I took a couple hours to implement the by-field format preserving printer in opam, and it works quite well in practice.
See a first PR here: https://github.com/ocaml/opam-repository/pull/5176/files I think this makes bulk updates much more acceptable. I'll push the new opam-admin.top code shortly. Le mardi 24 novembre 2015, 10:57:00 Louis Gesbert a écrit : > Hopping in a bit late... :) > > Indeed, my first approach for bulk-updating opam files was to first > normalise everything, so that diff could help me see what happened > thereafter. This loses a lot of history, and is difficult to maintain > afterwards -- but opam- fmt could help there. > > Another option would be to implement a format-preserving reprinter for bulk > updates, that would keep the original fields order, and check every field > for semantic changes before reprinting (we have precise file positions > already, so we could extract the raw string to reprint when there are no > changes). It shouldn't be too difficult to implement, doesn't require > changes to the parser or format, and using this for bulk updates would > already make them much more tolerable. Attaching comments to the AST would > be nice and allow to keep them even in rewritten fields, but require much > more dev time. > > Note 1: Gabriel, just making sure you are using opam trunk ? I rewrote big > parts of OpamFormat/OpamFile recently (merged like one or two months ago). > > Note 2: I think we can now go ahead and push bulk changes to the repo. It > should only break `opam init` on 1.1, and I seriously doubt anyone will > complain about it anymore. If the rewriting script breaks, we'll just have > to freeze the 1.1 updates and update the documentation pages accordingly. > > Best, > Louis > > Le lundi 23 novembre 2015, 13:15:29 David Allsopp a écrit : > > Tempting as it would be to spend the next couple of hours hacking it, my 2 > > euro-cents… why not just make the lexer in opam itself lossless, and > > expose > > that in the API? So every single token emitted by the lexer becomes a pair > > including the “whitespace” (= all whitespace, newlines, comments, etc.) > > which follow that token and any tokens which may be ambiguously lexed > > (e.g. > > integers where arbitrary zero prefixes or where bases are permitted) have > > to be deferred. All that’s needed then is a function which transforms > > these > > lossless tokens to the original lexer’s tokens (so dropping the > > whitespace/comment parts, possibly performing a few int_of_string and > > other > > related functions – but all aided by the type system) for plugging into > > the > > parsing stage. It’s even relatively transparent to have the “debugging” > > version of opam verify that the stream is actually reversible to the > > original file. > > > > A task like this then uses the full-parsed power of opam-lib to identify > > opam files which need updating (as you are) and then a fairly simple state > > machine over the lossless lexer stream to update it. > > > > I think that having a rigid format used for opam-repository is a good > > idea, > > but given that presumably that wouldn’t want to become mandatory for all > > repositories, being able to do formatting (and even version) preserving > > updates seems useful. Having effectively a richer lexer also means no fork > > required, so better maintainability, and also puts the onus of supporting > > the updating of an older version opam file on the script author rather > > than > > the opam dev team (as presumably OPAM will always remain capable of > > reading > > older format files??). Making the update be an FSM over raw lexer tokens > > is > > also slightly nicer and less error-prone than a regex approach. > > > > > > David > > > > From: opam-devel [mailto:[email protected]] On Behalf Of > > Gabriel Scherer > > Sent: 23 November 2015 12:19 > > > To: Thomas Gazagnaire > > Cc: opam-devel > > Subject: Re: [opam-devel] [ANN] opam-fmt 1.0 > > > > One idea I just had when re-reading the scavenged comments is to just > > consider comment lines as independent items. If you add ordering > > information to the internal opam representation to keep the items in the > > order, then I suspect that all the examples above would be reformatted in > > a > > way that is acceptable to the original author. One final bit of > > sophistication would be to store (in the comment items) a boolean for > > whether they started on their own line, or are to be inserted at