".into())
+    );
+}
+
+#[cfg(feature = "self-test")]
+#[proc_macro]
+#[doc(hidden)]
+/// Helper macro for the tests. Do not use
+pub fn self_test_helper(input: TokenStream) -> TokenStream {
+    process_toml((&input).to_string().trim_matches(|c| c == '"' || c == '#'), &Args::default())
+        .map_or_else(
+            |e| error(&e),
+            |r| {
+                std::iter::once(proc_macro::TokenTree::from(proc_macro::Literal::string(&r)))
+                    .collect()
+            },
+        )
+}
+
+#[cfg(feature = "self-test")]
+macro_rules! self_test {
+    (#[doc = $toml:literal] => #[doc = $md:literal]) => {
+        concat!(
+            "\n`````rust\n\
+            fn normalize_md(md : &str) -> String {
+               md.lines().skip_while(|l| l.is_empty()).map(|l| l.trim())
+                .collect::<Vec<_>>().join(\"\\n\")
+            }
+            assert_eq!(normalize_md(document_features::self_test_helper!(",
+            stringify!($toml),
+            ")), normalize_md(",
+            stringify!($md),
+            "));\n`````\n\n"
+        )
+    };
+}
+
+#[cfg(not(feature = "self-test"))]
+macro_rules! self_test {
+    (#[doc = $toml:literal] => #[doc = $md:literal]) => {
+        concat!(
+            "This contents in Cargo.toml:\n`````toml",
+            $toml,
+            "\n`````\n Generates the following:\n\
+            <table><tr><th>Preview</th></tr><tr><td>\n\n",
+            $md,
+            "\n</td></tr></table>\n\n&nbsp;\n",
+        )
+    };
+}
+
+// The following struct is inserted only during generation of the documentation in order to exploit doc-tests.
+// These doc-tests are used to check that invalid arguments to the `document_features!` macro cause a compile time error.
+// For a more principled way of testing compilation error, maybe investigate <https://docs.rs/trybuild>.
+//
+/// ```rust
+/// #![doc = document_features::document_features!()]
+/// #![doc = document_features::document_features!(feature_label = "**`{feature}`**")]
+/// #![doc = document_features::document_features!(feature_label = r"**`{feature}`**")]
+/// #![doc = document_features::document_features!(feature_label = r#"**`{feature}`**"#)]
+/// #![doc = document_features::document_features!(feature_label = "<span class=\"stab portability\"><code>{feature}</code></span>")]
+/// #![doc = document_features::document_features!(feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#)]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(feature_label > "<span>{feature}</span>")]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(label = "<span>{feature}</span>")]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(feature_label = "{feat}")]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(feature_label = 3.14)]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(feature_label = )]
+/// ```
+/// ```compile_fail
+/// #![doc = document_features::document_features!(feature_label = "**`{feature}`**" extra)]
+/// ```
+#[cfg(doc)]
+struct FeatureLabelCompilationTest;
+
+#[cfg(test)]
+mod tests {
+    use super::{process_toml, Args};
+
+    #[track_caller]
+    fn test_error(toml: &str, expected: &str) {
+        let err = process_toml(toml, &Args::default()).unwrap_err();
+        assert!(err.contains(expected), "{:?} does not contain {:?}", err, expected)
+    }
+
+    #[test]
+    fn only_get_balanced_in_correct_table() {
+        process_toml(
+            r#"
+
+[package.metadata.release]
+pre-release-replacements = [
+  {test=\"\#\# \"},
+]
+[abcd]
+[features]#xyz
+#! abc
+#
+###
+#! def
+#!
