explicit packages encoded as nested components

crates/wasm-encoder/src/component/builder.rs

@@ -41,6 +41,10 @@ pub struct ComponentBuilder {
 }
 
 impl ComponentBuilder {
+    /// Adds sub component names
+    pub fn names(&mut self, names: &ComponentNameSection) {
+        self.component.section(names);
+    }
     /// Returns the current number of core modules.
     pub fn core_module_count(&self) -> u32 {
         self.core_modules

crates/wasm-encoder/src/component/names.rs

@@ -16,6 +16,9 @@ enum Subsection {
 }
 
 impl ComponentNameSection {
+    /// Human readable component names
+    pub const SECTION_NAME: &'static str = "component-name";
+
     /// Creates a new blank `name` custom section.
     pub fn new() -> Self {
         Self::default()

crates/wit-component/src/encoding/wit/mod.rs

@@ -48,7 +48,7 @@ pub fn encode_component(
     if use_v2.unwrap_or_else(use_v2_encoding) {
         v2::encode_component(resolve, packages)
     } else {
-        v1::encode_component(resolve, packages)
+        v1::encode_component(resolve, packages[0])
     }
 }
 

crates/wit-component/src/encoding/wit/v1.rs

@@ -24,29 +24,27 @@ use wit_parser::*;
 ///
 /// The binary returned can be [`decode`d](crate::decode) to recover the WIT
 /// package provided.
-pub fn encode_component(resolve: &Resolve, packages: &[PackageId]) -> Result<ComponentBuilder> {
+pub fn encode_component(resolve: &Resolve, package: PackageId) -> Result<ComponentBuilder> {
     let mut encoder = Encoder {
         component: ComponentBuilder::default(),
         resolve,
-        packages,
+        package,
     };
     encoder.run()?;
 
-    for package in packages {
-        let package_metadata = PackageMetadata::extract(resolve, *package);
-        encoder.component.custom_section(&CustomSection {
-            name: PackageMetadata::SECTION_NAME.into(),
-            data: package_metadata.encode()?.into(),
-        });
-    }
+    let package_metadata = PackageMetadata::extract(resolve, package);
+    encoder.component.custom_section(&CustomSection {
+        name: PackageMetadata::SECTION_NAME.into(),
+        data: package_metadata.encode()?.into(),
+    });
 
     Ok(encoder.component)
 }
 
 struct Encoder<'a> {
     component: ComponentBuilder,
     resolve: &'a Resolve,
-    packages: &'a [PackageId],
+    package: PackageId,
 }
 
 impl Encoder<'_> {
@@ -59,69 +57,67 @@ impl Encoder<'_> {
         // decoding process where everyone's view of a foreign document agrees
         // notably on the order that types are defined in to assist with
         // roundtripping.
-        for pkg in self.packages {
-            let mut interfaces = IndexSet::new();
-            for (_, id) in self.resolve.packages[*pkg].interfaces.iter() {
-                self.add_live_interfaces(&mut interfaces, *id);
-            }
+        let mut interfaces = IndexSet::new();
+        for (_, id) in self.resolve.packages[self.package].interfaces.iter() {
+            self.add_live_interfaces(&mut interfaces, *id);
+        }
 
-            // Seed the set of used names with all exported interfaces to ensure
-            // that imported interfaces choose different names as the import names
-            // aren't used during decoding.
-            let mut used_names = IndexSet::new();
-            for id in interfaces.iter() {
-                let iface = &self.resolve.interfaces[*id];
-                if iface.package == Some(*pkg) {
-                    let first = used_names.insert(iface.name.as_ref().unwrap().clone());
-                    assert!(first);
-                }
-            }
-            for (name, _world) in self.resolve.packages[*pkg].worlds.iter() {
-                let first = used_names.insert(name.clone());
+        // Seed the set of used names with all exported interfaces to ensure
+        // that imported interfaces choose different names as the import names
+        // aren't used during decoding.
+        let mut used_names = IndexSet::new();
+        for id in interfaces.iter() {
+            let iface = &self.resolve.interfaces[*id];
+            if iface.package == Some(self.package) {
+                let first = used_names.insert(iface.name.as_ref().unwrap().clone());
                 assert!(first);
             }
+        }
+        for (name, _world) in self.resolve.packages[self.package].worlds.iter() {
+            let first = used_names.insert(name.clone());
+            assert!(first);
+        }
 
