Always add citeproc to filters when it is explicitly enabled

Fixes #2294

news/changelog-1.2.md

@@ -47,9 +47,10 @@
 
 - Handle CNAME file for `gh-pages` either without or without protocol prefix (e.g. https://)
 
-## Bibliographies
+## Bibliographies and Citations
 
 - Support formats `bibtex`, `biblatex`, and `csljson`. When rendered to one of these formats any citations within the document will be rendered as the specified bibliography format.
+- Always add citeproc filter if `citeproc: true` is specified, even if there isn't a bibliography or references in the document (#2294)
 
 ## Miscellaneous
 

src/command/render/filters.ts

@@ -582,13 +582,29 @@ function citeMethod(options: PandocOptions): CiteMethod | null {
   // no handler if no references
   const pandoc = options.format.pandoc;
   const metadata = options.format.metadata;
+
+  // determine the engine, if provided
+  const engine = bibEngine(options.format.pandoc, options.flags);
+
+  // If the user is explicitly enabling citeproc: true, use this as the citemethod
+  // even when there may be no bibliography (see
+  // https://github.com/quarto-dev/quarto-cli/issues/2294 for an example of why)
+  if (pandoc.citeproc) {
+    // If both citeproc and a bib engine are specified, throw an error
+    if (engine) {
+      throw new Error(
+        `The bibliography engine '${engine}' was set when 'citeproc' was also explicitly requested.`,
+      );
+    }
+
+    return "citeproc";
+  }
+
+  // No bibliography or refences, and no explicit request, so no engine specified
   if (!metadata[kBibliography] && !metadata.references) {
     return null;
   }
 
-  // collect config
-  const engine = bibEngine(options.format.pandoc, options.flags);
-
   // if it's pdf-based output check for natbib or biblatex
   if (engine) {
     return engine;