By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Add comments within declarations
A comment used to be a declaration of its own, so a comment between the lines
of a transaction was either a parse error or was moved onto its own line by
the formatter.
A comment can now be written on an indented line of its own within a
declaration, where it belongs to the line below it. That means 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 at the first column still starts a new declaration, so the lines
that a declaration cannot contain, an import, a currency, a tag, a price, an
account line and a timestamp line, hold no comment of their own: a comment
above those is a comment declaration already.
A run of comment lines is one comment, so 'Commented' holds at most one and a
run of comment lines at the first column is one declaration.
Note that both the lines of a transaction and the declarations of a module are
a chain of productions rather than a list. The comment above a line has to be
read before it is known which kind of line follows it, so a list makes the
description/posting and posting/extra boundaries reduce/reduce conflicts, and a
list of declarations that each start with a comment run makes another comment
line either extend the run or start the next declaration.
Fix two bugs in the process:
* 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 line is now a single token, so
there is no start code left to be stranded in.
* A description could be empty, or contain an empty line, neither of which
can be written down: an empty description formatted to no line at all and
was silently lost.