the end > > of > > the previous line. > > Of course this fake structure is less true to the real > > > document structure than properly placed attribute nodes would be. It seems > > easier to implement (and thus a decent compromise to make), but then maybe > > not: keeping an ordering may be non-trivial for data whose current > > internal > > representation is not a set of things (for example dependency formulas are > > actually full logic formulas; but then if we keep to Conjunctive Normal > > Forms they can have a list-like representation). > > On Mon, Nov 23, 2015 at 1:11 PM, Thomas Gazagnaire > > > <[email protected]<mailto:[email protected]>> wrote: > Thanks > > > Gabriel, that's very useful! > > > > For the various parsers, it might make sense to simply fork (or > > copy/paste) > > bits of opam parsers from various versions of opam and try to fix these > > parsers to: > > > > - keep comments > > - support some kind of alignments? > > > > Thomas > > > > > On 22 Nov 2015, at 20:55, Gabriel Scherer > > > > > > <[email protected]<mailto:[email protected]>> wrote: > > >> - Any chance you could use cmdliner instead of Arg? Fairly minor, but > > >> > > >> all the other plugins use it and it's nice to have the same behaviours > > >> for OPAM plugins where possible. > > > > > > I'm fond of Daniel's design work, so I would gladly move to > > > Cmdliner -- Arg was just what I could easily use "in anger" for > > > a first try. > > > > > >> - How does this behave on pre-1.2 files? I think it's about time that > > >> > > >> we deprecate pre-1.2 so that we can have clean metadata standards > > >> about the new fields such as dev-repo. > > > > > > opam-fmt updates older opam files to its own support version -- and > > > refuses to work on newer files. Two things: > > > > > > > > > > > > I think it would be a better design to have a family of scripts > > > opam-fmt-1.0, opam-fmt-1.1, opam-fmt-1.2 etc. and a "mother script" > > > opam-fmt that calls the right reformatter according to the file > > > version¹. However, that requires changes in the packaging of opam-lib, > > > so that the package for distinct versions can be installed > > > simultaneously (they would be separate packages > > > opam-lib-VER, and ocamlfind packages as well). > > > > > > > > > > > > ¹: another option would be for opam-lib to also support pairs of parsing > > > and printing functions for older format version specifically, but that > > > is an invasive choice to make in a codebase. Right now there is a tiny > > > bit of logic to know which fields are 1.0 or 1.1-specific, but this > > > would be much more ambitious. > > > > > > > > > > > > There are various warnings implemented in opam-lib that could be emitted > > > during the processing of files by opam-fmt -- they may be already > > > available depending on the OPAMDEBUG variable or something, but an > > > explicit support in the interface could be nice. When I tested > > > reformatting opam-repository, I observed that a large part of its opam > > > files raise such warnings (so indeed there seems to be a metadata > > > problem in the repository today). > > > > > >> - Having a bot regularly go through and reformat the entire repository > > >> > > >> also seems quite legit. The alternative would be to reformat at the > > >> merge point, but this would require a staging branch. > > > > > > I'm not sure what you call "merge point"; my idea was to put the burden > > > of reformatting onto users submitting PRs against the > > > repository. (Regular reformatting are a sensible idea, but they run in > > > the problem of loss of information, whether distributed manual > > > reformatting keeps humans closer in the loop) > > > > > >> - I would really like opam-fmt to be lossless, so preserving comments > > >> > > >> seems like an extension that we should implement. Ideally everyone > > >> can just call it on their packages without thinking about it. > > > > > > I have mixed feelings about trying to be lossless. At the very least, > > > one should recognize that setting this as a design goal would impose > > > a significant burden on the developers of the parsing/printing functions > > > in opam-lib. > > > > > > > > > > > > Some human choices (alignment of string fields for example) are rather > > > difficult and fragile to recognize -- and they could complexify the > > > codebase. Even for comments, right now you cannot tell to which > > > configuration item an element is