From b1911a30f250da09c737d5e68c644eff112a511a Mon Sep 17 00:00:00 2001
From: Lionel Henry <lionel.hry@gmail.com>
Date: Mon, 23 Nov 2015 16:08:42 +0000
Subject: [PATCH] Prevent infloops on blanks travelling

---
 lisp/ess-r-syntax.el         | 31 ++++++++++++++++++-------------
 test/generate-literate-cases |  2 +-
 test/literate/syntax.R       | 27 +++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 14 deletions(-)
 create mode 100644 test/literate/syntax.R

diff --git a/lisp/ess-r-syntax.el b/lisp/ess-r-syntax.el
index 476001e4e..35d155766 100644
--- a/lisp/ess-r-syntax.el
+++ b/lisp/ess-r-syntax.el
@@ -189,12 +189,13 @@ return the prefix."
 into account."
   (when (ess-skip-blanks-backward-1)
     (prog1 t
-      (when newlines
-        (while (= (point) (line-beginning-position))
-          (forward-line -1)
-          (goto-char (line-end-position))
-          (ess-climb-comment)
-          (ess-skip-blanks-backward-1))))))
+      (while (and newlines
+                  (/= (point) (point-min))
+                  (= (point) (line-beginning-position)))
+        (forward-line -1)
+        (goto-char (line-end-position))
+        (ess-climb-comment)
+        (ess-skip-blanks-backward-1)))))
 
 (defun ess-skip-blanks-backward-1 ()
   (and (/= (point) (point-min))
@@ -203,13 +204,17 @@ into account."
 (defun ess-skip-blanks-forward (&optional newlines)
   "Skip blanks and newlines forward, taking end-of-line comments
 into account."
-  (when (skip-chars-forward " \t")
-    (prog1 t
-      (when newlines
-        (while (= (point) (ess-code-end-position))
-          (forward-line)
-          (ess-back-to-indentation)
-          (skip-chars-forward " \t"))))))
+  (ess-any ((/= 0 (skip-chars-forward " \t")))
+           ((ess-while (and newlines
+                            (= (point) (ess-code-end-position))
+                            (when (ess-save-excursion-when-nil
+                                    ;; Handles corner cases such as point being on last line
+                                    (let ((orig-point (point)))
+                                      (forward-line)
+                                      (ess-back-to-indentation)
+                                      (> (point) orig-point)))
+                              (skip-chars-forward " \t")
+                              t))))))
 
 (defun ess-jump-char (char)
   (ess-save-excursion-when-nil
diff --git a/test/generate-literate-cases b/test/generate-literate-cases
index e6123ede1..2262d8686 100755
--- a/test/generate-literate-cases
+++ b/test/generate-literate-cases
@@ -14,4 +14,4 @@
 
 (mapc (lambda (file)
         (ess-ltest-R (expand-file-name file ess-literate-path)))
-      '("roxy.R" "code-fill.R" "misc.R"))
+      '("roxy.R" "code-fill.R" "misc.R" "syntax.R"))
diff --git a/test/literate/syntax.R b/test/literate/syntax.R
new file mode 100644
index 000000000..74ca46ed0
--- /dev/null
+++ b/test/literate/syntax.R
@@ -0,0 +1,27 @@
+
+##### Blanks, Characters and Comments
+
+### 1 ----------------------------------------------------------------
+
+text¶
+text
+
+##! (ess-skip-blanks-forward t)
+
+text
+¶text
+
+
+### 2 ----------------------------------------------------------------
+
+text¶ # comment
+
+##! (when (not (ess-skip-blanks-forward t))
+##!   (insert "failure"))
+
+text ¶# comment
+
+##> (when (ess-skip-blanks-forward t)
+##>   (insert "failure"))
+
+text ¶# comment