ANNOUNCE: GHC version 6.10.1 - MacOS installer

[Manuel M T Chakravarty]

Ian Lynagh:
> On Tue, Nov 04, 2008 at 09:02:12PM -0500, Brandon S. Allbery KF8NH  
> wrote:
>> On 2008 Nov 4, at 20:26, Jason Dagit wrote:
>>> On Tue, Nov 4, 2008 at 4:26 PM, Manuel M T Chakravarty
>>> <chak at cse.unsw.edu.au> wrote:
>>>>
>>>> Are you sure it does deinstall the 6.8 compiler?
>>>>
>>>> After installing 6.10, there should be a 608/ and a 610/
>>>> directory.  This
>>>> certainly happens on my Mac and I am not aware of an option to
>>>> change that
>>>> behaviour.
>>
>> I expect if you used the OSX installer then /Library/Receipts is
>> screwing you (it wipes the old files listed in the .bom file).  Try
>> finding and removing the receipt directory and bom file before
>> installing.
>
> The only file I can see that looks relevant is
>    /Library/Receipts/boms/ 
> org.haskell.glasgowHaskellCompiler.ghc.pkg.bom
>
> Wouldn't removing it make uninstall impossible?
>
> In fact, if you did manage to get 2 versions installed, how would
>    /Library/Frameworks/GHC.framework/Tools/Uninstaller
> know which version to uninstall? Wouldn't it only know how to  
> uninstall
> the version it came with? I'd suggest that the overlapping file
> "Uninstaller" could be why the older version gets removed, but that
> wouldn't explain why Manuel can install both at once.

A current limitation of the MacOS package system is that it does not  
support uninstalling of packages; cf

  http://developer.apple.com/documentation/DeveloperTools/Conceptual/SoftwareDistribution/Managed_Installs/chapter_5_section_7.html#/ 
/apple_ref/doc/uid/10000145i-CH6-DontLinkElementID_29

This is not a big drama on MacOS, as MacOS encourages the distribution  
of software packages as "bundles":

   http://developer.apple.com/documentation/CoreFoundation/Conceptual/CFBundles/CFBundles.html

This essentially means that instead of sprinkling files all over the  
file system (as is common in other OSes), MacOS applications and  
frameworks (Mac-speak for libraries) are kept in a single directory.   
Uninstalling then means doing an rm -rf on that directory.

Unfortunately, some applications (including GHC and Apple's Xcode IDE)  
can't be entirely contained in a single directory.  In the case of  
GHC, we want symlinks in /usr/bin.  The established way of  
uninstalling such applications is by supplying an Uninstaller script,  
just as I did for GHC.  (Apple does the same for Xcode.)

The purpose of the Uninstaller script is too completely remove  
GHC.framework from a machine - not just to remove one version.  In  
fact, if more than one version of GHC is installed, the Uninstaller  
will refuse to run and require the manual removal of all versions, but  
the current (easily achieved by a "rm -rf /Library/Frameworks/ 
GHC.framework/Versions/<version>").  The main feature of the  
Uninstaller script is to get rid of all symlinks pointing into  
GHC.framework.  The framework itself is just deleted by a "rm -rf" as  
expected.  (It also removes the above mentioned receipt file.)

So, to directly answer the above questions:
* The package manger (which uses the receipts) can't uninstall and the  
uninstaller script doesn't need the receipt.  So, even after deleteing  
the receibt, you can still uninstall.
* The Uninstaller can uninstall any version (at least as long as no  
symlinks are put into new directories outside of the bundle that the  
Uninstaller doesn't know about).

Manuel