04c59867

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Add end-of-line comments and comments within declarations

A comment used to be a declaration of its own, so a comment written at the
end of a line, or between the lines of a transaction, was either a parse
error or was moved onto its own line by the formatter.

Every line can now carry a comment at the end of it, and comments on
indented lines of their own.  A comment on a line of its own belongs to the
line below it, so a comment cannot be the last line of a declaration: it
would belong to no line at all, which is an error that points at the
comment.

A comment on a line of its own has to be indented to belong to the
declaration it is in: a "--" at the first column starts a new declaration.
Comments above a declaration are already declarations of their own, so the
lines that a declaration cannot contain, an import, a currency, a tag, a
price, an account line and a timestamp line, hold only an end-of-line
comment.

The one line that cannot carry a comment at the end of it is a description,
because a description is the whole rest of its line.

Note that the lines of a transaction are one chain of productions rather
than three lists.  The comments above a line have to be read before it is
known which kind of line follows them, so a list per kind of line makes the
description/posting and posting/extra boundaries reduce/reduce conflicts.

Fix two bugs in the process, both of which the extra comment positions would
otherwise have made much easier to hit:

  * A comment whose text was only whitespace swallowed the declaration below
    it.  Nothing could match the rest of the line, so '$white+' matched the
    newline instead and left the lexer in the comment start code, reading the
    next declaration as comment text.  A comment is now a single token, so
    there is no start code left to be stranded in.

  * A file path was lexed with a character set containing an unescaped '.',
    which means "any character but a newline", so a path ran to the end of
    the line.  A trailing comment ended up inside the path.  A path may now
    contain spaces but not the "-- " that starts a comment.

Timeline