Merge #5853

5853: Closes #4466, #5278: Migration: Filter about:home tabs and rewrite about:reader URLs. r=grigoryk a=pocmo

For #4466 an #5278.

We are now:
- Skipping tabs that are pointing to `about:home` - Fenix can't handle that URL.
- Rewriting `about:reader` URLs to the original URL. Fenix can't handle `about:reader` URLs but can just load the original URL.

Co-authored-by: Sebastian Kaspari <s.kaspari@gmail.com>

components/support/migration/src/main/java/mozilla/components/support/migration/FennecSessionMigration.kt

@@ -4,6 +4,7 @@
 
 package mozilla.components.support.migration
 
+import android.net.Uri
 import mozilla.components.browser.session.SessionManager
 import mozilla.components.lib.crash.CrashReporter
 import mozilla.components.support.base.log.logger.Logger
@@ -36,9 +37,9 @@ internal object FennecSessionMigration {
 
         for (file in sessionFiles) {
             try {
-                return StreamingSessionStoreParser.parse(file)
+                return StreamingSessionStoreParser.parse(file).filter(logger, crashReporter)
             } catch (e: FileNotFoundException) {
-                logger.warn("FileNotFoundException while trying to parse sessopm stpre", e)
+                logger.warn("FileNotFoundException while trying to parse session store", e)
             } catch (e: IOException) {
                 crashReporter.submitCaughtException(e)
                 logger.error("IOException while parsing Fennec session store", e)
@@ -73,3 +74,55 @@ internal object FennecSessionMigration {
         return files
     }
 }
+
+@Suppress("TooGenericExceptionCaught")
+private fun Result.Success<SessionManager.Snapshot>.filter(
+    logger: Logger,
+    crashReporter: CrashReporter
+): Result.Success<SessionManager.Snapshot> {
+    var selectedIndex = value.selectedSessionIndex
+
+    logger.debug("Filtering migrated sessions (size=${value.sessions.size}, index=$selectedIndex)")
+
+    val sessions = value.sessions.mapIndexedNotNull { index, item ->
+        when {
+            // We filter out about:home tabs since Fenix does not handle those URLs.
+            item.session.url == ABOUT_HOME -> {
+                logger.debug("- Filtering about:home URL")
+                if (index < selectedIndex) {
+                    selectedIndex--
+                }
+                null
+            }
+
+            // We rewrite about:reader URLs to their actual URLs. Fenix does not handle about:reader
+            // URLs, but it can load the original URL.
+            item.session.url.startsWith(ABOUT_READER) -> {
+                try {
+                    val url = Uri.decode(item.session.url.substring(ABOUT_READER.length))
+
+                    logger.debug("- Rewriting about:reader URL (${item.session.url}): $url")
+
+                    item.session.url = url
+                    item
+                } catch (e: Exception) {
+                    crashReporter.submitCaughtException(e)
+                    null
+                }
+            }
+
+            else -> item
+        }
+    }
+
+    if (sessions.isEmpty()) {
+        selectedIndex = -1
+    }
+
+    logger.debug("Migrated sessions filtered (size=${sessions.size}, index=$selectedIndex)")
+
+    return Result.Success(SessionManager.Snapshot(sessions, selectedIndex))
+}
+
+private const val ABOUT_HOME = "about:home"
+private const val ABOUT_READER = "about:reader?url="

components/support/migration/src/test/java/mozilla/components/support/migration/FennecSessionMigrationTest.kt

@@ -59,7 +59,7 @@ class FennecSessionMigrationTest {
         }
 
         snapshot.sessions[4].also {
-            assertEquals("about:reader?url=https%3A%2F%2Fwww.theverge.com%2F2019%2F9%2F18%2F20871860%2Fhuawei-mate-30-photos-videos-leak-watch-gt-2-fitness-band-tv-android-tablet-harmony-os",
+            assertEquals("https://www.theverge.com/2019/9/18/20871860/huawei-mate-30-photos-videos-leak-watch-gt-2-fitness-band-tv-android-tablet-harmony-os",
                 it.session.url)
 
             assertEquals("Huawei’s Thursday event lineup apparently leaks in full",
@@ -124,8 +124,6 @@ class FennecSessionMigrationTest {
         val profilePath = File(getTestPath("sessions"), "test-case2")
         val result = FennecSessionMigration.migrate(profilePath, mock())
 
-        assertTrue(result is Result.Success)
-
         assertTrue(result is Result.Success)
         val snapshot = (result as Result.Success).value
         assertEquals(2, snapshot.sessions.size)
@@ -154,11 +152,60 @@ class FennecSessionMigrationTest {
 
         val result = FennecSessionMigration.migrate(profilePath, mock())
 
-        assertTrue(result is Result.Success)
-
         assertTrue(result is Result.Success)
         val snapshot = (result as Result.Success).value
         assertEquals(21, snapshot.sessions.size)
         assertEquals(12, snapshot.selectedSessionIndex)
     }
+
+    /**
+     * We expect in this test run to:
+     * - Filter out the about:home tab.
+     * - Rewrite the about:reader tab to its original URL.
+     * - Rewrite the selected index after about:home was filtered out.
+     */
+    @Test
+    fun `about-home and about-reader URLs`() {
+        val profilePath = File(getTestPath("sessions"), "about-urls")
+
+        val result = FennecSessionMigration.migrate(profilePath, mock())
+
+        assertTrue(result is Result.Success)
+        val snapshot = (result as Result.Success).value
+        assertEquals(2, snapshot.sessions.size)
+        assertEquals(1, snapshot.selectedSessionIndex)
+
+        snapshot.sessions[0].also {
+            assertEquals("https://www.spiegel.de/",
+                it.session.url)
+
+            assertEquals("DER SPIEGEL | Online-Nachrichten",
+                it.session.title)
+        }
+
+        snapshot.sessions[1].also {
+            assertEquals("https://www.spiegel.de/politik/deutschland/fdp-parteivorstand-spricht-lindner-nach-kemmerich-wahl-vertrauen-aus-a-47e0a21c-7617-4549-b6dc-716c0363cbc2",
+                it.session.url)
+
+            assertEquals("FDP-Parteivorstand spricht Lindner Vertrauen aus - DER SPIEGEL - Politik",
+                it.session.title)
+        }
+    }
+
+    /**
+     * We expect in this test run to:
+     * - Filter out the single about:home tab.
+     * - Reset the selected index to -1.
+     */
+    @Test
+    fun `only about-home`() {
+        val profilePath = File(getTestPath("sessions"), "only-about-home")
+
+        val result = FennecSessionMigration.migrate(profilePath, mock())
+
+        assertTrue(result is Result.Success)
+        val snapshot = (result as Result.Success).value
+        assertEquals(0, snapshot.sessions.size)
+        assertEquals(-1, snapshot.selectedSessionIndex)
+    }
 }