[PATCH] ob-tangle: Correctly process tangling of single source block

[Rick Frankel <rick@rickster.com>]

Sorry, subject didn't get properly added:
----------------

* lisp/ob-tangle.el
  (org-babel-tangle):
    - remove un-executed attempt to ask user for file-name if
      tangling a single block (`:tangle' always has a value)
    - change handling of block accumulation

  (org-babel-tangle-collect-block): new function to collect a single block

When attempting to tangle a single block, `org-babel-tangle' would use
`narrow-to-region', causing any header arguments not on the
"#+BEGIN_SRC" line to be excluded from the tangled file.
---
 lisp/ob-tangle.el | 166 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 90 insertions(+), 76 deletions(-)

diff --git a/lisp/ob-tangle.el b/lisp/ob-tangle.el
index 0db4335..725d3af 100644
--- a/lisp/ob-tangle.el
+++ b/lisp/ob-tangle.el
@@ -192,18 +192,16 @@ source blocks.  Optional argument LANG can be used to limit the
 exported source code blocks by language."
   (interactive "P")
   (run-hooks 'org-babel-pre-tangle-hook)
-  ;; possibly restrict the buffer to the current code block
   (save-restriction
-    (when only-this-block
-      (unless (org-babel-where-is-src-block-head)
-	(error "Point is not currently inside of a code block"))
-      (save-match-data
-	(unless (or (cdr (assoc :tangle (nth 2 (org-babel-get-src-block-info))))
-		    target-file)
-	  (setq target-file
-		(read-from-minibuffer "Tangle to: " (buffer-file-name)))))
-      (narrow-to-region (match-beginning 0) (match-end 0)))
     (save-excursion
+      ;; check if tangle restricted to the current code block and
+      ;; move to beginning of block so begin_src line not
+      ;; included in commments
+      (when only-this-block
+	(let ((head (org-babel-where-is-src-block-head)))
+	  (if head
+	      (goto-char head)
+	    (error "Point is not currently inside of a code block"))))
       (let ((block-counter 0)
 	    (org-babel-default-header-args
 	     (if target-file
@@ -270,7 +268,9 @@ exported source code blocks by language."
 		      (setq block-counter (+ 1 block-counter))
 		      (add-to-list 'path-collector file-name)))))
 	      specs)))
-	 (org-babel-tangle-collect-blocks lang))
+	 (if only-this-block
+	     (org-babel-tangle-collect-block 1 t)
+	   (org-babel-tangle-collect-blocks lang)))
 	(message "Tangled %d code block%s from %s" block-counter
 		 (if (= block-counter 1) "" "s")
 		 (file-name-nondirectory
@@ -353,7 +353,7 @@ Return an association list of source-code block specifications of
 the form used by `org-babel-spec-to-string' grouped by language.
 Optional argument LANG can be used to limit the collected source
 code blocks by language."
-  (let ((block-counter 1) (current-heading "") blocks)
+  (let ((block-counter 1) (current-heading "") blocks by-lang)
     (org-babel-map-src-blocks (buffer-file-name)
       ((lambda (new-heading)
 	 (if (not (string= new-heading current-heading))
@@ -366,73 +366,18 @@ code blocks by language."
 				     (or (nth 4 (org-heading-components))
 					 "(dummy for heading without text)")
 				   (error (buffer-file-name)))))
-      (let* ((start-line (save-restriction (widen)
-					   (+ 1 (line-number-at-pos (point)))))
-	     (file (buffer-file-name))
-	     (info (org-babel-get-src-block-info 'light))
+      (let* ((info (org-babel-get-src-block-info 'light))
 	     (src-lang (nth 0 info)))
         (unless (string= (cdr (assoc :tangle (nth 2 info))) "no")
           (unless (and language (not (string= language src-lang)))
-	    (let* ((info (org-babel-get-src-block-info))
-		   (params (nth 2 info))
-		   (link ((lambda (link)
-			    (and (string-match org-bracket-link-regexp link)
-				 (match-string 1 link)))
-			  (org-no-properties
-			   (org-store-link nil))))
-		   (source-name
-		    (intern (or (nth 4 info)
-				(format "%s:%d"
-					current-heading block-counter))))
-		   (expand-cmd
-		    (intern (concat "org-babel-expand-body:" src-lang)))
-		   (assignments-cmd
-		    (intern (concat "org-babel-variable-assignments:" src-lang)))
-		   (body
-		    ((lambda (body) ;; run the tangle-body-hook
-		       (with-temp-buffer
-			 (insert body)
-			 (run-hooks 'org-babel-tangle-body-hook)
-			 (buffer-string)))
-		     ((lambda (body) ;; expand the body in language specific manner
-			(if (assoc :no-expand params)
-			    body
-			  (if (fboundp expand-cmd)
-			      (funcall expand-cmd body params)
-			    (org-babel-expand-body:generic
-			     body params
-			     (and (fboundp assignments-cmd)
-				  (funcall assignments-cmd params))))))
-		      (if (org-babel-noweb-p params :tangle)
-			  (org-babel-expand-noweb-references info)
-			(nth 1 info)))))
-		   (comment
-		    (when (or (string= "both" (cdr (assoc :comments params)))
-			      (string= "org" (cdr (assoc :comments params))))
-		      ;; from the previous heading or code-block end
-		      (funcall
-		       org-babel-process-comment-text
-		       (buffer-substring
-			(max (condition-case nil
-				 (save-excursion
-				   (org-back-to-heading t)  ; sets match data
-				   (match-end 0))
-			       (error (point-min)))
-			     (save-excursion
-			       (if (re-search-backward
-				    org-babel-src-block-regexp nil t)
-				   (match-end 0)
-				 (point-min))))
-			(point)))))
-		   by-lang)
-	      ;; add the spec for this block to blocks under it's language
-	      (setq by-lang (cdr (assoc src-lang blocks)))
-	      (setq blocks (delq (assoc src-lang blocks) blocks))
-	      (setq blocks (cons
-			    (cons src-lang
-				  (cons (list start-line file link
-					      source-name params body comment)
-					by-lang)) blocks)))))))
+	    ;; add the spec for this block to blocks under it's language
+	    (setq by-lang (cdr (assoc src-lang blocks)))
+	    (setq blocks (delq (assoc src-lang blocks) blocks))
+	    (setq blocks (cons
+			  (cons src-lang
+				(cons
+				 (org-babel-tangle-collect-block
+				  block-counter) by-lang)) blocks))))))
     ;; ensure blocks in the correct order
     (setq blocks
           (mapcar
@@ -440,6 +385,75 @@ code blocks by language."
 	   blocks))
     blocks))
 
