electron-builder nsis run other executable during install

I'm trying to run a different executable during install of my app but I cannot find the right path to do it. The program is added with the following electron-builder config:

extraFiles:
    -   from: tools/tapinstall/${arch}/
        to: resources/tapinstall/
        filter:
            - "**/*"

After installing my app I can see the files in the resources/tapinstall/ folder so it's being ported. Now, in my nsis installer.nsh I added an ExecWait directive to run an exe from that directory but it fails.

As a desperate measure I figured that prefixing everything with $INSTDIR was not the right move, maybe the path is not $INSTDIR and something else and I found 3 possible candidates:

$INSTDIR
$APPDATA
$BUILD_RESOURCES_DIR

I added this simple code to see which file gets created so I can figure out the right macro to use:

!macro customHeader
    RequestExecutionLevel admin
!macroend

!macro customInstall
    !system "echo 'as' > $INSTDIR/customInstall"
    !system "echo 'bs' > $APPDATA/customInstall"
    !system "echo 'cs' > $BUILD_RESOURCES_DIR/customInstall"

    ${ifNot} ${isUpdated}
        !system "echo 'a' > $INSTDIR/customInstall"
            !system "echo 'b' > $APPDATA/customInstall"
            !system "echo 'c' > $BUILD_RESOURCES_DIR/customInstall"
    ${endIf}
!macroend

I then did a full search on my computer for a file called customInstall...nothing. What am I doing wrong?

Solution

!system (and all other ! instructions) are executed at compile-time inside makensis.exe. You cannot access variables/constants at compile time, only defines and environment variables.

!define foo "Hello"
!warning "${NSISDIR} & $%Temp% & ${foo}"

Var Bar
Section
StrCpy $Bar "World"
MessageBox mb_ok "$InstDir & $Bar"
SectionEnd