Add support for eldoc

Eldoc wil show:
- a 'breadcrumb' of headers when on headerline
- properties of SRC block when on BEGIN/END_SRC line
- inside body of SRC block it will try to use that mode's eldoc function

contrib/org-eldoc.el

@@ -0,0 +1,159 @@
+;;; org-eldoc.el --- display org header and src block info using eldoc
+
+;; Copyright (c) 2014 Free Software Foundation, Inc.
+
+;; Author: Łukasz Gruner <lukasz@gruner.lu>
+;; Maintainer: Łukasz Gruner <lukasz@gruner.lu>
+;; Version: 6
+;; Package-Requires: ((org "8"))
+;; URL: https://bitbucket.org/ukaszg/org-eldoc
+;; Created: 25/05/2014
+;; Keywords: eldoc, outline, breadcrumb, org, babel, minibuffer
+
+;; This file is not part of 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:
+
+;;; Changelog:
+
+;; As of 01/11/14 switching license to GPL3 to allow submission to org-mode.
+;; 08/11/14 switch code to automatically define eldoc-documentation-function, but don't autostart eldoc-mode.
+
+;;; Code:
+
+(require 'org)
+(require 'ob-core)
+(require 'eldoc)
+
+(defgroup org-eldoc nil "" :group 'org)
+
+(defcustom org-eldoc-breadcrumb-separator "/"
+  "Breadcrumb separator."
+  :group 'org-eldoc
+  :type 'string)
+
+(defcustom org-eldoc-test-buffer-name " *Org-eldoc test buffer*"
+  "Name of the buffer used while testing for mode-local variable values."
+  :group 'org-eldoc
+  :type 'string)
+
+(defun org-eldoc-get-breadcrumb ()
+  "Return breadcrumb if on a headline or nil."
+  (let ((case-fold-search t) cur)
+    (save-excursion
+      (beginning-of-line)
+      (save-match-data
+        (when (looking-at org-complex-heading-regexp)
+          (setq cur (match-string 4))
+          (org-format-outline-path
+           (append (org-get-outline-path) (list cur))
+           (frame-width) "" org-eldoc-breadcrumb-separator))))))
+
+(defun org-eldoc-get-src-header ()
+  "Returns lang and list of header properties if on src definition line and nil otherwise."
+  (let ((case-fold-search t) info lang hdr-args)
+    (save-excursion
+      (beginning-of-line)
+      (save-match-data
+        (when (looking-at "^[ \t]*#\\+\\(begin\\|end\\)_src")
+          (setq info (org-babel-get-src-block-info 'light)
+                lang (propertize (nth 0 info) 'face 'font-lock-string-face)
+                hdr-args (nth 2 info))
+          (concat
+           lang
+           ": "
+           (mapconcat
+            (lambda (elem)
+              (when (and (cdr elem) (not (string= "" (cdr elem))))
+                (concat
+                 (propertize (symbol-name (car elem)) 'face 'org-list-dt)
+                 " "
+                 (propertize (cdr elem) 'face 'org-verbatim)
+                 " ")))
+            hdr-args " ")))))))
+
+(defun org-eldoc-get-src-lang ()
+  "Return value of lang for the current block if in block body and nil otherwise."
+  (let ((case-fold-search t))
+    (save-match-data
+      (when (org-between-regexps-p ".*#\\+begin_src"
+                                   ".*#\\+end_src")
+        (save-excursion
+          (goto-char (org-babel-where-is-src-block-head))
+          (car (org-babel-parse-src-block-match)))))))
+
+(defvar org-eldoc-local-functions-cache (make-hash-table :size 40 :test 'equal)
+  "Cache of major-mode's eldoc-documentation-functions,
+ used by \\[org-eldoc-get-mode-local-documentation-function].")
+
+(defun org-eldoc-get-mode-local-documentation-function (lang)
+  "Check if LANG-mode sets eldoc-documentation-function and return its value."
+  (let ((cached-func (gethash lang org-eldoc-local-functions-cache 'empty))
+        (mode-func (intern-soft (format "%s-mode" lang)))
+        doc-func)
+    (if (eq 'empty cached-func)
+        (when (fboundp mode-func)
+          (with-temp-buffer
+            (funcall mode-func)
+            (setq doc-func (and eldoc-documentation-function
+                                (symbol-value 'eldoc-documentation-function)))
+            (puthash lang doc-func org-eldoc-local-functions-cache))
+          doc-func)
+      cached-func)))
+
+(declare-function c-eldoc-print-current-symbol-info "c-eldoc" ())
+(declare-function css-eldoc-function "css-eldoc" ())
+(declare-function php-eldoc-function "php-eldoc" ())
+(declare-function go-eldoc--documentation-function "go-eldoc" ())
+
+(defun org-eldoc-documentation-function ()
+  "Return breadcrumbs when on a headline, args for src block header-line,
+  calls other documentation functions depending on lang when inside src body."
+  (or
+   (org-eldoc-get-breadcrumb)
+   (org-eldoc-get-src-header)
+   (let ((lang (org-eldoc-get-src-lang)))
+     (cond ((or
+             (string= lang "c") ;; http://github.com/nflath/c-eldoc
+             (string= lang "C")) (when (require 'c-eldoc nil t)
+                                   (c-eldoc-print-current-symbol-info)))
+           ;; https://github.com/zenozeng/css-eldoc
+           ((string= lang "css") (when (require 'css-eldoc nil t)
+                                   (css-eldoc-function)))
+           ;; https://github.com/zenozeng/php-eldoc
+           ((string= lang "php") (when (require 'php-eldoc nil t)
+                                   (php-eldoc-function)))
+           ((or
+             (string= lang "go")
+             (string= lang "golang")) (when (require 'go-eldoc nil t)
+                                        (go-eldoc--documentation-function)))
+           (t (let ((doc-fun (org-eldoc-get-mode-local-documentation-function lang)))
+                (when (fboundp doc-fun) (funcall doc-fun))))))))
+
+;;;###autoload
+(defun org-eldoc-load ()
+  "Set up org-eldoc documentation function."
+  (interactive)
+  (setq-local eldoc-documentation-function #'org-eldoc-documentation-function))
+
+;;;###autoload
+(add-hook 'org-mode-hook #'org-eldoc-load)
+
+(provide 'org-eldoc)
+
+;; -*- coding: utf-8-emacs; -*-
+
+;;; org-eldoc.el ends here