2 files changed, 106 insertions, 0 deletions
diff --git a/third_party/rust/clap/src/parse/features/mod.rs b/third_party/rust/clap/src/parse/features/mod.rs
new file mode 100644
index 0000000000..bdeb766ecd
--- /dev/null
+++ b/third_party/rust/clap/src/parse/features/mod.rs
@@ -0,0 +1 @@
+pub(crate) mod suggestions;
diff --git a/third_party/rust/clap/src/parse/features/suggestions.rs b/third_party/rust/clap/src/parse/features/suggestions.rs
new file mode 100644
index 0000000000..77ba8c7a25
--- /dev/null
+++ b/third_party/rust/clap/src/parse/features/suggestions.rs
@@ -0,0 +1,105 @@
+#[cfg(feature = "suggestions")]
+use std::cmp::Ordering;
+
+// Internal
+use crate::build::Command;
+
+/// Produces multiple strings from a given list of possible values which are similar
+/// to the passed in value `v` within a certain confidence by least confidence.
+/// Thus in a list of possible values like ["foo", "bar"], the value "fop" will yield
+/// `Some("foo")`, whereas "blark" would yield `None`.
+#[cfg(feature = "suggestions")]
+pub(crate) fn did_you_mean<T, I>(v: &str, possible_values: I) -> Vec<String>
+where
+    T: AsRef<str>,
+    I: IntoIterator<Item = T>,
+{
+    let mut candidates: Vec<(f64, String)> = possible_values
+        .into_iter()
+        .map(|pv| (strsim::jaro_winkler(v, pv.as_ref()), pv.as_ref().to_owned()))
+        .filter(|(confidence, _)| *confidence > 0.8)
+        .collect();
+    candidates.sort_by(|a, b| a.0.partial_cmp(&b.0).unwrap_or(Ordering::Equal));
+    candidates.into_iter().map(|(_, pv)| pv).collect()
+}
+
+#[cfg(not(feature = "suggestions"))]
+pub(crate) fn did_you_mean<T, I>(_: &str, _: I) -> Vec<String>
+where
+    T: AsRef<str>,
+    I: IntoIterator<Item = T>,
+{
+    Vec::new()
+}
+
+/// Returns a suffix that can be empty, or is the standard 'did you mean' phrase
+pub(crate) fn did_you_mean_flag<'a, 'help, I, T>(
+    arg: &str,
+    remaining_args: &[&str],
+    longs: I,
+    subcommands: impl IntoIterator<Item = &'a mut Command<'help>>,
+) -> Option<(String, Option<String>)>
+where
+    'help: 'a,
+    T: AsRef<str>,
+    I: IntoIterator<Item = T>,
+{
+    use crate::mkeymap::KeyType;
+
+    match did_you_mean(arg, longs).pop() {
+        Some(candidate) => Some((candidate, None)),
+        None => subcommands
+            .into_iter()
+            .filter_map(|subcommand| {
+                subcommand._build_self();
+
+                let longs = subcommand.get_keymap().keys().filter_map(|a| {
+                    if let KeyType::Long(v) = a {
+                        Some(v.to_string_lossy().into_owned())
+                    } else {
+                        None
+                    }
+                });
+
+                let subcommand_name = subcommand.get_name();
+
+                let candidate = did_you_mean(arg, longs).pop()?;
+                let score = remaining_args.iter().position(|x| *x == subcommand_name)?;
+                Some((score, (candidate, Some(subcommand_name.to_string()))))
+            })
+            .min_by_key(|(x, _)| *x)
+            .map(|(_, suggestion)| suggestion),
+    }
+}
+
+#[cfg(all(test, features = "suggestions"))]
+mod test {
+    use super::*;
+
+    #[test]
+    fn possible_values_match() {
+        let p_vals = ["test", "possible", "values"];
+        assert_eq!(did_you_mean("tst", p_vals.iter()), Some("test"));
+    }
+
+    #[test]
+    fn possible_values_match() {
+        let p_vals = ["test", "temp"];
+        assert_eq!(did_you_mean("te", p_vals.iter()), Some("test"));
+    }
+
+    #[test]
+    fn possible_values_nomatch() {
+        let p_vals = ["test", "possible", "values"];
+        assert!(did_you_mean("hahaahahah", p_vals.iter()).is_none());
+    }
+
+    #[test]
+    fn flag() {
+        let p_vals = ["test", "possible", "values"];
+        assert_eq!(
+            did_you_mean_flag("tst", p_vals.iter(), []),
+            Some(("test", None))
+        );
+    }
+}