|Merge Succeeds But Heaps of Validation Errors Produced|
Unlike the "merge fails with error message(s)" issue the merge and build actually completes but the validation step produces many messages (generally warnings but may include errors).
The reason for the messages is that merge modules generally seem to be written by idiots (and MS ones are certainly no exception)! Another reason is that Microsoft and others don't follow Microsofts own guidelines (some of which are unreasonable).
You should have a quick look at any messages and if they don't look critical (and testing doesn't show any issues) the you can use the "MsiValFilter" command to filter these out, the following example does this:
<$Feature "FRED"> ;;FRED must of course exist (or validation errors will result)... <$MergeModule "Merge Modules\comcat.msm"> <$MsiValFilter ".857CCBE2_47ED_4181_ABBC_4E2951155D44"> ;;Filter out ALL "comcat.msm" messages based on the Merge Module GUID <$MergeModule "Merge Modules\mfc42.msm" IgnoreErrors="Directory:SystemFolder"> <$MergeModule "Merge Modules\msvcrt.msm"> <$MergeModule "Merge Modules\oleaut32.msm" Comment="This module is a requirement for one of the other modules!"> <$/Feature>
As always I recommend you pick your filters carefully so they are unlikely to filter out other unintended messages!