gh-46927: Prevent readline from overriding environment #133585
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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool. If this change has little impact on Python users, wait for a maintainer to apply the |
Readline library will set the LINES and COLUMNS environment variables during initialization. One might expect these variables to be updated later on SIGWINCH, but this is not the case with cpython. As a consequence, when the readline module is imported, any process launched from cpython with the default environment will have LINES and COLUMNS variables set, potentially to a wrong value. Use the rl_change_environment global variable to disable this initial setup of the environment variables.
| @@ -1323,6 +1323,13 @@ setup_readline(readlinestate *mod_state) | |||
| /* The name must be defined before initialization */ | |||
| rl_readline_name = "python"; | |||
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| #if !defined(__APPLE__) | |||
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I'm a bit surprised I had to rely on the __APPLE__ define here. As I understand apple OS is using libedit, so I would have thought relying on WITH_EDITLINE would be enough. But the macOS pipeline proved me wrong...
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Please add a test case. The file you're looking for is test_readline.
Misc/NEWS.d/next/Core_and_Builtins/2025-05-07-18-31-31.gh-issue-46927.sF02gj.rst
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| @@ -405,6 +407,12 @@ def test_write_read_limited_history(self): | |||
| # So, we've only tested that the read did not fail. | |||
| # See TestHistoryManipulation for the full test. | |||
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| @requires_subprocess() | |||
| def test_environment_is_not_modified(self): | |||
| original_env = dict(os.environ) | |||
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Did you forget to add the use of subprocess here? This test always passes.
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Err sorry, I reworked the test and forgot to remove the subprocess requirement.
But I do confirm this test fails if I revert the initial commit of the PR.
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Hi! Any news about this PR? Is there anything I can do to help the this modification being accepted? |
Readline library will set the LINES and COLUMNS environment variables during initialization. One might expect these variables to be updated later on SIGWINCH, but this is not the case with cpython.
As a consequence, when the readline module is imported, any process launched from cpython with the default environment will have LINES and COLUMNS variables set, potentially to a wrong value.
Use the rl_change_environment global variable to disable this initial setup of the environment variables.