Support multiple package in a single WIT source

crates/wit-component/src/encoding.rs

@@ -2133,33 +2133,33 @@ mod test {
 
     use super::*;
     use std::path::Path;
-    use wit_parser::UnresolvedPackage;
+    use wit_parser::UnresolvedPackageGroup;
 
     #[test]
     fn it_renames_imports() {
         let mut resolve = Resolve::new();
-        let pkg = resolve
-            .push(
-                UnresolvedPackage::parse(
-                    Path::new("test.wit"),
-                    r#"
+        let UnresolvedPackageGroup {
+            mut packages,
+            source_map,
+        } = UnresolvedPackageGroup::parse(
+            Path::new("test.wit"),
+            r#"
 package test:wit;
 
 interface i {
-    f: func();
+f: func();
 }
 
 world test {
-    import i;
-    import foo: interface {
-        f: func();
-    }
+import i;
+import foo: interface {
+f: func();
+}
 }
 "#,
-                )
-                .unwrap(),
-            )
-            .unwrap();
+        )
+        .unwrap();
+        let pkg = resolve.push(packages.remove(0), &source_map).unwrap();
 
         let world = resolve.select_world(pkg, None).unwrap();
 

crates/wit-component/src/lib.rs

@@ -5,9 +5,9 @@
 use std::str::FromStr;
 use std::{borrow::Cow, fmt::Display};
 
-use anyhow::{bail, Result};
+use anyhow::{bail, Context, Result};
 use wasm_encoder::{CanonicalOption, Encode, Section};
-use wit_parser::{Resolve, WorldId};
+use wit_parser::{parse_use_path, PackageId, ParsedUsePath, Resolve, WorldId};
 
 mod encoding;
 mod gc;
@@ -79,6 +79,43 @@ impl From<StringEncoding> for wasm_encoder::CanonicalOption {
     }
 }
 
+/// Handles world name resolution for cases when multiple packages may have been resolved. If this
+/// is the case, and we're dealing with input that contains a user-supplied world name (like via a
+/// CLI command, for instance), we want to ensure that the world name follows the following rules:
+///
+///   * If there is a single resolved package with a single world, the world name name MAY be
+///     omitted.
+///   * If there is a single resolved package with multiple worlds, the world name MUST be supplied,
+///     but MAY or MAY NOT be fully-qualified.
+///   * If there are multiple resolved packages, the world name MUST be fully-qualified.
+pub fn resolve_world_from_name(
+    resolve: &Resolve,
+    resolved_packages: Vec<PackageId>,
+    world_name: Option<&str>,
+) -> Result<WorldId> {
+    match resolved_packages.len() {
+        0 => bail!("all of the supplied WIT source files were empty"),
+        1 => resolve.select_world(resolved_packages[0], world_name.as_deref()),
+        _ => match world_name.as_deref() {
+            Some(name) => {
+                let world_path = parse_use_path(name).with_context(|| {
+                    format!("failed to parse world specifier `{name}`")
+                })?;
+                match world_path {
+                        ParsedUsePath::Name(name) => bail!("the world specifier must be of the fully-qualified, id-based form (ex: \"wasi:http/proxy\" rather than \"proxy\"); you used {name}"),
+                        ParsedUsePath::Package(pkg_name, _) => {
+                            match resolve.package_names.get(&pkg_name) {
+                                Some(pkg_id) => resolve.select_world(pkg_id.clone(), world_name.as_deref()),
+                                None => bail!("the world specifier you provided named {pkg_name}, but no package with that name was found"),
+                            }
+                        }
+                    }
+            }
+            None => bail!("the supplied WIT source files describe multiple packages; please provide a fully-qualified world-specifier to the `embed` command"),
+        },
+    }
+}
+
 /// A producer section to be added to all modules and components synthesized by
 /// this crate
 pub(crate) fn base_producers() -> wasm_metadata::Producers {
@@ -112,7 +149,7 @@ mod tests {
 
     use anyhow::Result;
     use wasmparser::Payload;
-    use wit_parser::{Resolve, UnresolvedPackage};
+    use wit_parser::{Resolve, UnresolvedPackageGroup};
 
     use super::{embed_component_metadata, StringEncoding};
 
@@ -147,8 +184,11 @@ world test-world {}
 
         // Parse pre-canned WIT to build resolver
         let mut resolver = Resolve::default();
-        let pkg = UnresolvedPackage::parse(&Path::new("in-code.wit"), COMPONENT_WIT)?;
-        let pkg_id = resolver.push(pkg)?;
+        let UnresolvedPackageGroup {
+            mut packages,
+            source_map,
+        } = UnresolvedPackageGroup::parse(&Path::new("in-code.wit"), COMPONENT_WIT)?;
+        let pkg_id = resolver.push(packages.remove(0), &source_map)?;
         let world = resolver.select_world(pkg_id, Some("test-world").into())?;
 
         // Embed component metadata

crates/wit-component/src/metadata.rs

@@ -42,7 +42,7 @@
 //! the three arguments originally passed to `encode`.
 
 use crate::validation::BARE_FUNC_MODULE_NAME;
-use crate::{DecodedWasm, StringEncoding};
+use crate::{resolve_world_from_name, DecodedWasm, StringEncoding};
 use anyhow::{bail, Context, Result};
 use indexmap::IndexMap;
 use std::borrow::Cow;
@@ -259,12 +259,12 @@ impl Bindgen {
                 let world_name = reader.read_string()?;
                 wasm = &data[reader.original_position()..];
 
