Don't clean out merge directory before merging

Author: ghale

src/main/groovy/org/gradle/android/workarounds/RoomSchemaLocationWorkaround.groovy

@@ -33,6 +33,9 @@ import java.lang.reflect.Field
  * aforementioned merge task.  Note that this workaround only works with Kotlin Gradle plugin 1.3.70 or
  * higher.
  *
+ * There are multiple issues related to these problems:
+ *  - https://issuetracker.google.com/issues/132245929
+ *  - https://issuetracker.google.com/issues/139438151
  */
 @AndroidIssue(introducedIn = "3.5.0", fixedIn = [], link = "https://issuetracker.google.com/issues/132245929")
 class RoomSchemaLocationWorkaround implements Workaround {
@@ -106,7 +109,9 @@ class RoomSchemaLocationWorkaround implements Workaround {
         )
 
         // Change the room schema location back to an absolute path right before the kapt tasks execute.
-        // This allows other annotation processors that rely on the path being absolute to still function.
+        // This allows other annotation processors that rely on the path being absolute to still function and
+        // makes it resilient when the working directory is something other than the project directory.
+        // See https://issuetracker.google.com/issues/139438151
         project.plugins.withId("kotlin-kapt") {
             project.tasks.withType(kaptWithoutKotlincTaskClass).configureEach { Task task ->
                 task.finalizedBy mergeTask
@@ -313,7 +318,6 @@ class RoomSchemaLocationWorkaround implements Workaround {
         @TaskAction
         void mergeSourcesToDestinations() {
             roomSchemaMergeLocations.mergeAssociations.each { destination, source ->
-                project.delete(destination)
                 println "Merging schemas to ${destination}"
                 project.copy {
                     duplicatesStrategy(DuplicatesStrategy.INCLUDE)

src/test/groovy/org/gradle/android/RoomSchemaLocationWorkaroundTest.groovy

@@ -231,7 +231,9 @@ class RoomSchemaLocationWorkaroundTest extends AbstractTest {
 
     void assertMergedSchemaOutputsExist() {
         // Merged schemas
+        assert file("app/schemas/org.gradle.android.example.app.AppDatabase/1.json").exists()
         assert file("app/schemas/org.gradle.android.example.app.AppDatabase/2.json").exists()
+        assert file("library/schemas/org.gradle.android.example.library.AppDatabase/1.json").exists()
         assert file("library/schemas/org.gradle.android.example.library.AppDatabase/2.json").exists()
     }
 }

src/test/groovy/org/gradle/android/SimpleAndroidApp.groovy

@@ -257,6 +257,9 @@ class SimpleAndroidApp {
 
                     @ColumnInfo(name = "last_name")
                     public String lastName;
+
+                    @ColumnInfo(name = "last_update")
+                    public int lastUpdate;
                 }
             """.stripIndent()
 
@@ -329,6 +332,55 @@ class SimpleAndroidApp {
             }
         """.stripIndent()
 
+        file("${basedir}/schemas/${packageName}.AppDatabase/1.json") << '''
+            {
+              "formatVersion": 1,
+              "database": {
+                "version": 1,
+                "identityHash": "ce7bbbf6ddf39482eddc7248f4f61e8a",
+                "entities": [
+                  {
+                    "tableName": "user",
+                    "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`uid` INTEGER NOT NULL, `first_name` TEXT, `last_name` TEXT, PRIMARY KEY(`uid`))",
+                    "fields": [
+                      {
+                        "fieldPath": "uid",
+                        "columnName": "uid",
+                        "affinity": "INTEGER",
+                        "notNull": true
+                      },
+                      {
+                        "fieldPath": "firstName",
+                        "columnName": "first_name",
+                        "affinity": "TEXT",
+                        "notNull": false
+                      },
+                      {
+                        "fieldPath": "lastName",
+                        "columnName": "last_name",
+                        "affinity": "TEXT",
+                        "notNull": false
+                      }
+                    ],
+                    "primaryKey": {
+                      "columnNames": [
+                        "uid"
+                      ],
+                      "autoGenerate": false
+                    },
+                    "indices": [],
+                    "foreignKeys": []
+                  }
+                ],
+                "views": [],
+                "setupQueries": [
+                  "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+                  "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, 'ce7bbbf6ddf39482eddc7248f4f61e8a')"
+                ]
+              }
+            }
+        '''.stripIndent()
+
         file("${basedir}/src/main/res/layout/${resourceName}_layout.xml") << '''<?xml version="1.0" encoding="utf-8"?>
                 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                     android:orientation="vertical"