feat: initial error-context implementation

This commit implements error-context related functions inside the VM,
along with tests to ensure that basic error-context.new and
error-context.debug-message functionality works.

Signed-off-by: Victor Adossi <vadossi@cosmonic.com>

cranelift/entity/src/primary.rs

@@ -72,6 +72,17 @@ where
         self.elems.get_mut(k.index())
     }
 
+    /// Get the element at `k` if it exists, mutable version.
+    pub fn get_mut_or_insert_with(&mut self, k: K, f: impl FnOnce() -> V) -> &mut V {
+        if self.elems.get(k.index()).is_none() {
+            self.elems.insert(k.index(), f());
+        }
+
+        self.elems
+            .get_mut(k.index())
+            .expect("missing existing element")
+    }
+
     /// Is this map completely empty?
     pub fn is_empty(&self) -> bool {
         self.elems.is_empty()

crates/cranelift/src/compiler/component.rs

@@ -1288,7 +1288,7 @@ impl<'a> TrampolineCompiler<'a> {
 
     fn translate_error_context_call(
         &mut self,
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
         options: &CanonicalOptions,
         offset: u32,
         params: Vec<ir::AbiParam>,
@@ -1379,7 +1379,7 @@ impl<'a> TrampolineCompiler<'a> {
         }
     }
 
-    fn translate_error_context_drop_call(&mut self, ty: TypeErrorContextTableIndex) {
+    fn translate_error_context_drop_call(&mut self, ty: TypeComponentLocalErrorContextTableIndex) {
         match self.abi {
             Abi::Wasm => {}
 

crates/environ/src/component/dfg.rs

@@ -354,15 +354,15 @@ pub enum Trampoline {
         ty: TypeFutureTableIndex,
     },
     ErrorContextNew {
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
         options: CanonicalOptions,
     },
     ErrorContextDebugMessage {
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
         options: CanonicalOptions,
     },
     ErrorContextDrop {
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
     },
     ResourceTransferOwn,
     ResourceTransferBorrow,

crates/environ/src/component/info.rs

@@ -849,7 +849,7 @@ pub enum Trampoline {
     /// specified debug message.
     ErrorContextNew {
         /// The table index for the `error-context` type in the caller instance.
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
         /// String encoding, memory, etc. to use when loading debug message.
         options: CanonicalOptions,
     },
@@ -861,15 +861,15 @@ pub enum Trampoline {
     /// to `error.new`.
     ErrorContextDebugMessage {
         /// The table index for the `error-context` type in the caller instance.
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
         /// String encoding, memory, etc. to use when storing debug message.
         options: CanonicalOptions,
     },
 
     /// A `error-context.drop` intrinsic to drop a specified `error-context`.
     ErrorContextDrop {
         /// The table index for the `error-context` type in the caller instance.
-        ty: TypeErrorContextTableIndex,
+        ty: TypeComponentLocalErrorContextTableIndex,
     },
 
     /// An intrinsic used by FACT-generated modules which will transfer an owned

crates/environ/src/component/types.rs

@@ -103,11 +103,19 @@ indices! {
     /// This is analogous to `TypeResourceTableIndex` in that it tracks
     /// ownership of stream within each (sub)component instance.
     pub struct TypeStreamTableIndex(u32);
+
     /// Index pointing to a error context table within a component.
     ///
     /// This is analogous to `TypeResourceTableIndex` in that it tracks
     /// ownership of error contexts within each (sub)component instance.
-    pub struct TypeErrorContextTableIndex(u32);
+    pub struct TypeComponentLocalErrorContextTableIndex(u32);
+
+    /// Index pointing to a (component) globally tracked error context table entry
+    ///
+    /// Unlike [`TypeComponentLocalErrorContextTableIndex`], this index refers to
+    /// the global state table for error contexts at the level of the entire component,
+    /// not just a subcomponent.
+    pub struct TypeComponentGlobalErrorContextTableIndex(u32);
 