+(defun org-babel-tangle-collect-block
+  (block-counter &optional only-this-block)
+  "Collect tangled source for current block.
+Returns list of block attributes needed by 
+`org-babel-tangle-collect-blocks'. If ONLY-THIS-BLOCK is set,
+then return full association list in format needed for
+`org-babel-tangle' directly."
+  (let* ((info (org-babel-get-src-block-info))
+	 (start-line
+	  (save-restriction (widen)
+			    (+ 1 (line-number-at-pos (point)))))
+	 (file (buffer-file-name))
+	 (src-lang (nth 0 info))
+	 (params (nth 2 info))
+	 (link ((lambda (link)
+		  (and (string-match org-bracket-link-regexp link)
+		       (match-string 1 link)))
+		(org-no-properties
+		 (org-store-link nil))))
+	 (source-name
+	  (intern (or (nth 4 info)
+		      (format "%s:%d" (nth 4 (org-heading-components))
+			      block-counter))))
+	 (expand-cmd
+	  (intern (concat "org-babel-expand-body:" src-lang)))
+	 (assignments-cmd
+	  (intern (concat "org-babel-variable-assignments:" src-lang)))
+	 (body
+	  ((lambda (body) ;; run the tangle-body-hook
+	     (with-temp-buffer
+	       (insert body)
+	       (run-hooks 'org-babel-tangle-body-hook)
+	       (buffer-string)))
+	   ((lambda (body) ;; expand the body in language specific manner
+	      (if (assoc :no-expand params)
+		  body
+		(if (fboundp expand-cmd)
+		    (funcall expand-cmd body params)
+		  (org-babel-expand-body:generic
+		   body params
+		   (and (fboundp assignments-cmd)
+			(funcall assignments-cmd params))))))
+	    (if (org-babel-noweb-p params :tangle)
+		(org-babel-expand-noweb-references info)
+	      (nth 1 info)))))
+	 (comment
+	  (when (or (string= "both" (cdr (assoc :comments params)))
+		    (string= "org" (cdr (assoc :comments params))))
+	    ;; from the previous heading or code-block end
+	    (funcall
+	     org-babel-process-comment-text
+	     (buffer-substring
+	      (max (condition-case nil
+		       (save-excursion
+			 (org-back-to-heading t)  ; sets match data
+			 (match-end 0))
+		     (error (point-min)))
+		   (save-excursion
+		     (if (re-search-backward
+			  org-babel-src-block-regexp nil t)
+			 (match-end 0)
+		       (point-min))))
+	      (point)))))
+	 (result
+	  (list start-line file link source-name params body comment)))
+    (if only-this-block
+	(list (cons src-lang (list result)))
+      result)))
+
 (defun org-babel-tangle-comment-links ( &optional info)
   "Return a list of begin and end link comments for the code block at point."
   (let* ((start-line (org-babel-where-is-src-block-head))
-- 
1.8.0