Allow ::: without preceding empty line to be parsed as closing div (#875)

* allow ::: without preceding empty line to be parsed as closing div

* Add some tests for code cell detection

* Update CHANGELOG

---------

Co-authored-by: Julia Silge <julia.silge@gmail.com>

Author: jkrumbiegel

apps/vscode/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## 1.128.0 (Unreleased)
 
+- Fixed a bug where code blocks inside complex div structures (e.g., many `::: {.notes}` divs without preceding blank lines) were not detected as executable cells (<https://github.com/quarto-dev/quarto/pull/875>).
+
 ## 1.127.0 (Release on 2025-12-17)
 
 - By default, headers from markdown files _in R projects_ (projects with a `DESCRIPTION` file such as R package) are no longer exported as workspace symbols. They remain exported as usual in other projects. This behaviour can be controlled manually with the new `quarto.symbols.exportToWorkspace` setting.

apps/vscode/src/test/codeBlocks.test.ts

@@ -0,0 +1,66 @@
+import * as vscode from "vscode";
+import * as assert from "assert";
+import { WORKSPACE_PATH, examplesOutUri, openAndShowTextDocument } from "./test-utils";
+import { isExecutableLanguageBlock, languageNameFromBlock } from "quarto-core";
+import { MarkdownEngine } from "../markdown/engine";
+
+suite("Code block detection", function () {
+  const engine = new MarkdownEngine();
+
+  suiteSetup(async function () {
+    await vscode.workspace.fs.delete(examplesOutUri(), { recursive: true });
+    await vscode.workspace.fs.copy(vscode.Uri.file(WORKSPACE_PATH), examplesOutUri());
+  });
+
+  // Test for issue #521 / PR #875:
+  // Code blocks inside divs should be detected even when the closing :::
+  // doesn't have a preceding blank line. This real-world example has many
+  // .notes divs which caused later code blocks to not be detected.
+  test("Detects code blocks in document with many divs (issue #521)", async function () {
+    const { doc } = await openAndShowTextDocument("div-code-blocks.qmd");
+
+    const tokens = engine.parse(doc);
+    const executableBlocks = tokens.filter(isExecutableLanguageBlock);
+
+    // Count R code blocks and math blocks separately
+    const rBlocks = executableBlocks.filter(b => languageNameFromBlock(b) === "r");
+    const mathBlocks = executableBlocks.filter(b => languageNameFromBlock(b) === "tex");
+
+    // Should find all 3 R code blocks
+    assert.strictEqual(
+      rBlocks.length,
+      3,
+      `Expected 3 R code blocks, found ${rBlocks.length}`
+    );
+
+    // Should find all 3 math blocks (displayed as tex)
+    assert.strictEqual(
+      mathBlocks.length,
+      3,
+      `Expected 3 math blocks, found ${mathBlocks.length}`
+    );
+
+    // Total should be 6 executable blocks (3 R + 3 math)
+    assert.strictEqual(
+      executableBlocks.length,
+      6,
+      `Expected 6 executable blocks total, found ${executableBlocks.length}`
+    );
+  });
+
+  test("Detects code block in simple document", async function () {
+    const { doc } = await openAndShowTextDocument("hello.qmd");
+
+    const tokens = engine.parse(doc);
+    const executableBlocks = tokens.filter(isExecutableLanguageBlock);
+
+    assert.strictEqual(
+      executableBlocks.length,
+      1,
+      `Expected 1 executable block in hello.qmd, found ${executableBlocks.length}`
+    );
+
+    const language = languageNameFromBlock(executableBlocks[0]);
+    assert.strictEqual(language, "python", `Expected python, got ${language}`);
+  });
+});

apps/vscode/src/test/examples/div-code-blocks.qmd

@@ -0,0 +1,158 @@
+---
+title: "Div Code Blocks"
+format: html
+---
+
+## Code blocks in divs without blank lines
+
+This tests the fix for issue #521 where closing `:::` without a preceding
+blank line would cause code blocks to not be detected.
+
+## A slide with code
+
+```{r}
+library(tidyverse)
+head(mtcars)
+```
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+$$
+\mathbf{y} = \mathbf{X}^\top\beta + \varepsilon
+$$
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+```{r}
+head(mtcars)
+```
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+$$
+\mathbf{y} = \mathbf{X}^\top\beta + \varepsilon
+$$
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with code
+
+Did not previously display properly:
+
+```{r}
+head(mtcars)
+```
+
+::: {.notes}
+- test notes
+:::
+
+## A slide with math
+
+Did not previously display properly:
+
+$$
+\mathbf{y} = \mathbf{X}^\top\beta + \varepsilon
+$$
+
+::: {.notes}
+- test notes
+:::

packages/core/src/markdownit/divs.ts

@@ -139,7 +139,7 @@ export const divPlugin = (md: MarkdownIt) => {
         return false;
       }
     },
-    { alt: [] }
+    { alt: ["paragraph"] }
   )
 
   md.renderer.rules[kTokDivOpen] = renderStartDiv