     /// Index pointing to an interned `task.return` type within a component.
     pub struct TypeTaskReturnIndex(u32);
@@ -267,7 +275,7 @@ pub struct ComponentTypes {
     pub(super) future_tables: PrimaryMap<TypeFutureTableIndex, TypeFutureTable>,
     pub(super) streams: PrimaryMap<TypeStreamIndex, TypeStream>,
     pub(super) stream_tables: PrimaryMap<TypeStreamTableIndex, TypeStreamTable>,
-    pub(super) error_context_tables: PrimaryMap<TypeErrorContextTableIndex, TypeErrorContextTable>,
+    pub(super) error_context_tables: PrimaryMap<TypeComponentLocalErrorContextTableIndex, TypeErrorContextTable>,
     pub(super) task_returns: PrimaryMap<TypeTaskReturnIndex, TypeTaskReturn>,
 }
 
@@ -357,7 +365,7 @@ impl_index! {
     impl Index<TypeStreamIndex> for ComponentTypes { TypeStream => streams }
     impl Index<TypeFutureTableIndex> for ComponentTypes { TypeFutureTable => future_tables }
     impl Index<TypeStreamTableIndex> for ComponentTypes { TypeStreamTable => stream_tables }
-    impl Index<TypeErrorContextTableIndex> for ComponentTypes { TypeErrorContextTable => error_context_tables }
+    impl Index<TypeComponentLocalErrorContextTableIndex> for ComponentTypes { TypeErrorContextTable => error_context_tables }
 }
 
 // Additionally forward anything that can index `ModuleTypes` to `ModuleTypes`
@@ -518,7 +526,7 @@ pub enum InterfaceType {
     Borrow(TypeResourceTableIndex),
     Future(TypeFutureTableIndex),
     Stream(TypeStreamTableIndex),
-    ErrorContext(TypeErrorContextTableIndex),
+    ErrorContext(TypeComponentLocalErrorContextTableIndex),
 }
 
 impl From<&wasmparser::PrimitiveValType> for InterfaceType {

crates/environ/src/component/types_builder.rs

@@ -49,7 +49,7 @@ pub struct ComponentTypesBuilder {
     streams: HashMap<TypeStream, TypeStreamIndex>,
     future_tables: HashMap<TypeFutureTable, TypeFutureTableIndex>,
     stream_tables: HashMap<TypeStreamTable, TypeStreamTableIndex>,
-    error_context_tables: HashMap<TypeErrorContextTable, TypeErrorContextTableIndex>,
+    error_context_tables: HashMap<TypeErrorContextTable, TypeComponentLocalErrorContextTableIndex>,
     task_returns: HashMap<TypeTaskReturn, TypeTaskReturnIndex>,
 
     component_types: ComponentTypes,
@@ -210,7 +210,7 @@ impl ComponentTypesBuilder {
     }
 
     /// Returns the number of error-context tables allocated so far, or the maximum
-    /// `TypeErrorContextTableIndex`.
+    /// `TypeComponentLocalErrorContextTableIndex`.
     pub fn num_error_context_tables(&self) -> usize {
         self.component_types.error_context_tables.len()
     }
@@ -444,7 +444,7 @@ impl ComponentTypesBuilder {
     }
 
     /// Retrieve Wasmtime's type representation of the `error-context` type.
-    pub fn error_context_type(&mut self) -> Result<TypeErrorContextTableIndex> {
+    pub fn error_context_type(&mut self) -> Result<TypeComponentLocalErrorContextTableIndex> {
         self.error_context_table_type()
     }
 