attached. There are several ways around > > > this, which are interesting to consider but also involve a fair amount > > > of work: > > > > > > > > > > > > - You could use ocamldoc-like placement rules: "always after the > > > > > > relevant field" (a first comment would be a file-global comment), or > > > "either before or after, but an empty line between the comment and > > > a non-relevant field"; this seems painful and not-that-easy to > > > implement. > > > > > > - You could move to a docstring-like (or attribute-like) syntax where > > > > > > comments are explicitly attached to an AST node; from a language > > > design point of view this would be my preference, but it may require > > > a change in concrete syntax. > > > > > > - Finally, the choices you can make in this design space depend a lot on > > > > > > whether reformatting will be performed by humans or by bots. If your > > > comments-attachment rules are obscure, humans have the opportunity to > > > reformat, see that they got them wrong, and reiterate. Bots will just > > > put stuff at the wrong place. > > > > > > I think that the people that maintain this corner of opam today are > > > those that will pay the greater cost if "lossless" becomes a design > > > goal, so it should be their choice to make. > > > > > > > > > > > > > > > In the meantime, it would be interesting to have a look at how opam > > > files in the repository actually use comments. With > > > > > > find packages -name 'opam' | xargs grep --color=always " #" > > > > > > I see 75 occurences of comments, 38 of which are just "TODO fixme". The > > > 37 others seem rather interesting, below are a few representative > > > examples: > > > > > > packages/arakoon/arakoon.1.8.6/opam: > > >> "lwt" { = "2.4.8" } # 2.4.9 had an incompatible API change > > > > > > Having textual exaplanations for choice of bound is a reasonable > > > use-case for attributes. > > > > > > packages/camlp4/camlp4.4.01/opam: > > >> build: [] # dummy package > > > > > > This could be replaced by a dedicated note/comment field. > > > > > > packages/frama-c/frama-c.20150201/opam: > > >> "lablgtk" { >= "2.18.2" } #for ocaml >= 4.02.1 > > > > > > I don't understand the semantics of this one. > > > > > > packages/git/git.1.6.0/opam: > > >> depopts: [ > > >> > > >> # --enable-mirage > > >> "mirage-types-lwt" > > >> "mirage-http" > > >> "mirage-flow" > > >> "channel" > > >> # --enable-unix > > >> "cohttp" > > >> "conduit" > > >> "base-unix" > > >> > > >> ] > > > > > > This usage is very interesting, it seems to call for a hierarchy inside > > > the "depopts" list (and "dependencies" as well, I suppose), with > > > annotations on sub-groups of dependencies. > > > > > > packages/gsl/gsl.1.18.2/opam: > > >> depends: [ > > >> > > >> "base-bigarray" > > >> "camlp4" > > >> "ocamlfind" {>= "1.3.1"} > > >> # Included from _opam file > > >> "conf-gsl" > > >> > > >> ] > > > > > > I don't know what this comment means. > > > > > > packages/lz4/lz4.1.0.0/opam: > > >> depexts: [ > > >> > > >> [["debian"] ["liblz4-dev"]] > > >> # [["ubuntu"] ["liblz4-dev"]] reenable when CI updates its Ubuntu > > >> [["source"] ["https://.../install.sh";]] > > >> > > >> ] > > > > > > Again, this would require annotations. > > > > > > packages/ppx_deriving/ppx_deriving.0.3/opam: > > >> build: [ > > >> > > >> # If there is no native dynlink, we can't use native builds > > >> "ocaml" "pkg/build.ml<http://build.ml>" "native=true" > > >> > > >> "native-dynlink=true" > > >> > > >> ] > > > > > > packages/frama-c-e-acsl/frama-c-e-acsl.0.5/opam: > > >> build: [ > > >> > > >> ["ocaml" > > >> "run_autoconf_if_needed.ml<http://run_autoconf_if_needed.ml>"] > > >> #when used in pinned mode the configure *can* not yet be generated > > >> ["./configure" "--prefix" prefix] > > >> [make] > > >> > > >> ] > > > > > > packages/clangml/clangml.0.5.2/opam: > > >> depexts: [ > > >> > > >> [["debian"] ["libboost-dev" "llvm-3.4-dev" "clang-3.4" > > >> "libclang-3.4-dev" "binutils-dev"]] > > [["ubuntu"] ["libboost-dev" > > > >> "llvm-3.4-dev" "clang-3.4" "libclang-3.4-dev" "binutils-dev"]] > > >> [["gentoo"] ["dev-libs/boost" "sys-devel/llvm-3.4.1-r2" > > >> "sys-devel/clang-3.4.0-r100" "sys-devel/binutils"]] # archlinux has no > > >> package providing llvm and clang 3.4.1 > > >> [["archlinux"] ["boost" "binutils"]] > > >> > > >> ] > > > > > > packages/mtime/mtime.0.8.1/opam: > > >> depends: [ "ocamlfind" > > >> > > >> "js_of_ocaml" # FIXME should become a