patch 9.0.2040: trim(): hard to use default maskv9.0.2040

Problem:  trim(): hard to use default mask
Solution: Use default 'mask' when it is v:none

The default 'mask' value is pretty complex, as it includes many
characters.  Yet, if one needs to specify the trimming direction, the
third argument, 'trim()' currently requires the 'mask' value to be
provided explicitly.

'v:none' is already used to mean "use the default argument value" in
user defined functions.  See |none-function_argument| in help.

closes: #13363

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Illia Bobyr <illia.bobyr@gmail.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/src/typval.c b/src/typval.c
index 08dd2313f2..b6371aaa43 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -451,6 +451,37 @@ check_for_opt_string_arg(typval_T *args, int idx)
 }
 
 /*
+ * Check for an optional string argument at 'idx', that can also be 'v:none' to
+ * use the default value.
+ *
+ * If 'is_none' is non-NULL it is set to 0 and updated to 1 when "args[idx]" is
+ * 'v:none'.
+ */
+    int
+check_for_opt_string_or_none_arg(typval_T *args, int idx, int *is_none)
+{
+    if (is_none != NULL)
+	*is_none = 0;
+
+    if (args[idx].v_type == VAR_UNKNOWN)
+	return OK;
+
+    if (args[idx].v_type == VAR_SPECIAL
+	    && args[idx].vval.v_number == VVAL_NONE)
+    {
+	if (is_none != NULL)
+	    *is_none = 1;
+	return OK;
+    }
+
+    if (args[idx].v_type == VAR_STRING)
+	return OK;
+
+    semsg(_(e_string_or_none_required_for_argument_nr), idx + 1);
+    return FAIL;
+}
+
+/*
  * Give an error and return FAIL unless "args[idx]" is a number.
  */
     int