Speed up salt.matcher.confirm_top by using __context__

* Speed up salt.matcher.confirm_top by using __context__

* Add test for getting matchers from __context__ in matchers.confirm_top

salt/matchers/confirm_top.py

@@ -21,7 +21,11 @@ def confirm_top(match, data, nodegroups=None):
             if "match" in item:
                 matcher = item["match"]
 
-    matchers = salt.loader.matchers(__opts__)
+    if "matchers" in __context__:
+        matchers = __context__["matchers"]
+    else:
+        matchers = salt.loader.matchers(__opts__)
+        __context__["matchers"] = matchers
     funcname = matcher + "_match.match"
     if matcher == "nodegroup":
         return matchers[funcname](match, nodegroups)

tests/pytests/unit/matchers/test_confirm_top.py

@@ -2,6 +2,7 @@
 
 import salt.config
 import salt.loader
+from tests.support.mock import patch
 
 
 @pytest.fixture
@@ -12,3 +13,17 @@ def matchers(minion_opts):
 def test_sanity(matchers):
     match = matchers["confirm_top.confirm_top"]
     assert match("*", []) is True
+
+
+@pytest.mark.parametrize("in_context", [False, True])
+def test_matchers_from_context(matchers, in_context):
+    match = matchers["confirm_top.confirm_top"]
+    with patch.dict(
+        matchers.pack["__context__"], {"matchers": matchers} if in_context else {}
+    ), patch("salt.loader.matchers", return_value=matchers) as loader_matchers:
+        assert match("*", []) is True
+        assert id(matchers.pack["__context__"]["matchers"]) == id(matchers)
+        if in_context:
+            loader_matchers.assert_not_called()
+        else:
+            loader_matchers.assert_called_once()