Decouple install codegen handling, add error types for it

Author: tuguzT

Cargo.lock

@@ -5,58 +5,14 @@ use std::path::{Path, PathBuf};
 use anyhow::Context as _;
 use rustc_codegen_spirv_cache::{
     cache::cache_dir,
+    install::InstalledBackend,
     metadata::{query_metadata, MetadataExt as _},
     spirv_source::{rust_gpu_toolchain_channel, SpirvSource},
     target_specs::update_target_specs_files,
+    toolchain::ensure_toolchain_installation,
 };
-use spirv_builder::SpirvBuilder;
 
-/// Represents a functional backend installation, whether it was cached or just installed.
-#[derive(Clone, Debug, Default)]
-#[non_exhaustive]
-pub struct InstalledBackend {
-    /// path to the `rustc_codegen_spirv` dylib
-    pub rustc_codegen_spirv_location: PathBuf,
-    /// toolchain channel name
-    pub toolchain_channel: String,
-    /// directory with target-specs json files
-    pub target_spec_dir: PathBuf,
-}
-
-impl InstalledBackend {
-    /// Creates a new `SpirvBuilder` configured to use this installed backend.
-    #[expect(
-        clippy::unreachable,
-        reason = "it's unreachable, no need to return a Result"
-    )]
-    #[expect(clippy::impl_trait_in_params, reason = "forwarding spirv-builder API")]
-    #[inline]
-    pub fn to_spirv_builder(
-        &self,
-        path_to_crate: impl AsRef<Path>,
-        target: impl Into<String>,
-    ) -> SpirvBuilder {
-        let mut builder = SpirvBuilder::new(path_to_crate, target);
-        self.configure_spirv_builder(&mut builder)
-            .unwrap_or_else(|_| unreachable!("we set target before calling this function"));
-        builder
-    }
-
-    /// Configures the supplied [`SpirvBuilder`]. `SpirvBuilder.target` must be set and must not change after calling this function.
-    ///
-    /// # Errors
-    /// if `SpirvBuilder.target` is not set
-    #[inline]
-    pub fn configure_spirv_builder(&self, builder: &mut SpirvBuilder) -> anyhow::Result<()> {
-        builder.rustc_codegen_spirv_location = Some(self.rustc_codegen_spirv_location.clone());
-        builder.toolchain_overwrite = Some(self.toolchain_channel.clone());
-        builder.path_to_target_spec = Some(self.target_spec_dir.join(format!(
-            "{}.json",
-            builder.target.as_ref().context("expect target to be set")?
-        )));
-        Ok(())
-    }
-}
+use crate::user_consent::ask_for_user_consent;
 
 /// Args for an install
 #[expect(
@@ -203,7 +159,8 @@ package = "rustc_codegen_spirv"
         Ok(())
     }
 
-    /// Install the binary pair and return the [`InstalledBackend`], from which you can create [`SpirvBuilder`] instances.
+    /// Install the binary pair and return the [`InstalledBackend`],
+    /// from which you can create [`SpirvBuilder`](spirv_builder::SpirvBuilder) instances.
     ///
     /// # Errors
     /// If the installation somehow fails.
@@ -271,9 +228,9 @@ package = "rustc_codegen_spirv"
             .context("writing target spec files")?;
 
         log::debug!("ensure_toolchain_and_components_exist");
-        crate::install_toolchain::ensure_toolchain_and_components_exist(
+        ensure_toolchain_installation(
             &toolchain_channel,
-            self.auto_install_rust_toolchain,
+            ask_for_user_consent(&toolchain_channel, self.auto_install_rust_toolchain),
         )
         .context("ensuring toolchain and components exist")?;
 

crates/cargo-gpu-cache/src/install.rs

@@ -47,11 +47,11 @@ mod build;
 mod config;
 mod dump_usage;
 mod install;
-mod install_toolchain;
 mod linkage;
 mod lockfile;
 mod metadata;
 mod show;
+mod user_consent;
 
 pub use install::*;
 pub use spirv_builder;

crates/cargo-gpu-cache/src/lib.rs

@@ -1,20 +1,23 @@
-//! toolchain installation logic
+//! User consent acquiring logic.
 
 use anyhow::Context as _;
 use crossterm::tty::IsTty as _;
 use rustc_codegen_spirv_cache::toolchain::{
-    ensure_toolchain_installation, HaltToolchainInstallation, REQUIRED_TOOLCHAIN_COMPONENTS,
+    HaltToolchainInstallation, REQUIRED_TOOLCHAIN_COMPONENTS,
 };
 
 use crate::user_output;
 
