Add KeyContextView (#19872)

Release Notes:

- Added `cmd-shift-p debug: Open Key Context View` to help debug custom
key bindings



https://github.com/user-attachments/assets/de273c97-5b27-45aa-9ff1-f943b0ed7dfe

crates/gpui/src/keymap/binding.rs

@@ -69,6 +69,11 @@ impl KeyBinding {
     pub fn action(&self) -> &dyn Action {
         self.action.as_ref()
     }
+
+    /// Get the predicate used to match this binding
+    pub fn predicate(&self) -> Option<&KeyBindingContextPredicate> {
+        self.context_predicate.as_ref()
+    }
 }
 
 impl std::fmt::Debug for KeyBinding {

crates/gpui/src/keymap/context.rs

@@ -11,9 +11,12 @@ use std::fmt;
 pub struct KeyContext(SmallVec<[ContextEntry; 1]>);
 
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
-struct ContextEntry {
-    key: SharedString,
-    value: Option<SharedString>,
+/// An entry in a KeyContext
+pub struct ContextEntry {
+    /// The key (or name if no value)
+    pub key: SharedString,
+    /// The value
+    pub value: Option<SharedString>,
 }
 
 impl<'a> TryFrom<&'a str> for KeyContext {
@@ -39,6 +42,17 @@ impl KeyContext {
         context
     }
 
+    /// Returns the primary context entry (usually the name of the component)
+    pub fn primary(&self) -> Option<&ContextEntry> {
+        self.0.iter().find(|p| p.value.is_none())
+    }
+
+    /// Returns everything except the primary context entry.
+    pub fn secondary(&self) -> impl Iterator<Item = &ContextEntry> {
+        let primary = self.primary();
+        self.0.iter().filter(move |&p| Some(p) != primary)
+    }
+
     /// Parse a key context from a string.
     /// The key context format is very simple:
     /// - either a single identifier, such as `StatusBar`
@@ -178,6 +192,20 @@ pub enum KeyBindingContextPredicate {
     ),
 }
 
+impl fmt::Display for KeyBindingContextPredicate {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Identifier(name) => write!(f, "{}", name),
+            Self::Equal(left, right) => write!(f, "{} == {}", left, right),
+            Self::NotEqual(left, right) => write!(f, "{} != {}", left, right),
+            Self::Not(pred) => write!(f, "!{}", pred),
+            Self::Child(parent, child) => write!(f, "{} > {}", parent, child),
+            Self::And(left, right) => write!(f, "({} && {})", left, right),
+            Self::Or(left, right) => write!(f, "({} || {})", left, right),
+        }
+    }
+}
+
 impl KeyBindingContextPredicate {
     /// Parse a string in the same format as the keymap's context field.
     ///