deptopt > > >> > > >> ] > > > > > > On Sun, Nov 22, 2015 at 8:09 PM, Anil Madhavapeddy > > > > > > <[email protected]<mailto:[email protected]>> wrote: > > >> Thanks for this Gabriel! Quick notes: > > >> > > >> > > >> > > >> - I would really like opam-fmt to be lossless, so preserving comments > > >> > > >> seems like an extension that we should implement. Ideally everyone > > >> can just call it on their packages without thinking about it. > > >> > > >> - Having a bot regularly go through and reformat the entire repository > > >> > > >> also seems quite legit. The alternative would be to reformat at the > > >> merge point, but this would require a staging branch. > > >> > > >> - Any chance you could use cmdliner instead of Arg? Fairly minor, but > > >> > > >> all the other plugins use it and it's nice to have the same behaviours > > >> for OPAM plugins where possible. > > >> > > >> - How does this behave on pre-1.2 files? I think it's about time that > > >> > > >> we deprecate pre-1.2 so that we can have clean metadata standards > > >> about the new fields such as dev-repo. > > >> > > >> regards, > > >> Anil > > >> > > >>> On 21 Nov 2015, at 21:53, Gabriel Scherer > > >>> <[email protected]<mailto:[email protected]>> wrote: > > >>> > > >>> > > >>> > > >>> Hi opam-devel, > > >>> > > >>> > > >>> > > >>> As part of the discussion in > > >>> > > >>> > > >>> > > >>> bulk addition of 'ocamlbuild {build}' dependencies > > >>> https://github.com/ocaml/opam-repository/pull/5140 > > >>> > > >>> > > >>> > > >>> it became apparent that performing bulk updates on opam-repository is > > >>> made harder by the fact that the parse-print roundtrip does not > > >>> preserve human-formatted opam files. For my proposed patch I tried to > > >>> separate the reformatting of opam file (to follow the opam-lib printer > > >>> convention) from the actual changes in two separate commits, but that > > >>> means more work for script authors, and also creates patches that are > > >>> harder to review. (If (re)formatting was controlled by the maintainer > > >>> of the OPAM packages instead of authors of bulk updates, we would be > > >>> more confident in its correctness.) > > >>> > > >>> > > >>> > > >>> In order to move that discussion forward (how to maintain opam > > >>> metadata in a way that is easy for both human and scripts to work > > >>> with?), I propose the opam-fmt script that can be found at > > >>> https://github.com/gasche/opam-fmt/ > > >>> > > >>> > > >>> > > >>> I wrote it in the last few days and there are probably some rough > > >>> edges. Once I feel that it should work, I may try to package it on the > > >>> opam-repo (in the meantime, clone then pin). > > >>> > > >>> > > >>> > > >>> This suggests one possible way forward: publicize opam-fmt, encourage > > >>> users to reformat their opam files using it, adapt the opam-repository > > >>> QA to call `opam fmt --check` on opam files proposed in PR to enforce > > >>> it, and after some time (once we trust it works as expected thanks to > > >>> the human guinea pigs) reformat all older opam files to get a perfect > > >>> round-trip on all files of the repository. > > >>> It is not clear to me that this is the best way forward. (For example > > >>> it means that, in the current state of the opam file parsing/printing > > >>> code, comments in opam files would always be erased by reformatting. > > >>> Should we remove comments from the valid syntax of opam files, or > > >>> attach them to configuration lines to re-print them correctly later, > > >>> or maybe refuse to work on files with comments?) Opam developers and > > >>> repository maintainers may decide that the cost of caring about > > >>> reformatting outweigh the benefits in terms of scriptability. > > >>> > > >>> > > >>> > > >>> What do you think? > > >>> _______________________________________________ > > >>> opam-devel mailing list > > >>> [email protected]<mailto:[email protected]> > > >>> http://lists.ocaml.org/listinfo/opam-devel > > > > > > _______________________________________________ > > > opam-devel mailing list > > > [email protected]<mailto:[email protected]> > > > http://lists.ocaml.org/listinfo/opam-devel > > _______________________________________________ > opam-devel mailing list > [email protected] > http://lists.ocaml.org/listinfo/opam-devel _______________________________________________ opam-devel mailing list [email protected] http://lists.ocaml.org/listinfo/opam-devel
