Fix newline substitution.

Problem  : Command `s/\n//` is being translated into a call to do_join
           with a count of 1. But do_join asserts its precondition count
           >= 2, which is causing the program to abort.
Note     : This in fact revealed bigger problems: generated join command
           line count, as well as reported substitutions/lines were
           wrong in several cases, since patch 7.4.232.
           See:
           [patch] http://markmail.org/message/vo7ruair5raccawp
           [issue] https://code.google.com/p/vim/issues/detail?id=287
Solution : - Don't generate join command for single-line-range case.
           - Make generated join command include:
             * lines in range + 1, when range doesn't end at last line.
             * lines in range, when range ends at last line.
           - Make reported substitutions/lines always be
             number-of-lines-joined - 1.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 556e0c01e3..0829049e4d 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -3602,8 +3602,13 @@ void do_sub(exarg_T *eap)
       eap->flags = EXFLAG_PRINT;
     }
 
-    do_join(eap->line2 - eap->line1 + 1, FALSE, TRUE, FALSE, true);
-    sub_nlines = sub_nsubs = eap->line2 - eap->line1 + 1;
+    linenr_T joined_lines_count = eap->line2 < curbuf->b_ml.ml_line_count
+                                  ? eap->line2 - eap->line1 + 2
+                                  : eap->line2 - eap->line1 + 1;
+    if (joined_lines_count >= 2) {
+      do_join(joined_lines_count, FALSE, TRUE, FALSE, true);
+    }
+    sub_nlines = sub_nsubs = joined_lines_count - 1;
     do_sub_msg(false);
     ex_may_print(eap);