Migrate the wasmtime-types crate to no_std (#8485)

* Migrate the wasmtime-types crate to no_std

This commit is where no_std for Wasmtime starts to get a bit
interesting. Specifically the `wasmtime-types` crate is the first crate
that depends on some nontrivial crates that also need to be migrated to
`no_std`. This PR disables the default feature of `wasmparser` by
default and additionally does the same for `serde`. This enables them to
compile in `no_std` contexts by default and default features will be
enabled elsewhere in this repository as necessary.

This also opts to drop the `thiserror` dependency entirely in favor of a
manual `Display` implementation with a cfg'd implementation of `Error`.

As before CI checks are added for `wasmtime-types` with a `no_std`
target itself to ensure the crate and all dependencies all avoid `std`.

* Fix adapter build

.github/workflows/main.yml

@@ -375,6 +375,9 @@ jobs:
     - run: cargo check -p wasmtime-slab
       env:
         CARGO_BUILD_TARGET: x86_64-unknown-none
+    - run: cargo check -p wasmtime-types
+      env:
+        CARGO_BUILD_TARGET: x86_64-unknown-none
 
     # Check that wasmtime compiles with panic=abort since there's some `#[cfg]`
     # for specifically panic=abort there.

Cargo.lock

@@ -3803,7 +3803,6 @@ dependencies = [
  "serde",
  "serde_derive",
  "smallvec",
- "thiserror",
  "wasmparser 0.206.0",
 ]
 

Cargo.toml

@@ -231,7 +231,7 @@ rustix = "0.38.31"
 wit-bindgen = { version = "0.22.0", default-features = false }
 
 # wasm-tools family:
-wasmparser = "0.206.0"
+wasmparser = { version = "0.206.0", default-features = false }
 wat = "1.206.0"
 wast = "206.0.0"
 wasmprinter = "0.206.0"
@@ -270,7 +270,7 @@ proptest = "1.0.0"
 rand = { version = "0.8.3", features = ["small_rng"] }
 sptr = "0.3.2"
 # serde and serde_derive must have the same version
-serde = "1.0.188"
+serde = { version = "1.0.188", default-features = false, features = ['alloc'] }
 serde_derive = "1.0.188"
 serde_json = "1.0.80"
 glob = "0.3.0"

crates/environ/Cargo.toml

@@ -18,7 +18,7 @@ anyhow = { workspace = true, features = ['std'] }
 postcard = { workspace = true }
 cpp_demangle = { version = "0.4.3", optional = true }
 cranelift-entity = { workspace = true }
-wasmtime-types = { workspace = true }
+wasmtime-types = { workspace = true, features = ['std'] }
 wasmparser = { workspace = true }
 indexmap = { workspace = true, features = ["serde"] }
 thiserror = { workspace = true }

crates/types/Cargo.toml

@@ -13,8 +13,10 @@ cranelift-entity = { workspace = true, features = ['enable-serde'] }
 serde = { workspace = true }
 serde_derive = { workspace = true }
 smallvec = { workspace = true, features = ["serde"] }
-thiserror = { workspace = true }
 wasmparser = { workspace = true }
 
 [lints]
 workspace = true
+
+[features]
+std = ['wasmparser/std']

crates/types/src/error.rs

@@ -1,16 +1,16 @@
-use thiserror::Error;
+use alloc::string::String;
+use core::fmt;
 
 /// A WebAssembly translation error.
 ///
 /// When a WebAssembly function can't be translated, one of these error codes will be returned
 /// to describe the failure.
-#[derive(Error, Debug)]
+#[derive(Debug)]
 pub enum WasmError {
     /// The input WebAssembly code is invalid.
     ///
     /// This error code is used by a WebAssembly translator when it encounters invalid WebAssembly
     /// code. This should never happen for validated WebAssembly code.
-    #[error("Invalid input WebAssembly code at offset {offset}: {message}")]
     InvalidWebAssembly {
         /// A string describing the validation error.
         message: String,
@@ -21,7 +21,6 @@ pub enum WasmError {
     /// A feature used by the WebAssembly code is not supported by the embedding environment.
     ///
     /// Embedding environments may have their own limitations and feature restrictions.
-    #[error("Unsupported feature: {0}")]
     Unsupported(String),
 
     /// An implementation limit was exceeded.
@@ -30,11 +29,9 @@ pub enum WasmError {
     /// limits][limits] that cause compilation to fail when they are exceeded.
     ///
     /// [limits]: https://github.com/bytecodealliance/wasmtime/blob/main/cranelift/docs/ir.md#implementation-limits
-    #[error("Implementation limit exceeded")]
     ImplLimitExceeded,
 
     /// Any user-defined error.
-    #[error("User error: {0}")]
     User(String),
 }
 
@@ -42,7 +39,7 @@ pub enum WasmError {
 /// on the arguments to this macro.
 #[macro_export]
 macro_rules! wasm_unsupported {
-    ($($arg:tt)*) => { $crate::WasmError::Unsupported(format!($($arg)*)) }
+    ($($arg:tt)*) => { $crate::WasmError::Unsupported($crate::__format!($($arg)*)) }
 }
 
 impl From<wasmparser::BinaryReaderError> for WasmError {
@@ -57,3 +54,28 @@ impl From<wasmparser::BinaryReaderError> for WasmError {
 
 /// A convenient alias for a `Result` that uses `WasmError` as the error type.
 pub type WasmResult<T> = Result<T, WasmError>;
+
+impl fmt::Display for WasmError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            WasmError::InvalidWebAssembly { message, offset } => {
+                write!(
+                    f,
+                    "Invalid input WebAssembly code at offset {offset}: {message}"
+                )
+            }
+            WasmError::Unsupported(s) => {
+                write!(f, "Unsupported feature: {s}")
+            }
+            WasmError::ImplLimitExceeded => {
+                write!(f, "Implementation limit exceeded")
+            }
+            WasmError::User(s) => {
+                write!(f, "User error: {s}")
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for WasmError {}

crates/types/src/lib.rs

@@ -1,12 +1,22 @@
 //! Internal dependency of Wasmtime and Cranelift that defines types for
 //! WebAssembly.
 
-use smallvec::SmallVec;
+#![no_std]
+
+extern crate alloc;
+#[cfg(feature = "std")]
+extern crate std;
+
 pub use wasmparser;
 
+#[doc(hidden)]
+pub use alloc::format as __format;
+
+use alloc::boxed::Box;
+use core::{fmt, ops::Range};
 use cranelift_entity::entity_impl;
 use serde_derive::{Deserialize, Serialize};
-use std::{fmt, ops::Range};
+use smallvec::SmallVec;
 
 mod error;
 pub use error::*;

crates/wasi-preview1-component-adapter/verify/Cargo.toml

@@ -9,6 +9,6 @@ publish = false
 workspace = true
 
 [dependencies]
-wasmparser = { workspace = true }
+wasmparser = { workspace = true, features = ['std'] }
 wat = { workspace = true }
 anyhow = { workspace = true, features = ['std'] }