Warn on Unhandled commands

CHANGELOG.md

@@ -20,6 +20,8 @@ You can find its changes [documented below](#070---2021-01-01).
 
 ### Changed
 
+- Warn on unhandled Commands ([#1533] by [@Maan2003])
+
 ### Deprecated
 
 ### Removed
@@ -603,6 +605,7 @@ Last release without a changelog :(
 [#1523]: https://github.com/linebender/druid/pull/1523
 [#1526]: https://github.com/linebender/druid/pull/1526
 [#1532]: https://github.com/linebender/druid/pull/1532
+[#1533]: https://github.com/linebender/druid/pull/1533
 [#1534]: https://github.com/linebender/druid/pull/1534
 [#1254]: https://github.com/linebender/druid/pull/1254
 

druid/src/command.rs

@@ -25,7 +25,18 @@ use crate::{WidgetId, WindowId};
 /// The identity of a [`Selector`].
 ///
 /// [`Selector`]: struct.Selector.html
-pub(crate) type SelectorSymbol = &'static str;
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub(crate) struct SelectorSymbol {
+    str: &'static str,
+    must_use: bool,
+}
+
+impl std::fmt::Debug for SelectorSymbol {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let must_use = if self.must_use { " (must_use)" } else { "" };
+        write!(f, "{}{}", self.str, must_use)
+    }
+}
 
 /// An identifier for a particular command.
 ///
@@ -329,8 +340,25 @@ impl Selector<()> {
 
 impl<T> Selector<T> {
     /// Create a new `Selector` with the given string.
-    pub const fn new(s: &'static str) -> Selector<T> {
-        Selector(s, PhantomData)
+    pub const fn new(str: &'static str) -> Selector<T> {
+        Selector(
+            SelectorSymbol {
+                str,
+                must_use: false,
+            },
+            PhantomData,
+        )
+    }
+
+    /// Create a `Selector` that must be used.
+    pub const fn must_use(str: &'static str) -> Selector<T> {
+        Selector(
+            SelectorSymbol {
+                str,
+                must_use: true,
+            },
+            PhantomData,
+        )
     }
 
     /// Returns the `SelectorSymbol` identifying this `Selector`.
@@ -384,6 +412,11 @@ impl Command {
         .default_to(Target::Global)
     }
 
+    /// Checks if this command must be used.
+    pub fn must_be_used(&self) -> bool {
+        self.symbol.must_use
+    }
+
     /// A helper method for creating a `Notification` from a `Command`.
     ///
     /// This is slightly icky; it lets us do `SOME_SELECTOR.with(SOME_PAYLOAD)`
@@ -408,6 +441,14 @@ impl Command {
         self
     }
 
+    /// Make the `Command` must use.
+    ///
+    /// this will log warning if this `Command` is not handled.
+    pub fn must_use(mut self, must_use: bool) -> Self {
+        self.symbol.must_use = must_use;
+        self
+    }
+
     /// Set the correct default target when target is `Auto`.
     pub(crate) fn default_to(mut self, target: Target) -> Self {
         self.target.default(target);
@@ -446,7 +487,7 @@ impl Command {
         if self.symbol == selector.symbol() {
             Some(self.payload.downcast_ref().unwrap_or_else(|| {
                 panic!(
-                    "The selector \"{}\" exists twice with different types. See druid::Command::get for more information",
+                    "The selector {:?} exists twice with different types. See druid::Command::get for more information",
                     selector.symbol()
                 );
             }))
@@ -472,7 +513,7 @@ impl Command {
     pub fn get_unchecked<T: Any>(&self, selector: Selector<T>) -> &T {
         self.get(selector).unwrap_or_else(|| {
             panic!(
-                "Expected selector \"{}\" but the command was \"{}\".",
+                "Expected selector {:?} but the command was {:?}.",
                 selector.symbol(),
                 self.symbol
             )
@@ -499,7 +540,7 @@ impl Notification {
         if self.symbol == selector.symbol() {
             Some(self.payload.downcast_ref().unwrap_or_else(|| {
                 panic!(
-                    "The selector \"{}\" exists twice with different types. \
+                    "The selector {:?} exists twice with different types. \
                     See druid::Command::get for more information",
                     selector.symbol()
                 );
@@ -541,7 +582,7 @@ impl From<Selector> for Command {
 
 impl<T> std::fmt::Display for Selector<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        write!(f, "Selector(\"{}\", {})", self.0, any::type_name::<T>())
+        write!(f, "Selector({:?}, {})", self.0, any::type_name::<T>())
     }
 }
 
@@ -591,7 +632,7 @@ impl std::fmt::Debug for Notification {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         write!(
             f,
-            "Notification: Selector {} from {:?}",
+            "Notification: Selector {:?} from {:?}",
             self.symbol, self.source
         )
     }

druid/src/win_handler.rs

@@ -643,7 +643,10 @@ impl<T: Data> AppState<T> {
                 log::warn!("SHOW_WINDOW command must target a window.")
             }
             _ => {
-                self.inner.borrow_mut().dispatch_cmd(cmd);
+                let handled = self.inner.borrow_mut().dispatch_cmd(cmd.clone());
+                if !handled.is_handled() && cmd.must_be_used() {
+                    log::warn!("{:?} was not handled.", cmd);
+                }
             }
         }
     }