-            // Encode all interfaces, foreign and local, into this component type.
-            // Local interfaces get their functions defined as well and are
-            // exported. Foreign interfaces are imported and only have their types
-            // encoded.
-            let mut encoder = InterfaceEncoder::new(self.resolve);
-            for interface in interfaces {
-                encoder.interface = Some(interface);
-                let iface = &self.resolve.interfaces[interface];
-                let name = self.resolve.id_of(interface).unwrap();
-                log::trace!("encoding interface {name}");
-                if iface.package == Some(*pkg) {
-                    let idx = encoder.encode_instance(interface)?;
-                    encoder.outer.export(&name, ComponentTypeRef::Instance(idx));
-                } else {
-                    encoder.push_instance();
-                    for (_, id) in iface.types.iter() {
-                        encoder.encode_valtype(self.resolve, &Type::Id(*id))?;
-                    }
-                    let instance = encoder.pop_instance();
-                    let idx = encoder.outer.type_count();
-                    encoder.outer.ty().instance(&instance);
-                    encoder.import_map.insert(interface, encoder.instances);
-                    encoder.instances += 1;
-                    encoder.outer.import(&name, ComponentTypeRef::Instance(idx));
+        // Encode all interfaces, foreign and local, into this component type.
+        // Local interfaces get their functions defined as well and are
+        // exported. Foreign interfaces are imported and only have their types
+        // encoded.
+        let mut encoder = InterfaceEncoder::new(self.resolve);
+        for interface in interfaces {
+            encoder.interface = Some(interface);
+            let iface = &self.resolve.interfaces[interface];
+            let name = self.resolve.id_of(interface).unwrap();
+            log::trace!("encoding interface {name}");
+            if iface.package == Some(self.package) {
+                let idx = encoder.encode_instance(interface)?;
+                encoder.outer.export(&name, ComponentTypeRef::Instance(idx));
+            } else {
+                encoder.push_instance();
+                for (_, id) in iface.types.iter() {
+                    encoder.encode_valtype(self.resolve, &Type::Id(*id))?;
                 }
-            }
-            encoder.interface = None;
-
-            for (name, world) in self.resolve.packages[*pkg].worlds.iter() {
-                let component_ty = encode_world(self.resolve, *world)?;
+                let instance = encoder.pop_instance();
                 let idx = encoder.outer.type_count();
-                encoder.outer.ty().component(&component_ty);
-                let id = self.resolve.packages[*pkg].name.interface_id(name);
-                encoder.outer.export(&id, ComponentTypeRef::Component(idx));
+                encoder.outer.ty().instance(&instance);
+                encoder.import_map.insert(interface, encoder.instances);
+                encoder.instances += 1;
+                encoder.outer.import(&name, ComponentTypeRef::Instance(idx));
             }
+        }
+        encoder.interface = None;
 
-            let ty = self.component.type_component(&encoder.outer);
-            let id = self.resolve.packages[*pkg].name.interface_id("wit");
-            self.component
-                .export(&id, ComponentExportKind::Type, ty, None);
+        for (name, world) in self.resolve.packages[self.package].worlds.iter() {
+            let component_ty = encode_world(self.resolve, *world)?;
+            let idx = encoder.outer.type_count();
+            encoder.outer.ty().component(&component_ty);
+            let id = self.resolve.packages[self.package].name.interface_id(name);
+            encoder.outer.export(&id, ComponentTypeRef::Component(idx));
         }
+
+        let ty = self.component.type_component(&encoder.outer);
+        let id = self.resolve.packages[self.package].name.interface_id("wit");
+        self.component
+            .export(&id, ComponentExportKind::Type, ty, None);
         Ok(())
     }
 

crates/wit-component/src/encoding/wit/v2.rs

@@ -32,14 +32,6 @@ pub fn encode_component(resolve: &Resolve, packages: &[PackageId]) -> Result<Com
     };
     encoder.run()?;
 
-    for package in packages {
-        let package_metadata = PackageMetadata::extract(resolve, *package);
-        encoder.component.custom_section(&CustomSection {
-            name: PackageMetadata::SECTION_NAME.into(),
-            data: package_metadata.encode()?.into(),
-        });
-    }
-
     Ok(encoder.component)
 }
 
