| Message ID | 20210929194428.1038496-9-jsnow@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qapi: static typing conversion, pt5b | expand |
John Snow <jsnow@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 <jsnow@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 > 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 <jsnow@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"? > + """ > + def append(self, line): > + assert False, "BUG: Text appended after end_comment() called." How can a failing assertion *not* be a bug? > + > 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!
On Thu, Sep 30, 2021 at 5:35 AM Markus Armbruster <armbru@redhat.com> wrote: > John Snow <jsnow@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 <jsnow@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 <jsnow@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
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. + """ + def append(self, line): + assert False, "BUG: Text appended after end_comment() called." + 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)