From 840b980dcb96a11daeb27a6f70bcc44fd136c3a3 Mon Sep 17 00:00:00 2001
From: Jarrod Davis <developer@jarrodldavis.com>
Date: Wed, 16 Mar 2022 22:32:39 -0600
Subject: [PATCH] Add "impl bridges" to `Component` derive macro

---
 core/tests/component.rs | 40 +++++++++++++++++++++++++++++--
 derive/src/component.rs | 52 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 86 insertions(+), 6 deletions(-)

diff --git a/core/tests/component.rs b/core/tests/component.rs
index 79ddcccf..aacbd5ad 100644
--- a/core/tests/component.rs
+++ b/core/tests/component.rs
@@ -3,7 +3,10 @@
 mod example_app;
 
 use self::example_app::{ExampleApp, ExampleConfig};
-use abscissa_core::{component, Component, FrameworkError, FrameworkErrorKind::ComponentError};
+use abscissa_core::{
+    component, Application, Component, FrameworkError, FrameworkErrorKind::ComponentError, Shutdown,
+};
+use std::sync::atomic::{AtomicBool, Ordering};
 
 /// ID for `FoobarComponent` (example component #1)
 const FOOBAR_COMPONENT_ID: component::Id = component::Id::new("component::FoobarComponent");
@@ -30,7 +33,23 @@ impl FoobarComponent {
 
 /// Example component #2
 #[derive(Component, Debug, Default)]
-pub struct BazComponent {}
+#[component(after_config, before_shutdown)]
+pub struct BazComponent {
+    pub after_config_run: bool,
+    pub before_shutdown_run: AtomicBool,
+}
+
+impl BazComponent {
+    fn after_config<A: Application>(&mut self, _config: &A::Cfg) -> Result<(), FrameworkError> {
+        self.after_config_run = true;
+        Ok(())
+    }
+
+    fn before_shutdown(&self, _kind: Shutdown) -> Result<(), FrameworkError> {
+        self.before_shutdown_run.store(true, Ordering::Relaxed);
+        Ok(())
+    }
+}
 
 /// Example component #3
 #[derive(Component, Debug, Default)]
@@ -148,3 +167,20 @@ fn dependency_injection() {
     let quux = registry.get_downcast_ref::<QuuxComponent>().unwrap();
     assert_eq!(quux.foobar_state.as_ref().unwrap(), "original foobar state");
 }
+
+#[test]
+fn impl_bridges() {
+    let mut registry = component::Registry::default();
+    let components = init_components();
+
+    registry.register(components).unwrap();
+    registry.after_config(&ExampleConfig::default()).unwrap();
+
+    let baz = registry.get_downcast_ref::<BazComponent>().unwrap();
+    assert!(baz.after_config_run);
+
+    registry
+        .shutdown(&ExampleApp::default(), Shutdown::Graceful)
+        .unwrap();
+    assert!(baz.before_shutdown_run.load(Ordering::Relaxed));
+}
diff --git a/derive/src/component.rs b/derive/src/component.rs
index da1deaa6..a170202d 100644
--- a/derive/src/component.rs
+++ b/derive/src/component.rs
@@ -10,6 +10,8 @@ pub fn derive_component(s: Structure<'_>) -> TokenStream {
     let attrs = ComponentAttributes::from_derive_input(s.ast());
     let name = &s.ast().ident;
     let abscissa_core = attrs.abscissa_core_crate();
+    let after_config = attrs.after_config();
+    let before_shutdown = attrs.before_shutdown();
     let dependency_methods = attrs.dependency_methods();
 
     s.gen_impl(quote! {
@@ -29,6 +31,10 @@ pub fn derive_component(s: Structure<'_>) -> TokenStream {
             }
 
             #dependency_methods
+
+            #after_config
+
+            #before_shutdown
         }
     })
 }
@@ -36,6 +42,10 @@ pub fn derive_component(s: Structure<'_>) -> TokenStream {
 /// Parsed `#[component(...)]` attribute fields
 #[derive(Debug)]
 struct ComponentAttributes {
+    after_config: bool,
+
+    before_shutdown: bool,
+
     /// Special attribute used by `abscissa_core` to `derive(Component)`.
     ///
     /// Workaround for using custom derive on traits defined in the same crate:
@@ -49,6 +59,8 @@ struct ComponentAttributes {
 impl ComponentAttributes {
     /// Parse component attributes from custom derive input.
     pub fn from_derive_input(input: &DeriveInput) -> Self {
+        let mut after_config = false;
+        let mut before_shutdown = false;
         let mut core = false;
         let mut inject = Vec::new();
 
@@ -61,9 +73,12 @@ impl ComponentAttributes {
                 Meta::List(MetaList { nested, .. }) => {
                     for meta in &nested {
                         match meta {
-                            NestedMeta::Meta(Meta::Path(path)) if path.is_ident("core") => {
-                                core = true
-                            }
+                            NestedMeta::Meta(Meta::Path(path)) => match path.get_ident() {
+                                Some(id) if id == "after_config" => after_config = true,
+                                Some(id) if id == "before_shutdown" => before_shutdown = true,
+                                Some(id) if id == "core" => core = true,
+                                _ => panic!("malformed `component` attribute: {:?}", meta),
+                            },
                             NestedMeta::Meta(Meta::NameValue { .. }) => {
                                 inject.push(InjectAttribute::from_nested_meta(meta))
                             }
@@ -75,7 +90,12 @@ impl ComponentAttributes {
             };
         }
 
-        Self { core, inject }
+        Self {
+            after_config,
+            before_shutdown,
+            core,
+            inject,
+        }
     }
 
     /// Ident for the `abscissa_core` crate.
@@ -88,6 +108,30 @@ impl ComponentAttributes {
         Ident::new(crate_name, Span::call_site())
     }
 
+    pub fn after_config(&self) -> TokenStream {
+        if !self.after_config {
+            return quote!();
+        }
+
+        quote! {
+            fn after_config(&mut self, config: &A::Cfg) -> Result<(), FrameworkError> {
+                self.after_config::<A>(config)
+            }
+        }
+    }
+
+    pub fn before_shutdown(&self) -> TokenStream {
+        if !self.before_shutdown {
+            return quote!();
+        }
+
+        quote! {
+            fn before_shutdown(&self, kind: Shutdown) -> Result<(), FrameworkError> {
+                self.before_shutdown(kind)
+            }
+        }
+    }
+
     /// Generate `Component::dependencies()` and `register_dependencies()`
     pub fn dependency_methods(&self) -> TokenStream {
         if self.inject.is_empty() {