bug#58983: 28.2; nroff-mode misshandled quoting

[Gavin Jaeger-Freeborn]

Hello everyone,

Currently nroff-mode misidentifies double quotes in string definitions.
Currently all pairs of double quotes are highlighted as a string unless
used in a comment like in most languages. However, nroff/troff has one
special case where its is not the case. The following outlines how it should
work.

In nroff/troff you can define strings with the following format

.ds welcome hello world

This defines a `string` welcome with the contents `hello world'

Now if someone wanted to define a string that started with a space they
would instead use

.ds welcome " hello world

In addition you can call a macro with the same leeding `.` like so

.B "hello world"

This calls the macro `B` with it's first argument being `hello world`

The issue is that at the moment the strings are simply detected with the
code

(modify-syntax-entry ?\" "\"  2" st)

Meaning that (unless it's a comment) its assumed to be a string (at least
that is my understanding). Instead a special case needs to be added to
avoid doing this if the double quote is used in a string definition.

The closest thing to a language specification these languages have is
the troff user manual which defines the ds request as

> .ds xx
>
> Define a string xx containing string. Any initial double quote in string
> is stripped off to permit initial blanks.

The manual can be found at https://www.troff.org/54.pdf

For further examples on how this is used please see
https://raw.githubusercontent.com/aligrudi/neatroff_make/master/tmac/tmac.en

In addition https://github.com/aligrudi/neatroff_make/tree/master/demo
contains multiple other examples.

Thanks in advance!

Gavin



In GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo 
version 1.17.6)
 of 2022-09-12 built on frederik
Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
System Description: EndeavourOS

Configured using:
 'configure --with-x-toolkit=gtk3 --with-native-compilation
 --sysconfdir=/etc --prefix=/usr --libexecdir=/usr/lib
 --localstatedir=/var --with-cairo --with-harfbuzz --with-libsystemd
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 'LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -flto=auto''

Configured features:
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Important settings:
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Major mode: mu4e:main

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Load-path shadows:
/home/gavinok/.emacs.d/elpa/transient-20220918.2101/transient hides 
/usr/share/emacs/28.2/lisp/transient

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Memory information:
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