[bug #63202] [troff] missing delimiter diagnostics could say what they were expecting

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?63202>

                 Summary: [troff] missing delimiter diagnostics could say what
they were expecting
                 Project: GNU troff
               Submitter: gbranden
               Submitted: Wed 12 Oct 2022 06:33:11 PM UTC
                Category: Core
                Severity: 1 - Wish
              Item Group: Warning/Suspicious behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


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Date: Wed 12 Oct 2022 06:33:11 PM UTC By: G. Branden Robinson <gbranden>
In all of the escape sequences that accept user-determined delimiters, we have
diagnostic messages that complain of a missing closing one.

We could therefore say in those messages _which_ delimiter we were expecting,
which might make life easier, especially for users who bother to distinguish
their nested delimiters instead of just spraying apostrophes everywhere and
praying.  The opening delimiter is always stored already as `start`, or in one
case `delim`, so there's no overhead to giving the user this information.

However, an attempt to dash this off in five minutes revealed two problems:

1.  Those damnable newline-accepting escape sequences only throw the mismatch
diagnostic upon EOF.  When I try to make them complain when a newline is read
and it's NOT the delimiter, my regression test trips.  So this feature, apart
from being of dubious worth, is subtle and quick to anger.

2.  Having applied, I was sometimes told that the opening delimiter was a
"node".  This is not helpful feedback to the user.

Come back to this someday.  The fact that we now (post-groff 1.22.4) identify
_which_ escape sequence is being processed when trouble occurs may mitigate
the motivation I offered in paragraph 2 above.









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