🐛 fix(cli): make multiple -e flags additive#3755
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gaborbernat merged 1 commit intotox-dev:mainfrom Feb 18, 2026
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In tox 3, `tox -e a -e b` would run both environments. In tox 4 the second `-e` silently replaced the first, running only `b`. This broke CI pipelines that relied on the additive behavior. Replaced the default argparse store action with a custom action that accumulates values into the existing CliEnv via a new `__iadd__` method, so repeated `-e` flags merge their environment lists. Fixes tox-dev#3199
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In tox 3, running
tox -e a -e bwould execute both environments. In tox 4 the second-esilently replaced the first, so onlybwould run. 🔍 This broke CI pipelines and scripts that relied on the additive behavior, with no error or warning to indicate environments were being dropped.The fix uses a custom argparse action that accumulates values from repeated
-eflags into a singleCliEnvinstance instead of replacing it. This restores tox 3 behavior while preserving full backward compatibility —tox -e a,b(comma-separated) continues to work exactly as before.-eflags to override earlier ones will now get the union of all specified environments. The comma-separated formtox -e a,bremains the canonical way to specify multiple environments in a single flag.Fixes #3199