+1 I've noticed mtime changes in some scenarios related to CI and docker, that causes things to be recompiled again even though there's no other change to the files.
Allen Madsen http://www.allenmadsen.com On Mon, Jun 21, 2021 at 3:29 AM Marc-André Lafortune < marc-an...@marc-andre.ca> wrote: > > > On Mon, Jun 21, 2021 at 2:54 AM José Valim <jose.va...@dashbit.co> wrote: > >> Hi Marc-André! >> >> There is no particular reason, this is a functionality that could be >> added. In particular we can continue checking the mtime and file size but >> compare the contents if the mtime changed but the file size is the same. >> > > Yep 👍 > > >> I also think we should update the mtime anyway, even if the hash is the >> same. WDYT? >> > > Yes, otherwise we might keep re-hashing the file over and over again. > > >> Feel free to open up an issue or, if you want to tackle it, even send a >> PR! >> > > Awesome. I'll check if I can come up with a PR in the next few days, and > if not I'll create an issue. > > Thanks. It's so awesome to get such quick feedback 💛 > > >> >> Thanks! >> >> On Mon, Jun 21, 2021 at 8:20 AM Marc-André Lafortune < >> marc-an...@marc-andre.ca> wrote: >> >>> I'm a newbie, sorry if this has been asked before but I couldn't find >>> anything. >>> >>> Currently, elixir uses last modification dates to determine files that >>> need to be recompiled. >>> >>> ``` >>> $ mix compile >>> # ... >>> $ touch lib/some/file.ex >>> $ mix compile >>> Compiling <n> files (.ex) >>> ``` >>> >>> Could Elixir not verify that in addition to a modification time change, >>> that the actual text content has changed by comparing a hash of it? In the >>> example above, the file `lib/some/file.ex` would be hashed a second time, >>> but no recompilation would occur. >>> >>> Currently, many operations may change the last modification date even if >>> no content at all has changed: >>> * switch to a different branch, switch back >>> * do an interactive rebase: >>> - to rewrite a commit message, >>> - to reorder some commits >>> - to squash some commits together >>> - etc. >>> >>> While the content of the files does not change (at all) in these >>> examples, some very long recompilations may occur because elixir only >>> relies only on modification times and not on file hashes. >>> Hashing a file is orders of magnitude faster than compiling it, and >>> realizing that the potentially large number of compile-time dependencies of >>> a given file do not need to be recompiled is infinitely faster than >>> recompiling them all for nothing. >>> >>> I am presuming that hash collisions are deemed so incredible unlikely to >>> be acceptable, but if not, then I'd ask the same question but with using >>> the complete content of the source file instead of a hash of it. Copying a >>> source file is again an order of magnitude faster than the time it takes to >>> recompile it. >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "elixir-lang-core" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to elixir-lang-core+unsubscr...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/e7a68d8d-0102-483d-a4ec-58849eb88ef6n%40googlegroups.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/e7a68d8d-0102-483d-a4ec-58849eb88ef6n%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "elixir-lang-core" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/elixir-lang-core/8-30JVn_8M0/unsubscribe >> . >> To unsubscribe from this group and all its topics, send an email to >> elixir-lang-core+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4L-_BRhadhXVckZ5TX4wLqgmxm-iuGHQr4M5Kdq4xM_1w%40mail.gmail.com >> <https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4L-_BRhadhXVckZ5TX4wLqgmxm-iuGHQr4M5Kdq4xM_1w%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/CADwvmaWP%2BccDF9QRdDfL8_B8fXuFXeFSL-fV0vLgOVqFH8LiHw%40mail.gmail.com > <https://groups.google.com/d/msgid/elixir-lang-core/CADwvmaWP%2BccDF9QRdDfL8_B8fXuFXeFSL-fV0vLgOVqFH8LiHw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAK-y3CsU9wiNqQZG-V_cS-6g40tA1KFa44o825jb29-_5jMGRw%40mail.gmail.com.
