- cabal-devel - Haskell.org

RE: Cabal and GHC
by Simon Peyton-Jones 22 Nov '12

22 Nov '12

Having GHC support multiple copies of the same package/version would certainly be a step in the right direction. It still wouldn't completely address the goals I'm getting at in my blog post. What I'm really aiming for overall is to provide users with a stable, vetted set of packages that are known to work well together. But for those of us who will still be using plain Hackage, this improvement would be very helpful. Indeed. I've always thought of the Haskell Platform as doing the "stable set" part, though there must be plenty of space between HP at one end and Hackage at the other, and that's what you are exploring I think. Regardless, being able to install multiple instantiations of the same package/version is desirable for the "stable set" story, so that more than one stable set is possible; and so that trying to use a package outside the stable set doesn't mess up your stable-set installation. The question is: who will do the work? Simon From: michael.snoyman(a)gmail.com [mailto:michael.snoyman@gmail.com] On Behalf Of Michael Snoyman Sent: 22 November 2012 10:40 To: Simon Peyton-Jones Cc: Haskell Libraries (libraries(a)haskell.org) cabal-devel(a)haskell.org Subject: Re: Cabal and GHC On Thu, Nov 22, 2012 at 10:32 AM, Simon Peyton-Jones <simonpj(a)microsoft.com<mailto:simonpj@microsoft.com>> wrote: Michael Snoyman wrote a blog post about Solving Cabal Hall, which came across via the peerless Haskell Weekly News. http://www.yesodweb.com/blog/2012/11/solving-cabal-hell But I'd be unlikely to return there so I'm posting this to the libraries and cabal-devel lists. I'm not deep in Cabal lore, but it seems to me that there is a fairly easy way to do a Lot Better than we are now. Let's go back to "Identifying the Problem". Michael doesn't say, but I'm guessing that Fay depends on yesod-platform. Very well, so Cabal sees I'm installing Fay, which depends on yesod-platform, which dpends on data-default and depends directly on data-default If the package database was empty, Cabal would try to figure out a version of data-default that is acceptable to both yesod-platform and to Fay. And that's what we want! Suppose that Cabal figures out that yesod-platform-2.7 and data-default-0,4 would work. Then, in an empty package database, it could just go ahead and install those. But in your example, the database isn't empty; we have already isntalled yesod-platform-2.7, dependin gon data-default-0.5. And (here's the rub) you can only have yesod-platform-2.7 installed once. One solution might be 1. *un* install yesod-platform-2.7 (depending on data-default-0.5) and 2. *re* install it (depending on data-default-0.4). But that would break any programs that use both yesod-platform-2.7 and data-default-0.5. The solution is obvious: we should make it possible to instally yesod-platform-2.7 twice, once version depending on data-default-0.4 once version depending on data-default-0.5. Now, if Cabal can figure out a plan based on an empty database, it can deliver on that plan even in a non-empty database, without messing up any existing installations. Of course, if Fay depends exclusively on data-default-0.4, and yesod-platform depends exclusively on data-default-0.5, then they genuinely are incompatible, and Cabal can and should say so. That's not Cabal Hell. That's just saying that the package authors have *specified* that they are incompatible. Summary. I may be way off beam here, but I think we can easily make things way better than they are. By "easily" I mean with just design and implementation work. That's not free, and no one has any time.... but it's well within reach. I'd even been wondering about trying to crowd-fund this development so that Well Typed can do it. But let's first see if it'd solve the problem. There must be a wiki page somewhere that articulates the challenge, points to blog posts about it, and discusses solutions. Simon _______________________________________________ Libraries mailing list Libraries(a)haskell.org<mailto:Libraries@haskell.org> http://www.haskell.org/mailman/listinfo/libraries Hi Simon, Having GHC support multiple copies of the same package/version would certainly be a step in the right direction. It still wouldn't completely address the goals I'm getting at in my blog post. What I'm really aiming for overall is to provide users with a stable, vetted set of packages that are known to work well together. But for those of us who will still be using plain Hackage, this improvement would be very helpful. MIchael

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Cabal and GHC
by Simon Peyton-Jones 22 Nov '12

