[SOLVED] NSIS IfFileExists effectively returns False even though file exists according to ReadRegStr

NSIS IfFileExists effectively returns False even though file exists according to ReadRegStr

I am struggling to understand why IfFileExists essentially returns False even though the uninstall executable file $R0 returned by ReadRegStr below exists.

    ReadRegStr $R0 HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\${APPNAME}" "UninstallString"
    
    IfFileExists $R0 FileExists FileDoesNotExist
FileExists:
    MessageBox MB_OK "Installation file $R0 exists"

FileDoesNotExist:
    MessageBox MB_OK "Installation file $R0 does NOT exist"

What's even more confounding is that if I hardcode the test to

IfFileExists "C:\Program Files\App\UninstallApp.exe" ...

IfFileExists effectively returns True!!!

Update

I could use the != operator but it would be nice to additionally test the path.

    ${If} $R0 != ""
        MessageBox MB_OK "Installation file $R0 exists"
    ${Else}
        MessageBox MB_OK "Installation file $R0 does NOT exist"
    ${EndIf}

Solution

The registry path contains quotes?

Function PathRemoveQuotes
Exch $0
Push $1
StrCpy $1 $0 1
StrCmp $1 '"' 0 done
StrCpy $1 $0 1 -1
StrCmp $1 '"' 0 done
StrCpy $0 $0 -1 1
done:
Pop $1
Exch $0
FunctionEnd

...
ReadRegStr $R0 ...
Push $R0
Call PathRemoveQuotes
Pop $R0
${If} ${FileExists} $R0
...