Fix bug when pasting into cell in edit mode

mathesar_ui/src/AppContext.svelte

@@ -66,17 +66,17 @@
   // Data Explorer.
 
   function handleCopy(e: ClipboardEvent) {
-    if (clipboardHandler) {
-      clipboardHandler.handleCopy(e);
-      e.preventDefault();
-    }
+    if (!clipboardHandler) return;
+    if (!clipboardHandler.shouldHandleCopy(e)) return;
+    clipboardHandler.handleCopy(e);
+    e.preventDefault();
   }
 
   function handlePaste(e: ClipboardEvent) {
-    if (clipboardHandler) {
-      void clipboardHandler.handlePaste(e);
-      e.preventDefault();
-    }
+    if (!clipboardHandler) return;
+    if (!clipboardHandler.shouldHandlePaste(e)) return;
+    void clipboardHandler.handlePaste(e);
+    e.preventDefault();
   }
 </script>
 

mathesar_ui/src/components/sheet/clipboard/SheetClipboardHandler.ts

@@ -18,13 +18,27 @@ interface Dependencies {
   showToastError: (msg: string) => void;
 }
 
+function shouldHandleEvent(): boolean {
+  // Only handle clipboard events when a cell is focused. This prevents pasting
+  // into inputs while editing cells, and other unexpected behavior.
+  return document.activeElement?.hasAttribute('data-active-cell') ?? false;
+}
+
 export class SheetClipboardHandler implements ClipboardHandler {
   private readonly deps: Dependencies;
 
   constructor(deps: Dependencies) {
     this.deps = deps;
   }
 
+  shouldHandleCopy() {
+    return shouldHandleEvent();
+  }
+
+  shouldHandlePaste() {
+    return shouldHandleEvent();
+  }
+
   handleCopy(event: ClipboardEvent): void {
     if (event.clipboardData == null) return;
     try {

mathesar_ui/src/stores/clipboard.ts

@@ -2,6 +2,8 @@ import { getContext, setContext } from 'svelte';
 import { type Writable, writable } from 'svelte/store';
 
 export interface ClipboardHandler {
+  shouldHandleCopy: (event: ClipboardEvent) => boolean;
+  shouldHandlePaste: (event: ClipboardEvent) => boolean;
   handleCopy: (event: ClipboardEvent) => void;
   handlePaste: (event: ClipboardEvent) => Promise<void>;
 }