[tex-k] Bug report for the 2029 TeX tune-up - Error-message is expected but the text of the error-message is incorrect

[ud.usenetcorrespondence at web.de]

Bug report for the 2029 TeX tune-up

Subject: Error-message is expected but the text of the error-message is incorrect

Submitted by: Ulrich Diez (diez.ulrich at web.de / ud.usenetcorrespondence at web.de)


.tex-input-file FileA.tex contains:

   Line 1
   Line 2
   Line 3


.tex-input-file test.tex contains:

   \endinput\edef\foobar{\input FileA.tex }%
   \bye


I am aware of the circumstance that with \input "inside" \edef
you expect an error-message in any case. That is not what this
bug-report is about.

Be aware that in test.tex \endinput is _before_ \edef !

Chapter 20: Definitions (also called macros) of the TeXbook says
about \endinput:

| - \endinput. The expansion is null. The next time TeX gets to the end
| of an \input line, it will stop reading from the file containing that line.


Compiling test.tex via tex test.tex yields the following console-output:


   This is TeX, Version 3.14159265 (TeX Live 2020) (preloaded format=tex)
   (./test.tex (./FileA.tex)
   Runaway definition?
   ->Line 1
   ! File ended while scanning definition of \foobar.
   <inserted text>
   }
   l.1 \endinput\edef\foobar{\input FileA.tex
   }%
   ?
   ! Too many }'s.
   l.1 \endinput\edef\foobar{\input FileA.tex }
   %
   ?
   )
   No pages of output.
   Transcript written on test.log.



Do you see the statement

   ->Line 1
   ! File ended while scanning definition of \foobar.

?

That statement is not correct in this subtle case.

In this subtle case the reason for the runaway-definition
is not that TeX encountered the _end_ of a file.

In this subtle case the reason for the runaway-definition
is that reading from fileA.tex was ceased due to the
pending \endinput after reading and processing the
first line of fileA.tex.


In this subtle case a correct statement would be something
like:

   ->Line 1
   ! Due to pending \endinput reading from file was ceased
   ! after reading its first line while scanning definition
   ! of \foobar.


Shorter and less informative:

   ->Line 1
   ! Processing the file ended while scanning definition of \foobar.

This doesn't say anything about the reason (reaching the end/
pending \endinput and end of file's first line) for ending the
processing of the file.

Rectifying this would probably be nice for people who play
with TeX-engines where eTeX-extensions with things like
\everyeof{\noexpand}\edef\foobar{\scantokens{..}}
are possible and who seem to struggle with misleading
statements coming from error-messages.

See, e.g.,

https://groups.google.com/g/comp.text.tex/c/tdE_mQrMoiE/m/7l9MWXl7AwAJ


Sincerely

Ulrich Diez