Ask user if they want to install new toolchains

Also add some user output for the major steps of installing toolchains,
compiling `spirv-builder-cli` and compiling the actual shader.

Surprisingly there's no way in the standard library to get a single
keypress from the user! There's ways to get a line, therefore a keypress
then a newline, but that's not so conventional for responding to a "y/n"
prompt.

Fixes #14

Cargo.toml

@@ -17,6 +17,7 @@ resolver = "2"
 anyhow = "1.0.94"
 clap = { version = "4.4.8", features = ["derive"] }
 chrono = { version = "0.4.38", default-features = false, features = ["std"] }
+crossterm = "0.28.1"
 directories = "5.0.1"
 env_home = "0.1.0"
 env_logger = "0.10"
@@ -49,7 +50,6 @@ multiple_crate_versions = { level = "allow", priority = 1 }
 pub_with_shorthand = { level = "allow", priority = 1 }
 partial_pub_fields = { level = "allow", priority = 1 }
 pattern_type_mismatch = { level = "allow", priority = 1 }
-print_stdout = { level = "allow", priority = 1 }
 std_instead_of_alloc = { level = "allow", priority = 1 }
 
 

README.md

@@ -100,6 +100,9 @@ Options:
       --force-spirv-cli-rebuild
           Force `spirv-builder-cli` and `rustc_codegen_spirv` to be rebuilt
 
+      --auto-install-rust-toolchain
+          Assume "yes" to "Install Rust toolchain: [y/n]" prompt
+
   -h, --help
           Print help (see a summary with '-h')
 
@@ -134,6 +137,9 @@ Options:
       --force-spirv-cli-rebuild
           Force `spirv-builder-cli` and `rustc_codegen_spirv` to be rebuilt
 
+      --auto-install-rust-toolchain
+          Assume "yes" to "Install Rust toolchain: [y/n]" prompt
+
       --shader-target <SHADER_TARGET>
           Shader target
 
@@ -197,13 +203,44 @@ Options:
 
 Show some useful values
 
-Usage: cargo-gpu show [OPTIONS]
+Usage: cargo-gpu show <COMMAND>
 
-Options:
-      --cache-directory
-          Displays the location of the cache directory
+Commands:
+  cache-directory  Displays the location of the cache directory
+  spirv-source     The source location of spirv-std
+  help             Print this message or the help of the given subcommand(s)
 
+Options:
   -h, --help
           Print help
 
+
+    * Cache-directory
+
+    Displays the location of the cache directory
+
+    Usage: cargo-gpu show cache-directory
+
+    Options:
+      -h, --help
+              Print help
+
+
+    * Spirv-source
+
+    The source location of spirv-std
+
+    Usage: cargo-gpu show spirv-source [OPTIONS]
+
+    Options:
+          --shader-crate <SHADER_CRATE>
+              The location of the shader-crate to inspect to determine its spirv-std dependency
+
+              [default: ./]
+
+      -h, --help
+              Print help
+
+
+
 ````

crates/cargo-gpu/Cargo.toml

@@ -21,6 +21,7 @@ serde_json.workspace = true
 toml.workspace = true
 chrono.workspace = true
 http.workspace = true
+crossterm.workspace = true
 
 [dev-dependencies]
 test-log.workspace = true

crates/cargo-gpu/src/build.rs

@@ -1,7 +1,5 @@
 //! `cargo gpu build`, analogous to `cargo build`
 
-use std::io::Write as _;
-
 use anyhow::Context as _;
 use clap::Parser;
 use spirv_builder_cli::{Linkage, ShaderModule};
@@ -64,6 +62,11 @@ impl Build {
         let arg = serde_json::to_string_pretty(&spirv_builder_args)?;
         log::info!("using spirv-builder-cli arg: {arg}");
 
+        crate::user_output!(
+            "Running `spirv-builder-cli` to compile shader at {}...\n",
+            self.install.shader_crate.display()
+        );
+
         // Call spirv-builder-cli to compile the shaders.
         let output = std::process::Command::new(spirv_builder_cli_path)
             .arg(arg)
@@ -112,7 +115,6 @@ impl Build {
         let manifest_path = self.output_dir.join("manifest.json");
         // Sort the contents so the output is deterministic
         linkage.sort();
-        // UNWRAP: safe because we know this always serializes
         let json = serde_json::to_string_pretty(&linkage)?;
         let mut file = std::fs::File::create(&manifest_path).with_context(|| {
             format!(

crates/cargo-gpu/src/install.rs

@@ -118,6 +118,10 @@ pub struct Install {
     /// Force `spirv-builder-cli` and `rustc_codegen_spirv` to be rebuilt.
     #[clap(long)]
     force_spirv_cli_rebuild: bool,
+
+    /// Assume "yes" to "Install Rust toolchain: [y/n]" prompt.
+    #[clap(long, action)]
+    auto_install_rust_toolchain: bool,
 }
 
 impl Install {
@@ -128,6 +132,7 @@ impl Install {
             self.spirv_builder_source.clone(),
             self.spirv_builder_version.clone(),
             self.rust_toolchain.clone(),
+            self.auto_install_rust_toolchain,
         )
     }
 
@@ -230,6 +235,11 @@ impl Install {
             self.write_source_files()?;
             self.write_target_spec_files()?;
 
+            crate::user_output!(
+                "Compiling shader-specific `spirv-builder-cli` for {}\n",
+                self.shader_crate.display()
+            );
+
             let mut command = std::process::Command::new("cargo");
             command
                 .current_dir(&checkout)