fix(web): copy final code block lines as plain text

apps/web/src/markdown-clipboard.test.ts

@@ -1,6 +1,6 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vite-plus/test";
 
-import { serializeRenderedMarkdownFragment } from "./markdown-clipboard";
+import { plainTextForCodeSelection, serializeRenderedMarkdownFragment } from "./markdown-clipboard";
 
 const TEXT_NODE = 3;
 const ELEMENT_NODE = 1;
@@ -93,3 +93,74 @@ describe("serializeRenderedMarkdownFragment", () => {
     expect(serializeRenderedMarkdownFragment(asNode(container))).toBe("first line\nsecond line");
   });
 });
+
+function rangeNode(closestPre: Element | null): Node {
+  return {
+    nodeType: ELEMENT_NODE,
+    closest: () => closestPre,
+  } as unknown as Node;
+}
+
+function codeSelectionRange({
+  commonAncestorPre,
+  trailingText,
+  trailingElement,
+}: {
+  commonAncestorPre: Element | null;
+  trailingText: string;
+  trailingElement?: FakeElement;
+}): Range {
+  const trailingContent =
+    trailingElement ?? new FakeElement("DIV").append(new FakeText(trailingText));
+  return {
+    commonAncestorContainer: rangeNode(commonAncestorPre),
+    startContainer: rangeNode({} as Element),
+    cloneRange: () =>
+      ({
+        setStartAfter: vi.fn(),
+        cloneContents: () => asNode(trailingContent),
+      }) as unknown as Range,
+    toString: () => "sudo dnf remove alacritty",
+  } as unknown as Range;
+}
+
+describe("plainTextForCodeSelection", () => {
+  beforeEach(() => {
+    vi.stubGlobal("Node", { TEXT_NODE, ELEMENT_NODE });
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it("keeps a selection contained by pre plain", () => {
+    const range = codeSelectionRange({ commonAncestorPre: {} as Element, trailingText: "unused" });
+
+    expect(plainTextForCodeSelection(range)).toBe("sudo dnf remove alacritty");
+  });
+
+  it("keeps a final-line selection plain when only its trailing boundary leaves pre", () => {
+    const range = codeSelectionRange({ commonAncestorPre: null, trailingText: "\n" });
+
+    expect(plainTextForCodeSelection(range)).toBe("sudo dnf remove alacritty");
+  });
+
+  it("preserves markdown serialization when a code selection continues into prose", () => {
+    const range = codeSelectionRange({
+      commonAncestorPre: null,
+      trailingText: "The following paragraph",
+    });
+
+    expect(plainTextForCodeSelection(range)).toBeNull();
+  });
+
+  it("preserves markdown serialization for selected trailing nodes without text", () => {
+    const range = codeSelectionRange({
+      commonAncestorPre: null,
+      trailingText: "",
+      trailingElement: new FakeElement("DIV").append(new FakeElement("HR")),
+    });
+
+    expect(plainTextForCodeSelection(range)).toBeNull();
+  });
+});

apps/web/src/markdown-clipboard.ts

@@ -309,6 +309,28 @@ function sanitizedHtmlFrom(container: Element): string {
   return `<meta charset="utf-8">${container.innerHTML}`;
 }
 
+function elementForNode(node: Node): Element | null {
+  return node.nodeType === Node.ELEMENT_NODE ? (node as Element) : node.parentElement;
+}
+
+/**
+ * Returns raw code for selections contained by `pre`, including final-line
+ * triple-click ranges whose trailing boundary leaves the block without
+ * selecting any following text.
+ */
+export function plainTextForCodeSelection(range: Range): string | null {
+  if (elementForNode(range.commonAncestorContainer)?.closest("pre")) {
+    return range.toString();
+  }
+
+  const startPre = elementForNode(range.startContainer)?.closest("pre");
+  if (!startPre) return null;
+
+  const trailingRange = range.cloneRange();
+  trailingRange.setStartAfter(startPre);
+  return serializeRenderedMarkdownFragment(trailingRange.cloneContents()) ? null : range.toString();
+}
+
 export function chatMarkdownClipboardPayload(
   selection: Selection,
 ): MarkdownClipboardPayload | null {
@@ -319,11 +341,9 @@ export function chatMarkdownClipboardPayload(
     if (range.collapsed) continue;
     const container = document.createElement("div");
     container.appendChild(range.cloneContents());
-    const ancestor = range.commonAncestorContainer;
-    const ancestorElement =
-      ancestor.nodeType === Node.ELEMENT_NODE ? (ancestor as Element) : ancestor.parentElement;
-    if (ancestorElement?.closest("pre")) {
-      const text = range.toString();
+    const plainCodeText = plainTextForCodeSelection(range);
+    if (plainCodeText !== null) {
+      const text = plainCodeText;
       if (text) {
         texts.push(text);
         htmls.push(sanitizedHtmlFrom(container));