On Thu, Jan 14, 2021 at 02:39:35PM +0100, Markus Armbruster wrote: > John Snow <js...@redhat.com> writes: > > > On 1/13/21 10:39 AM, Markus Armbruster wrote: > >> Spelling nitpick: s/builtin/built-in/ in the title. > >> > > > > Sure. > > > >> John Snow <js...@redhat.com> writes: > >> > >>> We use None to represent an object that has no source information > >>> because it's a builtin. This complicates interface typing, since many > >>> interfaces expect that there is an info object available to print errors > >>> with. > >>> > >>> Introduce a special QAPISourceInfo that represents these built-ins so > >>> that if an error should so happen to occur relating to one of these > >>> builtins that we will be able to print its information, and interface > >>> typing becomes simpler: you will always have a source info object. > >>> > >>> This object will evaluate as False, so "if info" remains a valid > >>> idiomatic construct. > >>> > >>> NB: It was intentional to not allow empty constructors or similar to > >>> create "empty" source info objects; callers must explicitly invoke > >>> 'builtin()' to pro-actively opt into using the sentinel. This should > >>> prevent use-by-accident. > >>> > >>> Signed-off-by: John Snow <js...@redhat.com> > >> > >> As I pointed out in review of v1, this patch has two aspects mixed up: > >> > >> 1. Represent "no source info" as special QAPISourceInfo instead of > >> None > >> > >> 2. On error with "no source info", don't crash. > >> > >> The first one is what de-complicates interface typing. It's clearly > >> serving this patch series' stated purpose: "static typing conversion". > >> > >> The second one is not. It sidetracks us into a design discussion that > >> isn't related to static typing. Maybe it's something we should discuss. > >> Maybe the discussion will make us conclude we want to do this. But > >> letting the static typing work get delayed by that discussion would be > >> stupid, and I'll do what I can to prevent that. > >> > > > > It's not unrelated. It's about finding the most tactical incision to > > make the types as we actually use them correct from a static analysis > > context. > > > > Maybe there's another tactical incision to make that's "smaller", for > > some perception of "smaller", but it's not unrelated. > > We don't have to debate, let alone agree on relatedness. > > >> The stupidest possible solution that preserves the crash is adding an > >> assertion right where it crashes before this patch: in > >> QAPISourceInfo.__str__(). Yes, crashing in a __str__() method is not > >> nice, but it's no worse than before. Making it better than before is a > >> good idea, and you're quite welcome to try, but please not in this > >> series. Add a TODO comment asking for "make it better", then sit on > >> your hands. > > > > I'm recently back from a fairly long PTO, so forgive me if I am > > forgetting something, but I am not really sure I fundamentally > > understand the nature of this critique. > > > > Making functions not "crash" is a side-effect of making the types > > correct. I don't see it as scope-creep, it's a solution to a problem > > under active consideration. > > I disagree. > > The crash you "fix" is *intentional*. I was too lazy to write something > like > > assert self.info > > and instead relied in self.info.whatever to crash. I don't care how it > crashes, as long as it does crash. > > I *like* qapi-gen to crash on such internal errors. It's easy, and > makes "this is a bug, go report it" perfectly clear. > > I'd also be fine with reporting "internal error, this is a bug, go > report it". Not in this series, unless it's utterly trivial, which I > doubt. > > I'm *not* fine with feeding made-up info objects to the user error > reporting machinery without proof that it'll actually produce a useful > error message. Definitely not trivial, thus not in this series.
If you really don't want to change the existing behavior of the code, I believe we have only two options: 1) Annotate self.info as QAPISourceInfo (not Optional), and add a hack to make the expression `self.info` crash if the argument to __init__() was None. 2) Annotate self.info as Optional[QAPISourceInfo], and adding manual asserts everywhere self.info is used. Which of those two options do you find acceptable, Markus? -- Eduardo
