nix_expr: Make list ordering deterministic

NixOS · Mar 27, 2020 · 1badb89 · 1badb89
1 parent 628b560
commit 1badb89
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/nixops/nix_expr.py b/nixops/nix_expr.py
@@ -333,7 +333,13 @@ def _merge(e1, e2):
         if isinstance(e1, dict) and isinstance(e2, dict):
             return _merge_dicts(e1, e2)
         elif isinstance(e1, list) and isinstance(e2, list):
-            return list(set(e1).union(e2))
+            l = []
+            seen = set()
+            for x in e1 + e2:
+                if x not in seen:
+                    seen.add(x)
+                    l.append(x)
+            return l
         else:
             err = "unable to merge {0} with {1}".format(type(e1), type(e2))
             raise ValueError(err)

diff --git a/tests/unit/test_nix_expr.py b/tests/unit/test_nix_expr.py
@@ -324,7 +324,7 @@ def assert_merge(self, sources, expect):
     def test_merge_list(self):
         self.assert_merge(
             [[1, 2, 3], [4, 5, 6], [7, 6, 5], ["abc", "def"], ["ghi", "abc"],],
-            [1, 2, 3, 4, 5, 6, 7, "ghi", "def", "abc"],
+            [1, 2, 3, 4, 5, 6, 7, "abc", "def", "ghi"],
         )
 
     def test_merge_dict(self):