22 Nov '12

Michael Snoyman wrote a blog post about Solving Cabal Hall, which came across via the peerless Haskell Weekly News. http://www.yesodweb.com/blog/2012/11/solving-cabal-hell But I'd be unlikely to return there so I'm posting this to the libraries and cabal-devel lists. I'm not deep in Cabal lore, but it seems to me that there is a fairly easy way to do a Lot Better than we are now. Let's go back to "Identifying the Problem". Michael doesn't say, but I'm guessing that Fay depends on yesod-platform. Very well, so Cabal sees I'm installing Fay, which depends on yesod-platform, which dpends on data-default and depends directly on data-default If the package database was empty, Cabal would try to figure out a version of data-default that is acceptable to both yesod-platform and to Fay. And that's what we want! Suppose that Cabal figures out that yesod-platform-2.7 and data-default-0,4 would work. Then, in an empty package database, it could just go ahead and install those. But in your example, the database isn't empty; we have already isntalled yesod-platform-2.7, dependin gon data-default-0.5. And (here's the rub) you can only have yesod-platform-2.7 installed once. One solution might be 1. *un* install yesod-platform-2.7 (depending on data-default-0.5) and 2. *re* install it (depending on data-default-0.4). But that would break any programs that use both yesod-platform-2.7 and data-default-0.5. The solution is obvious: we should make it possible to instally yesod-platform-2.7 twice, once version depending on data-default-0.4 once version depending on data-default-0.5. Now, if Cabal can figure out a plan based on an empty database, it can deliver on that plan even in a non-empty database, without messing up any existing installations. Of course, if Fay depends exclusively on data-default-0.4, and yesod-platform depends exclusively on data-default-0.5, then they genuinely are incompatible, and Cabal can and should say so. That's not Cabal Hell. That's just saying that the package authors have *specified* that they are incompatible. Summary. I may be way off beam here, but I think we can easily make things way better than they are. By "easily" I mean with just design and implementation work. That's not free, and no one has any time.... but it's well within reach. I'd even been wondering about trying to crowd-fund this development so that Well Typed can do it. But let's first see if it'd solve the problem. There must be a wiki page somewhere that articulates the challenge, points to blog posts about it, and discusses solutions. Simon

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patch applied (hackage-server): "Fix the import of package deprecation info" and 1 others
by devnull＠community.haskell.org 21 Nov '12

21 Nov '12

Wed Nov 21 14:58:56 GMT 2012 Duncan Coutts <duncan(a)well-typed.com> * Fix the import of package deprecation info Ignore-this: c4b7f4bb7bfc0ac6ffadd86e56b05cf0 M ./Distribution/Server/Features/PreferredVersions.hs -4 +31 M ./Distribution/Server/Framework/Validation.hs +16 M ./ImportClient.hs -1 +1 Wed Nov 21 15:03:10 GMT 2012 Duncan Coutts <duncan(a)well-typed.com> * A couple trivial bits Ignore-this: 2186524b4d1d1ec77a8abd4afff37f2e M ./ImportClient.hs -2 +2

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patch applied (hackage-server): "Add descriptions of what each feature backs up"
by devnull＠community.haskell.org 21 Nov '12

21 Nov '12

Wed Nov 21 13:49:19 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Add descriptions of what each feature backs up Ignore-this: 8e5390238ec1d5d4d129c8da2daa04 M ./Distribution/Server.hs -8 +8 M ./Distribution/Server/Features/BuildReports.hs -9 +14 M ./Distribution/Server/Features/Core.hs -1 +5 M ./Distribution/Server/Features/Distro.hs -8 +14 M ./Distribution/Server/Features/Documentation.hs -6 +13 M ./Distribution/Server/Features/DownloadCount.hs -10 +10 M ./Distribution/Server/Features/Mirror.hs -6 +14 M ./Distribution/Server/Features/ServerApiDoc.hs +6 M ./Distribution/Server/Features/Tags.hs -6 +13 M ./Distribution/Server/Features/Upload.hs -2 +8 M ./Distribution/Server/Features/Users.hs -1 +5 M ./Distribution/Server/Framework/BackupRestore.hs -1 M ./Distribution/Server/Framework/Feature.hs -2 +22

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patch applied (hackage-server): "Improve feature/resource descriptions"
by devnull＠community.haskell.org 21 Nov '12

