"Scanning new and updated MEF components" and "Composing MEF graph..." runs every time I launch VS 2017, slowing start-up time. In the past these steps only appeared to be performed after a new extension was installed or after a significant system change such as a new Windows 10 build was installed.
Visual Studio 2017 version 15.0.0+26228.9 Windows 10 Pro build 15058
Added a solution by Daniel Richter · Mar 24 at 11:35 AM
Found the malefactor: "Peak Help" (extension)
If (and only if) I have Peak Help activated as extension, the CompomentModelCache folder gets emptied at startup. So the cache has to be restored at the next start-up of VS (that made the search for responsible extensions slightly difficult, because the effects weren't visible after (de)activating extensions and (de)activating extensions itself triggers scanning MEF).
After deactivating Peak Help, there should be one (single) cyle of scanning; afterwards ComponentModelCache keeps its content and VS starts without scanning for new and updated MEF components at startup.
Further information: Before deleting the entire content of ComponentModelCache, there is a file microsoftvisualstudiodefaulterr.txt created.
EDIT: Seems it could be a different combination of activated extensions, too. In my case the easiest way to find the problematic extension(s) was to open the ComponentModelCache directory side-by-side with Visual Studio and watch whether the contents will be deleted at startup. If ComponentCache is empty after VS' startup, the bad extension is still active; if the content (five files) is still there when the solution is loaded, the bad extension is not active anymore.
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