Support format-specific snippets; pandoc target for snippets/blocks

Alex Fenton · Alex Fenton · commit 0a35d0fbfa56 · 2022-04-19T09:50:14.000+02:00
Snippets with the @@ syntax should be supported in the same way as
blocks already are. Adds 'pandoc as a possible target, allowing passing
content only to this backend.
diff --git a/README.org b/README.org
@@ -217,9 +217,17 @@ settings in your init file.
 * Feature Support 
 ** Source Code Blocks
 =ox-pandoc= supports the export of code blocks, including code blocks
-for specific formats (e.g. LaTeX). Code wrapped in =BEGIN_EXPORT
-[format]= will be passed to pandoc and included in the final output if
-the output is of the appropriate format.
+for specific output formats (e.g. LaTeX, HTML). Code wrapped in
+=#+BEGIN_EXPORT [format]= will be passed to pandoc as-is. Pandoc knows how
+to handle these blocks correctly and will include them in the final
+output if they match the target format. The same applies for short
+format-specific snippets using Org's =@@format:= syntax.
+
+Blocks and snippets intended only for the pandoc backend can be
+specified using =#+BEGIN_EXPORT pandoc= and =@@pandoc:=. The inner
+content of these blocks and snippets will be passed to pandoc. This may
+be useful for adding extra information for output formats only supported
+by pandoc, not by Org's own native converters.
 
 =ox-pandoc= also supports the evaluation of embedded code blocks wrapped
 with =BEGIN_SRC [language]=. The various options described by the
diff --git a/ox-pandoc.el b/ox-pandoc.el
@@ -247,6 +247,7 @@ version. If nil, no checks are performed and no warnings generated."
 (org-export-define-derived-backend 'pandoc 'org
   :translate-alist '((entity    . org-pandoc-entity)
 					 (export-block . org-pandoc-export-block)
+					 (export-snippet . org-pandoc-export-snippet)
 					 (latex-environment . org-pandoc-latex-environ)
                      (link      . org-pandoc-link)
                      (paragraph . org-pandoc-paragraph)
@@ -1752,9 +1753,24 @@ contextual information."
   "Transcode a EXPORT-BLOCK element from Org to Pandoc.
 This might be EXPORT_HTML or EXPORT_LATEX, and is simply
 duplicated into the temporary org file that pandoc converts.
-CONTENTS is the contents of the block. INFO is a plist holding
-contextual information."
-  (org-pandoc-identity export-block contents info))
+Special: if the block is BEGIN_EXPORT pandoc, pass the value to
+pandoc. CONTENTS is the contents of the block. INFO is a plist
+holding contextual information."
+  (if  (string= (org-element-property :type export-block) "PANDOC")
+	  (org-element-property :value export-block)
+	(org-pandoc-identity export-block contents info)))
+
+(defun org-pandoc-export-snippet (export-snippet contents info)
+  "Transcode a @@format:snippet@@ from Org to Pandoc.
+If it is an output format, such as latex or html, the snippet is
+duplicated in full for pandoc to handle as Org's own exporters
+would. If the snippet specifies 'pandoc' as the format, the inner
+content of the snippet is passed to pandoc. CONTENTS is the
+contents of the block. INFO is a plist holding contextual
+information."
+  (if (eq (org-export-snippet-backend export-snippet) 'pandoc)
+	  (org-element-property :value export-snippet)
+	(org-pandoc-identity export-snippet contents info)))
 
 (defun org-pandoc-identity (blob contents _info)
   "Transcode BLOB element or object back into Org syntax.