+## 123
+## 456
+feat1 = ["plop"]
+#! ghi
+no_doc = []
+##
+feat2 = ["momo"]
+#! klm
+default = ["feat1", "something_else"]
+#! end
+            "#,
+            &Args::default(),
+        )
+        .unwrap();
+    }
+
+    #[test]
+    fn no_features() {
+        let r = process_toml(
+            r#"
+[features]
+[dependencies]
+foo = 4;
+"#,
+            &Args::default(),
+        )
+        .unwrap();
+        assert_eq!(r, "*No documented features in Cargo.toml*");
+    }
+
+    #[test]
+    fn no_features2() {
+        let r = process_toml(
+            r#"
+[packages]
+[dependencies]
+"#,
+            &Args::default(),
+        )
+        .unwrap();
+        assert_eq!(r, "*No documented features in Cargo.toml*");
+    }
+
+    #[test]
+    fn parse_error3() {
+        test_error(
+            r#"
+[features]
+ff = []
+[abcd
+efgh
+[dependencies]
+"#,
+            "Parse error while parsing line: [abcd",
+        );
+    }
+
+    #[test]
+    fn parse_error4() {
+        test_error(
+            r#"
+[features]
+## dd
+## ff
+#! ee
+## ff
+"#,
+            "Cannot mix",
+        );
+    }
+
+    #[test]
+    fn parse_error5() {
+        test_error(
+            r#"
+[features]
+## dd
+"#,
+            "not associated with a feature",
+        );
+    }
+
+    #[test]
+    fn parse_error6() {
+        test_error(
+            r#"
+[features]
+# ff
+foo = []
+default = [
+#ffff
+# ff
+"#,
+            "Parse error while parsing value default",
+        );
+    }
+
+    #[test]
+    fn parse_error7() {
+        test_error(
+            r#"
+[features]
+# f
+foo = [ x = { ]
+bar = []
+"#,
+            "Parse error while parsing value foo",
+        );
+    }
+
+    #[test]
+    fn not_a_feature1() {
+        test_error(
+            r#"
+## hallo
+[features]
+"#,
+            "Not a feature: `[features]`",
+        );
+    }
+
+    #[test]
+    fn not_a_feature2() {
+        test_error(
+            r#"
+[package]
+## hallo
+foo = []
+"#,
+            "Comment cannot be associated with a feature: \"hallo\"",
+        );
+    }
+
+    #[test]
+    fn non_optional_dep1() {
+        test_error(
+            r#"
+[dev-dependencies]
+## Not optional
+foo = { version = "1.2", optional = false }
+"#,
+            "Dependency foo is not an optional dependency",
+        );
+    }
+
+    #[test]
+    fn non_optional_dep2() {
+        test_error(
+            r#"
+[dev-dependencies]
+## Not optional
+foo = { version = "1.2" }
+"#,
+            "Dependency foo is not an optional dependency",
+        );
+    }
+
+    #[test]
+    fn basic() {
+        let toml = r#"
+[abcd]
+[features]#xyz
+#! abc
+#
+###
+#! def
+#!
+## 123
+## 456
+feat1 = ["plop"]
+#! ghi
+no_doc = []
+##
+feat2 = ["momo"]
+#! klm
+default = ["feat1", "something_else"]
+#! end
+        "#;
+        let parsed = process_toml(toml, &Args::default()).unwrap();
+        assert_eq!(
+            parsed,
+            " abc\n def\n\n* **`feat1`** *(enabled by default)* —  123\n  456\n\n ghi\n* **`feat2`**\n\n klm\n end\n"
+        );
+        let parsed = process_toml(
+            toml,
+            &Args {
+                feature_label: Some(
+                    "<span class=\"stab portability\"><code>{feature}</code></span>".into(),
+                ),
+            },
+        )
+        .unwrap();
+        assert_eq!(
+            parsed,
+            " abc\n def\n\n* <span class=\"stab portability\"><code>feat1</code></span> *(enabled by default)* —  123\n  456\n\n ghi\n* <span class=\"stab portability\"><code>feat2</code></span>\n\n klm\n end\n"
+        );
+    }
+
+    #[test]
+    fn dependencies() {
+        let toml = r#"
+#! top
+[dev-dependencies] #yo
+## dep1
+dep1 = { version="1.2", optional=true}
+#! yo
+dep2 = "1.3"
+## dep3
+[target.'cfg(unix)'.build-dependencies.dep3]
+version = "42"
+optional = true
+        "#;
+        let parsed = process_toml(toml, &Args::default()).unwrap();
+        assert_eq!(parsed, " top\n* **`dep1`** —  dep1\n\n yo\n* **`dep3`** —  dep3\n");
+        let parsed = process_toml(
+            toml,
+            &Args {
+                feature_label: Some(
+                    "<span class=\"stab portability\"><code>{feature}</code></span>".into(),
+                ),
+            },
+        )
+        .unwrap();
