fix(editor): toggle blocks not functioning as actual toggles (#206)

src/app/globals.css

@@ -204,3 +204,12 @@
 .editor-checklist-checked:focus::before {
   box-shadow: 0 0 0 2px var(--ring);
 }
+
+/*
+ * Collapsible toggle chevron rotation.
+ * Rotates the chevron 90° when the parent <details> is open.
+ * Tailwind cannot target details[open] > summary > button.
+ */
+details[open] > summary > .collapsible-toggle {
+  transform: rotate(90deg);
+}

src/components/editor/collapsible-node.tsx

@@ -54,7 +54,8 @@ export class CollapsibleContainerNode extends ElementNode {
 
   createDOM(): HTMLElement {
     const details = document.createElement("details");
-    details.className = "mt-3 border border-white/[0.06] text-sm";
+    details.className =
+      "mt-3 border border-white/[0.06] text-sm rounded-sm";
     if (this.__open) {
       details.open = true;
     }
@@ -123,7 +124,20 @@ export class CollapsibleTitleNode extends ElementNode {
   createDOM(): HTMLElement {
     const summary = document.createElement("summary");
     summary.className =
-      "cursor-pointer select-none p-3 text-sm font-medium text-foreground hover:bg-white/[0.04] list-none";
+      "flex items-center gap-1.5 p-3 text-sm font-medium text-foreground hover:bg-white/[0.04] list-none";
+
+    // Add a toggle chevron button as the visual affordance.
+    // The chevron rotates when the parent <details> is open.
+    const chevron = document.createElement("button");
+    chevron.type = "button";
+    chevron.contentEditable = "false";
+    chevron.className =
+      "collapsible-toggle flex-shrink-0 flex items-center justify-center w-5 h-5 rounded-sm text-muted-foreground hover:text-foreground hover:bg-white/[0.08] transition-transform duration-150";
+    chevron.setAttribute("aria-label", "Toggle section");
+    chevron.innerHTML =
+      '<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><polyline points="9 18 15 12 9 6"></polyline></svg>';
+    summary.prepend(chevron);
+
     return summary;
   }
 

src/components/editor/collapsible-plugin.tsx

@@ -77,7 +77,10 @@ export function CollapsiblePlugin(): null {
     );
   }, [editor]);
 
-  // Handle toggle open/close via DOM events on <details>
+  // Handle toggle open/close via the chevron button.
+  // The native <summary> click toggles <details>, which conflicts with
+  // Lexical text editing in the title. We prevent the native toggle on
+  // summary clicks and instead toggle only when the chevron is clicked.
   useEffect(() => {
     const cleanupMap = new Map<string, () => void>();
 
@@ -102,19 +105,56 @@ export function CollapsiblePlugin(): null {
           ) as HTMLDetailsElement | null;
           if (!dom) continue;
 
-          const handleToggle = () => {
+          const summary = dom.querySelector("summary");
+          if (!summary) continue;
+
+          const chevron = summary.querySelector(
+            ".collapsible-toggle"
+          ) as HTMLButtonElement | null;
+
+          // Prevent the native <details> toggle when clicking the summary
+          // text area — this allows Lexical to handle cursor placement
+          // and text editing without the section collapsing.
+          const handleSummaryClick = (e: MouseEvent) => {
+            const target = e.target;
+            // Allow the chevron button (and its SVG children) to toggle
+            if (
+              chevron &&
+              target instanceof Node &&
+              (chevron === target || chevron.contains(target))
+            ) {
+              return;
+            }
+            // Prevent native toggle for all other summary clicks (text editing)
+            e.preventDefault();
+          };
+
+          // Toggle via the chevron button only
+          const handleChevronClick = (e: MouseEvent) => {
+            e.preventDefault();
+            e.stopPropagation();
             editor.update(() => {
               const node = $getNodeByKey(nodeKey);
               if (node instanceof CollapsibleContainerNode) {
-                node.setOpen(dom.open);
+                const newOpen = !node.getOpen();
+                node.setOpen(newOpen);
+                // Sync the DOM immediately since we prevented native toggle
+                dom.open = newOpen;
               }
             });
           };
 
