Pass cache_dir to pip_args for backtracking resolver (#1827)

piptools/scripts/compile.py

@@ -424,6 +424,8 @@ def cli(
  pip_args.append("--no-build-isolation")
  if resolver_name == "legacy":
  pip_args.extend(["--use-deprecated", "legacy-resolver"])
+ if resolver_name == "backtracking" and cache_dir:
+ pip_args.extend(["--cache-dir", cache_dir])
  pip_args.extend(right_args)
 
  repository: BaseRepository

tests/test_cli_compile.py

@@ -2853,3 +2853,18 @@ def test_raise_error_when_input_and_output_filenames_are_matched(
  f"Error: input and output filenames must not be matched: {req_out_path}"
  )
  assert expected_error in out.stderr.splitlines()
+
+
+@pytest.mark.network
+@backtracking_resolver_only
+def test_pass_pip_cache_to_pip_args(tmpdir, runner, current_resolver):
+ cache_dir = tmpdir.mkdir("cache_dir")
+
+ with open("requirements.in", "w") as fp:
+ fp.write("six==1.15.0")
+
+ out = runner.invoke(
+ cli, ["--cache-dir", str(cache_dir), "--resolver", current_resolver]
+ )
+ assert out.exit_code == 0
+ assert os.listdir(os.path.join(str(cache_dir), "http"))