oc-csl.el: Add support for sub-bibliographies

* lisp/oc-csl.el (org-cite-csl--rendered-bibliographies): New function to collect all #+print_bibliography keywords with their properties and call Citeproc to render all sub-bibliographies in one go as required by the API. Return the formatted bibliographies as values in an alist in which keys are the #+print_bibliography keyword options as plists. Cache the return value in the export communication channel. (org-cite-csl--bibliography-filter): New helper function to convert plists representing #+print_bibliography options to the alist filter form expected by Citeproc. (org-cite-csl--rendered-citations): Call `org-cite-csl--rendered-bibliographies' before rendering citations to make sure that the complete sub-bibliography information is added to the processor and, therefore, citation numbers are correct. (org-cite-csl--render-bibliography): Instead of directly calling Citeproc to render the bibliography, call `org-cite-csl--rendered-bibliographies' and retrieve the formatted bibliography from its return value based on the options passed as the `props' argument.

Author: andras-simonyi

etc/ORG-NEWS

@@ -239,7 +239,7 @@ This behaviour can be changed by supplying a =:align= parameter.
 
 The tabbing environment can be useful when generating simple tables which
 can be span multiple pages and when table cells are allowed to overflow.
-*** Support for =nocite= citations in the "csl" export processor
+*** Support for =nocite= citations and sub-bibliographies in the "csl" export processor
 
 The "csl" citation export processor now supports =nocite= style
 citations that add items to the printed bibliography without visible
@@ -251,6 +251,17 @@ instance,
 #+end_src
 
 includes all available items in the printed bibliography.
+
+The "csl" export processor now also supports sub-bibliographies that
+show only a subset of the references based on some criterion. For
+example,
+
+#+begin_src org
+#+print_bibliography: :type book :keyword ai
+#+end_src
+
+prints a sub-bibliography containing the book entries with =ai= among
+their keywords.
 ** New functions and changes in function arguments
 *** ~org-fold-show-entry~ does not fold drawers by default anymore
 

lisp/oc-csl.el

@@ -90,11 +90,23 @@
 ;; The part of the suffix before the locator is appended to reference's prefix.
 ;; If no locator term is used, but a number is present, then "page" is assumed.
 
+;; Filtered sub-bibliographies can be printed by passing filtering
+;; options to the "print_bibliography" keywords. E.g.,
+;;
+;; #+print_bibliography: :type book keyword: emacs
+;;
+;; If you need to use a key multiple times, you can separate its
+;; values with commas, but without any space in-between:
+;;
+;; #+print_bibliography: :keyword abc,xyz :type article
+
 ;; This library was heavily inspired by and borrows from András Simonyi's
 ;; Citeproc Org (<https://github.com/andras-simonyi/citeproc-org>) library.
 ;; Many thanks to him!
 
 ;;; Code:
+(require 'cl-lib)
+(require 'map)
 (require 'bibtex)
 (require 'json)
 (require 'oc)
@@ -559,6 +571,10 @@ OUTPUT using Citeproc."
  (citeproc-append-citations structures processor))
 (when nocite-ids
  (citeproc-add-uncited nocite-ids processor))
+ ;; All bibliographies have to be rendered in order to have
+ ;; correct citation numbers even if there are several
+ ;; sub-bibliograhies.
+ (org-cite-csl--rendered-bibliographies info)
 (let (result
  (rendered (citeproc-render-citations
  processor
@@ -572,6 +588,62 @@ OUTPUT using Citeproc."
  (plist-put info :cite-citeproc-rendered-citations result)
  result))))
 
+(defun org-cite-csl--bibliography-filter (bib-props)
+ "Return the sub-bibliography filter corresponding to bibliography properties.
+
+BIB-PROPS should be a plist representing the properties
+associated with a \"print_bibliography\" keyword, as returned by
+`org-cite-bibliography-properties'."
+ (let (result
+(remove-keyword-colon (lambda (x) (intern (substring (symbol-name x) 1)))))
+ (map-do
+ (lambda (key value)
+ (pcase key
+ ((or :keyword :notkeyword :nottype :notcsltype :filter)
+ (dolist (v (split-string value ","))
+ (push (cons (funcall remove-keyword-colon key) v) result)))
+ ((or :type :csltype)
+ (if (string-match-p "," value)
+ (user-error "The \"%s\" print_bibliography option does not support comma-separated values" key)
+ (push (cons (funcall remove-keyword-colon key) value) result)))))
+ bib-props)
+ result))
+
+(defun org-cite-csl--rendered-bibliographies (info)
+ "Return the rendered bibliographies.
+
+INFO is the export state, as a property list.
+
+Return an (OUTPUTS PARAMETERS) list where OUTPUTS is an alist
+of (BIB-PROPS . OUTPUT) pairs where each key is a property list
+of a \"print_bibliography\" keyword and the corresponding OUTPUT
+value is the bibliography as rendered by Citeproc."
+ (or (plist-get info :cite-citeproc-rendered-bibliographies)
+ (let (bib-plists bib-filters)
+ ;; Collect bibliography property lists and the corresponding
+ ;; Citeproc sub-bib filters.
+(org-element-map (plist-get info :parse-tree) 'keyword
+ (lambda (keyword)
+ (when (equal "PRINT_BIBLIOGRAPHY" (org-element-property :key keyword))
+ (let ((bib-plist (org-cite-bibliography-properties keyword)))
+ (push bib-plist bib-plists)
+ (push (org-cite-csl--bibliography-filter bib-plist) bib-filters)))))
+ (setq bib-filters (nreverse bib-filters)
+ bib-plists (nreverse bib-plists))
+ ;; Render and return all bibliographies.
+ (let ((processor (org-cite-csl--processor info)))
+ (citeproc-add-subbib-filters bib-filters processor)
+ (pcase-let* ((format (org-cite-csl--output-format info))
+ (`(,rendered-bibs . ,parameters)
+ (citeproc-render-bib
+ (org-cite-csl--processor info)
+ format
+ (org-cite-csl--no-citelinks-p info)))
+ (outputs (cl-mapcar #'cons bib-plists rendered-bibs))
+ (result (list outputs parameters)))
+ (plist-put info :cite-citeproc-rendered-bibliographies result)
+ result)))))
+
 
 ;;; Export capability
 (defun org-cite-csl-render-citation (citation _style _backend info)
@@ -585,16 +657,13 @@ INFO is the export state, as a property list."
  ;; process.
  (org-cite-parse-objects output))))
 
-(defun org-cite-csl-render-bibliography (_keys _files _style _props _backend info)
+(defun org-cite-csl-render-bibliography (_keys _files _style props _backend info)
  "Export bibliography.
 INFO is the export state, as a property list."
  (org-cite-csl--barf-without-citeproc)
- (pcase-let* ((format (org-cite-csl--output-format info))
- (`(,output . ,parameters)
- (citeproc-render-bib
- (org-cite-csl--processor info)
- format
- (org-cite-csl--no-citelinks-p info))))
+ (pcase-let* ((format (org-cite-csl--output-format info))
+(`(,outputs ,parameters) (org-cite-csl--rendered-bibliographies info))
+(output (cdr (assoc props outputs))))
  (pcase format
  ('html
  (concat