Hummmm, actually another problem of this approach: Nodes are created and modified after the optimization pass, so the AST produced by the parser is not enough to reconstruct the actual information, we need to also run the optimization passes, but unfortunately, this is (by design) not don't in the Python API (to preserve all possible information about the original code), so this complicates quite a lot the API to get this, as `ast.parse` is not enough to get the original tree.
On Tue, 18 May 2021 at 08:53, Pablo Galindo Salgado <pablog...@gmail.com> wrote: > Hi Nathaniel, > > Thanks a lot for your suggestion! I like the idea although I still think > is more complex than our current proposal, but on the other hand it allows > for a much richer results so I'm quite excited to try it out. We are going > to give it a go to explore it with a prototype and if we are convinced we > will update the PEP. > > One thing I'm not a fan of is that tools that want to leverage this > information (notice our pep also offers this info for tools as an important > aspect of it) will need to reparse the file AND search the AST node, which > also involves transforming the full tree to Python objects, which is even > slower. This is unfortunately a worse API than just get the full location > given an instruction offset. Also, while displaying tracebacks may be a > good scenario for the speed tradeoff, it may not be for other tools. > Finally, if there is no file available all this information is lost, > although one could argue that then is not extremely useful... > > Regards from sunny London, > Pablo Galindo Salgado > > On Tue, 18 May 2021, 01:43 Nathaniel Smith, <n...@pobox.com> wrote: > >> On Mon, May 17, 2021 at 6:18 AM Mark Shannon <m...@hotpy.org> wrote: >> > 2. Repeated binary operations on the same line. >> > >> > A single location can also be clearer when all the code is on one line. >> > >> > i1 + i2 + s1 >> > >> > PEP 657: >> > >> > i1 + i2 + s1 >> > ^^^^^^^^^^^^ >> > >> > Using a single location: >> > >> > i1 + i2 + s1 >> > ^ >> >> It's true this case is a bit confusing with the whole operation span >> highlighted, but I'm not sure the single location version is much better. I >> feel like a Really Good UI would like, highlight the two operands in >> different colors or something, or at least underline the two separate items >> whose type is incompatible separately: >> >> TypeError: unsupported operand type(s) for +: 'int' + 'str': >> i1 + i2 + s1 >> ^^^^^^^ ~~ >> >> More generally, these error messages are the kind of thing where the UI >> can always be tweaked to improve further, and those tweaks can make good >> use of any rich source information that's available. >> >> So, here's another option to consider: >> >> - When parsing, assign each AST node a unique, deterministic id (e.g. >> sequentially across the AST tree from top-to-bottom, left-to-right). >> - For each bytecode offset, store the corresponding AST node id in an >> lnotab-like table >> - When displaying a traceback, we already need to go find and read the >> original .py file to print source code at all. Re-parse it, and use the ids >> to find the original AST node, in context with full structure. Let the >> traceback formatter do whatever clever stuff it wants with this info. >> >> Of course if the .py and .pyc files don't match, this might produce >> gibberish. We already have that problem with showing source lines, but it >> might be even more confusing if we get some random unrelated AST node. This >> could be avoided by storing some kind of hash in the code object, so that >> we can validate the .py file we find hasn't changed (sha512 if we're >> feeling fancy, crc32 if we want to save space, either way is probably fine). >> >> This would make traceback printing more expensive, but only if you want >> the fancy features, and traceback printing is already expensive (it does >> file I/O!). Usually by the time you're rendering a traceback it's more >> important to optimize for human time than CPU time. It would take less >> memory than PEP 657, and the same as Mark's proposal (both only track one >> extra integer per bytecode offset). And it would allow for arbitrarily rich >> traceback display. >> >> (I guess in theory you could make this even cheaper by using it to >> replace lnotab, instead of extending it. But I think keeping lnotab around >> is a good idea, as a fallback for cases where you can't find the original >> source but still want some hint at location information.) >> >> -n >> >> -- >> Nathaniel J. Smith -- https://vorpus.org >> _______________________________________________ >> Python-Dev mailing list -- python-dev@python.org >> To unsubscribe send an email to python-dev-le...@python.org >> https://mail.python.org/mailman3/lists/python-dev.python.org/ >> Message archived at >> https://mail.python.org/archives/list/python-dev@python.org/message/BUXFOSAEBXLIHH432PKBCXOGXUAHQIVP/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> >
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