Added toolchain check to rustc_codegen_spirv (#919)

* Added toolchain check to rustc_codegen_spirv

* Removed unused dependency

* Reworked the toolchain check

* Removed some debug code

crates/rustc_codegen_spirv/Cargo.toml

@@ -26,6 +26,12 @@ use-installed-tools = ["spirv-tools/use-installed-tools"]
 # If enabled will compile and link the C++ code for the spirv tools, the compiled
 # version is preferred if both this and `use-installed-tools` are enabled
 use-compiled-tools = ["spirv-tools/use-compiled-tools"]
+# If enabled, this will not check whether the current rustc version is set to the
+# appropriate channel. rustc_cogeden_spirv requires a specific nightly version,
+# and will likely produce compile errors when built against a different toolchain.
+# Enable this feature to be able to experiment with other versions.
+skip-toolchain-check = []
+
 
 [dependencies]
 # HACK(eddyb) these only exist to unify features across dependency trees,

crates/rustc_codegen_spirv/build.rs

@@ -0,0 +1,70 @@
+//! This custom build script merely checks whether we're compiling with the appropriate Rust toolchain
+
+#![allow(clippy::string_add)]
+
+use std::error::Error;
+use std::process::{Command, ExitCode};
+
+/// Current `rust-toolchain` file
+/// Unfortunately, directly including the actual workspace `rust-toolchain` doesn't work together with
+/// `cargo publish`. We need to figure out a way to do this properly, but let's hardcode it for now :/
+//const REQUIRED_RUST_TOOLCHAIN: &str = include_str!("../../rust-toolchain");
+const REQUIRED_RUST_TOOLCHAIN: &str = r#"[toolchain]
+channel = "nightly-2022-08-29"
+components = ["rust-src", "rustc-dev", "llvm-tools-preview"]
+# commit_hash = ce36e88256f09078519f8bc6b21e4dc88f88f523"#;
+
+fn get_rustc_commit_hash() -> Result<String, Box<dyn Error>> {
+    let rustc = std::env::var("RUSTC").unwrap_or_else(|_| String::from("rustc"));
+    String::from_utf8(Command::new(rustc).arg("-vV").output()?.stdout)?
+        .lines()
+        .find_map(|l| l.strip_prefix("commit-hash: "))
+        .map(|s| s.to_string())
+        .ok_or_else(|| Box::<dyn Error>::from("`commit-hash` not found in `rustc -vV` output"))
+}
+
+fn get_required_commit_hash() -> Result<String, Box<dyn Error>> {
+    REQUIRED_RUST_TOOLCHAIN
+        .lines()
+        .find_map(|l| l.strip_prefix("# commit_hash = "))
+        .map(|s| s.to_string())
+        .ok_or_else(|| Box::<dyn Error>::from("`commit_hash` not found in `rust-toolchain`"))
+}
+
+fn check_toolchain_version() -> Result<(), Box<dyn Error>> {
+    if !cfg!(feature = "skip-toolchain-check") {
+        // gets the commit hash from current rustc
+
+        let current_hash = get_rustc_commit_hash()?;
+        let required_hash = get_required_commit_hash()?;
+        if current_hash != required_hash {
+            let stripped_toolchain = REQUIRED_RUST_TOOLCHAIN
+                .lines()
+                .filter(|l| !l.trim().is_empty() && !l.starts_with("# "))
+                .map(|l| l.to_string())
+                .reduce(|a, b| a + "\n" + &b)
+                .unwrap_or_default();
+
+            return Err(Box::<dyn Error>::from(format!(
+                r#"
+error: wrong toolchain detected (found commit hash `{current_hash}`, expected `{required_hash}`).
+Make sure your `rust_toolchain` file contains the following:
+-------------
+{stripped_toolchain}
+-------------"#
+            )));
+        }
+    }
+
+    Ok(())
+}
+
+fn main() -> ExitCode {
+    match check_toolchain_version() {
+        Ok(_) => ExitCode::SUCCESS,
+        Err(e) => {
+            eprint!("{}", e);
+            ExitCode::FAILURE
+        }
+    }
+}

crates/spirv-builder/Cargo.toml

@@ -12,6 +12,7 @@ description = "Helper for building shaders with rust-gpu"
 default = ["use-compiled-tools"]
 use-installed-tools = ["rustc_codegen_spirv/use-installed-tools"]
 use-compiled-tools = ["rustc_codegen_spirv/use-compiled-tools"]
+skip-toolchain-check = ["rustc_codegen_spirv/skip-toolchain-check"]
 watch = ["notify"]
 
 [dependencies]

rust-toolchain

@@ -7,3 +7,8 @@
 [toolchain]
 channel = "nightly-2022-08-29"
 components = ["rust-src", "rustc-dev", "llvm-tools-preview"]
+# commit_hash = ce36e88256f09078519f8bc6b21e4dc88f88f523
+
+# Whenever changing the nightly channel, update the commit hash above, and make
+# sure to change REQUIRED_TOOLCHAIN in crates/rustc_codegen_spirv/src/build.rs also.
+