21 Nov '12

Wed Nov 21 12:46:50 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Improve feature/resource descriptions Ignore-this: b45d88f2e718036f811615761409f0e4 M ./Distribution/Server/Features/Upload.hs -5 +10 M ./Distribution/Server/Features/Users.hs -8 +12

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patch applied (hackage-server): "Document (almost) all the features of 'users'" and 1 others
by devnull＠community.haskell.org 21 Nov '12

21 Nov '12

Wed Nov 21 10:06:19 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Document (almost) all the features of 'users' Ignore-this: 6596974e93d29360c930e7faae075f1f M ./Distribution/Server/Features/Html.hs -3 +15 M ./Distribution/Server/Features/ServerApiDoc.hs -4 +7 M ./Distribution/Server/Features/Users.hs -8 +21 Wed Nov 21 11:59:19 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * More feature/resource descriptions Ignore-this: c2aead08a78cc079b967704ec635bf81 M ./Distribution/Server/Features/Check.hs -19 +39 M ./Distribution/Server/Features/Core.hs -21 +55 M ./Distribution/Server/Features/Html.hs -11 +28 M ./Distribution/Server/Features/ServerApiDoc.hs -6 +11 M ./Distribution/Server/Framework/Feature.hs -1 +1

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patch applied (hackage-server): "Fix tarball upload in import-client" and 1 others
by devnull＠community.haskell.org 20 Nov '12

20 Nov '12

Tue Nov 20 19:48:30 GMT 2012 Duncan Coutts <duncan(a)well-typed.com> * Fix tarball upload in import-client Ignore-this: b4b871f4ec20d39d92ea503b8f1761 M ./ImportClient.hs -5 +9 Tue Nov 20 19:53:18 GMT 2012 Duncan Coutts <duncan(a)well-typed.com> * Add concurrent upload support for tarballs to import-client Ignore-this: 1f0cf6f59cf4e3c71ccb0de17eec201b When the server is running using +RTS -N${X}, and the import-client is uploading concurrently with --jobs=${X}, the import goes a whole lot faster. M ./ImportClient.hs -10 +60 M ./hackage-server.cabal -1 +1

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patch applied (hackage-server): "Use :path instead of {path}" and 1 others
by devnull＠community.haskell.org 20 Nov '12

20 Nov '12

Tue Nov 20 17:31:55 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Use :path instead of {path} Ignore-this: 6c62295abbfc0b631dafa43fc306972d M ./Distribution/Server/Features/ServerApiDoc.hs -2 +2 Tue Nov 20 17:32:11 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Increase descriptions of Users feature Ignore-this: 86897c5aa676392041bbe9501e3b0212 M ./Distribution/Server/Features/Html.hs -2 +6

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patch applied (hackage-server): "Split resource descriptions per method"
by devnull＠community.haskell.org 20 Nov '12

20 Nov '12

Tue Nov 20 17:15:25 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Split resource descriptions per method Ignore-this: 4f8a55645852b7571e3a0b05a5bd422e M ./Distribution/Server/Features/Html.hs -10 +16 M ./Distribution/Server/Features/ServerApiDoc.hs -12 +12 M ./Distribution/Server/Features/Users.hs -1 +3 M ./Distribution/Server/Framework/Resource.hs -1 +1

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patch applied (hackage-server): "Fix (some) layout" and 1 others
by devnull＠community.haskell.org 20 Nov '12

20 Nov '12

Tue Nov 20 14:20:23 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Fix (some) layout Ignore-this: 5d5122a73dfa552f91332add689abac2 M ./Distribution/Server/Features/Html.hs -84 +190 Tue Nov 20 16:26:01 GMT 2012 Edsko de Vries <edsko(a)well-typed.com> * Modify api/ to show extensions of resources Ignore-this: 3cdcbcb79b94ff3ed8bdbf4a0bf05aab This makes it much easier to understand what particular resources are doing, in particular because many features define "empty" resources which are then extended in the Html module. M ./Distribution/Server/Features/Html.hs -6 +9 M ./Distribution/Server/Features/ServerApiDoc.hs -10 +35 M ./Distribution/Server/Features/Users.hs -19 +26 M ./Distribution/Server/Framework/Feature.hs -2 +2 M ./Distribution/Server/Framework/Resource.hs -10 +17

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