rebuild autolinking cache if empty or invalid

Summary:
Our test for rebuilding the `autolinking.json` file currently rebuilds everytime if the cached json file ISN'T empty.  This means users who have an empty entry get stuck there.

I've also added more validation that the contents of the cached config have at a minimum the `.project.android.packageName` entry in it, otherwise it rebuilds.

Reviewed By: cortinico

Differential Revision: D61911114

packages/gradle-plugin/settings-plugin/src/main/kotlin/com/facebook/react/ReactSettingsExtension.kt

@@ -7,6 +7,7 @@
 
 package com.facebook.react
 
+import com.facebook.react.model.ModelAutolinkingConfigJson
 import com.facebook.react.utils.JsonUtils
 import com.facebook.react.utils.windowsAwareCommandLine
 import java.io.File
@@ -54,7 +55,8 @@ abstract class ReactSettingsExtension @Inject constructor(val settings: Settings
   ) {
     outputFile.parentFile.mkdirs()
     val lockFilesChanged = checkAndUpdateLockfiles(lockFiles, outputFolder)
-    if (lockFilesChanged || outputFile.exists().not() || outputFile.length() != 0L) {
+    val invalidConfig = !validateConfigModel(JsonUtils.fromAutolinkingConfigJson(outputFile))
+    if (lockFilesChanged || invalidConfig) {
       val process =
           ProcessBuilder(command)
               .directory(workingDirectory)
@@ -150,5 +152,8 @@ abstract class ReactSettingsExtension @Inject constructor(val settings: Settings
 
     internal fun computeSha256(lockFile: File) =
         String.format("%032x", BigInteger(1, md.digest(lockFile.readBytes())))
+
+    internal fun validateConfigModel(model: ModelAutolinkingConfigJson?) =
+        model?.project?.android?.packageName != null
   }
 }