Support resource maps in component::bindgen! (#7069)

* Support resource maps in `component::bindgen!`

This commit adds support to `component::bindgen!` to specify resource
types using the `with` key of the macro. This can be used to configure
the `T` of `Resource<T>` to use a preexisting type rather than
unconditionally generating a new empty enum to have a fresh type.

* Reenable tests

crates/component-macro/tests/codegen.rs

@@ -24,3 +24,85 @@ macro_rules! gentest {
 }
 
 component_macro_test_helpers::foreach!(gentest);
+
+mod with_key_and_resources {
+    use anyhow::Result;
+    use wasmtime::component::Resource;
+
+    wasmtime::component::bindgen!({
+        inline: "
+            package demo:pkg
+
+            interface bar {
+                resource a
+                resource b
+            }
+
+            world foo {
+                resource a
+                resource b
+
+                import foo: interface {
+                    resource a
+                    resource b
+                }
+
+                import bar
+            }
+        ",
+        with: {
+            "a": MyA,
+            "b": MyA,
+            "foo/a": MyA,
+            "foo/b": MyA,
+            "demo:pkg/bar/a": MyA,
+            "demo:pkg/bar/b": MyA,
+        },
+    });
+
+    pub struct MyA;
+
+    struct MyComponent;
+
+    impl FooImports for MyComponent {}
+
+    impl HostA for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+
+    impl HostB for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+
+    impl foo::Host for MyComponent {}
+
+    impl foo::HostA for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+
+    impl foo::HostB for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+
+    impl demo::pkg::bar::Host for MyComponent {}
+
+    impl demo::pkg::bar::HostA for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+
+    impl demo::pkg::bar::HostB for MyComponent {
+        fn drop(&mut self, _: Resource<MyA>) -> Result<()> {
+            loop {}
+        }
+    }
+}

crates/wasmtime/src/component/mod.rs

@@ -326,16 +326,20 @@ pub(crate) use self::store::ComponentStoreData;
 ///     // Restrict the code generated to what's needed for the interface
 ///     // imports in the inlined WIT document fragment.
 ///     interfaces: "
-///         import package.foo
+///         import wasi:cli/command
 ///     ",
 ///
-///     // Remap interface names to module names, imported from elsewhere.
-///     // Using this option will prevent any code from being generated
-///     // for the names mentioned in the mapping, assuming instead that the
-///     // names mentioned come from a previous use of the `bindgen!` macro
-///     // with `only_interfaces: true`.
+///     // Remap imported interfaces or resources to types defined in Rust
+///     // elsewhere. Using this option will prevent any code from being
+///     // generated for interfaces mentioned here. Resources named here will
+///     // not have a type generated to represent the resource.
+///     //
+///     // Interfaces mapped with this option should be previously generated
+///     // with an invocation of this macro. Resources need to be mapped to a
+///     // Rust type name.
 ///     with: {
-///         "a": somewhere::else::a,
+///         "wasi:random/random": some::other::wasi::random::random,
+///         "wasi:filesystem/types/descriptor": MyDescriptorType,
 ///     },
 /// });
 /// ```

crates/wit-bindgen/src/lib.rs

@@ -912,16 +912,28 @@ impl<'a> InterfaceGenerator<'a> {
         self.assert_type(id, &name);
     }
 
-    fn type_resource(&mut self, id: TypeId, _name: &str, resource: &TypeDef, docs: &Docs) {
-        let camel = resource
-            .name
-            .as_ref()
-            .expect("resources are required to be named")
-            .to_upper_camel_case();
+    fn type_resource(&mut self, id: TypeId, name: &str, resource: &TypeDef, docs: &Docs) {
+        let camel = name.to_upper_camel_case();
 
         if self.types_imported() {
             self.rustdoc(docs);
-            uwriteln!(self.src, "pub enum {camel} {{}}");
+
+            let with_key = match self.current_interface {
+                Some((_, key, _)) => format!("{}/{name}", self.resolve.name_world_key(key)),
+                None => name.to_string(),
+            };
+            match self.gen.opts.with.get(&with_key) {
+                Some(path) => {
+                    uwriteln!(
+                        self.src,
+                        "pub use {}{path} as {camel};",
+                        self.path_to_root()
+                    );
+                }
+                None => {
+                    uwriteln!(self.src, "pub enum {camel} {{}}");
+                }
+            }
 
             if self.gen.opts.async_.maybe_async() {
                 uwriteln!(self.src, "#[wasmtime::component::__internal::async_trait]")
@@ -1913,6 +1925,24 @@ impl<'a> InterfaceGenerator<'a> {
             self.push_str("\n");
         }
     }
+
+    fn path_to_root(&self) -> String {
+        let mut path_to_root = String::new();
+        if let Some((_, key, is_export)) = self.current_interface {
+            match key {
+                WorldKey::Name(_) => {
+                    path_to_root.push_str("super::");
+                }
+                WorldKey::Interface(_) => {
+                    path_to_root.push_str("super::super::super::");
+                }
+            }
+            if is_export {
+                path_to_root.push_str("super::");
+            }
+        }
+        path_to_root
+    }
 }
 
 impl<'a> RustGenerator<'a> for InterfaceGenerator<'a> {
@@ -1925,23 +1955,12 @@ impl<'a> RustGenerator<'a> for InterfaceGenerator<'a> {
     }
 
     fn path_to_interface(&self, interface: InterfaceId) -> Option<String> {
-        let mut path_to_root = String::new();
-        if let Some((cur, key, is_export)) = self.current_interface {
+        if let Some((cur, _, _)) = self.current_interface {
             if cur == interface {
                 return None;
             }
-            match key {
-                WorldKey::Name(_) => {
-                    path_to_root.push_str("super::");
-                }
-                WorldKey::Interface(_) => {
-                    path_to_root.push_str("super::super::super::");
-                }
-            }
-            if is_export {
-                path_to_root.push_str("super::");
-            }
         }
+        let mut path_to_root = self.path_to_root();
         let InterfaceName { path, .. } = &self.gen.interface_names[&interface];
         path_to_root.push_str(path);
         Some(path_to_root)