feat(complete): Add dynamic-support shell enum

clap_complete/src/dynamic/mod.rs

@@ -1,6 +1,8 @@
 //! Complete commands within shells
 
-pub mod bash;
 mod completer;
 
+pub mod bash;
+pub mod shells;
+
 pub use completer::*;

clap_complete/src/dynamic/shells/mod.rs

@@ -0,0 +1,5 @@
+//! Shell support
+
+mod shell;
+
+pub use shell::*;

clap_complete/src/dynamic/shells/shell.rs

@@ -0,0 +1,48 @@
+use std::fmt::Display;
+use std::str::FromStr;
+
+use clap::builder::PossibleValue;
+use clap::ValueEnum;
+
+/// Shell with auto-generated completion script available.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[non_exhaustive]
+pub enum Shell {
+    /// Bourne Again SHell (bash)
+    Bash,
+}
+
+impl Display for Shell {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.to_possible_value()
+            .expect("no values are skipped")
+            .get_name()
+            .fmt(f)
+    }
+}
+
+impl FromStr for Shell {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        for variant in Self::value_variants() {
+            if variant.to_possible_value().unwrap().matches(s, false) {
+                return Ok(*variant);
+            }
+        }
+        Err(format!("invalid variant: {s}"))
+    }
+}
+
+// Hand-rolled so it can work even when `derive` feature is disabled
+impl ValueEnum for Shell {
+    fn value_variants<'a>() -> &'a [Self] {
+        &[Shell::Bash]
+    }
+
+    fn to_possible_value<'a>(&self) -> Option<PossibleValue> {
+        Some(match self {
+            Shell::Bash => PossibleValue::new("bash"),
+        })
+    }
+}