On Mon, Apr 26 2021, Han-Wen Nienhuys wrote: > On Mon, Apr 26, 2021 at 4:28 PM Ævar Arnfjörð Bjarmason > <avarab@xxxxxxxxx> wrote: >> I agree that whether or not we should have any tests at all is a matter >> of opinion and circumstance. I don't think in general that someone using >> some random internal API needs to be checking what is and isn't tested >> in that API. >> >> I do think in this case that it's worth digging a bit further. The APIs >> in question are using EINVAL and EISDIR to pass up errors that are had a >> 1:1 mapping into the FS historically. >> >> Are we really better off faking those up, or is some of that perhaps not >> used at all? Maybe we'd find that this level of abstraction isn't what >> we need, and it could actually be much simpler. > > I think none of these error functions are being used at all, and I've > made a start at removing them in https://github.com/git/git/pull/1012 > (see also my discussion with peff.) > >> It seems to me that a good way to get there is to seek some systematic >> ways of focusing review onto various edge cases of this series. I.e. to >> begin with having GIT_TEST_REFTABLE pass as noted elsewhere, and in this >> case calling attention to some of the underlying assumptions behind this >> series. > >> One of the hardest things I've found about trying to review this has >> been closing the gap between things that exist in your mind and commit >> messages / code. > > thanks, that is valuable feedback. > >> something like this in the commit message (and other applicable commits >> etc.) would be *very* valuable: >> >> In functions such as git_reftable_read_raw_ref() (and ????, are >> there more?) we're diligently emulating the documented behavior and >> return values of the refs file backend. According to "make gcov" we >> can see we don't have coverage for this, in particular the behavior >> of EINVAL etc. > > I haven't done this, because a lot of these considerations are > transient, and I'd rather not spend a lot of time documenting what I > don't know. > >> I.e. per [1] once if and when we have GIT_TEST_REFTABLE passing surely >> one of the best way to garner feedback on the rest is to discover those >> parts (using "make gcov", after running with/without >> GIT_TEST_REFTABLE=[true|false]) where we still have outstanding blind >> spots between the tests and code. > > Getting GIT_TEST_REFTABLE=1 passing is the hard part, because it means > having to understand exactly how the current code is supposed to > work. Once I get to that point (with knowledge being complete and > tests passing), it will be easy to document what is happening and why. > > I was hoping that by posting these series with known test failures, > and questions marked "XXX" in reftable-backend.c, I would get feedback > from the other people who know exactly how this part of the code > works. But from your mail, I get the sense that nobody understands > how the whole picture fits together? Almost definitely not. I don't know about you but when I'm looking at code I wrote 6 months ago handling some special case it takes me a while to get up to speed on just knowing what I knew then, and when we're talking about something like refs.c ... On the topic of the way forward: I for one would very much be for a plan where step 0 is to just a series import the reftable code you have as-is. I.e. we'd include it as an imported external library, maybe have some light test-tool integration and compile it / run its own tests, but not have/advertise the "git init" etc. integration yet. I.e. my opinion on GIT_TEST_REFTABLE=1 needing to pass is implicit (but I now realize I haven't explicitly said this) on that happening before the tree is in a state where we'd code/doc-wise be in a state of shipping this to users. Whereas just importing the library != that, and I think we'd be in much better shape if we had it in-tree and would incrementally work on integration from that point, v.s. having more re-rolls of mostly-the-same big codebase being re-submitted. I'm sure there's some things that'll need to change as we start the test/integration work, e.g. the reflog topic that's been discussed. But that's surely better done as some patches on top of the already-landed library import at this point v.s. trying to get the library perfect before getting it in-tree. Maybe Junio disagrees, just my 0.02....
