Added support for PDFs specified in a BibTeX field.

README.org

@@ -4,6 +4,7 @@
 [[http://melpa.org/#/helm-bibtex][http://melpa.org/packages/helm-bibtex-badge.svg]]
 
 * News
+- [2015-11-10 Tue] :: Added support for PDFs specified in a BibTeX field.  See customization variable ~helm-bibtex-pdf-field~.
 - [2015-11-09 Mon] :: Improved insertion of LaTeX cite commands.
 - [2015-05-14 Thu] :: Added support for multiple PDF directories.
 - [2015-02-23 Mon] :: Added a workaround for a bug in Emacs 24.3.1.  If you
@@ -73,6 +74,14 @@ Specify where PDFs can be found:
 
 Helm-bibtex assumes that the name of a PDF consists of the BibTeX key followed by the suffix ~.pdf~.  Example, if a BibTeX entry has the key ~Darwin1859~, helm-bibtex searches for ~Darvin1859.pdf~ when trying to open the corresponding PDF.
 
+If the BibTeX entries have a field that specifies the full path to the PDFs, that field can also be used.  For example, JabRef stores the location of the PDFs in a field called ~File~:
+
+#+BEGIN_SRC emacs-lisp
+(setq helm-bibtex-pdf-field "File")
+#+END_SRC
+
+If ~helm-bibtex-pdf-field~ is non-nil, helm-bibtex will first try to retrieve the file specified in this field.  If the field is not set for an entry or if the specified file does not exists, helm-bibtex falls back to the method described above (searching for key + ~.pdf~ in the directories listed in ~helm-bibtex-library-path~).
+
 ** Notes
 
 Notes for a publication are currently stored in separate files, one file per publication.  The names of these files consist of the BibTeX key plus a user-defined suffix (~.org~ by default).

helm-bibtex.el

@@ -25,6 +25,9 @@
 ;; A BibTeX bibliography manager based on Helm.
 ;;
 ;; News:
+;; - 11/10/2015: Added support for PDFs specified in a BibTeX
+;;               field.  See customization variable
+;;               `helm-bibtex-pdf-field'.
 ;; - 11/09/2015: Improved insertion of LaTeX cite commands.
 ;; - 05/14/2015: Added support for multiple PDF directories.
 ;; - 02/23/2015: Added a workaround for a bug in Emacs 24.3.1.  If you
@@ -267,6 +270,15 @@ it is used as the default if the user doesn't enter anything."
   :group 'helm-bibtex
   :type 'boolean)
 
+(defcustom helm-bibtex-pdf-field nil
+  "The name of the BibTeX field in which the path to PDF files is
+stored or nil if no such field should be used.  If an entry has
+no value for this field, or if the specified file does not exist,
+or if this variable is nil, helm-bibtex will look up the PDF in
+the directories listed in `helm-bibtex-library-path'."
+  :group 'helm-bibtex
+  :type 'string)
+
 (easy-menu-add-item nil '("Tools" "Helm" "Tools") ["BibTeX" helm-bibtex t])
 
 (defvar helm-bibtex-bibliography-hash nil
@@ -360,7 +372,7 @@ appended to the requested entry."
                           :test (lambda (x y) (string= (s-downcase x) (s-downcase y)))
                           :key 'car :from-end t)))
 
-(defun helm-bibtex-get-entry1 (entry-key)
+(defun helm-bibtex-get-entry1 (entry-key &optional do-not-find-pdf)
   (with-temp-buffer
     (mapc #'insert-file-contents
           (-flatten (list helm-bibtex-bibliography)))
@@ -369,7 +381,7 @@ appended to the requested entry."
                                "\\)[[:space:]]*[\(\{][[:space:]]*"
                                (regexp-quote entry-key) "[[:space:]]*,"))
     (let ((entry-type (match-string 1)))
-      (reverse (helm-bibtex-prepare-entry (parsebib-read-entry entry-type))))))
+      (reverse (helm-bibtex-prepare-entry (parsebib-read-entry entry-type) nil do-not-find-pdf)))))
 
