Isolate RustPython bytecode caches during the 3.15 transition

Assisted-by: OpenAI Codex:model identifier unavailable

crates/vm/src/stdlib/sys.rs

@@ -667,8 +667,8 @@ pub mod sys {
     fn implementation(vm: &VirtualMachine) -> PyRef<PyNamespace> {
         const NAME: &str = "rustpython";
 
-        // cache tag uses 'cpython' because our compiler is cpython compatible
-        let cache_tag = format!("cpython-{}{}", version::MAJOR, version::MINOR);
+        // Keep implementation-specific bytecode caches separate.
+        let cache_tag = format!("{NAME}-{}{}", version::MAJOR, version::MINOR);
         let ctx = &vm.ctx;
         py_namespace!(vm, {
             "name" => ctx.new_str(NAME),

crates/vm/src/vm/mod.rs

@@ -1607,7 +1607,7 @@ impl VirtualMachine {
     /// ```no_run
     /// use rustpython_vm::Interpreter;
     /// Interpreter::without_stdlib(Default::default()).enter(|vm| {
-    ///     let bytes = std::fs::read("__pycache__/<input>.cpython-315.pyc").unwrap();
+    ///     let bytes = std::fs::read("__pycache__/<input>.rustpython-315.pyc").unwrap();
     ///     let main_scope = vm.new_scope_with_main().unwrap();
     ///     vm.run_pyc_bytes(&bytes, main_scope);
     /// });

extra_tests/snippets/stdlib_sys.py

@@ -28,7 +28,9 @@ assert isinstance(sys.implementation.cache_tag, str)
 assert sys.version_info[:3] == (3, 15, 0)
 assert sys.hexversion >> 8 == 0x030F00
 assert sys.version.startswith("3.15.0")
-assert sys.implementation.cache_tag == "cpython-315"
+assert sys.implementation.cache_tag == (
+    f"{sys.implementation.name}-{sys.version_info.major}{sys.version_info.minor}"
+)
 
 assert sys.getfilesystemencoding() == "utf-8"
 assert sys.getfilesystemencodeerrors().startswith("surrogate")