Apple

Hello,

I am currently converting a non-flat installer package to a flat installer package, but I'm facing some problems regaring the prevention of downgrade installations:

The old non-flat installer package would display a nice warning message to the user that says "<PackageName> can't be installed on this disk. A newer version of this software already exists on this disk." That screen's "Continue" button would be disabled.

The new flat installation package doesn't present any warning message, though: instead, it's simply stuck in the "Installation Type" screen, where it says "Click Install to perform a standard installation of this software on the disk <RootVolumeName>." The "Install" button is disabled.

So my question is:
How to configure a flat distribution package to display the "cannot downgrade" warning message to the user?

What I have achieved so far:
I have created a flat standard package using the "pkgbuild" tool, then I wrapped that standard package in a flat distribution package, using the "productbuild" tool and a customized distribution configuration file.
I configured the distribution package to prevent downgrades by creating a "choice" which enables/disables the standard package, and setting the choice's "start_selected" attribute using a "choiceIsADowngrade()" _javascript_ (similar to this one: <http://code.google.com/p/openvanilla/source/browse/trunk/Distributions/OpenVanilla-Leopard-0.8/PackageMaker.app/Contents/Resources/choiceIsADowngrade.js?r=3281>).

Some more information:
The choice itself is neither customizable nor visible, and the _javascript_ mechanism to prevent downgrades works perfectly fine.
Also, the package is not relocatable, so the "Destination Select" screen is usually skipped. When a downgrade installation is detected for the old non-flat package, though, the above mentioned warning message is displayed within the (otherwise skipped) "Destination Select" screen.

The packages are built on a Mac OS X 10.7.5 system, the described behaviour is the same on Mac OS X 10.6.8, 10.7.5 and 10.8.2.

The distribution configuration file looks like this:

----- snip -----
<?xml version="1.0" encoding="utf-8"?>
<installer-gui-script minSpecVersion="1">
<title>MyPackage</title>
<background alignment="topleft" file="background.png" scaling="none"/>
<welcome file="Welcome.rtf"/>
<readme file="ReadMe.rtf"/>
<license file="License.rtf"/>
<options rootVolumeOnly="true" allow-external-scripts="yes" customize="never"/>
<pkg-ref id="my.installer.package"/>
<pkg-ref id="my.installer.package" _onConclusion_="none">MyPackage.pkg</pkg-ref>
<choice id="choice-id.MyPackage" start_visible="false" start_enabled="false" start_selected='!choiceIsADowngrade();' title="MyPackage">
<pkg-ref id="my.installer.package"/>
</choice>
<choices-outline>
<line choice="choice-id.MyPackage"/>
</choices-outline>
<installation-check script="pm_install_check();"/>

<script>
function pm_install_check() {
try {
var checkResult = system.run("InstallationCheck")

// Check for system version.
if (checkResult == 113) {
my.result.title = system.localizedString('Error');
my.result.message = system.localizedString('OperatingSystemTooOld');
my.result.type = 'Fatal';
return false;
}

// Check for architecture.
if (checkResult == 114) {
my.result.title = system.localizedString('Error');
my.result.message = system.localizedString('IntelOnly');
my.result.type = 'Fatal';
return false;
}

} catch (e) {}

return true;
}
</script>

<script>
function choiceIsADowngrade() {
return checkChoiceUpgradeAction()
}
</script>

<script>
function checkChoiceUpgradeAction() {
var result = false
try {
result = my.choice.packageUpgradeAction == 'downgrade' || my.choice.packageUpgradeAction == 'mixed'
} catch (e) {}

return result
}
</script>
</installer-gui-script>----- snip -----