From 6ade74128cdbfe290df2040144f26575a2034e61 Mon Sep 17 00:00:00 2001
From: Tony Arcieri <tony@iqlusion.io>
Date: Fri, 28 Jun 2019 20:11:25 -0700
Subject: [PATCH] component: impl PartialOrd for Box<dyn Component>

A pattern that may prove useful for `dyn Component` generally...
---
 src/component.rs          | 30 +++++++++++++++++++++++++++++-
 src/component/registry.rs | 16 +++-------------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/src/component.rs b/src/component.rs
index c896cdcd..9ea9e689 100644
--- a/src/component.rs
+++ b/src/component.rs
@@ -7,7 +7,7 @@ mod registry;
 
 pub use self::{name::Name, registry::Registry};
 use crate::{application::Application, error::FrameworkError, shutdown::Shutdown, Version};
-use std::{fmt::Debug, slice::Iter};
+use std::{cmp::Ordering, fmt::Debug, slice::Iter};
 
 /// Application components.
 ///
@@ -47,3 +47,31 @@ where
         Ok(())
     }
 }
+
+impl<A> PartialEq for Box<dyn Component<A>>
+where
+    A: Application,
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.name() == other.name()
+    }
+}
+
+impl<A> PartialOrd for Box<dyn Component<A>>
+where
+    A: Application,
+{
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if other.dependencies().any(|dep| *dep == self.name()) {
+            if self.dependencies().any(|dep| *dep == other.name()) {
+                None
+            } else {
+                Some(Ordering::Greater)
+            }
+        } else if self.dependencies().any(|dep| *dep == other.name()) {
+            Some(Ordering::Less)
+        } else {
+            Some(Ordering::Equal)
+        }
+    }
+}
diff --git a/src/component/registry.rs b/src/component/registry.rs
index a7e3075c..2274de5b 100644
--- a/src/component/registry.rs
+++ b/src/component/registry.rs
@@ -6,7 +6,7 @@ use crate::{
     error::{FrameworkError, FrameworkErrorKind::ComponentError},
     shutdown::Shutdown,
 };
-use std::{borrow::Borrow, cmp::Ordering, collections::HashSet, slice};
+use std::{borrow::Borrow, collections::HashSet, slice};
 
 /// The component registry provides a system for runtime registration of
 /// application components which can interact with each other dynamically.
@@ -86,20 +86,10 @@ where
     /// on others after their dependencies.
     ///
     /// Exits the application if the ordering cannot be resolved.
-    // TODO(tarcieri): impl `PartialOrd` on `Component`
     fn sort(&mut self) {
         self.components.sort_by(|a, b| {
-            if b.dependencies().any(|dep| *dep == a.name()) {
-                if a.dependencies().any(|dep| *dep == b.name()) {
-                    application::exit::bad_component_order(a.borrow(), b.borrow());
-                } else {
-                    Ordering::Greater
-                }
-            } else if a.dependencies().any(|dep| *dep == b.name()) {
-                Ordering::Less
-            } else {
-                Ordering::Equal
-            }
+            a.partial_cmp(b)
+                .unwrap_or_else(|| application::exit::bad_component_order(a.borrow(), b.borrow()))
         })
     }
 }