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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`readline.set_completer_delims` has no effect with libedit","articleBody":"# Bug report\n\n### Bug description:\n\n`readline.set_completer_delims` works fine with GNU readline, but not with libedit.\n\nA quick example:\n\n```python\nimport readline\n\nreadline.set_completer_delims(\"\\n\")\nif \"libedit\" in getattr(readline, \"__doc__\", \"\"):\n    readline.parse_and_bind(\"bind ^I rl_complete\")\nelse:\n    readline.parse_and_bind(\"tab: complete\")\n\ndef completer(text, state):\n    if text == \"$\" and state == 0:\n        return \"$complete\"\n    return None\n\nreadline.set_completer(completer)\n\ninput()\n# Type $ then \u003ctab\u003e\n```\n\nWith GNU readline, it completes correctly, but with libedit, it can't - libedit still considers `$` as a delimiter. You can confirm that by printing the text in `completer` function.\n\nThe issue is in `readline.c`:\n\nhttps://github.com/python/cpython/blob/d4f83e1e3a19e2f881115f20d58ae6a019ddb48f/Modules/readline.c#L576-L581\n\n`readline.c` writes to `rl_completer_word_break_characters`, which works fine [source](https://git.savannah.gnu.org/cgit/readline.git/tree/complete.c#n1079).\n\nHowever, libedit does not do the same thing, it uses `rl_basic_word_break_characters` [instead](https://opensource.apple.com/source/libedit/libedit-40/src/readline.c):\n\n```C\nif (rl_completion_word_break_hook != NULL)\n\tbreakchars = (*rl_completion_word_break_hook)();\nelse\n\tbreakchars = rl_basic_word_break_characters;\n```\n\nThus, writing to `rl_completer_word_break_characters` will not have any effect on libedit. The simplest way I can think of, is to write to both `rl_completer_word_break_characters` and `rl_basic_word_break_characters`. They both exist in GNU readline and libedit, for slightly different purposes.\n\n* GNU readline:\n    * `rl_completer_word_break_characters` is the one that takes effect\n    * `rl_basic_word_break_characters` just keeps a string as default value for `rl_completer_word_break_characters`\n* libedit\n    * `rl_completer_word_break_characters` is not used at all\n    * `rl_basic_word_break_characters` is used for break words\n\nFrom what I can observe, writing to both variables has no unexpected side effect, because `rl_basic_word_break_characters` is not used on CPython with GNU readline.\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux, macOS\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-112106\n* gh-112487\n* gh-112488\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/gaogaotiantian","@type":"Person","name":"gaogaotiantian"},"datePublished":"2023-11-15T04:52:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/112105/cpython/issues/112105"}