Require the use of remappings provided via --with (#842)

Signed-off-by: Brian H <brian.hardock@fermyon.com>

Author: fibonacci1729

crates/c/src/lib.rs

@@ -270,7 +270,7 @@ impl WorldGenerator for C {
         gen.gen.src.append(&gen.src);
     }
 
-    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) -> Result<()> {
         let linking_symbol = component_type_object::linking_symbol(&self.world);
         self.include("<stdlib.h>");
         let snake = self.world.to_snake_case();
@@ -463,6 +463,8 @@ impl WorldGenerator for C {
                 .as_slice(),
             );
         }
+
+        Ok(())
     }
 
     fn pre_export_interface(&mut self, resolve: &Resolve, _files: &mut Files) -> Result<()> {

crates/core/src/lib.rs

@@ -294,8 +294,7 @@ pub trait WorldGenerator {
         for (name, id) in interfaces {
             self.export_interface(resolve, name, *id, files)?;
         }
-        self.finish(resolve, id, files);
-        Ok(())
+        self.finish(resolve, id, files)
     }
 
     fn finish_imports(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) {
@@ -348,7 +347,7 @@ pub trait WorldGenerator {
         types: &[(&str, TypeId)],
         files: &mut Files,
     );
-    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files);
+    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) -> Result<()>;
 }
 
 /// This is a possible replacement for the `Generator` trait above, currently

crates/csharp/src/lib.rs

@@ -269,7 +269,7 @@ impl WorldGenerator for CSharp {
         gen.add_world_fragment();
     }
 
-    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) -> Result<()> {
         let world = &resolve.worlds[id];
         let world_namespace = self.qualifier();
         let world_namespace = world_namespace.strip_suffix(".").unwrap();
@@ -654,6 +654,8 @@ impl WorldGenerator for CSharp {
                 generate_stub(name.to_string(), files, Stubs::Interface(fragments));
             }
         }
+
+        Ok(())
     }
 }
 

crates/go/src/lib.rs

@@ -286,7 +286,7 @@ impl WorldGenerator for TinyGo {
         self.src.push_str(&src);
     }
 
-    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) -> Result<()> {
         // make sure all types are defined on top of the file
         let src = mem::take(&mut self.src);
         self.src.push_str(&src);
@@ -351,7 +351,9 @@ impl WorldGenerator for TinyGo {
         opts.no_object_file = true;
         opts.build()
             .generate(resolve, id, files)
-            .expect("C generator should be infallible")
+            .expect("C generator should be infallible");
+
+        Ok(())
     }
 }
 

crates/markdown/src/lib.rs

@@ -200,7 +200,7 @@ impl WorldGenerator for Markdown {
         }
     }
 
-    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) -> Result<()> {
         let world = &resolve.worlds[world];
         let parser = Parser::new(&self.src);
         let mut events = Vec::new();
@@ -227,6 +227,8 @@ impl WorldGenerator for Markdown {
             files.push(&format!("{}.md", world.name), self.src.as_bytes());
             files.push(&format!("{}.html", world.name), html_output.as_bytes());
         }
+
+        Ok(())
     }
 }
 

crates/rust/src/lib.rs

@@ -48,6 +48,9 @@ struct RustWasm {
     resources: HashMap<TypeId, ResourceInfo>,
     import_funcs_called: bool,
     with_name_counter: usize,
+    // Track the with options that were used. Remapped interfaces provided via `with`
+    // are required to be used.
+    used_with_opts: HashSet<String>,
 }
 
 #[cfg(feature = "clap")]
@@ -288,6 +291,7 @@ impl RustWasm {
         let with_name = resolve.name_world_key(name);
         let entry = if let Some(remapped_path) = self.opts.with.get(&with_name) {
             let name = format!("__with_name{}", self.with_name_counter);
+            self.used_with_opts.insert(with_name);
             self.with_name_counter += 1;
             uwriteln!(self.src, "use {remapped_path} as {name};");
             InterfaceName {
@@ -459,7 +463,7 @@ impl WorldGenerator for RustWasm {
         }
     }
 
-    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, world: WorldId, files: &mut Files) -> Result<()> {
         let name = &resolve.worlds[world].name;
 
         let imports = mem::take(&mut self.import_modules);
@@ -582,6 +586,20 @@ impl WorldGenerator for RustWasm {
 
         let module_name = name.to_snake_case();
         files.push(&format!("{module_name}.rs"), src.as_bytes());
+
+        let remapping_keys = self.opts.with.keys().cloned().collect::<HashSet<String>>();
+
+        let mut unused_keys = remapping_keys
+            .difference(&self.used_with_opts)
+            .collect::<Vec<&String>>();
+
+        unused_keys.sort();
+
+        if !unused_keys.is_empty() {
+            bail!("unused remappings provided via `with`: {unused_keys:?}");
+        }
+
+        Ok(())
     }
 }
 

crates/teavm-java/src/lib.rs

@@ -177,7 +177,7 @@ impl WorldGenerator for TeaVmJava {
         gen.add_world_fragment();
     }
 
-    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) {
+    fn finish(&mut self, resolve: &Resolve, id: WorldId, files: &mut Files) -> Result<()> {
         let name = world_name(resolve, id);
         let (package, name) = split_qualified_name(&name);
 
@@ -431,6 +431,8 @@ impl WorldGenerator for TeaVmJava {
                 generate_stub(&package, format!("{name}Impl"), fragments, files);
             }
         }
+
+        Ok(())
     }
 }
 

src/bin/wit-bindgen.rs

@@ -158,12 +158,15 @@ fn gen_world(
     let (pkg, _files) = resolve.push_path(&opts.wit)?;
     let world = resolve.select_world(pkg, opts.world.as_deref())?;
     if let Err(e) = generator.generate(&resolve, world, files) {
-        eprintln!(
-            "{e:?}\n\n\
-             help: Specify export implementations using the `--exports` option.\n    \
-             For example: `--exports world=MyWorld,ns:pkg/iface=MyIface`\n    \
-             Alternatively, specify `--stubs` to generate stub implementations."
-        );
+        if e.to_string().starts_with("no `exports` map provided") {
+            bail!(
+                "{e:?}\n\n\
+                help: Specify export implementations using the `--exports` option.\n    \
+                For example: `--exports world=MyWorld,ns:pkg/iface=MyIface`\n    \
+                Alternatively, specify `--stubs` to generate stub implementations."
+            );
+        }
+        bail!("{e:?}");
     }
 
     Ok(())