[Tickets #6559] Re: DIMP should fail gracefully if IMP not installed

[bugs at horde.org]

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Ticket URL: http://bugs.horde.org/ticket/6559
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 Ticket             | 6559
 Updated By         | php at ideacode.com
 Summary            | DIMP should fail gracefully if IMP not installed
 Queue              | DIMP
 Version            | HEAD
 Type               | Bug
 State              | Not A Bug
 Priority           | 1. Low
 Milestone          |
 Patch              |
 Owners             |
+New Attachment     | issue6559.diff
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php at ideacode.com (2008-04-02 14:26) wrote:

> I appreciate the thought that the application should degrade
> gracefully even if random files are deleted from it - which is along
> the same lines as saying it should function without its requirements
> installed - but there's, to be buzzwordy about it, low ROI there for
> an open source project.

A requirement in the documentation is only as good as its enforcement in
the software.  If IMP is a required module, then I should not be able to
run a Horde framework with only nag, mnemo, whups, and wicked.  But I can,
which demonstrates a discrepancy between what the documentation states are
requirements and what the software states are requirements.  In the
presence of such a discrepancy, the software's view wins.

> And I'm sorry, but how is IMP not a requirement for DIMP?

Foremost because the software doesn't enforce the requirement.  I
recognize the documentation states that IMP is a requirement, and that's
great, but the reality is that Horde (the collection) is a complex
organism, comprised of many different modules all with differing
requirements and implementation strategies, constrained by a loose hegemony
armed with guidelines designed to move everyone toward a common goal.
Recognizing that complexity, the purpose of this request -- as low a
priority as it may be -- is to provide a product that remains strong in the
face of users' errors.

And since I'm the type of guy to put my mouth where my bug reports are,
here's a patch.  This patch adds "requirement" support to configuration XML
documents.  The completely optional <requires> container lists the
mandatory applications that the given configuration needs.  DIMP, for
example, might read:
 <requires>
   <require app="imp" />
   <require extension="imap" />
 </requires>

All requirements must be satisfied, or a warning is emitted on the
configuration page.  In this case, both the imp application and the PHP
imap extension must be installed and loaded.  The parser also supports a
version attribute for the requirement element, but I do not immediately
know how to get the version information consistently from the registry or
from an extension, so that's left as an exercise for the reader.