cabal build command and package versions
I have a question about cabal's behavior for the build command. When using the build command on a cabalized project, any version changes for installed packages go unnoticed - the necessary modules in the project are not re-compiled. If however, you run the configure command (though the .cabal file for the project has not changed) and then the build command, the appropriate modules (and only the appropriate modules) are re-compiled. Not knowing that the configure command is necessary to detect changes in package that the current project depends on and proceeding only with the build command has led to BusErrors and GHC incurring the impossible in my exploration. Is there a reason that the build command does not check the packages for version changes? It seems fair to expect package-sensitivity of the process that determines if modules need to be re-compiled. This process, I think, is part of the build command and not the configure command. Here's an example scenario: - Imagine package Q depends on package P. - We "runhaskell Setup.hs clean/configure/build/install" them both, from scratch, at version 0. - Then we change package P (by, say, introducing new fields to a constructor that Q cases over), bump its version to 1, and "runhaskell Setup.hs clean/configure/build/install" on it. - If we now "runhaskell build" on package Q, nothing is re-compiled, though a package dependency has changed. "runhaskell Setup.hs build" does not notice this. - However, if we "runhaskell configure/build" on package Q, then the (necessary) modules are re-compiled. Thanks for your time.
On Wed, 2008-08-20 at 13:53 -0500, Nicolas Frisby wrote:
I have a question about cabal's behavior for the build command. When using the build command on a cabalized project, any version changes for installed packages go unnoticed - the necessary modules in the project are not re-compiled.
Yes. That's a ghc bug.
If however, you run the configure command (though the .cabal file for the project has not changed) and then the build command, the appropriate modules (and only the appropriate modules) are re-compiled.
Really? I didn't think that made any difference. I've no idea what configure would be doing that would get ghc to notice when it simply lacks the ability to do so in general.
Not knowing that the configure command is necessary to detect changes in package that the current project depends on and proceeding only with the build command has led to BusErrors and GHC incurring the impossible in my exploration.
Yes, it's a pretty annoying ghc bug. You'll be glad to know that it is fixed in ghc-6.10: http://hackage.haskell.org/trac/ghc/ticket/1372 You'll notice a lot of people have commented on this one. It's tripped up a lot of people.
Is there a reason that the build command does not check the packages for version changes? It seems fair to expect package-sensitivity of the process that determines if modules need to be re-compiled. This process, I think, is part of the build command and not the configure command.
There's really not much we can do in Cabal itself. It has to be fixed in ghc and fortunately it now is fixed. That's because Cabal just uses ghc --make for builds and rebuilds, so if it doesn't realise that it has to rebuild after dependent packages change then we can't do much. As I say, I've no idea why configure should make any difference. If it does it's only by fluke and not design. Duncan
| On Wed, 2008-08-20 at 13:53 -0500, Nicolas Frisby wrote: | > I have a question about cabal's behavior for the build command. When | > using the build command on a cabalized project, any version changes | > for installed packages go unnoticed - the necessary modules in the | > project are not re-compiled. | | Yes. That's a ghc bug. Different to the one below? Is it in Trac? | > Not knowing that the configure command is necessary to detect changes | > in package that the current project depends on and proceeding only | > with the build command has led to BusErrors and GHC incurring the | > impossible in my exploration. | | Yes, it's a pretty annoying ghc bug. You'll be glad to know that it is | fixed in ghc-6.10: | | http://hackage.haskell.org/trac/ghc/ticket/1372 | | You'll notice a lot of people have commented on this one. It's tripped | up a lot of people. And happily it's fixed for 6.10! Simon
On Thu, 2008-08-21 at 08:23 +0100, Simon Peyton-Jones wrote:
| On Wed, 2008-08-20 at 13:53 -0500, Nicolas Frisby wrote: | > I have a question about cabal's behavior for the build command. When | > using the build command on a cabalized project, any version changes | > for installed packages go unnoticed - the necessary modules in the | > project are not re-compiled. | | Yes. That's a ghc bug.
Different to the one below? Is it in Trac?
Same one, the one recently fixed.
| Yes, it's a pretty annoying ghc bug. You'll be glad to know that it is | fixed in ghc-6.10: | | http://hackage.haskell.org/trac/ghc/ticket/1372 | | You'll notice a lot of people have commented on this one. It's tripped | up a lot of people.
And happily it's fixed for 6.10!
yay :-) Duncan
participants (3)
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Duncan Coutts -
Nicolas Frisby -
Simon Peyton-Jones