-/// Uses `rustup` to install the toolchain and all the [required components](REQUIRED_TOOLCHAIN_COMPONENTS),
-/// if not already installed, while additionally asking for the user consent.
-pub fn ensure_toolchain_and_components_exist(
+/// Halts the installation process of toolchain or its required components
+/// if the user does not consent to install either of them.
+pub fn ask_for_user_consent(
     channel: &str,
     skip_toolchain_install_consent: bool,
-) -> anyhow::Result<()> {
-    let on_toolchain_install = || {
+) -> HaltToolchainInstallation<
+    impl FnOnce() -> Result<(), anyhow::Error> + use<'_>,
+    impl FnOnce() -> Result<(), anyhow::Error> + use<'_>,
+> {
+    let on_toolchain_install = move || {
         let message = format!("Rust {channel} with `rustup`");
         get_consent_for_toolchain_install(
             format!("Install {message}").as_ref(),
@@ -24,7 +27,7 @@ pub fn ensure_toolchain_and_components_exist(
         user_output!("Installing {message}\n")?;
         Ok(())
     };
-    let on_components_install = || {
+    let on_components_install = move || {
         let message = format!(
             "components {REQUIRED_TOOLCHAIN_COMPONENTS:?} for toolchain {channel} with `rustup`"
         );
@@ -37,11 +40,10 @@ pub fn ensure_toolchain_and_components_exist(
         Ok(())
     };
 
-    let halt_installation = HaltToolchainInstallation {
+    HaltToolchainInstallation {
         on_toolchain_install,
         on_components_install,
-    };
-    ensure_toolchain_installation(channel, halt_installation)
+    }
 }
 
 /// Prompt user if they want to install a new Rust toolchain.

crates/cargo-gpu-cache/src/install_toolchain.rs renamed to crates/cargo-gpu-cache/src/user_consent.rs

@@ -8,6 +8,7 @@ keywords.workspace = true
 license.workspace = true
 
 [dependencies]
+spirv-builder.workspace = true
 legacy_target_specs.workspace = true
 thiserror.workspace = true
 directories.workspace = true

crates/rustc_codegen_spirv-cache/Cargo.toml

@@ -0,0 +1,63 @@
+//! Install a dedicated per-shader crate that has the `rust-gpu` compiler in it.
+
+use std::path::{Path, PathBuf};
+
+use spirv_builder::SpirvBuilder;
+
+/// Represents a functional backend installation, whether it was cached or just installed.
+#[derive(Debug, Default, Clone)]
+// #[non_exhaustive] // TODO: uncomment
+#[expect(clippy::exhaustive_structs, reason = "this is temporary")] // TODO: remove
+pub struct InstalledBackend {
+    /// Path to the `rustc_codegen_spirv` dylib.
+    pub rustc_codegen_spirv_location: PathBuf,
+    /// Toolchain channel name.
+    pub toolchain_channel: String,
+    /// Directory with target specs json files.
+    pub target_spec_dir: PathBuf,
+}
+
+impl InstalledBackend {
+    /// Creates a new [`SpirvBuilder`] configured to use this installed backend.
+    #[expect(
+        clippy::unreachable,
+        reason = "it's unreachable, no need to return a Result"
+    )]
+    #[expect(clippy::impl_trait_in_params, reason = "forwarding spirv-builder API")]
+    #[inline]
+    pub fn to_spirv_builder(
+        &self,
+        path_to_crate: impl AsRef<Path>,
+        target: impl Into<String>,
+    ) -> SpirvBuilder {
+        let mut builder = SpirvBuilder::new(path_to_crate, target);
+        self.configure_spirv_builder(&mut builder)
+            .unwrap_or_else(|_| unreachable!("we set target before calling this function"));
+        builder
+    }
+
+    /// Configures the supplied [`SpirvBuilder`].
+    /// [`SpirvBuilder::target`] must be set and must not change after calling this function.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if [`SpirvBuilder::target`] is not set.
+    #[inline]
+    pub fn configure_spirv_builder(
+        &self,
+        builder: &mut SpirvBuilder,
+    ) -> Result<(), TargetNotSetError> {
+        builder.rustc_codegen_spirv_location = Some(self.rustc_codegen_spirv_location.clone());
+        builder.toolchain_overwrite = Some(self.toolchain_channel.clone());
+
+        let target = builder.target.as_deref().ok_or(TargetNotSetError)?;
+        builder.path_to_target_spec = Some(self.target_spec_dir.join(format!("{target}.json")));
+        Ok(())
+    }
+}
+
+/// An error indicating that [`SpirvBuilder::target`] was not set.
+#[derive(Debug, Clone, thiserror::Error)]
+#[non_exhaustive]
+#[error("target should be set")]
+pub struct TargetNotSetError;

crates/rustc_codegen_spirv-cache/src/install.rs

@@ -19,8 +19,10 @@
 #![expect(clippy::pub_use, reason = "reexport for convenience")]
 
 pub use cargo_metadata;
+pub use spirv_builder;
 
 pub mod cache;
+pub mod install;
 pub mod metadata;
 pub mod spirv_source;
 pub mod target_specs;