fix: quote copied cells so values with delimiters survive paste

README.md

@@ -159,7 +159,7 @@ Per-file (stored by the extension; set via commands):
 - Selection improvements: Shift+Click on headers selects column ranges; Shift+Click on the serial index selects row ranges; right‑click preserves current selection.
 - Batch actions: Context menu adapts to multi‑selection (Add/Delete X Rows/Columns) and performs exact counts in a single operation.
 - Delete to clear: Press Delete/Backspace to clear contents of selected cells (skips serial index column).
-- Copy fidelity: Copies with the active delimiter and skips the serial index column for full‑row copies.
+- Copy fidelity: Copies with the active delimiter, quotes values containing the delimiter, quotes, or newlines, and skips the serial index column for full‑row copies.
 - Encoding: New command “CSV: Change File Encoding” integrates VS Code’s encoding picker and returns to the CSV view.
 - Enable/disable UX: Toggling the extension on instantly upgrades open CSV/TSV tabs to this view; toggling off reverts immediately to the default view.
 

REVIEW.md

@@ -12,7 +12,6 @@ P0 (Critical)
 P1 (High)
 - State persistence: Ensure scroll + selection restore across config changes and chunk loads; add targeted tests (including very large files and header on/off).
 - Selection semantics: Preserve selection on right‑click; Shift+Click ranges on headers and serial index; add tests for row/column/rectangular cases.
-- Copy fidelity: Confirm delimiter, quoting, and skipped serial index column for whole‑row copies; add tests.
 
 P2 (Medium)
 - CSP tightening: Replace `style-src 'unsafe-inline'` with nonce‑only styles (we already nonce the tag; remove the policy’s unsafe‑inline if feasible without regressions).

media/main.js

@@ -6,7 +6,6 @@ try { document.body.focus({ preventScroll: true }); } catch { try { document.bod
 const vscode = acquireVsCodeApi();
 
 const root = document.getElementById('csv-root');
-const CSV_SEPARATOR = String.fromCodePoint(parseInt(root?.dataset?.sepcode || '44', 10)); // default ','
 const parsePositiveNumber = value => {
   const parsed = typeof value === 'string' ? Number.parseFloat(value) : Number(value);
   if (!Number.isFinite(parsed) || parsed <= 0) return undefined;
@@ -2027,17 +2026,19 @@ const copySelectionToClipboard = () => {
   if (coords.length === 0) return;
   const minRow = Math.min(...coords.map(c => c.row)), maxRow = Math.max(...coords.map(c => c.row));
   const minCol = Math.min(...coords.map(c => c.col)), maxCol = Math.max(...coords.map(c => c.col));
-  let csv = '';
+  // Send raw cell values; the host serializes them with the active delimiter
+  // and quotes values containing the delimiter, quotes, or newlines.
+  const cells = [];
   for(let r = minRow; r <= maxRow; r++){
-    let rowVals = [];
+    const rowVals = [];
     for(let c = minCol; c <= maxCol; c++){
       const selector = (hasHeader && r === 0 ? 'th' : 'td') + '[data-row="'+r+'"][data-col="'+c+'"]';
       const cell = table.querySelector(selector);
-      rowVals.push(cell ? cell.innerText : '');
+      rowVals.push(cell ? (cell.textContent || '') : '');
     }
-    csv += rowVals.join(CSV_SEPARATOR) + '\n';
+    cells.push(rowVals);
   }
-  vscode.postMessage({ type: 'copyToClipboard', text: csv.trimEnd() });
+  vscode.postMessage({ type: 'copyToClipboard', cells });
 };
 
 window.addEventListener('message', event => {

src/CsvEditorProvider.ts

@@ -141,10 +141,15 @@ class CsvEditorController {
         case 'save':
           await this.handleSave();
           break;
-        case 'copyToClipboard':
-          await vscode.env.clipboard.writeText(e.text);
+        case 'copyToClipboard': {
+          if (!Array.isArray(e.cells)) {
+            break;
+          }
+          const text = CsvEditorController.serializeClipboardMatrix(e.cells, this.getSeparator());
+          await vscode.env.clipboard.writeText(text);
           console.log('CSV: Copied to clipboard');
           break;
+        }
         case 'insertColumn':
           await this.insertColumn(e.index);
           break;
@@ -528,6 +533,16 @@ class CsvEditorController {
     }
   }
 
