[meld] filters: New filter-checking API for preferences use

[Kai Willadsen <kaiw src gnome org>]

commit 50c78198406788bc61e30b300ac000d470fef63b
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Oct 28 07:32:23 2018 +1000

    filters: New filter-checking API for preferences use
    
    This is just a more convenient version of compile_filter(), which is
    about to go away.

 meld/filters.py     | 8 ++++++++
 meld/preferences.py | 3 +--
 2 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/meld/filters.py b/meld/filters.py
index c2701511..cedf24eb 100644
--- a/meld/filters.py
+++ b/meld/filters.py
@@ -96,6 +96,14 @@ class FilterEntry:
             raise ValueError("Unknown filter type")
         return compiled
 
+    @classmethod
+    def check_filter(cls, filter_string, filter_type):
+        if filter_type == cls.REGEX:
+            compiled = cls._compile_regex(filter_string)
+        elif filter_type == cls.SHELL:
+            compiled = cls._compile_shell_pattern(filter_string)
+        return compiled is not None
+
     def __copy__(self):
         new = type(self)(
             self.label, self.active, None, None, self.filter_string)
diff --git a/meld/preferences.py b/meld/preferences.py
index d5f5ba80..b59bfdaa 100644
--- a/meld/preferences.py
+++ b/meld/preferences.py
@@ -66,8 +66,7 @@ class FilterList(ListWidget):
         self.model[path][1] = not ren.get_active()
 
     def on_pattern_edited(self, ren, path, text):
-        filt = FilterEntry.compile_filter(text, self.filter_type)
-        valid = filt is not None
+        valid = FilterEntry.check_filter(text, self.filter_type)
         self.model[path][2] = text
         self.model[path][3] = valid