Merge pull request #3201 from pre-commit/rust-default-language-version

determine rust default language version independent of rust-toolchain.toml

pre_commit/languages/rust.py

@@ -34,7 +34,7 @@ def get_default_version() -> str:
     # Just detecting the executable does not suffice, because if rustup is
     # installed but no toolchain is available, then `cargo` exists but
     # cannot be used without installing a toolchain first.
-    if cmd_output_b('cargo', '--version', check=False)[0] == 0:
+    if cmd_output_b('cargo', '--version', check=False, cwd='/')[0] == 0:
         return 'system'
     else:
         return C.DEFAULT

tests/languages/rust_test.py

@@ -9,6 +9,7 @@
 from pre_commit.languages import rust
 from pre_commit.store import _make_local_repo
 from testing.language_helpers import run_language
+from testing.util import cwd
 
 ACTUAL_GET_DEFAULT_VERSION = rust.get_default_version.__wrapped__
 
@@ -29,6 +30,14 @@ def test_uses_default_when_rust_is_not_available(cmd_output_b_mck):
     assert ACTUAL_GET_DEFAULT_VERSION() == C.DEFAULT
 
 
+def test_selects_system_even_if_rust_toolchain_toml(tmp_path):
+    toolchain_toml = '[toolchain]\nchannel = "wtf"\n'
+    tmp_path.joinpath('rust-toolchain.toml').write_text(toolchain_toml)
+
+    with cwd(tmp_path):
+        assert ACTUAL_GET_DEFAULT_VERSION() == 'system'
+
+
 def _make_hello_world(tmp_path):
     src_dir = tmp_path.joinpath('src')
     src_dir.mkdir()