-          dom.addEventListener("toggle", handleToggle);
-          cleanupMap.set(nodeKey, () =>
-            dom.removeEventListener("toggle", handleToggle)
-          );
+          summary.addEventListener("click", handleSummaryClick);
+          if (chevron) {
+            chevron.addEventListener("click", handleChevronClick);
+          }
+
+          cleanupMap.set(nodeKey, () => {
+            summary.removeEventListener("click", handleSummaryClick);
+            if (chevron) {
+              chevron.removeEventListener("click", handleChevronClick);
+            }
+          });
         }
       }
     );

src/components/editor/collapsible-toggle.test.ts

@@ -0,0 +1,89 @@
+import { describe, it, expect } from "vitest";
+import { readFileSync } from "fs";
+import { resolve } from "path";
+
+/**
+ * Regression tests for issue #206: toggle blocks not functioning as toggles.
+ *
+ * The root cause was threefold:
+ * 1. No visual toggle indicator (chevron) — list-none removed the browser
+ *    disclosure triangle with no replacement.
+ * 2. select-none on <summary> prevented text editing in the title.
+ * 3. Native <summary> click toggled <details>, conflicting with Lexical
+ *    text editing — clicking to place cursor collapsed the section.
+ *
+ * These static tests verify the structural fixes remain in place.
+ */
+
+function readSource(relativePath: string): string {
+  return readFileSync(resolve(__dirname, relativePath), "utf-8");
+}
+
+describe("collapsible-node toggle affordance", () => {
+  const source = readSource("./collapsible-node.tsx");
+
+  it("summary does not use select-none (title must be editable)", () => {
+    // select-none prevents cursor placement and text selection in the
+    // title, breaking inline editing.
+    const summaryClass = source.match(/summary\.className\s*=\s*\n?\s*"([^"]*)"/);
+    expect(summaryClass).not.toBeNull();
+    expect(summaryClass![1]).not.toContain("select-none");
+  });
+
+  it("summary includes a toggle chevron button", () => {
+    // A dedicated button with class collapsible-toggle must be created
+    // as the visual affordance for expand/collapse.
+    expect(source).toContain("collapsible-toggle");
+    expect(source).toContain('aria-label", "Toggle section"');
+  });
+
+  it("chevron button is not contentEditable", () => {
+    // The chevron must be excluded from Lexical's editable content
+    // so it doesn't interfere with text editing.
+    expect(source).toContain('contentEditable = "false"');
+  });
+
+  it("summary uses flex layout for chevron + text alignment", () => {
+    const summaryClass = source.match(/summary\.className\s*=\s*\n?\s*"([^"]*)"/);
+    expect(summaryClass).not.toBeNull();
+    expect(summaryClass![1]).toContain("flex");
+    expect(summaryClass![1]).toContain("items-center");
+  });
+});
+
+describe("collapsible-plugin toggle handling", () => {
+  const source = readSource("./collapsible-plugin.tsx");
+
+  it("prevents native summary click from toggling details", () => {
+    // The plugin must call preventDefault on summary clicks (except
+    // on the chevron) to stop the native <details> toggle from
+    // conflicting with Lexical text editing.
+    expect(source).toContain("e.preventDefault()");
+    expect(source).toContain("handleSummaryClick");
+  });
+
+  it("toggles via chevron button click only", () => {
+    // A dedicated chevron click handler must toggle the node state
+    // and sync the DOM.
+    expect(source).toContain("handleChevronClick");
+    expect(source).toContain("collapsible-toggle");
+  });
+
+  it("syncs DOM open state when toggling via chevron", () => {
+    // After updating the Lexical node, the DOM must be synced since
+    // we prevented the native toggle behavior.
+    expect(source).toContain("dom.open = newOpen");
+  });
+});
+
+describe("collapsible chevron CSS rotation", () => {
+  const css = readFileSync(
+    resolve(__dirname, "../../app/globals.css"),
+    "utf-8"
+  );
+
+  it("rotates chevron when details is open", () => {
+    expect(css).toContain("details[open] > summary > .collapsible-toggle");
+    expect(css).toContain("rotate(90deg)");
+  });
+});