What if the documentation is found in the applicationDirectory and not in the prefixDirectory?  Then viewHelp won't find it.

viewHelp = key -> (
     checkLoadDocumentation();
     if prefixDirectory === null then error "can't run viewHelp from build tree";
     show new URL from { fix if key === () then applicationDirectory() | "index.html" else prefixDirectory | htmlFilename key }
     )
viewHelp = new Command from viewHelp
