🐛 fix(env): break circular dependency in environment_variables resolution#3816
Merged
gaborbernat merged 3 commits intotox-dev:mainfrom Feb 23, 2026
Merged
🐛 fix(env): break circular dependency in environment_variables resolution#3816gaborbernat merged 3 commits intotox-dev:mainfrom
gaborbernat merged 3 commits intotox-dev:mainfrom
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set_env substitutions like {env_site_packages_dir} trigger virtualenv
session creation which re-enters environment_variables, causing a
RecursionError silently caught as RuntimeError. Add a re-entrancy guard
that returns pass_env + PATH without set_env on recursive calls.
Also fix tests asserting VirtualEnvOptions.copies which is only present
when the creator's meta reports can_copy (not all platforms).
for more information, see https://pre-commit.ci
set_env substitutions like {env_site_packages_dir} trigger virtualenv
session creation which re-enters environment_variables, causing a
RecursionError silently caught as RuntimeError. Add a re-entrancy guard
that returns pass_env + PATH without set_env on recursive calls.
Also fix tests asserting VirtualEnvOptions.copies which is only present
when the creator's meta reports can_copy (not all platforms).
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When
set_envcontains substitutions referencing{env_site_packages_dir},{env_bin_dir}, or similar lazy constants, resolving them triggers virtualenv session creation. The session creation callsvirtualenv_env_vars()which callsself.environment_variables, re-entering the property that's already mid-resolution. This causes aRecursionErrorwhich, being a subclass ofRuntimeError, gets silently caught by_get_python-- making tox report "could not find python interpreter" when the interpreter is perfectly findable.🔧 The fix adds a re-entrancy guard (
_resolving_env_varsflag) toToxEnv.environment_variables. When a recursive call is detected duringset_envloading or key resolution, it returnspass_env + PATHwithoutset_envvalues. This is sufficient for virtualenv's discovery and session creation, and the fullset_envresolution completes normally once the session exists. The guard preserves fullset_envsupport -- values set viaset_envintox.tomlstill work correctly forVIRTUALENV_*variables.Additionally fixes
test_virtualenv_apitests that unconditionally assertVirtualEnvOptions.copies, which is only present when the creator's meta reportscan_copy. On platforms like macOS with Homebrew CPython,--copiesis never added to argparse so the attribute doesn't exist.