@@ -599,7 +599,7 @@ impl ComponentTypesBuilder {
         }))
     }
 
-    fn error_context_table_type(&mut self) -> Result<TypeErrorContextTableIndex> {
+    fn error_context_table_type(&mut self) -> Result<TypeComponentLocalErrorContextTableIndex> {
         Ok(self.add_error_context_table_type(TypeErrorContextTable {
             instance: self.resources.get_current_instance().unwrap(),
         }))
@@ -694,7 +694,7 @@ impl ComponentTypesBuilder {
     pub fn add_error_context_table_type(
         &mut self,
         ty: TypeErrorContextTable,
-    ) -> TypeErrorContextTableIndex {
+    ) -> TypeComponentLocalErrorContextTableIndex {
         intern(
             &mut self.error_context_tables,
             &mut self.component_types.error_context_tables,

crates/environ/src/fact/trampoline.rs

@@ -17,7 +17,7 @@
 
 use crate::component::{
     CanonicalAbiInfo, ComponentTypesBuilder, FixedEncoding as FE, FlatType, InterfaceType,
-    StringEncoding, Transcode, TypeEnumIndex, TypeErrorContextTableIndex, TypeFlagsIndex,
+    StringEncoding, Transcode, TypeEnumIndex, TypeComponentLocalErrorContextTableIndex, TypeFlagsIndex,
     TypeFutureTableIndex, TypeListIndex, TypeOptionIndex, TypeRecordIndex, TypeResourceTableIndex,
     TypeResultIndex, TypeStreamTableIndex, TypeTupleIndex, TypeVariantIndex, VariantInfo,
     FLAG_MAY_ENTER, FLAG_MAY_LEAVE, MAX_FLAT_PARAMS, MAX_FLAT_RESULTS,
@@ -2935,7 +2935,7 @@ impl Compiler<'_, '_> {
 
     fn translate_error_context_context(
         &mut self,
-        src_ty: TypeErrorContextTableIndex,
+        src_ty: TypeComponentLocalErrorContextTableIndex,
         src: &Source<'_>,
         dst_ty: &InterfaceType,
         dst: &Destination,

crates/misc/component-async-tests/src/lib.rs

@@ -1289,4 +1289,9 @@ mod test {
             &fs::read(test_programs_artifacts::ASYNC_HTTP_MIDDLEWARE_COMPONENT).await?;
         test_http_echo(&compose(middleware, echo).await?, true).await
     }
+
+    #[tokio::test]
+    async fn async_error_context() -> Result<()> {
+        test_run(&fs::read(test_programs_artifacts::ASYNC_ERROR_CONTEXT_COMPONENT).await?).await
+    }
 }

crates/misc/component-async-tests/wit/test.wit

@@ -129,3 +129,7 @@ world borrowing-host {
   import borrowing-types;
   export run-bool;
 }
+
+world error-context-usage {
+  export run;
+}

crates/test-programs/Cargo.toml

@@ -15,7 +15,8 @@ anyhow = { workspace = true, features = ['std'] }
 wasi = "0.11.0"
 wasi-nn = "0.6.0"
 wit-bindgen = { workspace = true, features = ['default'] }
-wit-bindgen-rt = { workspace = true }
+#wit-bindgen-rt = { workspace = true }
+wit-bindgen-rt = { path = "../../../wit-bindgen/crates/guest-rust/rt", features = [ 'async'] }
 libc = { workspace = true }
 getrandom = "0.2.9"
 futures = { workspace = true, default-features = false, features = ['alloc'] }

crates/test-programs/src/bin/async_error_context.rs

@@ -0,0 +1,29 @@
+mod bindings {
+    wit_bindgen::generate!({
+        path: "../misc/component-async-tests/wit",
+        world: "error-context-usage",
+        async: {
+            exports: [
+                "local:local/run#run",
+            ],
+        }
+    });
+
+    use super::Component;
+    export!(Component);
+}
+use bindings::exports::local::local::run::Guest;
+
+use wit_bindgen_rt::async_support::error_context_new;
+
+struct Component;
+
+impl Guest for Component {
+    async fn run() {
+        let err_ctx = error_context_new("error".into());
+        _ = err_ctx.debug_message();
+    }
+}
+
+// Unused function; required since this file is built as a `bin`:
+fn main() {}