Adding Warning Badge for Cards with Empty Fronts in Previewer

Added code in TemplatePreviewerViewModel to compute whether cards have empty fronts, and added warning badges to previewer tabs in TemplatePreviewerPage accordingly

Author: ericli3690

AnkiDroid/src/main/java/com/ichi2/anki/previewer/TemplatePreviewerPage.kt

@@ -55,8 +55,14 @@ class TemplatePreviewerPage : Fragment(R.layout.template_previewer_container) {
         val tabLayout = view.findViewById<TabLayout>(R.id.tab_layout)
 
         lifecycleScope.launch {
-            for (templateName in viewModel.getTemplateNames()) {
-                tabLayout.addTab(tabLayout.newTab().setText(templateName))
+            val cardsWithEmptyFronts = viewModel.cardsWithEmptyFronts?.await()
+            for ((index, templateName) in viewModel.getTemplateNames().withIndex()) {
+                val newTab = tabLayout.newTab().setText(templateName)
+                if (cardsWithEmptyFronts?.get(index) == true) {
+                    val badge = newTab.getOrCreateBadge()
+                    badge.horizontalOffset = -4
+                }
+                tabLayout.addTab(newTab)
             }
             tabLayout.selectTab(tabLayout.getTabAt(viewModel.getCurrentTabIndex()))
             tabLayout.addOnTabSelectedListener(

AnkiDroid/src/main/java/com/ichi2/anki/previewer/TemplatePreviewerViewModel.kt

@@ -39,6 +39,7 @@ import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.parcelize.Parcelize
+import org.intellij.lang.annotations.Language
 import org.jetbrains.annotations.VisibleForTesting
 
 class TemplatePreviewerViewModel(
@@ -63,6 +64,11 @@ class TemplatePreviewerViewModel(
     override var currentCard: Deferred<Card>
     override val server = AnkiServer(this).also { it.start() }
 
+    /**
+     * Ordered list of cards with empty fronts
+     */
+    internal val cardsWithEmptyFronts: Deferred<List<Boolean>>?
+
     init {
         note =
             asyncIO {
@@ -105,9 +111,28 @@ class TemplatePreviewerViewModel(
                     val tr = CollectionManager.TR
                     clozeNumbers.await().map { tr.cardTemplatesCard(it) }
                 }
+            cardsWithEmptyFronts = null
         } else {
             clozeOrds = null
             templateNames = CompletableDeferred(notetype.templatesNames)
+            cardsWithEmptyFronts =
+                asyncIO {
+                    val note = note.await()
+                    List(templateNames.await().size) { ord ->
+                        val questionText =
+                            withCol {
+                                note
+                                    .ephemeralCard(
+                                        col = this,
+                                        ord = ord,
+                                        customNoteType = notetype,
+                                        fillEmpty = fillEmpty,
+                                        deckId = arguments.deckId,
+                                    ).renderOutput(this)
+                            }.questionText
+                        EMPTY_FRONT_LINK in questionText
+                    }
+                }
         }
     }
 
@@ -205,6 +230,9 @@ class TemplatePreviewerViewModel(
         }
 
     companion object {
+        @Language("HTML")
+        private const val EMPTY_FRONT_LINK = """<a href='https://docs.ankiweb.net/templates/errors.html#front-of-card-is-blank'>"""
+
         fun factory(
             arguments: TemplatePreviewerArguments,
             cardMediaPlayer: CardMediaPlayer,

AnkiDroid/src/test/java/com/ichi2/anki/previewer/TemplatePreviewerViewModelTest.kt

@@ -57,6 +57,21 @@ class TemplatePreviewerViewModelTest : JvmTest() {
         }
     }
 
+    @Test
+    fun `empty front field detected correctly for tab badge`() =
+        runOptionalReversedTest(
+            fields =
+                mutableListOf(
+                    "we have two normal fields",
+                    "and purposefully leave the third blank",
+                    "",
+                ),
+        ) {
+            onPageFinished(false)
+            assertThat(this.cardsWithEmptyFronts!!.await()[0], equalTo(false))
+            assertThat(this.cardsWithEmptyFronts!!.await()[1], equalTo(true))
+        }
+
     private fun runClozeTest(
         ord: Int = 0,
         fields: MutableList<String>? = null,
@@ -73,4 +88,21 @@ class TemplatePreviewerViewModelTest : JvmTest() {
         val viewModel = TemplatePreviewerViewModel(arguments, mock())
         block(viewModel)
     }
+
+    private fun runOptionalReversedTest(
+        ord: Int = 0,
+        fields: MutableList<String>? = null,
+        block: suspend TemplatePreviewerViewModel.() -> Unit,
+    ) = runTest {
+        val notetype = col.notetypes.byName("Basic (optional reversed card)")!!
+        val arguments =
+            TemplatePreviewerArguments(
+                notetypeFile = NotetypeFile(tempDirectory.root, notetype),
+                fields = fields ?: mutableListOf("question text", "answer text", "y"),
+                tags = mutableListOf(),
+                ord = ord,
+            )
+        val viewModel = TemplatePreviewerViewModel(arguments, mock())
+        block(viewModel)
+    }
 }