CLN: remove obsolete code in Categorical.fillna (#19880)

Author: cfgong

.gitignore

@@ -61,6 +61,7 @@ dist
 .coverage
 coverage.xml
 coverage_html_report
+*.pytest_cache
 
 # OS generated files #
 ######################
@@ -90,7 +91,6 @@ scikits
 
 # Unit / Performance Testing #
 ##############################
-.pytest_cache/
 asv_bench/env/
 asv_bench/html/
 asv_bench/results/

pandas/core/arrays/categorical.py

@@ -1627,14 +1627,6 @@ def fillna(self, value=None, method=None, limit=None):
 
         values = self._codes
 
-        # Make sure that we also get NA in categories
-        if self.categories.dtype.kind in ['S', 'O', 'f']:
-            if np.nan in self.categories:
-                values = values.copy()
-                nan_pos = np.where(isna(self.categories))[0]
-                # we only have one NA in categories
-                values[values == nan_pos] = -1
-
         # pad / bfill
         if method is not None: