oc: Be stricter when introducing spaces before citations

* lisp/oc.el (org-cite-process-citations): Add a space before citation
only if it is preceded by a quotation mark.
* testing/lisp/test-oc.el (test-org-cite/export-capability): Add
tests.

Reported-by: Denis Maier <denismaier@mailbox.org>
<http://lists.gnu.org/r/emacs-orgmode/2021-09/msg00085.html>

lisp/oc.el

@@ -1274,11 +1274,13 @@ by side-effect."
           ;; Before removing the citation, transfer its `:post-blank'
           ;; property to the object before, if any.
           (org-cite--set-previous-post-blank cite blanks info)
-        ;; We want to be sure any non-note citation is preceded by
-        ;; a space.  This is particularly important when using
+        ;; Make sure there is a space between a quotation mark and
+        ;; a citation.  This is particularly important when using
         ;; `adaptive' note rule.  See `org-cite-note-rules'.
-        (unless (org-cite-inside-footnote-p cite t)
-          (org-cite--set-previous-post-blank cite 1 info))
+        (let ((previous (org-export-get-previous-element cite info)))
+          (when (and (org-string-nw-p previous)
+                     (string-suffix-p "\"" previous))
+            (org-cite--set-previous-post-blank cite 1 info)))
         (pcase replacement
           ;; String.
           ((pred stringp)

testing/lisp/test-oc.el

@@ -1273,7 +1273,7 @@ arguments.  Replace citation with \"@\" character in the output."
                   (list "b" (org-element-create 'bold nil "c"))) " ")))))
 
 
-;;; TEST capabilities.
+;;; Test capabilities.
 (ert-deftest test-org-cite/activate-capability ()
   "Test \"activate\" capability."
   ;; Standard test.
@@ -1393,6 +1393,29 @@ arguments.  Replace citation with \"@\" character in the output."
                               '((section . (lambda (_ c _) c))
                                 (paragraph . (lambda (_ c _) c))
                                 (bold . (lambda (&rest _) "bold")))))))))
+  ;; Make sure to have a space between a quote and a citation.
+  (should
+   (equal "\"quotation\" citation\n"
+          (org-test-with-temp-text "\"quotation\"[cite:@key]"
+            (let ((org-cite--processors nil)
+                  (org-cite-export-processors '((t . (foo nil nil)))))
+              (org-cite-register-processor 'foo
+                :export-citation (lambda (&rest _) "citation"))
+              (org-export-as (org-export-create-backend
+                              :transcoders
+                              '((section . (lambda (_ c _) c))
+                                (paragraph . (lambda (_ c _) c)))))))))
+  (should
+   (equal "\"quotation\"  citation\n"
+          (org-test-with-temp-text "\"quotation\"  [cite:@key]"
+            (let ((org-cite--processors nil)
+                  (org-cite-export-processors '((t . (foo nil nil)))))
+              (org-cite-register-processor 'foo
+                :export-citation (lambda (&rest _) "citation"))
+              (org-export-as (org-export-create-backend
+                              :transcoders
+                              '((section . (lambda (_ c _) c))
+                                (paragraph . (lambda (_ c _) c)))))))))
   ;; Regular bibliography export.
   (should
    (eq 'success