+  private static serializeClipboardMatrix(matrix: string[][], delimiter: string): string {
+    if (!Array.isArray(matrix) || matrix.length === 0) {
+      return '';
+    }
+    const rows = matrix.map(row => (Array.isArray(row) ? row : [row]).map(cell => String(cell ?? '')));
+    // Papa quotes any field containing the delimiter, a quote, or a newline, so
+    // copied values survive a round trip through parseClipboardMatrix.
+    return Papa.unparse(rows, { delimiter, newline: '\n' });
+  }
+
   private parseClipboardMatrix(text: string): string[][] {
     if (!text || text.length === 0) {
       return [];
@@ -2773,6 +2788,13 @@ export class CsvEditorProvider implements vscode.CustomTextEditorProvider {
     ): string | undefined {
       return CsvEditorProvider.applyFieldUpdatesPreservingFormat(text, delimiter, updates);
     },
+    serializeClipboardMatrix(matrix: string[][], delimiter: string): string {
+      return (CsvEditorController as any).serializeClipboardMatrix(matrix, delimiter);
+    },
+    parseClipboardMatrix(text: string): string[][] {
+      const c: any = new (CsvEditorController as any)({} as any);
+      return c.parseClipboardMatrix(text);
+    },
     computePastePlan(
       matrix: string[][],
       anchorRow: number,

src/test/provider-utils.test.ts

@@ -274,4 +274,32 @@ describe('CsvEditorProvider utility methods', () => {
     assert.strictEqual(meta.nextChunkStart, 80);
     assert.strictEqual(meta.hasRemoteChunks, true);
   });
+
+  it('quotes copied cells containing the delimiter so they survive a paste round trip', () => {
+    const { serializeClipboardMatrix, parseClipboardMatrix } = CsvEditorProvider.__test;
+    const cases: string[][][] = [
+      [['a,b']],
+      [['say "hi"']],
+      [['line1\nline2']],
+      [['a,b', 'c'], ['d', 'e']]
+    ];
+    for (const matrix of cases) {
+      const text = serializeClipboardMatrix(matrix, ',');
+      assert.deepStrictEqual(parseClipboardMatrix(text), matrix, `round trip failed for ${JSON.stringify(matrix)}`);
+    }
+  });
+
+  it('serializes copied cells with the active delimiter and only quotes when needed', () => {
+    const { serializeClipboardMatrix } = CsvEditorProvider.__test;
+    assert.strictEqual(serializeClipboardMatrix([['x\ty', 'z']], '\t'), '"x\ty"\tz');
+    assert.strictEqual(serializeClipboardMatrix([['a,b']], '\t'), 'a,b');
+    assert.strictEqual(serializeClipboardMatrix([['a', 'b'], ['c', 'd']], ','), 'a,b\nc,d');
+  });
+
+  it('preserves trailing empty cells and omits a trailing newline when copying', () => {
+    const { serializeClipboardMatrix } = CsvEditorProvider.__test;
+    assert.strictEqual(serializeClipboardMatrix([['a', '']], '\t'), 'a\t');
+    assert.strictEqual(serializeClipboardMatrix([['a'], ['']], ','), 'a\n');
+    assert.strictEqual(serializeClipboardMatrix([], ','), '');
+  });
 });

src/test/webview-edit-shortcuts.test.ts

@@ -55,4 +55,9 @@ describe('Webview edit shortcuts', () => {
     assert.ok(webviewSource.includes("} else if (message.type === 'pasteApplied') {"));
     assert.ok(webviewSource.includes("selectRange({ row: startRow, col: startCol }, { row: endRow, col: endCol });"));
   });
+
+  it('sends the copied selection as a cell matrix so the host can quote it', () => {
+    assert.ok(webviewSource.includes("vscode.postMessage({ type: 'copyToClipboard', cells });"));
+    assert.ok(!webviewSource.includes('rowVals.join(CSV_SEPARATOR)'));
+  });
 });