Handle no comments and comments disabled scenarios

app/src/main/java/org/schabi/newpipe/fragments/detail/VideoDetailFragment.java

@@ -882,8 +882,7 @@ public final class VideoDetailFragment
         tabContentDescriptions.clear();
 
         if (shouldShowComments()) {
-            pageAdapter.addFragment(
-                    CommentsFragment.getInstance(serviceId, url), COMMENTS_TAB_TAG);
+            pageAdapter.addFragment(CommentsFragment.getInstance(serviceId, url), COMMENTS_TAB_TAG);
             tabIcons.add(R.drawable.ic_comment);
             tabContentDescriptions.add(R.string.comments_tab_description);
         }

app/src/main/java/org/schabi/newpipe/fragments/list/comments/Comment.kt

@@ -69,7 +69,6 @@ fun Comment(comment: CommentsInfoItem) {
     var isExpanded by rememberSaveable { mutableStateOf(false) }
     var showReplies by rememberSaveable { mutableStateOf(false) }
 
-    Surface(color = MaterialTheme.colorScheme.background) {
     Row(
         modifier = Modifier
             .fillMaxWidth()
@@ -152,7 +151,6 @@ fun Comment(comment: CommentsInfoItem) {
             }
         }
     }
-    }
 
     if (showReplies) {
         ModalBottomSheet(onDismissRequest = { showReplies = false }) {
@@ -190,7 +188,7 @@ fun CommentsInfoItem(
     this.replyCount = replyCount
 }
 
-class DescriptionPreviewProvider : PreviewParameterProvider<Description> {
+private class DescriptionPreviewProvider : PreviewParameterProvider<Description> {
     override val values = sequenceOf(
         Description("Hello world!<br><br>This line should be hidden by default.", Description.HTML),
         Description("Hello world!\n\nThis line should be hidden by default.", Description.PLAIN_TEXT),
@@ -214,6 +212,8 @@ private fun CommentPreview(
     )
 
     AppTheme {
+        Surface(color = MaterialTheme.colorScheme.background) {
             Comment(comment)
         }
     }
+}

app/src/main/java/org/schabi/newpipe/fragments/list/comments/CommentSection.kt

@@ -1,18 +1,33 @@
 package org.schabi.newpipe.fragments.list.comments
 
 import android.content.res.Configuration
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.tooling.preview.PreviewParameter
+import androidx.compose.ui.tooling.preview.PreviewParameterProvider
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.paging.LoadState
+import androidx.paging.LoadStates
 import androidx.paging.PagingData
 import androidx.paging.compose.collectAsLazyPagingItems
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flowOf
 import my.nanihadesuka.compose.LazyColumnScrollbar
 import my.nanihadesuka.compose.ScrollbarSettings
+import org.schabi.newpipe.R
 import org.schabi.newpipe.extractor.comments.CommentsInfoItem
 import org.schabi.newpipe.extractor.stream.Description
 import org.schabi.newpipe.ui.theme.AppTheme
@@ -23,6 +38,13 @@ fun CommentSection(
     parentComment: CommentsInfoItem? = null,
 ) {
     val replies = flow.collectAsLazyPagingItems()
+    val itemCount by remember { derivedStateOf { replies.itemCount } }
+
+    Surface(color = MaterialTheme.colorScheme.background) {
+        val refresh = replies.loadState.refresh
+        if (itemCount == 0 && refresh !is LoadState.Loading) {
+            NoCommentsMessage((refresh as? LoadState.Error)?.error)
+        } else {
             val listState = rememberLazyListState()
 
             LazyColumnScrollbar(state = listState, settings = ScrollbarSettings.Default) {
@@ -34,27 +56,63 @@ fun CommentSection(
                         }
                     }
 
-            items(replies.itemCount) {
+                    items(itemCount) {
                         Comment(comment = replies[it]!!)
                     }
                 }
             }
         }
+    }
+}
 
-@Preview(name = "Light mode", uiMode = Configuration.UI_MODE_NIGHT_NO)
-@Preview(name = "Dark mode", uiMode = Configuration.UI_MODE_NIGHT_YES)
 @Composable
-private fun CommentSectionPreview() {
-    val comments = (1..100).map {
+private fun NoCommentsMessage(error: Throwable?) {
+    val message = if (error is CommentsDisabledException) {
+        R.string.comments_are_disabled
+    } else {
+        R.string.no_comments
+    }
+
+    Column(horizontalAlignment = Alignment.CenterHorizontally) {
+        Text(text = "(╯°-°)╯", fontSize = 35.sp)
+        Text(text = stringResource(id = message), fontSize = 24.sp)
+    }
+}
+
+private class CommentDataProvider : PreviewParameterProvider<PagingData<CommentsInfoItem>> {
+    private val notLoading = LoadState.NotLoading(true)
+
+    override val values = sequenceOf(
+        // Normal view
+        PagingData.from(
+            (1..100).map {
                 CommentsInfoItem(
                     commentText = Description("Comment $it", Description.PLAIN_TEXT),
                     uploaderName = "Test"
                 )
             }
-    val flow = flowOf(PagingData.from(comments))
+        ),
+        // Comments disabled
+        PagingData.from(
+            listOf<CommentsInfoItem>(),
+            LoadStates(LoadState.Error(CommentsDisabledException()), notLoading, notLoading)
+        ),
+        // No comments
+        PagingData.from(
+            listOf<CommentsInfoItem>(),
+            LoadStates(notLoading, notLoading, notLoading)
+        )
+    )
+}
 
+@Preview(name = "Light mode", uiMode = Configuration.UI_MODE_NIGHT_NO)
+@Preview(name = "Dark mode", uiMode = Configuration.UI_MODE_NIGHT_YES)
+@Composable
+private fun CommentSectionPreview(
+    @PreviewParameter(CommentDataProvider::class) pagingData: PagingData<CommentsInfoItem>
+) {
     AppTheme {
-        CommentSection(flow = flow)
+        CommentSection(flow = flowOf(pagingData))
     }
 }
 

app/src/main/java/org/schabi/newpipe/fragments/list/comments/CommentsSource.kt

@@ -25,7 +25,7 @@ class CommentsSource(
             .subscribeOn(Schedulers.io())
             .map {
                 if (it.isCommentsDisabled) {
-                    LoadResult.Invalid()
+                    LoadResult.Error(CommentsDisabledException())
                 } else {
                     LoadResult.Page(it.relatedItems, null, it.nextPage)
                 }
@@ -34,3 +34,5 @@ class CommentsSource(
 
     override fun getRefreshKey(state: PagingState<Page, CommentsInfoItem>) = null
 }
+
+class CommentsDisabledException : RuntimeException()