Fix book title-block template path being mangled by pandoc escaping

news/changelog-1.11.md

@@ -43,6 +43,7 @@ All changes included in 1.11:
 - ([#10114](https://github.com/quarto-dev/quarto-cli/issues/10114)): Support `announcement` under the `book` key, which previously had no effect.
 - ([#14276](https://github.com/quarto-dev/quarto-cli/issues/14276)): Support `llms-txt` under the `book` key, which previously had no effect.
 - ([#14879](https://github.com/quarto-dev/quarto-cli/issues/14879)): Support `plausible-analytics`, `back-to-top-navigation`, and `image-alt` under the `book` key, which previously had no effect.
+- ([#14929](https://github.com/quarto-dev/quarto-cli/pull/14929)): Fix `Error compiling template` when rendering a book to `pdf`, `docx` or `epub` on Windows with Quarto located under a directory whose name starts with `_`, `.`, `-` or another punctuation character.
 
 ## Commands
 

src/core/pandoc/pandoc-attr.ts

@@ -7,6 +7,15 @@
 
 import { PandocAttr } from "./types.ts";
 
+// Pandoc's markdown reader resolves backslash escapes inside a quoted
+// attribute value, so a value written into an attribute list has to escape
+// backslashes and the quote character to survive being read back. Windows
+// paths are the case that bites: a directory whose name starts with
+// punctuation (D:\a\_temp) otherwise loses its separator.
+export function pandocQuotedAttrValue(value: string): string {
+  return `'${value.replaceAll(/['\\]/g, "\\$&")}'`;
+}
+
 export function pandocAttrParseText(attr: string): PandocAttr | null {
   attr = attr.trim();
 

src/project/types/book/book-render.ts

@@ -14,6 +14,7 @@ import {
   parsePandocTitle,
   partitionMarkdown,
 } from "../../../core/pandoc/pandoc-partition.ts";
+import { pandocQuotedAttrValue } from "../../../core/pandoc/pandoc-attr.ts";
 
 import {
   kAbstract,
@@ -469,35 +470,10 @@ async function mergeExecutedFiles(
             return createMarkdownTitle(titleText, titleAttr);
           };
 
-          // If there is front matter for this chapter, this will generate a code
-          // cell that will be rendered a LUA filter (the code cell will provide the
-          // path to the template that should be used as well as the front matter
-          // to use when rendering)
-          const resolveTitleBlockMarkdown = (yaml?: Metadata) => {
-            if (yaml) {
-              const titleBlockPath = resourcePath(
-                "projects/book/pandoc/title-block.md",
-              );
-
-              const titleAttr = `template='${titleBlockPath}'`;
-              const frontMatter = `---\n${
-                stringify(yaml, { indent: 2 })
-              }\n---\n`;
-
-              const titleBlockMd = "```````{.quarto-title-block " +
-                titleAttr + "}\n" +
-                frontMatter +
-                "\n```````\n\n";
-
-              return titleBlockMd;
-            } else {
-              return "";
-            }
-          };
-
           // Compose the markdown for this chapter
           const titleMarkdown = resolveTitleMarkdown(partitioned);
-          const titleBlockMarkdown = resolveTitleBlockMarkdown(
+          const titleBlockMarkdown = bookTitleBlockMarkdown(
+            resourcePath("projects/book/pandoc/title-block.md"),
             partitioned.yaml,
           );
           const bodyMarkdown = partitioned.yaml?.title
@@ -692,6 +668,26 @@ function cleanupExecutedFile(
   );
 }
 
+// If there is front matter for a chapter, this generates a code cell that will
+// be rendered by a LUA filter (the code cell provides the path to the template
+// that should be used as well as the front matter to use when rendering)
+export function bookTitleBlockMarkdown(
+  templatePath: string,
+  yaml?: Metadata,
+) {
+  if (yaml) {
+    const titleAttr = `template=${pandocQuotedAttrValue(templatePath)}`;
+    const frontMatter = `---\n${stringify(yaml, { indent: 2 })}\n---\n`;
+
+    return "```````{.quarto-title-block " +
+      titleAttr + "}\n" +
+      frontMatter +
+      "\n```````\n\n";
+  } else {
+    return "";
+  }
+}
+
 function bookItemMetadata(
   project: ProjectContext,
   item: BookRenderItem,

tests/unit/book-title-block-attr.test.ts

@@ -0,0 +1,67 @@
+/*
+ * book-title-block-attr.test.ts
+ *
+ * Copyright (C) 2026 Posit Software, PBC
+ */
+
+import { unitTest } from "../test.ts";
+import { assertEquals } from "testing/asserts";
+import { execProcess } from "../../src/core/process.ts";
+import { pandocBinaryPath } from "../../src/core/resources.ts";
+import { bookTitleBlockMarkdown } from "../../src/project/types/book/book-render.ts";
+
+// Pandoc's markdown reader consumes a backslash that precedes an ASCII
+// punctuation character inside a quoted attribute value, so a Windows path
+// with a directory whose name starts with punctuation loses that separator
+// unless the value is escaped when the attribute is generated.
+const kTemplatePath =
+  "D:\\a\\_temp\\quarto-under-test\\share\\projects\\book\\pandoc\\title-block.md";
+
+async function templateAttrAfterPandocRoundTrip(
+  markdown: string,
+): Promise<string> {
+  const result = await execProcess(
+    {
+      cmd: pandocBinaryPath(),
+      args: ["--from", "markdown", "--to", "json"],
+      stdout: "piped",
+      stderr: "piped",
+    },
+    markdown,
+  );
+  assertEquals(result.code, 0, `pandoc failed: ${result.stderr}`);
+
+  // deno-lint-ignore no-explicit-any
+  const doc = JSON.parse(result.stdout!) as any;
+  // deno-lint-ignore no-explicit-any
+  const titleBlock = doc.blocks.find((block: any) =>
+    block.t === "CodeBlock" && block.c[0][1].includes("quarto-title-block")
+  );
+  assertEquals(
+    titleBlock !== undefined,
+    true,
+    "no quarto-title-block code cell in the generated markdown",
+  );
+  const template = titleBlock.c[0][2].find(
+    (keyvalue: [string, string]) => keyvalue[0] === "template",
+  );
+  assertEquals(
+    template !== undefined,
+    true,
+    "quarto-title-block code cell has no template attribute",
+  );
+  return template[1];
+}
+
+unitTest(
+  "book title block - template path survives pandoc attribute parsing",
+  async () => {
+    const markdown = bookTitleBlockMarkdown(kTemplatePath, {
+      title: "A Chapter",
+    });
+    assertEquals(
+      await templateAttrAfterPandocRoundTrip(markdown),
+      kTemplatePath,
+    );
+  },
+);