Each time I would re-open Flash Builder, our Flex Library projects would get their “Framework linkage” settings in the “Flex Library Build Path” project properties reset to “Merged into code” instead of keeping my preferred setting of “Use default (external).” I couldn’t figure out why until I noticed one day that any new Flex Library project I created did not have this problem. After doing some folder/file comparisons, I figured out how to fix it.
In your Flex Library project folder, open this file:
(For those of us on Macs, this file is hidden since it begins with a period.)
The first line of the file will look like this:
<flexLibProperties includeAllClasses="false" useMultiPlatformConfig="false" version="1">/code>
Change the version value to "3" instead:
<flexLibProperties includeAllClasses="false" useMultiPlatformConfig="false" version="3">/code>
Now, close and re-open your project.
Change the "Framework linkage" back to "Use Default (external)" it will retain its framework linkage setting next time it is re-opened!
Why it happened
I think this was due to a bug in the way Flash Builder upgraded these projects, since it was only happening with projects that we had originally created in earlier versions of Flash Builder.