Re: Check for file before installing
Re: Check for file before installing
- Subject: Re: Check for file before installing
- From: Peter Bierman <email@hidden>
- Date: Fri, 21 Sep 2007 14:08:07 -0700
At 12:32 PM -0700 9/21/07, Jack Repenning wrote:
On Sep 21, 2007, at 11:46 AM, Peter Bierman wrote:
While I agree that this situation makes life hard for the
installer, the Mac OS X Installer handles this as well as can be
expected. The OS itself installs many many files that overlap
between packages.
The consequences are that when multiple packages own the same file,
upgrading any one of those packages has the potential to replace or
remove that file, leaving the other packages in an inconsistent
state.
When you know the circumstances of upgrading, you can work around
this issue. For example, with Annette's issue, if she replaces a
font that should exist anyway, then system upgrades will update or
replace that font as necessary.
Sure, I didn't mean to dis the Apple installer. But we're still --
inescapably, so far as I can see -- left with those potential
inconsistent states. If for example, Annette cares about this font
because she wants to use it (seems a safe guess!), and she wants to
use this particular font because its metrics make some tricky form
layout work better than any other font (wouldn't surprise me, given
her return address and implied product), then a change to the font
that altered the layout metrix (a thing outside her control, since
she doesn't actually own this font) would be a big deal for her:
when half her customers start complaining that the form lays out
wrong, she'll have a very hard time figuring out why it fails at all
("works for me"), let alone why it only fails for half her customers.
Absolutely. Those are all big warning flags for anyone going into
this situation. The most obvious solution would be for Annette to
ship her own copy of the font in a location private to her software.
But she's chosen to use a system font. Her software is making an API
contract with the OS over that font. She's trusting that Apple will
only alter that font in compatible ways (which may or may not be true
over a long timeframe.)
Presumably the risk of using the system font is outweighed by other
factors such as its availability. (Although if she has permission to
ship it to repair a broken system, she probably has permission to
install it somewhere private.)
The biggest risk here is probably to the OS itself. Annette's product
will continue to install that font even after the OS removes it. If
the OS does remove it, it'll probably be for a good reason. That
illustrates the common problem with multiple packages owning the same
file... any of the several owners could choose to remove the file.
-pmb
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