+        assert_eq!(parsed, " top\n* <span class=\"stab portability\"><code>dep1</code></span> —  dep1\n\n yo\n* <span class=\"stab portability\"><code>dep3</code></span> —  dep3\n");
+    }
+
+    #[test]
+    fn multi_lines() {
+        let toml = r#"
+[package.metadata.foo]
+ixyz = [
+    ["array"],
+    [
+        "of",
+        "arrays"
+    ]
+]
+[dev-dependencies]
+## dep1
+dep1 = {
+    version="1.2-}",
+    optional=true
+}
+[features]
+default = [
+    "goo",
+    "\"]",
+    "bar",
+]
+## foo
+foo = [
+   "bar"
+]
+## bar
+bar = [
+
+]
+        "#;
+        let parsed = process_toml(toml, &Args::default()).unwrap();
+        assert_eq!(
+            parsed,
+            "* **`dep1`** —  dep1\n* **`foo`** —  foo\n* **`bar`** *(enabled by default)* —  bar\n"
+        );
+        let parsed = process_toml(
+            toml,
+            &Args {
+                feature_label: Some(
+                    "<span class=\"stab portability\"><code>{feature}</code></span>".into(),
+                ),
+            },
+        )
+        .unwrap();
+        assert_eq!(
+            parsed,
+            "* <span class=\"stab portability\"><code>dep1</code></span> —  dep1\n* <span class=\"stab portability\"><code>foo</code></span> —  foo\n* <span class=\"stab portability\"><code>bar</code></span> *(enabled by default)* —  bar\n"
+        );
+    }
+
+    #[test]
+    fn dots_in_feature() {
+        let toml = r#"
+[features]
+## This is a test
+"teßt." = []
+default = ["teßt."]
+[dependencies]
+## A dep
+"dep" = { version = "123", optional = true }
+        "#;
+        let parsed = process_toml(toml, &Args::default()).unwrap();
+        assert_eq!(
+            parsed,
+            "* **`teßt.`** *(enabled by default)* —  This is a test\n* **`dep`** —  A dep\n"
+        );
+        let parsed = process_toml(
+            toml,
+            &Args {
+                feature_label: Some(
+                    "<span class=\"stab portability\"><code>{feature}</code></span>".into(),
+                ),
+            },
+        )
+        .unwrap();
+        assert_eq!(
+            parsed,
+            "* <span class=\"stab portability\"><code>teßt.</code></span> *(enabled by default)* —  This is a test\n* <span class=\"stab portability\"><code>dep</code></span> —  A dep\n"
+        );
+    }
+}
diff --git a/third_party/rust/document-features/rustfmt.toml b/third_party/rust/document-features/rustfmt.toml
new file mode 100644
index 0000000000..2a35f0230c
--- /dev/null
+++ b/third_party/rust/document-features/rustfmt.toml
@@ -0,0 +1 @@
+use_small_heuristics = "Max"
diff --git a/third_party/rust/document-features/tests/self-doc.rs b/third_party/rust/document-features/tests/self-doc.rs
new file mode 100644
index 0000000000..4e27113145
--- /dev/null
+++ b/third_party/rust/document-features/tests/self-doc.rs
@@ -0,0 +1,37 @@
+#[test]
+fn ensure_it_compiles() {
+    document_features::document_features!();
+    document_features::document_features!(feature_label = "**`{feature}`**");
+    document_features::document_features!(feature_label = r"**`{feature}`**");
+    document_features::document_features!(feature_label = r#"**`{feature}`**"#);
+    document_features::document_features!(
+        feature_label = "<span class=\"stab portability\"><code>{feature}</code></span>"
+    );
+    document_features::document_features!(
+        feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#
+    );
+    document_features::document_features!(
+        feature_label = r##"<span class="stab portability"><code>{feature}</code></span>"##
+    );
+}
+
+#[test]
+fn self_doc() {
+    let actual = document_features::document_features!();
+    let expected = "* **`self-test`** —  Internal feature used only for the tests, don't enable\n";
+    assert_eq!(actual, expected);
+}
+
+#[test]
+fn self_doc_with_custom_label() {
+    let actual = document_features::document_features!(
+        feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#
+    );
+    let expected =
+        "* <span class=\"stab portability\"><code>self-test</code></span> —  Internal feature used only for the tests, don't enable\n";
+    assert_eq!(actual, expected);
+    let actual2 = document_features::document_features!(
+        feature_label = "<span class=\"stab\u{0020}portability\"><code>{feature}</code></span>"
+    );
+    assert_eq!(actual2, expected);
+}