Author: Jonathan Marten
Updated:
Major mode for editing Sendmail configuration files
Sendmail configuration files are usually pretty unintelligible, so
some help with syntax colouring and comment indentation is always
welcome. This mode attempts to do that.
The fontification rules and the list of keywords were derived from
the O'Reilly book and the online documentation included with the
latest versions of sendmail. They may be neither complete nor 100%
accurate; since the configuration file syntax is not particularly
rigourous or consistent a totally accurate fontification might not
be possible. However, it has been tested on as many configuration
files as I could find, from a number of systems and of various
vintages. Additional keywords or examples of incorrect fontification
or comment indentation would be most welcome.
Syntactic fontification is done, but only for quoted strings.
No comment syntax is defined, because Emacs' built-in indentation and
fontification cannot handle the varying rules for placement and
validity of comments, especially with the differences between pre-V8
and later sendmail. Comments are fontified using the font-lock
regexps, and comment indentation is handled specially using
`sendmail-indent-for-comment'. This is because the syntax of a comment,
or even whether one is allowed at all, varies depending on what sort of
line the comment is on and the version of the configuration file. The
only particularly complex case is for an "R" line, where the comment
has no delimiter but is separated from the RHS by at least one tab.
We have to take care that there is at least that one tab here, even
in the case where the indent is past the comment column and normally
only a single space would be inserted.
All brackets ("[]", "<>", "()" and "{}") are normally considered
worthy of matching. However, "<>" sometimes leads to anomalous
indications because "$>" does not have a matching open "<". This
should be fixed in paren.el by not considering a character to be
a paren if the character preceding it has char-quote syntax
("/" in syntax table). In this mode, "$" has such syntax.
There is no indentation in the configuration file, so (contrary to the
usual Emacs convention), the TAB key is defined to self-insert.
Sendmail is very sensitive to the format of the configuration file, and
small and sometimes invisible errors can cause serious problems. This
mode attempts to help as far as is possible:
1. Additional spaces before or after tabs, and lines containing only
whitespace, are highlighted. This can help to avoid unintended
addition of whitespace tokens and continuation lines.
2. Pre-V8 sendmail requires a final newline in the configuration file,
otherwise the last line of the file is silently ignored. This is
enforced by ensuring that `require-final-newline' is forced to
"add always" if it is set to "never" by default. If the setting is
"ask" then it stays.