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Prompt user to use the backtracking resolver on errors #1719

Merged
merged 10 commits into from
Nov 10, 2022
12 changes: 11 additions & 1 deletion piptools/scripts/compile.py
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@

from .._compat import IS_CLICK_VER_8_PLUS, parse_requirements
from ..cache import DependencyCache
from ..exceptions import PipToolsError
from ..exceptions import NoCandidateFound, PipToolsError
from ..locations import CACHE_DIR
from ..logging import log
from ..repositories import LocalRequirementsRepository, PyPIRepository
Expand Down Expand Up @@ -547,6 +547,16 @@ def cli(
)
results = resolver.resolve(max_rounds=max_rounds)
hashes = resolver.resolve_hashes(results) if generate_hashes else None
except NoCandidateFound as e:
if resolver_cls == LegacyResolver: # pragma: no branch
log.error(
"Using legacy resolver. "
"Consider using backtracking resolver with "
"`--resolver=backtracking`."
)

log.error(str(e))
sys.exit(2)
except PipToolsError as e:
log.error(str(e))
sys.exit(2)
Expand Down
33 changes: 33 additions & 0 deletions tests/test_cli_compile.py
Original file line number Diff line number Diff line change
Expand Up @@ -2489,3 +2489,36 @@ def test_preserve_via_requirements_constrained_dependencies_when_run_twice(
for output in (first_out, second_out):
assert output.exit_code == 0, output
assert output.stderr == expected_output


def test_failure_of_legacy_resolver_prompts_for_backtracking(
pip_conf, runner, tmpdir, make_package, make_wheel, current_resolver
):
"""Test that pip-compile prompts to use the backtracking resolver"""
pkgs = [
make_package("a", version="0.1", install_requires=["b==0.1"]),
make_package("a", version="0.2", install_requires=["b==0.2"]),
make_package("b", version="0.1"),
make_package("b", version="0.2"),
make_package("c", version="1", install_requires=["b==0.1", "a"]),
]

dists_dir = tmpdir / "dists"
for pkg in pkgs:
make_wheel(pkg, dists_dir)

with open("requirements.in", "w") as req_in:
req_in.writelines(["c"])

out = runner.invoke(
cli,
["--resolver", current_resolver, "--find-links", str(dists_dir)],
)

if current_resolver == "legacy":
assert out.exit_code == 2, out
assert "Consider using backtracking resolver with" in out.stderr
elif current_resolver == "backtracking":
assert out.exit_code == 0, out
else: # pragma: no cover
raise AssertionError("unreachable")