Add one-of crate for mutually exclusive features (#625)

crates/api/CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Patch
 
+- Make sure at compile-time that exactly one `host` or `wasm` feature is enabled
 - Update dependencies
 
 ## 0.6.1

crates/api/Cargo.toml

@@ -21,6 +21,7 @@ sealed = { version = "0.5.0", default-features = false, optional = true }
 wasefire-applet-api-macro = { version = "0.7.0-git", path = "../api-macro" }
 wasefire-error = { version = "0.1.2-git", path = "../error" }
 wasefire-logger = { version = "0.1.5", path = "../logger", optional = true }
+wasefire-one-of = { version = "0.1.0-git", path = "../one-of" }
 
 [features]
 # Compiles for host or wasm (choose exactly one).

crates/api/src/lib.rs

@@ -24,12 +24,15 @@ extern crate alloc;
 #[cfg(feature = "host")]
 pub use host::*;
 use wasefire_error as _;
+use wasefire_one_of::exactly_one_of;
 
 #[cfg(feature = "host")]
 mod host;
 #[cfg(feature = "wasm")]
 pub(crate) mod wasm;
 
+exactly_one_of!["host", "wasm"];
+
 #[cfg(feature = "wasm")]
 wasefire_applet_api_macro::wasm!();
 

crates/one-of/CHANGELOG.md

@@ -0,0 +1,5 @@
+# Changelog
+
+## 0.1.0-git
+
+<!-- Increment to skip CHANGELOG.md test: 0 -->

crates/one-of/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "wasefire-one-of"
+version = "0.1.0-git"
+authors = ["Julien Cretin <cretin@google.com>"]
+license = "Apache-2.0"
+publish = true
+edition = "2021"
+description = "Macros for mutually exclusive features"
+repository = "https://github.com/google/wasefire"
+include = ["/LICENSE", "/src/"]
+keywords = ["macro", "no-std"]
+categories = ["no-std"]
+
+[lints]
+clippy.unit-arg = "allow"
+rust.missing-docs = "warn"
+rust.unreachable-pub = "warn"
+rust.unsafe-op-in-unsafe-fn = "warn"
+rust.unused-crate-dependencies = "warn"

crates/one-of/LICENSE

@@ -0,0 +1 @@
+../../LICENSE

crates/one-of/src/lib.rs

@@ -0,0 +1,91 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Provides macros to check mutually exclusive features.
+
+#![no_std]
+
+// TODO(https://github.com/rust-lang/rust/issues/122105): Remove when fixed.
+extern crate alloc;
+
+/// Makes sure exactly one of the provided feature is enabled.
+///
+/// For example, `exactly_one_of!["a", "b", "c"]` will expand to:
+///
+/// ```ignore
+/// #[cfg(any(
+///     not(any(feature = "a", feature = "b", feature = "c")),
+///     all(feature = "a", feature = "b"),
+///     all(feature = "a", feature = "c"),
+///     all(feature = "b", feature = "c"),
+/// ))]
+/// compile_error!("Exactly one of feature \"a\", \"b\", or \"c\" can be enabled.");
+/// ```
+#[macro_export]
+macro_rules! exactly_one_of {
+    ($f:literal, $($fs:literal),+$(,)?) => {
+        $crate::internal_one_of!(0 [$f $($fs)*] "Exactly");
+    };
+}
+
+/// Makes sure at most one of the provided feature is enabled.
+///
+/// For example, `at_most_one_of!["a", "b", "c"]` will expand to:
+///
+/// ```ignore
+/// #[cfg(any(
+///     all(feature = "a", feature = "b"),
+///     all(feature = "a", feature = "c"),
+///     all(feature = "b", feature = "c"),
+/// ))]
+/// compile_error!("At most one of feature \"a\", \"b\", or \"c\" can be enabled.");
+/// ```
+#[macro_export]
+macro_rules! at_most_one_of {
+    ($f:literal, $($fs:literal),+$(,)?) => {
+        $crate::internal_one_of!(1 [$f $($fs)*] () ["At most";]);
+    };
+}
+
+#[doc(hidden)]
+#[macro_export]
+macro_rules! internal_one_of {
+    (0 [$($f:literal)*] $p:literal) => {
+        $crate::internal_one_of!(1 [$($f)*] (not(any($(feature = $f),*)),) [$p;]);
+    };
+
+    (1 [$f:literal $($fs:literal)*] $r:tt [$($ds:literal)*; $($d:literal)?]) => {
+        $crate::internal_one_of!(2 [$($fs)*] $f [$($fs)*] $r [$($ds)* $($d)?; $f]);
+    };
+    (1 [] $r:tt $ds:tt) => {
+        #[cfg(any $r)]
+        $crate::internal_one_of!(3 $ds);
+    };
+
+    (2 $s:tt $g:literal [$f:literal $($fs:literal)*] ($($r:tt)*) $d:tt) => {
+        $crate::internal_one_of!(2 $s $g [$($fs)*] ($($r)* all(feature = $g, feature = $f),) $d);
+    };
+    (2 $s:tt $g:literal [] $r:tt $d:tt) => {
+        $crate::internal_one_of!(1 $s $r $d);
+    };
+
+    (3 [$p:literal $a:literal; $b:literal]) => {
+        compile_error!(concat!($p, " one of feature ", stringify!($a), " or ", stringify!($b),
+          " can be enabled."));
+    };
+    (3 [$p:literal $($as:literal)*; $b:literal]) => {
+        compile_error!(concat!($p, " one of feature ",$(stringify!($as), ", ",)* "or ",
+          stringify!($b), " can be enabled."));
+    };
+}

