fix(table-paste): surface first batch paste error

Closes #4832

apps/desktop/src/components/sidebar/SidebarTreeRuntimeHost.vue

@@ -149,7 +149,18 @@ import { formatSqlForDisplay, sqlFormatDialectForDbType } from "@/lib/sql/sqlFor
 import { getTableStructureCapabilities } from "@/lib/table/tableStructureCapabilities";
 import { connectionObjectTreeNodeSchema, connectionObjectTreeQuerySchema, connectionUsesDatabaseObjectTreeMode, effectiveDatabaseTypeForConnection, tableStructureDatabaseTypeForConnection } from "@/lib/database/jdbcDialect";
 import { hasTreeNodeDatabaseContext } from "@/lib/sidebar/treeNodeContext";
-import { defaultPasteTableMode, pasteTableModeCopiesData, supportsWholeRowTableDataCopy, tableClipboardMatchesTarget, tableClipboardMenuState, tableClipboardSourceContext, tableDataCopyColumnOptions, type TableClipboardContext, type TableClipboardTableContext } from "@/lib/table/tableClipboard";
+import {
+  defaultPasteTableMode,
+  pasteTableModeCopiesData,
+  supportsWholeRowTableDataCopy,
+  tableClipboardMatchesTarget,
+  tableClipboardMenuState,
+  tableClipboardSourceContext,
+  tableDataCopyColumnOptions,
+  tablePasteFeedback,
+  type TableClipboardContext,
+  type TableClipboardTableContext,
+} from "@/lib/table/tableClipboard";
 import { selectedSidebarBatchTargets, selectedTreeNodesInVisibleOrder as orderSelectedTreeNodes } from "@/lib/sidebar/sidebarTreeSelection";
 import { connectionPasteTargetGroupId, selectedConnectionClipboardTargets, selectedConnectionEditTarget, selectedConnectionMoveTargets } from "@/lib/sidebar/sidebarConnectionSelection";
 import { connectionSupportsDatabaseUserAdmin, resolveDatabaseUserAdminProviderForConnection, type DatabaseUserIdentity } from "@/lib/database/databaseUserAdmin";
@@ -3831,6 +3842,7 @@ async function confirmPasteTable() {
   showPasteDialog.value = false;
   let successCount = 0;
   let pasteFailCount = 0;
+  let firstPasteError: unknown;
   let refreshFailCount = 0;
   let refreshError: unknown;
   let pasteCancelled = false;
@@ -3902,6 +3914,7 @@ async function confirmPasteTable() {
       successCount++;
     } catch (e: any) {
       pasteFailCount++;
+      firstPasteError ??= e;
       console.error(`Failed to paste table "${entry.sourceName}" -> "${targetName}":`, e);
     }
   }
@@ -3924,13 +3937,14 @@ async function confirmPasteTable() {
     }
     return;
   }
-  if (pasteFailCount === 0) {
+  const pasteFeedback = tablePasteFeedback(successCount, pasteFailCount, firstPasteError);
+  if (pasteFeedback.failedCount === 0) {
     if (connectionStore.treeClipboard === clipboardAtPasteStart) {
       connectionStore.treeClipboard = null;
     }
     toast(t("contextMenu.batchPasteSuccess", { count: successCount }), 3000);
   } else {
-    toast(t("contextMenu.batchPastePartialFail", { success: successCount, failed: pasteFailCount }), 5000);
+    toast(`${t("contextMenu.batchPastePartialFail", { success: pasteFeedback.successCount, failed: pasteFeedback.failedCount })}\n${t("contextMenu.tableOperationFailed", { message: translateBackendError(t, pasteFeedback.firstError) })}`, 5000);
   }
   if (refreshFailCount > 0) {
     const refreshMessage = refreshError instanceof Error ? refreshError.message : String(refreshError);

apps/desktop/src/components/sidebar/__tests__/crossDatabaseTablePaste.spec.ts

@@ -41,4 +41,10 @@ describe("cross-database table paste", () => {
     expect(runtimeSource).toMatch(/buildDuplicateTableStructurePlan\(\{[\s\S]*?connectionId: entry\.connectionId[\s\S]*?sourceName: entry\.sourceName[\s\S]*?tableComment: entry\.tableComment/);
     expect(runtimeSource).toContain("sourceColumns = plan.sourceColumns");
   });
+
+  it("shows the first paste failure reason without concatenating every error", () => {
+    expect(runtimeSource).toMatch(/pasteFailCount\+\+/);
+    expect(runtimeSource).toMatch(/firstPasteError \?\?= e/);
+    expect(runtimeSource).toMatch(/batchPastePartialFail[\s\S]*?tableOperationFailed[\s\S]*?translateBackendError\(t, pasteFeedback\.firstError\)/);
+  });
 });