Babel support for hledger accounting tool

* lisp/ob-hledger.el: New file.
* lisp/org.el (org-babel-load-languages):
* lisp/ox-html.el (org-html-style-default): Allow calling hledger from
  Babel.

etc/ORG-NEWS

@@ -96,6 +96,7 @@ directories in published site-maps.
 
 *** Babel
 
+**** Support for hledger accounting reports added
 **** Clojure: new setting ~org-babel-clojure-sync-nrepl-timeout~
 
 Creation of a new setting to specify the Cider timeout.  By setting

lisp/ob-hledger.el

@@ -0,0 +1,70 @@
+;;  ob-ledger.el --- Babel Functions for hledger      -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2010-2017 Free Software Foundation, Inc.
+
+;; Author: Simon Michael
+;; Keywords: literate programming, reproducible research, plain text accounting
+;; Homepage: http://orgmode.org
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Babel support for evaluating hledger entries.
+;;
+;; Based on ob-ledger.el.
+;; If the source block is empty, hledger will use a default journal file,
+;; probably ~/.hledger.journal (it may not notice your $LEDGER_FILE env var).
+;; So make ~/.hledger.journal a symbolic link to the real file if necessary.
+
+;;; Code:
+(require 'ob)
+
+(defvar org-babel-default-header-args:hledger
+  '((:results . "output") (:exports . "results") (:cmdline . "bal"))
+  "Default arguments to use when evaluating a hledger source block.")
+
+(defun org-babel-execute:hledger (body params)
+  "Execute a block of hledger entries with org-babel.
+This function is called by `org-babel-execute-src-block'."
+  (message "executing hledger source code block")
+  (letrec ( ;(result-params (split-string (or (cdr (assq :results params)) "")))
+	   (cmdline (cdr (assq :cmdline params)))
+	   (in-file (org-babel-temp-file "hledger-"))
+	   (out-file (org-babel-temp-file "hledger-output-"))
+	   (hledgercmd (concat "hledger"
+			       (if (> (length body) 0)
+				   (concat " -f " (org-babel-process-file-name in-file))
+				 "")
+			       " " cmdline)))
+    (with-temp-file in-file (insert body))
+;; TODO This is calling for some refactoring:
+;;  (concat "hledger" (if ...) " " cmdline)
+;; could be built only once and bound to a symbol.
+    (message "%s" hledgercmd)
+    (with-output-to-string
+      (shell-command (concat hledgercmd " > " (org-babel-process-file-name out-file))))
+    (with-temp-buffer (insert-file-contents out-file) (buffer-string))))
+
+(defun org-babel-prep-session:hledger (_session _params)
+  (error "hledger does not support sessions"))
+
+(provide 'ob-hledger)
+
+
+
+;;; ob-hledger.el ends here
+;; TODO Unit tests are more than welcome, too.

lisp/org.el

@@ -268,6 +268,7 @@ requirements) is loaded."
 		 (const :tag "Fortran" fortran)
 		 (const :tag "Gnuplot" gnuplot)
 		 (const :tag "Haskell" haskell)
+		 (const :tag "hledger" hledger)
 		 (const :tag "IO" io)
 		 (const :tag "J" J)
 		 (const :tag "Java" java)

lisp/ox-html.el

@@ -333,6 +333,7 @@ for the JavaScript code in this tag.
   pre.src-fortran:before { content: 'Fortran'; }
   pre.src-gnuplot:before { content: 'gnuplot'; }
   pre.src-haskell:before { content: 'Haskell'; }
+  pre.src-hledger:before { content: 'hledger'; }
   pre.src-java:before { content: 'Java'; }
   pre.src-js:before { content: 'Javascript'; }
   pre.src-latex:before { content: 'LaTeX'; }