custom_params: register ReplacePrefix before ReplaceFeature

This way, ReplacePrefix will be applied before ReplaceFeature.
This is important because, when these two params are used in combination
and the replaced feature contains a reference to a lookup only contained
in the prefix to be replaced, feaLib Parser will trigger an error if
it cannot resolve the lookup reference. Thus it is important to replace
the prefix before the feature body.

Lib/glyphsLib/builder/custom_params.py

@@ -650,27 +650,6 @@ def to_ufo(self, builder, glyphs, ufo):
 register(FilterParamHandler())
 
 
-class ReplaceFeatureParamHandler(AbstractParamHandler):
-    def to_ufo(self, builder, glyphs, ufo):
-        for value in glyphs.get_custom_values("Replace Feature"):
-            tag, repl = re.split(r"\s*;\s*", value, 1)
-            ufo._owner.features.text = replace_feature(
-                tag, repl, ufo._owner.features.text or ""
-            )
-
-    def to_glyphs(self, glyphs, ufo):
-        # TODO: (jany) The "Replace Feature" custom parameter can be used to
-        # have one master/instance with different features than what is stored
-        # in the GSFont. When going from several UFOs to one GSFont, we could
-        # detect when UFOs have different features, put the common ones in
-        # GSFont and replace the different ones with this custom parameter.
-        # See the file `tests/builder/features_test.py`.
-        pass
-
-
-register(ReplaceFeatureParamHandler())
-
-
 class ReplacePrefixParamHandler(AbstractParamHandler):
     def to_ufo(self, builder, glyphs, ufo):
         repl_map = {}
@@ -699,6 +678,27 @@ def to_glyphs(self, glyphs, ufo):
 register(ReplacePrefixParamHandler())
 
 
+class ReplaceFeatureParamHandler(AbstractParamHandler):
+    def to_ufo(self, builder, glyphs, ufo):
+        for value in glyphs.get_custom_values("Replace Feature"):
+            tag, repl = re.split(r"\s*;\s*", value, 1)
+            ufo._owner.features.text = replace_feature(
+                tag, repl, ufo._owner.features.text or ""
+            )
+
+    def to_glyphs(self, glyphs, ufo):
+        # TODO: (jany) The "Replace Feature" custom parameter can be used to
+        # have one master/instance with different features than what is stored
+        # in the GSFont. When going from several UFOs to one GSFont, we could
+        # detect when UFOs have different features, put the common ones in
+        # GSFont and replace the different ones with this custom parameter.
+        # See the file `tests/builder/features_test.py`.
+        pass
+
+
+register(ReplaceFeatureParamHandler())
+
+
 class ReencodeGlyphsParamHandler(AbstractParamHandler):
     """ The "Reencode Glyphs" custom parameter contains a list of
     'glyphname=unicodevalue' strings: e.g., ["smiley=E100", "logo=E101"].