crates/one-of/test.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -e
+
+. "$(git rev-parse --show-toplevel)"/scripts/test-helper.sh
+
+test_helper
+
+cargo test --lib
+cargo check --lib --target=thumbv7em-none-eabi

crates/prelude/CHANGELOG.md

@@ -13,6 +13,7 @@
 
 ### Patch
 
+- Make sure at compile-time that at most one `native`, `test`, or `wasm` feature is enabled
 - Update dependencies
 
 ## 0.6.0

crates/prelude/Cargo.toml

@@ -26,6 +26,7 @@ sealed = { version = "0.5.0", default-features = false, optional = true }
 typenum = { version = "1.17.0", default-features = false, optional = true }
 wasefire-applet-api = { version = "0.7.0-git", path = "../api", features = ["wasm"] }
 wasefire-error = { version = "0.1.2-git", path = "../error" }
+wasefire-one-of = { version = "0.1.0-git", path = "../one-of" }
 wasefire-sync = { version = "0.1.1", path = "../sync" }
 zeroize = { version = "1.7.0", default-features = false, features = ["derive"], optional = true }
 

crates/prelude/src/lib.rs

@@ -38,6 +38,7 @@ extern crate alloc;
 
 use wasefire_applet_api as api;
 pub use wasefire_error::Error;
+use wasefire_one_of::at_most_one_of;
 #[cfg(feature = "rust-crypto")]
 use {aead as _, crypto_common as _, digest as _, typenum as _, zeroize as _};
 
@@ -77,6 +78,8 @@ pub mod uart;
 #[cfg(feature = "internal-api-usb")]
 pub mod usb;
 
+at_most_one_of!["native", "test", "wasm"];
+
 /// Board-specific syscalls.
 ///
 /// Those calls are directly forwarded to the board by the scheduler.

crates/protocol-tokio/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-tokio/Cargo.toml

@@ -18,6 +18,7 @@ features = ["device"]
 anyhow = { version = "1.0.86", default-features = false, features = ["std"] }
 wasefire-error = { version = "0.1.2-git", path = "../error", optional = true }
 wasefire-logger = { version = "0.1.5", path = "../logger" }
+wasefire-one-of = { version = "0.1.0-git", path = "../one-of" }
 
 [dependencies.tokio]
 version = "1.40.0"

crates/protocol-tokio/src/lib.rs

@@ -21,9 +21,12 @@
 pub use device::*;
 #[cfg(feature = "host")]
 pub use host::*;
+use wasefire_one_of::exactly_one_of;
 
 mod common;
 #[cfg(feature = "device")]
 mod device;
 #[cfg(feature = "host")]
 mod host;
+
+exactly_one_of!["device", "host"];

crates/protocol-usb/CHANGELOG.md

@@ -21,4 +21,4 @@
 
 ## 0.1.0
 
-<!-- Increment to skip CHANGELOG.md test: 4 -->
+<!-- Increment to skip CHANGELOG.md test: 5 -->