schema_editor: sort listdir output, copy schema before merging (#227)

CHANGES.rst

@@ -9,6 +9,9 @@ Bug Fixes
 - Fix ``rebuild_fits_rec_dtype`` handling of unsigned integer columns
   with shapes [#213]
 
+- Sort keyword files used for schema_editor to make output non-arbitrary
+  copy schema before merging to avoid schema modification [#227]
+
 Changes to API
 --------------
 

src/stdatamodels/jwst/datamodels/schema_editor.py

@@ -44,6 +44,7 @@
 
 import argparse
 from collections import OrderedDict
+import copy
 import datetime
 import inspect
 import os
@@ -228,7 +229,7 @@ def __init__(self, directory=""):
             raise ValueError("Cannot locate keyword database directory")
 
         self.schema = None
-        for filename in os.listdir(directory):
+        for filename in sorted(os.listdir(directory)):
             if filename.startswith("top."):
                 keyword_db = os.path.abspath(os.path.join(directory, filename))
                 schema = aschema.load_schema(keyword_db, resolve_references=False)
@@ -381,7 +382,7 @@ def merge_enums(merged_subschema, dictionary):
                                             set(dictionary["enum"]))
 
         merged_subschema = OrderedDict()
-        for dictionary in schema:
+        for dictionary in copy.deepcopy(schema):
             if merged_subschema:
                 merge_dictionaries(merged_subschema, dictionary)
             else:
@@ -448,7 +449,7 @@ def __init__(self, exclude=None):
                                      'schemas', '')
         self.schema_files = []
 
-        for filename in os.listdir(self.base_url):
+        for filename in sorted(os.listdir(self.base_url)):
             if filename.endswith(".yaml") and filename not in exclude:
                 self.schema_files.append(filename)