spirv-builder: make required extra arg -Zjson-target-spec backwards compatible

Author: Firestar99

crates/rustc_codegen_spirv-types/src/target_spec.rs

@@ -1,14 +1,15 @@
 use crate::SpirvTarget;
 use semver::Version;
-use std::ffi::OsString;
+use std::ffi::OsStr;
 use std::path::Path;
 
 /// Enum for different versions of target specs, to allow changing the target spec for different rust versions.
 /// The version listed in the enum is always the minimum version to require said target spec, with the newest version
 /// always at the top.
 #[allow(non_camel_case_types)]
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd)]
 pub enum TargetSpecVersion {
+    Older,
     /// Introduced in `489c3ee6fd63da3ca7cf2b15e1ee709d8e078aab` in the old v2 target spec way, later ported to here.
     /// remove `os: unknown`, add `crt-static-respected: true`
     Rustc_1_85_0,
@@ -18,47 +19,67 @@ pub enum TargetSpecVersion {
     Rustc_1_76_0,
     /// rustc 1.93 requires that the value of "target-pointer-width" is no longer a string but u16
     Rustc_1_93_0,
+    /// rustc 1.94.0 destabilised json target specs, requiring `-Ztarget-spec-json`
+    /// see https://github.com/rust-lang/rust/pull/150151
+    Rustc_1_94_0,
 }
 
 impl TargetSpecVersion {
     /// Format the `--target` arg. On newer rustc versions, will create a compatible target spec json file and return
     /// the absolute path to it, on older rustc versions may return the target name.
-    pub fn target_arg(
+    pub fn append_target_arg(
         rustc_version: Version,
         target: &SpirvTarget,
         target_spec_folder: &Path,
-    ) -> std::io::Result<OsString> {
-        if let Some(target_spec) = Self::from_rustc_version(rustc_version) {
-            std::fs::create_dir_all(target_spec_folder)?;
-            let spec_file = target_spec_folder.join(format!("{}.json", target.target()));
-            std::fs::write(&spec_file, target_spec.format_spec(target))?;
-            Ok(std::fs::canonicalize(spec_file)?.into_os_string())
-        } else {
-            Ok(OsString::from(target.target()))
+        mut push_arg: impl FnMut(&OsStr),
+    ) -> std::io::Result<()> {
+        let target_spec = Self::from_rustc_version(rustc_version);
+        if target_spec >= Self::Rustc_1_94_0 {
+            push_arg("-Zjson-target-spec".as_ref());
+        }
+
+        push_arg("--target".as_ref());
+        match target_spec {
+            TargetSpecVersion::Older => {
+                push_arg(target.target().as_ref());
+            }
+            _ => {
+                std::fs::create_dir_all(target_spec_folder)?;
+                let spec_file = target_spec_folder.join(format!("{}.json", target.target()));
+                std::fs::write(&spec_file, target_spec.format_spec(target))?;
+                let spec_file = std::fs::canonicalize(spec_file)?.into_os_string();
+                push_arg(&spec_file);
+            }
         }
+        Ok(())
     }
 
     /// Returns the version of the target spec required for a certain rustc version. May return `None` if the version
     /// is old enough to not need target specs.
-    pub fn from_rustc_version(rustc_version: Version) -> Option<Self> {
-        if rustc_version >= Version::new(1, 93, 0) {
-            Some(Self::Rustc_1_93_0)
+    pub fn from_rustc_version(rustc_version: Version) -> Self {
+        if rustc_version >= Version::new(1, 94, 0) {
+            Self::Rustc_1_94_0
+        } else if rustc_version >= Version::new(1, 93, 0) {
+            Self::Rustc_1_93_0
         } else if rustc_version >= Version::new(1, 85, 0) {
-            Some(Self::Rustc_1_85_0)
+            Self::Rustc_1_85_0
         } else if rustc_version >= Version::new(1, 76, 0) {
-            Some(Self::Rustc_1_76_0)
+            Self::Rustc_1_76_0
         } else {
-            None
+            Self::Older
         }
     }
 
     /// format the target spec json
     pub fn format_spec(&self, target: &SpirvTarget) -> String {
         let target_env = target.env();
         let (extra, target_pointer_width) = match self {
+            TargetSpecVersion::Older => panic!("no target specs for older rustc versions"),
             TargetSpecVersion::Rustc_1_76_0 => (r#""os": "unknown","#, "\"32\""),
             TargetSpecVersion::Rustc_1_85_0 => (r#""crt-static-respected": true,"#, "\"32\""),
-            TargetSpecVersion::Rustc_1_93_0 => (r#""crt-static-respected": true,"#, "32"),
+            TargetSpecVersion::Rustc_1_93_0 | TargetSpecVersion::Rustc_1_94_0 => {
+                (r#""crt-static-respected": true,"#, "32")
+            }
         };
         format!(
             r#"{{

crates/spirv-builder/src/lib.rs

@@ -1046,14 +1046,14 @@ fn invoke_rustc(builder: &SpirvBuilder) -> Result<PathBuf, SpirvBuilderError> {
     }
 
     let target_spec_dir = target_dir.join("target-specs");
-    let target = TargetSpecVersion::target_arg(toolchain_rustc_version, &target, &target_spec_dir)?;
-    if Path::new(&target)
-        .extension()
-        .is_some_and(|ext| ext == "json")
-    {
-        cargo.arg("-Zjson-target-spec");
-    }
-    cargo.arg("--target").arg(target);
+    TargetSpecVersion::append_target_arg(
+        toolchain_rustc_version,
+        &target,
+        &target_spec_dir,
+        |arg| {
+            cargo.arg(arg);
+        },
+    )?;
 
     if !builder.shader_crate_features.default_features {
         cargo.arg("--no-default-features");

tests/compiletests/src/main.rs

@@ -268,7 +268,7 @@ impl Runner {
 
     fn target_spec_json(&self, target: &SpirvTarget) -> OsString {
         let rustc_version = query_rustc_version(None).unwrap();
-        TargetSpecVersion::target_arg(rustc_version, target, &self.deps_target_dir).unwrap()
+        TargetSpecVersion::append_target_arg(rustc_version, target, &self.deps_target_dir).unwrap()
     }
 }