My Results

[christocracy]

After cloning this app, I successfully built locally without a problem.

I do not use 3rd party build systems.

Add the following logging lines to the plugin's build.gradle and show me the result:

def TAG = "[cordova-background-geolocation] "

def userDir = System.getProperty("user.dir")
def libDir = "${projectDir}/libs"

+println("userDir: $userDir");
+println("projectDir: $projectDir");

Here's what I see:

userDir: /Volumes/Glyph2TB/Users/chris/workspace/background-geolocation/capacitor/tmp/helloworld-background-geolocation/android
projectDir: /Volumes/Glyph2TB/Users/chris/workspace/background-geolocation/capacitor/tmp/helloworld-background-geolocation/android/app

[christocracy]

Try replacing the plugin's build.gradle with this one, which is purely based upon $projectDir (no userDir).

def TAG = "[cordova-background-geolocation] "

def userDir = System.getProperty("user.dir")
def libDir = "${projectDir}/libs"

println("userDir: $userDir");
println("projectDir: $projectDir");

File capacitorConfig = new File("${projectDir}/../../capacitor.config.json")

if (capacitorConfig.exists()) {
  def pluginName = ""
  def CORDOVA_BACKGROUND_GEOLOCATION_LT = "cordova-background-geolocation-lt"
  def CORDOVA_BACKGROUND_GEOLOCATION    = "cordova-background-geolocation"

  // Capacitor app
  libDir = "${projectDir}/../../node_modules"

  File folder = new File("${libDir}/${CORDOVA_BACKGROUND_GEOLOCATION}")

  if (folder.exists() && folder.isDirectory()) {
    pluginName = CORDOVA_BACKGROUND_GEOLOCATION
  } else {
    folder = new File("${libDir}/${CORDOVA_BACKGROUND_GEOLOCATION_LT}")
    if (folder.exists() && folder.isDirectory()) {
      pluginName = CORDOVA_BACKGROUND_GEOLOCATION_LT
    } else {
      println("$TAG Gradle error: Failed to locate plugin directory")
    }
  }
  libDir = "${libDir}/${pluginName}/src/android/libs"
  println("${TAG} Capacitor detected")
} else {
  // Capacitor does not have the scope here to use android.applicationVariants.
  // Capacitor users must manually include app.gradle in their app's gradle file.
  cdvPluginPostBuildExtras.add({
    android {
      purgeBackgroundGeolocationDebugResources(applicationVariants)
    }
  })
}

println("${TAG} libDir: ${libDir}")

dependencies {
  // Load tslocationmanager.aar
  implementation fileTree(include: ['*.aar'], dir: "${libDir}/tslocationmanager")
}

/**
* Background Geolocation's aar includes about 1.5M of mp3 sound-files for its debugging sound FX.
* This method strips those mp3s out in RELEASE builds.
*/

def purgeBackgroundGeolocationDebugResources(applicationVariants) {
    if ((ext.has("removeBackgroundGeolocationDebugSoundsInRelease")) && (ext.removeBackgroundGeolocationDebugSoundsInRelease == false)) return

    applicationVariants.all { variant ->
        // Only Gradle v3.3.0 has this method.  Bail out for older versions of Cordova.
        if (!variant.hasProperty('mergeResourcesProvider')) return

        if (variant.buildType.name == "release") {
            println("[cordova-background-geolocation] Purging debug resources in release build")
            variant.mergeResourcesProvider.configure {
                doLast {
                    delete(fileTree(dir: outputDir, includes: ["raw_tslocationmanager*"]))
                }
            }
        }
    }
}

[soleary1222]

My original results where:

[19:21:32]: ▸ [cordova-background-geolocation] : userDir: /builds/soleary1222/helloworld-background-geolocation

[19:21:32]: ▸ [cordova-background-geolocation] : projectDir: /builds/soleary1222/helloworld-background-geolocation/android/app

I think your second post is the correct solution. From my limited knowledge and what I read, "System.getProperty("user.dir")" is not globally reliable across platforms and build systems.

[christocracy]

Please let me know ASAP if my modified build.gradle above works for you.

[soleary1222]

Yes - your modified build.gradle did in fact work for me.