@@ -59,30 +51,80 @@ impl Encoder<'_> {
         // decoding process where everyone's view of a foreign document agrees
         // notably on the order that types are defined in to assist with
         // roundtripping.
+        let mut names = NameMap::new();
         for pkg in self.packages {
-            for (name, &id) in self.resolve.packages[*pkg].interfaces.iter() {
-                let component_ty = self.encode_interface(id, pkg)?;
-                let ty = self.component.type_component(&component_ty);
-                self.component
-                    .export(name.as_ref(), ComponentExportKind::Type, ty, None);
-            }
-
-            for (name, &world) in self.resolve.packages[*pkg].worlds.iter() {
-                // Encode the `world` directly as a component, then create a wrapper
-                // component that exports that component.
-                let component_ty = super::encode_world(self.resolve, world)?;
-
-                let world = &self.resolve.worlds[world];
-                let mut wrapper = ComponentType::new();
-                wrapper.ty().component(&component_ty);
-                let pkg = &self.resolve.packages[world.package.unwrap()];
-                wrapper.export(&pkg.name.interface_id(name), ComponentTypeRef::Component(0));
+            let package = &self.resolve.packages[*pkg];
+            if let PackageKind::Explicit = package.kind {
+                let mut sub_encoder = Encoder {
+                    component: ComponentBuilder::default(),
+                    resolve: self.resolve,
+                    packages: self.packages,
+                };
+                let package_metadata = PackageMetadata::extract(self.resolve, *pkg);
+                sub_encoder.component.custom_section(&CustomSection {
+                    name: PackageMetadata::SECTION_NAME.into(),
+                    data: package_metadata.encode()?.into(),
+                });
+                for (name, &id) in self.resolve.packages[*pkg].interfaces.iter() {
+                    let component_ty = sub_encoder.encode_interface(id, pkg)?;
+                    let ty = sub_encoder.component.type_component(&component_ty);
+                    sub_encoder.component.export(
+                        name.as_ref(),
+                        ComponentExportKind::Type,
+                        ty,
+                        None,
+                    );
+                }
+                for (name, &world) in self.resolve.packages[*pkg].worlds.iter() {
+                    // Encode the `world` directly as a component, then create a wrapper
+                    // component that exports that component.
+                    let component_ty = super::encode_world(self.resolve, world)?;
 
-                let ty = self.component.type_component(&wrapper);
-                self.component
-                    .export(name.as_ref(), ComponentExportKind::Type, ty, None);
+                    let world = &sub_encoder.resolve.worlds[world];
+                    let mut wrapper = ComponentType::new();
+                    wrapper.ty().component(&component_ty);
+                    let pkg = &sub_encoder.resolve.packages[world.package.unwrap()];
+                    wrapper.export(&pkg.name.interface_id(name), ComponentTypeRef::Component(0));
+                    let ty = sub_encoder.component.type_component(&wrapper);
+                    sub_encoder.component.export(
+                        name.as_ref(),
+                        ComponentExportKind::Type,
+                        ty,
+                        None,
+                    );
+                }
+                let sub = self.component.component(sub_encoder.component);
+                names.append(sub, &package.name.to_string());
+            } else {
+                for (name, &id) in self.resolve.packages[*pkg].interfaces.iter() {
+                    let component_ty = self.encode_interface(id, pkg)?;
+                    let ty = self.component.type_component(&component_ty);
+                    self.component
+                        .export(name.as_ref(), ComponentExportKind::Type, ty, None);
+                }
+                for (name, &world) in self.resolve.packages[*pkg].worlds.iter() {
+                    // Encode the `world` directly as a component, then create a wrapper
+                    // component that exports that component.
+                    let component_ty = super::encode_world(self.resolve, world)?;
+                    let world = &self.resolve.worlds[world];
+                    let mut wrapper = ComponentType::new();
+                    wrapper.ty().component(&component_ty);
+                    let pkg = &self.resolve.packages[world.package.unwrap()];
+                    wrapper.export(&pkg.name.interface_id(name), ComponentTypeRef::Component(0));
+                    let ty = self.component.type_component(&wrapper);
+                    self.component
+                        .export(name.as_ref(), ComponentExportKind::Type, ty, None);
+                }
+                let package_metadata = PackageMetadata::extract(self.resolve, *pkg);
+                self.component.custom_section(&CustomSection {
+                    name: PackageMetadata::SECTION_NAME.into(),
+                    data: package_metadata.encode()?.into(),
+                });
             }
         }
+        let mut final_names = ComponentNameSection::new();
+        final_names.components(&names);
+        self.component.names(&final_names);
 
         Ok(())
     }

crates/wit-component/src/metadata.rs

@@ -51,7 +51,7 @@ use wasm_encoder::{
 };
 use wasm_metadata::Producers;
 use wasmparser::{BinaryReader, Encoding, Parser, Payload, WasmFeatures};
-use wit_parser::{Package, PackageName, Resolve, World, WorldId, WorldItem};
+use wit_parser::{Package, PackageKind, PackageName, Resolve, World, WorldId, WorldItem};
 
 const CURRENT_VERSION: u8 = 0x04;
 const CUSTOM_SECTION_NAME: &str = "wit-component-encoding";
@@ -80,6 +80,7 @@ impl Default for Bindgen {
                 name: "root".to_string(),
                 version: None,
             },
+            kind: PackageKind::Implicit,
             docs: Default::default(),
             interfaces: Default::default(),
             worlds: Default::default(),

crates/wit-component/src/printing.rs

@@ -70,7 +70,6 @@ impl WitPrinter {
 
             if has_multiple_packages {
                 self.output.push_str(" {\n");
-                self.output.indent += 1
             } else {
                 self.print_semicolon();
                 self.output.push_str("\n\n");
@@ -98,7 +97,6 @@ impl WitPrinter {
 
             if has_multiple_packages {
                 self.output.push_str("}");
-                self.output.indent -= 1
             }
         }