Implement Wire for never type (#497)

Also enable the CI test for the platform protocol schema.

.github/actions/ci-checks/action.yml

@@ -9,7 +9,9 @@ inputs:
 runs:
   using: composite
   steps:
-    - if: ${{ contains(fromJSON(inputs.checks), 'changelog') }}
+    - if: >-
+        ${{ contains(fromJSON(inputs.checks), 'changelog')
+         || contains(fromJSON(inputs.checks), 'sync') }}
       uses: actions/checkout@v4
       with:
         fetch-depth: 0

.github/workflows/pages.yml

@@ -4,6 +4,8 @@ on:
   push:
     branches:
       - main
+    paths:
+      - 'book/**'
 
 permissions: {}
 

crates/protocol/CHANGELOG.md

@@ -2,4 +2,4 @@
 
 ## 0.1.0-git
 
-<!-- Increment to skip CHANGELOG.md test: 5 -->
+<!-- Increment to skip CHANGELOG.md test: 6 -->

crates/protocol/crates/schema/src/main.rs

@@ -42,14 +42,11 @@ fn check(old: &View, new: &View) -> Result<()> {
     for (_, tag, api) in get_enum(&old).context("in old")? {
         ensure!(old_map.insert(tag, api).is_none(), "duplicate tag {tag}");
     }
-    for (name, tag, new_api) in get_enum(&new).context("in new")? {
+    for (_, tag, new_api) in get_enum(&new).context("in new")? {
         if let Some(old_api) = old_map.remove(tag) {
             let old_api = ViewFields(old_api);
             let new_api = ViewFields(new_api);
-            ensure!(
-                old_api == new_api,
-                "incompatible API for {name}={tag}: {old_api} vs {new_api}"
-            );
+            ensure!(old_api == new_api, "incompatible API for {tag}: {old_api} != {new_api}");
         }
     }
     #[cfg(feature = "full")]

crates/protocol/src/lib.rs

@@ -26,11 +26,11 @@
 
 #![no_std]
 #![feature(doc_auto_cfg)]
+#![feature(never_type)]
 
 extern crate alloc;
 
 use alloc::boxed::Box;
-use core::convert::Infallible;
 
 use wasefire_error::Error;
 use wasefire_wire::Wire;
@@ -105,7 +105,7 @@ api! {
     /// Errors reported by the device.
     ///
     /// This may be returned regardless of the request type.
-    0 DeviceError: Infallible => Error,
+    0 DeviceError: ! => Error,
 
     /// Sends a request to an applet.
     1 AppletRequest: applet::Request<'a> => (),
@@ -114,8 +114,7 @@ api! {
     2 AppletResponse: applet::AppletId => applet::Response<'a>,
 
     /// Reboots the platform.
-    // TODO: Should return unit. Device should always respond.
-    3 PlatformReboot: () => Infallible,
+    3 PlatformReboot: () => !,
 
     /// Starts a direct tunnel with an applet.
     4 AppletTunnel: applet::Tunnel<'a> => (),

crates/wire/CHANGELOG.md

@@ -2,4 +2,4 @@
 
 ## 0.1.0-git
 
-<!-- Increment to skip CHANGELOG.md test: 1 -->
+<!-- Increment to skip CHANGELOG.md test: 2 -->

crates/wire/src/lib.rs

@@ -37,6 +37,7 @@
 #![no_std]
 #![feature(array_try_from_fn)]
 #![feature(doc_auto_cfg)]
+#![feature(never_type)]
 #![feature(try_blocks)]
 
 extern crate alloc;
@@ -298,6 +299,21 @@ impl<'a> internal::Wire<'a> for Error {
     }
 }
 
+impl<'a> internal::Wire<'a> for ! {
+    #[cfg(feature = "schema")]
+    type Static = !;
+    #[cfg(feature = "schema")]
+    fn schema(rules: &mut Rules) {
+        if rules.enum_::<Self::Static>(Vec::new()) {}
+    }
+    fn encode(&self, _: &mut Writer<'a>) -> Result<(), Error> {
+        match *self {}
+    }
+    fn decode(_: &mut Reader<'a>) -> Result<Self, Error> {
+        Err(Error::user(Code::InvalidArgument))
+    }
+}
+
 #[internal_wire]
 #[wire(crate = crate)]
 enum Infallible {}

scripts/sync.sh

@@ -49,6 +49,11 @@ for dir in $(find crates -name Cargo.toml -printf '%h\n' | sort); do
   # add_lint $file warn rust.unused-results
 done
 
+( cd crates/protocol/crates/schema
+  cargo run --features=full
+  cargo run
+)
+
 book_example() {
   local src=book/src/applet/prelude/$1.rs
   local dst=examples/rust/$2/src/lib.rs