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Re: Bash completion fails if command results from alias expansion

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On Tuesday, June 14, 2022 at 3:22:59 AM UTC-7, Tasos Papastylianou wrote:
> Dear bash maintainers. 
> 
> I posted this at the SuperUser stackexchange forum (here: https://superuser.com/q/1725872/717607), so please see that post too if you like (especially if it generates separate conversaion, which it has not so far) but I thought I might as well ask straight from the horses mouth and submit this as a bug after all. 
> 
> There are several posts online (e.g. https://superuser.com/q/436314/717607) suggesting workarounds for bash completing aliases whose commands have established completions defined. 
> 
> However, in the bash manual (i.e. man bash, currently using GNU bash, version 5.0.17), section Programmable Completion, it states that: 
> 
> > If there is no default compspec, bash attempts alias expansion on the command word as a final resort, and attempts to find a compspec for the command word from any successful expansion. 
> 
> In other words one would have expected this to work: 
> 
> function foobar () { echo "Hello from foobar"; } 
> function _foobar () { COMPREPLY=( foo bar baz ); } && complete -F _foobar foobar 
> alias foo='foobar' 
> 
> Typing `foobar[TAB][TAB]` autocompletes as expected. 
> 
> However, typing `foo[TAB][TAB]` does not work, and shows a default completion instead. 
> 
> Given the linked posts suggesting workarounds, I don't think it's just me doing something wrong here. But then what does the quote from the bash manual actually refer to then? Am I misunderstanding the quote from the manual? Or is bash simply not doing what is says it should have been doing here? (i.e. is this simply a bug?) 
> 
> I note a nearly identical question was asked in the bash bug tracker back in 2011 (with yet another nice workaround: https://groups.google.com/g/gnu.bash.bug/c/gENuqpAUTUg/m/JpHbe7KmpGgJ), but the phrasing of that question implies that this was not mentioned in the manual back then, and I haven't seen any sign of addressing this issue on the official group page since. 
> 
> Also, I've checked the changelogs up to the latest version of Bash, as announced here, but it doesn't seem to me this has been addressed. 
> 
> I don't know if "completion of alias expanded commands" is a good idea or not, that's a matter for debate among the maintainers (I'm of a split mind myself!); but if it *is* intended behaviour, then I'm reporting it as a bug, since it doesn't actually work as documented; and if it is not desired behaviour, then perhaps that statement about completion of alias-expanded commands should be removed from the bash man page. 
> 
> Best, 
> Tasos
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Bash completion fails if command results from alias expansion Tasos Papastylianou <tpapastylianou@gmail.com> - 2022-06-14 03:22 -0700
  Re: Bash completion fails if command results from alias expansion GODSWILL DUKE <dukegodswill2022@gmail.com> - 2023-02-15 10:25 -0800

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