"Merge pull request #461 from Kazade/master\n\nAdd a ReplaceFilter fo…

…r search/replacing strings"

src/webassets/filter/replace.py

@@ -0,0 +1,52 @@
+import re
+from webassets.filter import (
+    Filter,
+    register_filter
+)
+
+
+class ReplaceFilter(Filter):
+    """
+        A filter that allows arbitrary search/replace of strings using a source
+        regex and a replacement string. Unlike cssrewrite this works on strings
+        which are not paths and can be used as an output filter.
+
+        Usage:
+
+            replace_static_urls = ReplaceFilter(
+                pattern=r'\s*{{\s*STATIC_URL\s*}}\s*',
+                repl=settings.STATIC_URL,
+            )
+    """
+
+    name = 'replace'
+    max_debug_level = None
+
+    def __init__(self, pattern=None, repl=None, as_output=True, **kwargs):
+        self.pattern = pattern
+        self.repl = repl
+        self.as_output = as_output
+
+        super(ReplaceFilter, self).__init__(**kwargs)
+
+    def unique(self):
+        """ Return a hashable representation of the parameters to allow different instances of this filter. """
+        return self.pattern, self.repl
+
+    def _process(self, _in, out, **kwargs):
+        out.write(re.sub(self.pattern, self.repl, _in.read()))
+
+    def output(self, _in, out, **kwargs):
+        if self.as_output:
+            self._process(_in, out, **kwargs)
+        else:
+            out.write(_in.read())
+
+    def input(self, _in, out, **kwargs):
+        if self.as_output:
+            out.write(_in.read())
+        else:
+            self._process(_in, out, **kwargs)
+
+
+register_filter(ReplaceFilter)