[codex] Improve code block insertion

src/renderer/editor/codemirror/commands.ts

@@ -483,6 +483,7 @@ export const toggleBlockquoteCommand = (
 export const toggleFencedCodeBlockCommand = (
   view: import("@codemirror/view").EditorView
 ): boolean => {
+  const { from, to } = view.state.selection.main;
   const { start, end } = getSelectedLineNumbers(view);
   const doc = view.state.doc;
   const firstLine = doc.line(start);
@@ -504,6 +505,18 @@ export const toggleFencedCodeBlockCommand = (
     return true;
   }
 
+  if (from === to && firstLine.text.trim() === "") {
+    const indent = firstLine.text.match(/^\s*/)?.[0] ?? "";
+    const snippet = `${indent}\`\`\`\n${indent}\n${indent}\`\`\``;
+    const cursor = firstLine.from + indent.length + 4 + indent.length;
+    view.dispatch({
+      changes: { from: firstLine.from, to: firstLine.to, insert: snippet },
+      selection: { anchor: cursor },
+      scrollIntoView: true,
+    });
+    return true;
+  }
+
   const before = firstLine.from;
   const after = lastLine.to;
 

tests/controllerShortcuts.test.ts

@@ -196,6 +196,24 @@ runTest("code block command wraps and unwraps selected lines", () => {
   assert.equal(view.text, "const x = 1;");
 });
 
+runTest("code block command inserts editable empty fenced block", () => {
+  const view = new FakeView("", { from: 0, to: 0 });
+
+  toggleFencedCodeBlockCommand(view as unknown as EditorView);
+
+  assert.equal(view.text, "```\n\n```");
+  assert.deepEqual(view.state.selection.main, { from: 4, to: 4 });
+});
+
+runTest("code block command preserves indentation for empty fenced blocks", () => {
+  const view = new FakeView("  ", { from: 2, to: 2 });
+
+  toggleFencedCodeBlockCommand(view as unknown as EditorView);
+
+  assert.equal(view.text, "  ```\n  \n  ```");
+  assert.deepEqual(view.state.selection.main, { from: 8, to: 8 });
+});
+
 if (process.exitCode && process.exitCode !== 0) {
   throw new Error("One or more tests failed.");
 }