rust: improve external detection (#50232)

Signed-off-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>

var/spack/repos/builtin/packages/rust/detection_test.yaml

@@ -0,0 +1,55 @@
+paths:
+- layout:
+  - executables:
+    - "bin/rustc"
+    script: |
+      echo "rustc 1.75.0 (82e1608df 2023-12-21) (built from a source tarball)"
+  - executables:
+    - "bin/cargo"
+    script: |
+      echo "cargo 1.75.0"
+  platforms: ["darwin", "linux"]
+  results:
+  - spec: 'rust@1.75.0'
+    extra_attributes:
+      compilers:
+        rust: ".*/bin/rustc"
+      cargo: ".*/bin/cargo"
+# If rustc is missing, then we don't detect specs
+- layout:
+  - executables:
+    - "bin/cargo"
+    script: |
+      echo "cargo 1.75.0"
+  platforms: ["darwin", "linux"]
+  results: []
+# Check we can detect 2 different versions in the same folder
+- layout:
+  - executables:
+    - "bin/rustc"
+    script: |
+      echo "rustc 1.75.0 (82e1608df 2023-12-21) (built from a source tarball)"
+  - executables:
+    - "bin/rustc-1.80"
+    script: |
+      echo "rustc 1.80.1 (3f5fd8dd4 2024-08-06) (built from a source tarball)"
+  - executables:
+    - "bin/cargo"
+    script: |
+      echo "cargo 1.75.0"
+  - executables:
+    - "bin/cargo-1.80"
+    script: |
+      echo "cargo 1.80.1 (376290515 2024-07-16)"
+  platforms: ["darwin", "linux"]
+  results:
+  - spec: 'rust@1.75.0'
+    extra_attributes:
+      compilers:
+        rust: ".*/bin/rustc"
+      cargo: ".*/bin/cargo"
+  - spec: 'rust@1.80.1'
+    extra_attributes:
+      compilers:
+        rust: ".*/bin/rustc-1.80"
+      cargo: ".*/bin/cargo-1.80"

var/spack/repos/builtin/packages/rust/package.py

@@ -102,22 +102,36 @@ class Rust(Package):
     conflicts("%oneapi", msg="Rust not compatible with Intel oneAPI compilers")
 
     extendable = True
-    executables = ["^rustc$", "^cargo$"]
+    executables = [r"^rustc(-[\d.]*)?$", r"^cargo(-[\d.]*)?$"]
 
     phases = ["configure", "build", "install"]
 
     @classmethod
-    def determine_spec_details(cls, prefix, exes_in_prefix):
-        rustc_candidates = [x for x in exes_in_prefix if os.path.basename(x) == "rustc"]
-        cargo_candidates = [x for x in exes_in_prefix if os.path.basename(x) == "cargo"]
-        # Both rustc and cargo must be present
-        if not (rustc_candidates and cargo_candidates):
-            return
-        output = Executable(rustc_candidates[0])("--version", output=str, error=str)
-        match = re.match(r"rustc (\S+)", output)
-        if match:
-            version_str = match.group(1)
-            return Spec.from_detection(f"rust@{version_str}", external_path=prefix)
+    def determine_version(csl, exe):
+        output = Executable(exe)("--version", output=str, error=str)
+        match = re.match(r"(rustc|cargo) (\S+)", output)
+        return match.group(2) if match else None
+
+    @classmethod
+    def determine_variants(cls, exes, version_str):
+        rustc_candidates = [x for x in exes if "rustc" in os.path.basename(x)]
+        cargo_candidates = [x for x in exes if "cargo" in os.path.basename(x)]
+        extra_attributes = {}
+        if rustc_candidates:
+            extra_attributes.setdefault("compilers", {})["rust"] = rustc_candidates[0]
+
+        if cargo_candidates:
+            extra_attributes["cargo"] = cargo_candidates[0]
+
+        return "", extra_attributes
+
+    @classmethod
+    def validate_detected_spec(cls, spec, extra_attributes):
+        if "cargo" not in extra_attributes:
+            raise RuntimeError(f"discarding {spec} since 'cargo' is missing")
+
+        if not extra_attributes.get("compilers", {}).get("rust"):
+            raise RuntimeError(f"discarding {spec} since 'rustc' is missing")
 
     def setup_dependent_package(self, module, dependent_spec):
         module.cargo = Executable(os.path.join(self.spec.prefix.bin, "cargo"))