On Thu, Sep 30, 2021 at 5:35 AM Markus Armbruster <arm...@redhat.com> wrote:
> John Snow <js...@redhat.com> writes:
>
> > Here's the weird bit. QAPIDoc generally expects -- virtually everywhere
> > -- that it will always have a current section. The sole exception to
> > this is in the case that end_comment() is called, which leaves us with
> > *no* section. However, in this case, we also don't expect to actually
> > ever mutate the comment contents ever again.
> >
> > NullSection is just a Null-object that allows us to maintain the
> > invariant that we *always* have a current section, enforced by static
> > typing -- allowing us to type that field as QAPIDoc.Section instead of
> > the more ambiguous Optional[QAPIDoc.Section].
> >
> > end_section is renamed to switch_section and now accepts as an argument
> > the new section to activate, clarifying that no callers ever just
> > unilaterally end a section; they only do so when starting a new section.
> >
> > Signed-off-by: John Snow <js...@redhat.com>
> >
> > ---
> >
> > For my money: Optional types can be a nuisance because an unfamiliar
> > reader may wonder in what circumstances the field may be unset. This
> > makes the condition quite a bit more explicit and statically provable.
> >
> > Doing it in this way (and not by creating a dummy section) will also
>
("And not by creating a [mutable] dummy section" ... but this wasn't
destined for the git log anyway.)
> > continue to reject (rather noisily) any erroneous attempts to append
> > additional lines after end_comment() has been called.
> >
> > Also, this section isn't indexed into .sections[] and isn't really
> > visible in any way to external users of the class, so it seems like a
> > harmless and low-cost way to formalize the "life cycle" of a QAPIDoc
> > parser.
> >
> > Clean and clear as I can make it, in as few lines as I could muster.
> >
> > Signed-off-by: John Snow <js...@redhat.com>
> > ---
> > scripts/qapi/parser.py | 27 ++++++++++++++++-----------
> > 1 file changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
> > index 1fdc5bc7056..123fc2f099c 100644
> > --- a/scripts/qapi/parser.py
> > +++ b/scripts/qapi/parser.py
> > @@ -478,6 +478,13 @@ def __init__(self, parser, name, indent=0):
> > def connect(self, member):
> > self.member = member
> >
> > + class NullSection(Section):
> > + """
> > + Empty section that signifies the end of a doc block.
>
> What about "Dummy section for use at the end of a doc block"?
>
>
Sure. "Immutable dummy section for use at the end of a doc block."
> > + """
> > + def append(self, line):
> > + assert False, "BUG: Text appended after end_comment()
> called."
>
> How can a failing assertion *not* be a bug?
>
>
Haha. I'll drop the prefix. (I'll update my branch with these tiny edits
and you can decide what you'd like to do with that.)
> > +
> > def __init__(self, parser, info):
> > # self._parser is used to report errors with QAPIParseError.
> The
> > # resulting error position depends on the state of the parser.
> > @@ -525,7 +532,7 @@ def append(self, line):
> > self._append_line(line)
> >
> > def end_comment(self):
> > - self._end_section()
> > + self._switch_section(QAPIDoc.NullSection(self._parser))
> >
> > @staticmethod
> > def _is_section_tag(name):
> > @@ -702,9 +709,9 @@ def _start_symbol_section(self, symbols_dict, name,
> indent):
> > raise QAPIParseError(self._parser,
> > "'%s' parameter name duplicated" %
> name)
> > assert not self.sections
> > - self._end_section()
> > - self._section = QAPIDoc.ArgSection(self._parser, name, indent)
> > - symbols_dict[name] = self._section
> > + new_section = QAPIDoc.ArgSection(self._parser, name, indent)
> > + self._switch_section(new_section)
> > + symbols_dict[name] = new_section
> >
> > def _start_args_section(self, name, indent):
> > self._start_symbol_section(self.args, name, indent)
> > @@ -716,13 +723,11 @@ def _start_section(self, name=None, indent=0):
> > if name in ('Returns', 'Since') and self.has_section(name):
> > raise QAPIParseError(self._parser,
> > "duplicated '%s' section" % name)
> > - self._end_section()
> > - self._section = QAPIDoc.Section(self._parser, name, indent)
> > - self.sections.append(self._section)
> > -
> > - def _end_section(self):
> > - assert self._section is not None
> > + new_section = QAPIDoc.Section(self._parser, name, indent)
> > + self._switch_section(new_section)
> > + self.sections.append(new_section)
> >
> > + def _switch_section(self, new_section):
> > text = self._section.text = self._section.text.strip()
> >
> > # Only the 'body' section is allowed to have an empty body.
> > @@ -735,7 +740,7 @@ def _end_section(self):
> > self._parser,
> > "empty doc section '%s'" % self._section.name)
> >
> > - self._section = None
> > + self._section = new_section
> >
> > def _append_freeform(self, line):
> > match = re.match(r'(@\S+:)', line)
>
> Feels clearer, thanks!
>
>
Relieved you think so O:-)
--js