 (defun helm-bibtex-prepare-entries (entries)
   "Do some preprocessing of the entries."
@@ -381,36 +393,54 @@ appended to the requested entry."
    collect (helm-bibtex-prepare-entry entry
             (cons (if (assoc-string "author" entry 'case-fold) "author" "editor") fields))))
 
-(defun helm-bibtex-find-pdf (key)
-  "Searches in all directories in `helm-bibtex-library-path' for
-a PDF whose name is KEY + \".pdf\".  Returns the first matching PDF."
-  (-first 'f-exists?
-          (--map (f-join it (s-concat key ".pdf"))
-                 (-flatten (list helm-bibtex-library-path)))))
-
-(defun helm-bibtex-prepare-entry (entry &optional fields)
+(defun helm-bibtex-find-pdf (key-or-entry)
+  "Returns the path of the PDF associated with the specified
+entry.  This is either the path specified in the field
+`helm-bibtex-pdf-field' or if that path doesn't exists the first
+PDF in any of the directories in `helm-bibtex-library-path' whose
+name is key + \".pdf\"."
+  (let ((pdf-path (and helm-bibtex-pdf-field
+                       (let* ((entry (if (stringp key-or-entry)
+                                         (helm-bibtex-get-entry1 key-or-entry t)
+                                       key-or-entry))
+                              (pdf-path (helm-bibtex-get-value helm-bibtex-pdf-field entry)))
+                         (and pdf-path (f-exists? pdf-path) pdf-path)))))
+    (or pdf-path
+        (let ((key (if (stringp key-or-entry)
+                       key-or-entry
+                     (helm-bibtex-get-value "=key=" key-or-entry))))
+          (-first 'f-exists?
+                  (--map (f-join it (s-concat key ".pdf"))
+                         (-flatten (list helm-bibtex-library-path))))))))
+
+(defun helm-bibtex-prepare-entry (entry &optional fields do-not-find-pdf)
   "Prepare ENTRY for display.
 ENTRY is an alist representing an entry as returned by
 parsebib-read-entry. All the fields not in FIELDS are removed
 from ENTRY, with the exception of the \"=type=\" and \"=key=\"
 fields. If FIELDS is empty, all fields are kept. Also add a
-=has-pdf= and/or =has-notes= field, if they exist for ENTRY."
+=has-pdf= and/or =has-notes= field, if they exist for ENTRY.  If
+DO-NOT-FIND-PDF is non-nil, this function does not attempt to
+find a PDF file."
   (when entry ; entry may be nil, in which case just return nil
-    (when fields
-      (setq fields (append fields (list "=type=" "=key="))))
-    (let* ((entry (if fields
+    (let* ((fields (when fields (append fields (list "=type=" "=key=" "=has-pdf=" "=has-note="))))
+           ; Check for PDF:
+           (entry (if (and (not do-not-find-pdf) (helm-bibtex-find-pdf entry))
+                      (setq entry (cons (cons "=has-pdf=" helm-bibtex-pdf-symbol) entry))
+                    entry))
+           ; Check for notes:
+           (entry (if (and helm-bibtex-notes-path
+                           (f-exists? (f-join helm-bibtex-notes-path
+                                              (s-concat entry-key helm-bibtex-notes-extension))))
+                      (cons (cons "=has-note=" helm-bibtex-notes-symbol) entry)
+                    entry))
+           ; Remove unwanted fields:
+           (entry (if fields
                        (--filter (member-ignore-case (car it) fields) entry)
                      entry))
            (entry-key (cdr (assoc "=key=" entry))))
       ;; Normalize case of entry type:
       (setcdr (assoc "=type=" entry) (downcase (cdr (assoc "=type=" entry))))
-      ;; Check for PDF and notes:
-      (if (helm-bibtex-find-pdf entry-key)
-          (setq entry (cons (cons "=has-pdf=" helm-bibtex-pdf-symbol) entry)))
-      (if (and helm-bibtex-notes-path
-               (f-exists? (f-join helm-bibtex-notes-path
-                                  (s-concat entry-key helm-bibtex-notes-extension))))
-          (setq entry (cons (cons "=has-note=" helm-bibtex-notes-symbol) entry)))
       ;; Remove duplicated fields:
       (cl-remove-duplicates entry
                             :test (lambda (x y) (string= (s-downcase x) (s-downcase y)))