-                let (r, pkg) = match crate::decode(wasm)? {
-                    DecodedWasm::WitPackage(resolve, pkg) => (resolve, pkg),
-                    DecodedWasm::Component(..) => bail!("expected an encoded wit package"),
+                let (r, pkgs) = match crate::decode(wasm)? {
+                    DecodedWasm::WitPackages(resolve, pkgs) => (resolve, pkgs),
+                    DecodedWasm::Component(..) => bail!("expected encoded wit package(s)"),
                 };
                 resolve = r;
-                world = resolve.packages[pkg].worlds[world_name];
+                world = resolve_world_from_name(&resolve, pkgs, Some(world_name.into()))?;
             }
 
             // Current format where `data` is a wasm component itself.

crates/wit-component/src/printing.rs

@@ -50,37 +50,56 @@ impl WitPrinter {
         self
     }
 
-    /// Print the given WIT package to a string.
-    pub fn print(&mut self, resolve: &Resolve, pkgid: PackageId) -> Result<String> {
-        let pkg = &resolve.packages[pkgid];
-        self.print_docs(&pkg.docs);
-        self.output.push_str("package ");
-        self.print_name(&pkg.name.namespace);
-        self.output.push_str(":");
-        self.print_name(&pkg.name.name);
-        if let Some(version) = &pkg.name.version {
-            self.output.push_str(&format!("@{version}"));
-        }
-        self.print_semicolon();
-        self.output.push_str("\n\n");
-        for (name, id) in pkg.interfaces.iter() {
-            self.print_docs(&resolve.interfaces[*id].docs);
-            self.print_stability(&resolve.interfaces[*id].stability);
-            self.output.push_str("interface ");
-            self.print_name(name);
-            self.output.push_str(" {\n");
-            self.print_interface(resolve, *id)?;
-            writeln!(&mut self.output, "}}\n")?;
-        }
+    /// Print a set of one or more WIT packages into a string.
+    pub fn print(&mut self, resolve: &Resolve, pkg_ids: &[PackageId]) -> Result<String> {
+        let has_multiple_packages = pkg_ids.len() > 1;
+        for (i, pkg_id) in pkg_ids.into_iter().enumerate() {
+            if i > 0 {
+                self.output.push_str("\n\n");
+            }
 
-        for (name, id) in pkg.worlds.iter() {
-            self.print_docs(&resolve.worlds[*id].docs);
-            self.print_stability(&resolve.worlds[*id].stability);
-            self.output.push_str("world ");
-            self.print_name(name);
-            self.output.push_str(" {\n");
-            self.print_world(resolve, *id)?;
-            writeln!(&mut self.output, "}}")?;
+            let pkg = &resolve.packages[pkg_id.clone()];
+            self.print_docs(&pkg.docs);
+            self.output.push_str("package ");
+            self.print_name(&pkg.name.namespace);
+            self.output.push_str(":");
+            self.print_name(&pkg.name.name);
+            if let Some(version) = &pkg.name.version {
+                self.output.push_str(&format!("@{version}"));
+            }
+
+            if has_multiple_packages {
+                self.output.push_str("{");
+                self.output.indent += 1
+            } else {
+                self.print_semicolon();
+                self.output.push_str("\n\n");
+            }
+
+            for (name, id) in pkg.interfaces.iter() {
+                self.print_docs(&resolve.interfaces[*id].docs);
+                self.print_stability(&resolve.interfaces[*id].stability);
+                self.output.push_str("interface ");
+                self.print_name(name);
+                self.output.push_str(" {\n");
+                self.print_interface(resolve, *id)?;
+                writeln!(&mut self.output, "}}\n")?;
+            }
+
+            for (name, id) in pkg.worlds.iter() {
+                self.print_docs(&resolve.worlds[*id].docs);
+                self.print_stability(&resolve.worlds[*id].stability);
+                self.output.push_str("world ");
+                self.print_name(name);
+                self.output.push_str(" {\n");
+                self.print_world(resolve, *id)?;
+                writeln!(&mut self.output, "}}")?;
+            }
+
+            if has_multiple_packages {
+                self.output.push_str("}");
+                self.output.indent -= 1
+            }
         }
 
         Ok(std::mem::take(&mut self.output).into())

crates/wit-component/src/semver_check.rs

@@ -2,7 +2,7 @@ use crate::{
     dummy_module, embed_component_metadata, encoding::encode_world, ComponentEncoder,
     StringEncoding,
 };
-use anyhow::{Context, Result};
+use anyhow::{bail, Context, Result};
 use wasm_encoder::{ComponentBuilder, ComponentExportKind, ComponentTypeRef};
 use wasmparser::{Validator, WasmFeatures};
 use wit_parser::{Resolve, WorldId};
@@ -47,6 +47,18 @@ pub fn semver_check(mut resolve: Resolve, prev: WorldId, new: WorldId) -> Result
         pkg.name.version = None;
     }
 
+    let old_pkg_id = resolve.worlds[prev]
+        .package
+        .context("old world not in named package")?;
+    let old_pkg_name = &resolve.packages[old_pkg_id].name;
+    let new_pkg_id = resolve.worlds[new]
+        .package
+        .context("new world not in named package")?;
+    let new_pkg_name = &resolve.packages[new_pkg_id].name;
+    if old_pkg_id != new_pkg_id {
+        bail!("the old world is in package {old_pkg_name}, which is not the same as the new world, which is in package {new_pkg_name}", )
+    }
+
     // Component that will be validated at the end.
     let mut root_component = ComponentBuilder::default();