Add reference numbers to links to numbered items in pandoc export.

When referring to a Table, Figure, Listing, Equation or other numbered
item, then the link description should contain that number.

This allows the pandoc backend to include automatically numbered
references to Figures, Tables, etc., similarly to the other standard
org-mode backends.

ox-pandoc.el

@@ -1371,14 +1371,75 @@ INFO is a plist holding contextual information."
  ;; (faked) equation numbering.
  output)))
 
-(defun org-pandoc-link (link contents _info)
+(defun org-pandoc-link (link contents info)
  "Transcode LINK object using the registered formatter for the
 'pandoc backend. If none exists, transcode using the registered
-formatter for the 'org export backend. CONTENTS is the
-description of the link, as a string, or nil. INFO is ignored."
- (or (org-export-custom-protocol-maybe link contents 'pandoc)
- (org-export-custom-protocol-maybe link contents 'org)
- (org-element-link-interpreter link contents)))
+formatter for the 'org export backend. For fuzzy (internal)
+links, resolve the link destination in order to determine the
+appropriate reference number of the target Table/Figure/Equation
+etc. CONTENTS is the description of the link, as a string, or
+nil. INFO is a plist holding contextual information."
+ (let ((type (org-element-property :type link)))
+ (cond
+ ;; Try exporting with a registered formatter for 'pandoc
+ ((org-export-custom-protocol-maybe link contents 'pandoc))
+ ;; Try exporting with a registered formatter for 'org
+ ((org-export-custom-protocol-maybe link contents 'org))
+
+ ;; Otherwise, override fuzzy (internal) links that point to
+ ;; numbered items such as Tables, Figures, Sections, etc.
+ ((string= type "fuzzy")
+ (let* ((path (org-element-property :path link))
+ (destination (org-export-resolve-fuzzy-link link info))
+ (dest-type (when destination (org-element-type destination)))
+ (number nil))
+ ;; Different link targets require different predicates to the
+ ;; `org-export-get-ordinal' function in order to resolve to
+ ;; the correct number. NOTE: Should be the same predicate
+ ;; function as used to generate the number in the
+ ;; caption/label/listing etc.
+ (cond
+ ((eq dest-type 'paragraph) ; possible figure
+ (setq number (org-export-get-ordinal
+ destination info nil #'org-html-standalone-image-p)))
+
+ ((eq dest-type 'latex-environment)
+ (setq number (org-export-get-ordinal
+ destination info nil #'org-pandoc--numbered-equation-p)))
+
+ (t ; captioned items
+ (setq number (org-export-get-ordinal
+ destination info nil #'org-pandoc--has-caption-p))))
+
+ ;; Numbered items have the number listed in the link
+ ;; description, , fall back on the text in `contents'
+ ;; if there's no resolvable destination
+ (cond
+ ;; Numbered items have the number listed in the link description
+ (number
+ (format "[[#%s][%s]]" path
+ (if (atom number) (number-to-string number)
+ (mapconcat #'number-to-string number "."))))
+
+ ;; Unnumbered headlines have the heading name in the link
+ ;; description
+ ((eq dest-type 'headline)
+ (format "[[#%s][%s]]" path
+ (org-export-data
+ (org-element-property :title destination) info)))
+
+ ;; No resolvable destination, fallback on the text in `contents'
+ ((eq destination nil)
+ (when (org-string-nw-p contents) contents))
+
+ ;; Valid destination, but without a numbered caption/equation
+ ;; and not a heading, fallback to standard org-mode link format
+ (t
+ (org-element-link-interpreter link contents))
+ )))
+
+ ;; Otherwise, fallback to standard org-mode link format
+ ((org-element-link-interpreter link contents)))))
 
 (defun org-pandoc-table (table contents info)
  "Transcode a TABLE element from Org to Pandoc.