add a second case for multiple error mappings

crates/wiggle/tests/errors.rs

@@ -1,3 +1,5 @@
+/// Execute the wiggle guest conversion code to exercise it
+mod convert_just_errno {
     use wiggle_test::{impl_errno, HostMemory, WasiCtx};
 
     /// The `errors` argument to the wiggle gives us a hook to map a rich error
@@ -11,8 +13,8 @@ pub enum RichError {
         PicketLine(String),
     }
 
-/// Define an errno with variants corresponding to RichError. Use it in a
-/// trivial function.
+    // Define an errno with variants corresponding to RichError. Use it in a
+    // trivial function.
     wiggle::from_witx!({
         witx_literal: "
 (typename $errno (enum u8 $ok $invalid_arg $picket_line))
@@ -25,6 +27,8 @@ wiggle::from_witx!({
         errors: { errno => RichError },
     });
 
+    // The impl of GuestErrorConversion works just like in every other test where
+    // we have a single error type with witx `$errno` with the success called `$ok`
     impl_errno!(types::Errno, types::GuestErrorConversion);
 
     /// When the `errors` mapping in witx is non-empty, we need to impl the
@@ -95,3 +99,81 @@ fn one_error_conversion_test() {
             "Expected log entry for strike=2",
         );
     }
+}
+
+/// Type-check the wiggle guest conversion code against a more complex case where
+/// we use two distinct error types.
+mod convert_multiple_error_types {
+    pub use super::convert_just_errno::RichError;
+    use wiggle_test::WasiCtx;
+
+    /// Test that we can map multiple types of errors.
+    #[derive(Debug, thiserror::Error)]
+    #[allow(dead_code)]
+    pub enum AnotherRichError {
+        #[error("I've had this many cups of coffee and can't even think straight: {0}")]
+        TooMuchCoffee(usize),
+    }
+
+    // Just like the other error, except that we have a second errno type:
+    // trivial function.
+    wiggle::from_witx!({
+        witx_literal: "
+(typename $errno (enum u8 $ok $invalid_arg $picket_line))
+(typename $errno2 (enum u8 $ok $too_much_coffee))
+(module $two_error_conversions
+  (@interface func (export \"foo\")
+     (param $strike u32)
+     (result $err $errno))
+  (@interface func (export \"bar\")
+     (param $drink u32)
+     (result $err $errno2)))
+    ",
+        ctx: WasiCtx,
+        errors: { errno => RichError, errno2 => AnotherRichError },
+    });
+
+    // Can't use the impl_errno! macro as usual here because the conversion
+    // trait ends up having two methods.
+    // We aren't going to execute this code, so the bodies are elided.
+    impl<'a> types::GuestErrorConversion for WasiCtx<'a> {
+        fn into_errno(&self, _e: wiggle::GuestError) -> types::Errno {
+            unimplemented!()
+        }
+        fn into_errno2(&self, _e: wiggle::GuestError) -> types::Errno2 {
+            unimplemented!()
+        }
+    }
+    impl wiggle::GuestErrorType for types::Errno {
+        fn success() -> types::Errno {
+            <types::Errno>::Ok
+        }
+    }
+    impl wiggle::GuestErrorType for types::Errno2 {
+        fn success() -> types::Errno2 {
+            <types::Errno2>::Ok
+        }
+    }
+
+    // The UserErrorConversion trait will also have two methods for this test. They correspond to
+    // each member of the `errors` mapping.
+    // Bodies elided.
+    impl<'a> types::UserErrorConversion for WasiCtx<'a> {
+        fn errno_from_rich_error(&self, _e: RichError) -> types::Errno {
+            unimplemented!()
+        }
+        fn errno2_from_another_rich_error(&self, _e: AnotherRichError) -> types::Errno2 {
+            unimplemented!()
+        }
+    }
+
+    // And here's the witx module trait impl, bodies elided
+    impl<'a> two_error_conversions::TwoErrorConversions for WasiCtx<'a> {
+        fn foo(&self, _: u32) -> Result<(), RichError> {
+            unimplemented!()
+        }
+        fn bar(&self, _: u32) -> Result<(), AnotherRichError> {
+            unimplemented!()
+        }
+    }
+}