indent=Tab setting not respected #2693

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1. pradip-pawar1 commented on Sep 30, 2026

   

   pradip-pawar1

   on Sep 30, 2026

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   I've confirmed this. Using .isort.cfg with [settings] and indent=tab (plain, unquoted, lowercase) correctly produces a real tab character in output. However, every other form fails and silently falls back to 4 spaces:

   • indent="tab" (quoted),
   • indent=Tab (capitalized),
   • indent=\t,
   • indent=\\t,
   • and even a literal tab byte in the config value itself.

   Tested on isort 9.0.2.dev20 (editable install from main), Windows 11.

   I found existing tab-handling logic:

   if "indent" in combined_config:
     indent = str(combined_config["indent"])
     if indent.isdigit():
         indent = " " * int(indent)
     else:
         indent = indent.strip("'").strip('"')
         if indent.lower() == "tab":
             indent = "\t"
     combined_config["indent"] = indent

   This logic should handle the quoted and capitalized cases correctly by my reading, which suggests the .isort.cfg values may be reaching combined_config through a different path than expected, or something upstream is altering them before this code runs.

   Still investigating.
2. shan3520 commented on Oct 2, 2026

   

   shan3520

   on Oct 2, 2026

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   I dug into this on main (9.0.3.dev) and the 9.0.2 wheel. Findings:

   1. Tab / "tab" / TAB do work. indent=Tab in .isort.cfg gives config.indent == "\t" both via isort.Config(settings_path=...) and the CLI. I couldn't reproduce the capitalised/quoted failures.

   2. The likely cause of "only ever spaces" is the wrap mode. With the default multi_line_output (GRID), as well as VERTICAL and BACKSLASH_GRID, continuation lines are aligned to the opening bracket with spaces, so indent isn't used at all. The hanging-indent modes (2, 3, 4, 5, 8, 10, e.g. profile=black) do emit tabs. @clayote, does adding multi_line_output=3 fix it for you?

   3. Two real bugs I found along the way:

   • indent=\t in a config file is taken literally, so isort writes \tname, into the output, which is a SyntaxError.
   • A literal tab character as the value is stripped by configparser, leaving indent="", and isort silently writes unindented continuation lines.

   Proposed fix, if you're happy with it:

   • interpret \t in the indent value as a tab
   • reject an empty or whitespace-stripped-to-empty indent with a clear error instead of producing unindented output
   • document in the indent option that it accepts tab, a number of spaces, or a string, and that it only applies to the hanging-indent multi_line_output modes

   I'm happy to open a PR for this. (I used Claude to help investigate and reproduce this; I've verified the results.)
3. pradip-pawar1 commented on Oct 2, 2026

   

   pradip-pawar1

   on Oct 2, 2026

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   I've opened a PR with a fix and regression test: #2704
4. clayote commented on Oct 6, 2026

   

   clayote

   on Oct 6, 2026

   Author

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   On 9.0.2, multi_line_output=3 still gets me spaces, but in 9.0.3.dev11, I get the tabs I wanted. Thanks!
5. clayote

   closed this as completedon Oct 6, 2026