Vim issue #1590

evalfunc.patch

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 83bc8f379..884f4501c 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -7092,9 +7092,9 @@ shellescape({string} [, {special}])                       *shellescape()*
                {special}) when 'shell' contains "csh" in the tail.  That is
                because for csh and tcsh "!" is used for history replacement
                even when inside single quotes.
-               The <NL> character is also escaped.  With a |non-zero-arg|
-               {special} and 'shell' containing "csh" in the tail it's
-               escaped a second time.
+               The <NL> character is also escaped when {special} is set.
+               With a |non-zero-arg| {special} and 'shell' containing "csh" in
+               the tail it's escaped a second time.
                Example of use with a |:!| command: >
                    :exe '!dir ' . shellescape(expand('<cfile>'), 1)
 <              This results in a directory listing for the file under the
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 45c43f685..e1986e6c4 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -10473,8 +10473,10 @@ f_sha256(typval_T *argvars, typval_T *rettv)
     static void
 f_shellescape(typval_T *argvars, typval_T *rettv)
 {
+    int do_special = non_zero_arg(&argvars[1]);
+
     rettv->vval.v_string = vim_strsave_shellescape(
-               get_tv_string(&argvars[0]), non_zero_arg(&argvars[1]), TRUE);
+               get_tv_string(&argvars[0]), do_special, do_special);
     rettv->v_type = VAR_STRING;
 }

The current behavior is the other way around for when 'shell' is "csh".
Thus the code should check for that.