Don’t eat header line when title specified via yaml

fixes #3653

Author: dragonstyle

src/core/pandoc/pandoc-partition.ts

@@ -88,5 +88,6 @@ export function partitionMarkdown(markdown: string): PartitionedMarkdown {
     headingAttr: markdownHeadingAttr,
     containsRefs: markdownContainsRefs,
     markdown: markdownLines.join("\n"),
+    srcMarkdownNoYaml: partitioned?.markdown || "",
   };
 }

src/core/pandoc/types.ts

@@ -19,4 +19,5 @@ export interface PartitionedMarkdown {
   headingAttr?: PandocAttr;
   containsRefs: boolean;
   markdown: string;
+  srcMarkdownNoYaml: string;
 }

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

@@ -485,10 +485,14 @@ async function mergeExecutedFiles(
           const titleBlockMarkdown = resolveTitleBlockMarkdown(
             partitioned.yaml,
           );
+          const bodyMarkdown = partitioned.yaml?.title
+            ? partitioned.srcMarkdownNoYaml
+            : partitioned.markdown;
+
           itemMarkdown = bookItemMetadata(project, item, file) +
             titleMarkdown +
             titleBlockMarkdown +
-            partitioned.markdown;
+            bodyMarkdown;
         } else {
           throw new Error(
             "Executed file not found for book item: " + item.file,