Allow event defaults on index for text data transfer (#9840)

app/javascript/mastodon/features/ui/index.js

@@ -243,6 +243,7 @@ class UI extends React.PureComponent {
   }
 
   handleDragOver = (e) => {
+    if (this.dataTransferIsText(e.dataTransfer)) return false;
     e.preventDefault();
     e.stopPropagation();
 
@@ -256,6 +257,7 @@ class UI extends React.PureComponent {
   }
 
   handleDrop = (e) => {
+    if (this.dataTransferIsText(e.dataTransfer)) return;
     e.preventDefault();
 
     this.setState({ draggingOver: false });
@@ -279,6 +281,10 @@ class UI extends React.PureComponent {
     this.setState({ draggingOver: false });
   }
 
+  dataTransferIsText = (dataTransfer) => {
+    return (dataTransfer && Array.from(dataTransfer.types).includes('text/plain') && dataTransfer.items.length === 1);
+  }
+
   closeUploadModal = () => {
     this.setState({ draggingOver: false });
   }