Rust: move rust_sysroot_src to its own session fixture

Author: Paolo Tranquilli

rust/ql/integration-tests/conftest.py

@@ -4,18 +4,24 @@
 import pathlib
 
 
+@pytest.fixture
 def cargo(cwd):
     assert (cwd / "Cargo.toml").exists()
     (cwd / "rust-project.json").unlink(missing_ok=True)
 
+@pytest.fixture(scope="session")
+def rust_sysroot_src() -> str:
+    rust_sysroot = pathlib.Path(commands.run("rustc --print sysroot", _capture=True))
+    ret = rust_sysroot.joinpath("lib", "rustlib", "src", "rust", "library")
+    assert ret.exists()
+    return str(ret)
 
 @pytest.fixture
-def rust_project(cwd):
+def rust_project(cwd, rust_sysroot_src):
     project_file = cwd / "rust-project.json"
     assert project_file.exists()
-    rust_sysroot = pathlib.Path(commands.run("rustc --print sysroot", _capture=True))
     project = json.loads(project_file.read_text())
-    project["sysroot_src"] = str(rust_sysroot.joinpath("lib", "rustlib", "src", "rust", "library"))
+    project["sysroot_src"] = rust_sysroot_src
     project_file.write_text(json.dumps(project, indent=4))
     (cwd / "Cargo.toml").unlink(missing_ok=True)