Change BibTeX "I couldn't open database file" message to include double extension

[moewew]

• I have read the MiKTeX Contributing Guidelines

Consider the following MWE which fails because of the incorrect inclusion of .bib in the file name argument to \bibliography

\documentclass{article}

\bibliographystyle{plain}

\begin{document}
\cite{incollection-full}
\bibliography{xampl.bib}
\end{document}

BibTeX (MiKTeX-BibTeX 2.9.7388 (0.99d) (MiKTeX 2.9.7420 64-bit)) reports

I couldn't open database file xampl.bib
---line 4 of file Namenlsasos-9.aux
 : \bibdata{xampl.bib
 :                    }
I'm skipping whatever remains of this command
I found no database files---while reading file Namenlsasos-9.aux
Warning--I didn't find a database entry for "incollection-full"
(There were 2 error messages)

This is a bit confusing, because BibTeX claims xampl.bib could not be found (that file is present and would be found), but it actually looks for xampl.bib.bib, which can not be found. Compare this to

\documentclass{article}

\bibliographystyle{plain}

\begin{document}
\cite{incollection-full}
\bibliography{filethatdoesnotexist}
\end{document}

where BibTeX appends .bib to the file name

I couldn't open database file filethatdoesnotexist.bib
---line 4 of file hagasgjasgjs.aux
 : \bibdata{filethatdoesnotexist
 :                              }
I'm skipping whatever remains of this command
I found no database files---while reading file hagasgjasgjs.aux
Warning--I didn't find a database entry for "incollection-full"
(There were 2 error messages)

I think up until a while ago BibTeX correctly reported xampl.bib.bib as not found. (On a quick Google search I found https://stackoverflow.com/q/53969663 and https://www.reddit.com/r/LaTeX/comments/2wip2b/new_to_latex_first_time_bibliography_ive_been/)

So I suggest to re-instate the behaviour to always append .bib to the file not found message and not to strip a double .bib. I.e. the first message should read

I couldn't open database file xampl.bib.bib
---line 4 of file Namenlsasos-9.aux
 : \bibdata{xampl.bib
 :                    }
I'm skipping whatever remains of this command
I found no database files---while reading file Namenlsasos-9.aux
Warning--I didn't find a database entry for "incollection-full"
(There were 2 error messages)

That way the message can at least give a hint as to what might be going wrong.

---

Of course an alternative solution would be to strip double .bib extensions to avoid the issue in the first place (TeX live seems to accept \bibliography{xampl.bib}), but that is not what I'm primarily asking for. I think it is perfectly fine to support only documented use of the command (without the .bib file extension).

[edocevoli]

MiKTeX-BibTeX now accepts \bibliography{file.bib} just as file.aux is accepted on the command-line.

[moewew]

I'm not going to have a good argument any more to tell people to stop using the strictly speaking incorrect \bibliography{file.bib} now, but I guess this is the more user friendly outcome.

Is this already part of This is BibTeX, Version 0.99d (MiKTeX 2.9.7440 64-bit)?

Anyway, while I'm here, could you have a look at

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}

\begin{filecontents}{section.tex}
\section{My section}
I need to test the citations, so see \cite{incollection-full}.
\end{filecontents}

\begin{document}
\include{section}
\bibliography{xampl}
\bibliographystyle{plain}
\end{document}

(from https://tex.stackexchange.com/q/544949/35864).
When I run BibTeX I now get

This is BibTeX, Version 0.99d (MiKTeX 2.9.7440 64-bit)
Capacity: max_strings=200000, hash_size=200000, hash_prime=170003
The top-level auxiliary file: includetest.aux
Reallocating 'name_of_file' (item size: 1) to 12 items.
I couldn't open auxiliary file section.aux
---line 3 of file includetest.aux
 : \@input{section.aux
 :                    }
I'm skipping whatever remains of this command
Reallocating 'name_of_file' (item size: 1) to 6 items.
Reallocating 'name_of_file' (item size: 1) to 6 items.
The style file: plain.bst
I found no \citation commands---while reading file includetest.aux
Database file #1: xampl.bib
You've used 0 entries,
            2118 wiz_defined-function locations,
            505 strings with 4256 characters,
and the built_in function-call counts, 20 in all, are:
= -- 0
> -- 0
< -- 0
+ -- 0
- -- 0
* -- 2
:= -- 7
add.period$ -- 0
call.type$ -- 0
change.case$ -- 0
chr.to.int$ -- 0
cite$ -- 0
duplicate$ -- 0
empty$ -- 1
format.name$ -- 0
if$ -- 1
int.to.chr$ -- 0
int.to.str$ -- 0
missing$ -- 0
newline$ -- 4
num.names$ -- 0
pop$ -- 0
preamble$ -- 2
purify$ -- 0
quote$ -- 0
skip$ -- 0
stack$ -- 0
substring$ -- 0
swap$ -- 0
text.length$ -- 0
text.prefix$ -- 0
top$ -- 0
type$ -- 0
warning$ -- 0
while$ -- 0
width$ -- 0
write$ -- 3
(There were 2 error messages)

I think something like this used to work. (And in fact it does work in TeX live.)

[edocevoli]

Is this already part of This is BibTeX, Version 0.99d (MiKTeX 2.9.7440 64-bit)?

Yes.

Anyway, while I'm here, could you have a look at

Thank you, yet another bug. Deserves a new ticket.

[moewew]

I'll open another ticket about the .aux issue shortly. (edit #546)