vim-patch:7.4.1017

Problem:    When there is a backslash in an option ":set -=" doesn't work.
Solution:   Handle a backslash better. (Jacob Niehus)  Add a new test, merge
            in old test.

https://github.com/vim/vim/commit/8f79acdf7ede2693fbda53c3c9693f16db4f193b

3 files changed, 27 insertions, 9 deletions

diff --git a/src/nvim/option.c b/src/nvim/option.c
index 2f22c245dd..45ebb4fa4c 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -1639,18 +1639,21 @@ do_set (
                       && STRNCMP(s, newval, i) == 0
                       && (!(flags & P_COMMA)
                           || s[i] == ','
-                          || s[i] == NUL))
+                          || s[i] == NUL)) {
                     break;
-                  /* Count backslashes.  Only a comma with an
-                   * even number of backslashes before it is
-                   * recognized as a separator */
-                  if (s > origval && s[-1] == '\\')
-                    ++bs;
-                  else
+                  }
+                  // Count backslashes.  Only a comma with an even number of
+                  // backslashes or a single backslash preceded by a comma
+                  // before it is recognized as a separator
+                  if ((s > origval + 1 && s[-1] == '\\' && s[-2] != ',')
+                      || (s == origval + 1 && s[-1] == '\\')) {
+                    bs++;
+                  } else {
                     bs = 0;
+                  }
                 }
 
-                /* do not add if already there */
+                // do not add if already there
                 if ((adding || prepending) && *s) {
                   prepending = FALSE;
                   adding = FALSE;
diff --git a/src/nvim/version.c b/src/nvim/version.c
index 82a15f9833..b6b55964f3 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -667,7 +667,7 @@ static int included_patches[] = {
   // 1020 NA
   // 1019 NA
   // 1018,
-  // 1017,
+  1017,
   // 1016 NA
   1015,
   // 1014 NA
diff --git a/test/functional/legacy/set_spec.lua b/test/functional/legacy/set_spec.lua
index f81fcd3700..f2c907084e 100644
--- a/test/functional/legacy/set_spec.lua
+++ b/test/functional/legacy/set_spec.lua
@@ -7,6 +7,21 @@ local clear, execute, eval, eq =
 describe(':set', function()
   before_each(clear)
 
+  it('handles backslash properly', function()
+    execute('set iskeyword=a,b,c')
+    execute('set iskeyword+=d')
+    eq('a,b,c,d', eval('&iskeyword'))
+
+    execute([[set iskeyword+=\\,e]])
+    eq([[a,b,c,d,\,e]], eval('&iskeyword'))
+
+    execute('set iskeyword-=e')
+    eq([[a,b,c,d,\]], eval('&iskeyword'))
+
+    execute([[set iskeyword-=\]])
+    eq('a,b,c,d', eval('&iskeyword'))
+  end)
+
   it('recognizes a trailing comma with +=', function()
     execute('set wildignore=*.png,')
     execute('set wildignore+=*.jpg')