Getting this (The harvest type was not found in the list of loaded Heat extensions) error while trying to build a project in Visual Studio 2010.
MSBuild from cmdline builds it just fine.
Having this problem at least since 3.5
procmon showed that devenv.exe tries to open heat.exe.config from the ShadowCopy folder which looks like: C:\Users\UserName\AppData\Local\assembly\dl3\XG2847ZD.KP3\P7E7516P.3XC\c2e44358\5e5d6435_2dfecd01\heat.exe.config
The file is not there of course, so it doesn't load any extensions and eventually fails with the above error.
Downloaded the source, changed \src\wix\AppCommon.cs line 106:
string toolPath = Assembly.GetCallingAssembly().Location;
string toolPath = (new System.Uri(Assembly.GetCallingAssembly().CodeBase)).LocalPath;
Tested by copying the contents of the build folder to C:\Program Files (x86)\WiX Toolset v3.7\bin
and it seems to work fine now.
I'm pretty sure this issue http://stackoverflow.com/questions/9290586/wix-darice-cub-file-missing-when-building-from-visual-studio-2010 is related to the above. It also happens only in Visual Studio. Probably \src\wix\Binder.cs(558) or \src\smoke\smoke.cs(168).