Fix View instrument-name matching to be case-insensitive and platform-independent

.changelog/5430.fixed

@@ -0,0 +1 @@
+`opentelemetry-sdk`: fix `View` instrument-name matching so a view configured with an instrument's real (mixed-case) name is applied; matching is now case-insensitive and platform-independent instead of relying on `fnmatch`'s OS-dependent case handling

opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/view.py

@@ -3,7 +3,7 @@
 
 
 from collections.abc import Callable
-from fnmatch import fnmatch
+from fnmatch import fnmatchcase
 from logging import getLogger
 
 from opentelemetry.metrics import Instrument
@@ -146,11 +146,17 @@ def _match(self, instrument: _Instrument) -> bool:
                 return False
 
         if self._instrument_name is not None:
-            if not fnmatch(instrument.name, self._instrument_name):
+            # Instrument names are treated case-insensitively and are stored
+            # lower-cased by the SDK, so the pattern is lower-cased to match.
+            # fnmatchcase is used instead of fnmatch so it does not rely
+            # on the host platform's filename case sensitivity (normcase).
+            if not fnmatchcase(instrument.name, self._instrument_name.lower()):
                 return False
 
         if self._instrument_unit is not None:
-            if not fnmatch(instrument.unit, self._instrument_unit):
+            # Units are case-sensitive; fnmatchcase keeps matching consistent
+            # across platforms.
+            if not fnmatchcase(instrument.unit, self._instrument_unit):
                 return False
 
         if self._meter_name is not None:

opentelemetry-sdk/tests/metrics/test_view.py

@@ -23,12 +23,32 @@ def test_instrument_name(self):
 
         self.assertTrue(View(instrument_name="instrument_name")._match(mock_instrument))
 
+    def test_instrument_name_case_insensitive(self):
+        # The SDK stores instrument names lower-cased, so a view pattern that
+        # reuses the instrument's original name must still match regardless of
+        # case (and regardless of the host platform).
+        mock_instrument = Mock()
+        mock_instrument.configure_mock(**{"name": "instrument_name"})
+
+        self.assertTrue(View(instrument_name="Instrument_Name")._match(mock_instrument))
+        self.assertTrue(View(instrument_name="INSTRUMENT_*")._match(mock_instrument))
+        self.assertFalse(View(instrument_name="other_name")._match(mock_instrument))
+
     def test_instrument_unit(self):
         mock_instrument = Mock()
         mock_instrument.configure_mock(**{"unit": "instrument_unit"})
 
         self.assertTrue(View(instrument_unit="instrument_unit")._match(mock_instrument))
 
+    def test_instrument_unit_case_sensitive(self):
+        # Units are case-sensitive and matching must not depend on the host
+        # platform's filename case sensitivity.
+        mock_instrument = Mock()
+        mock_instrument.configure_mock(**{"unit": "By"})
+
+        self.assertTrue(View(instrument_unit="By")._match(mock_instrument))
+        self.assertFalse(View(instrument_unit="by")._match(mock_instrument))
+
     def test_meter_name(self):
         self.assertTrue(View(meter_name="meter_name")._match(Mock(**{"instrumentation_scope.name": "meter_name"})))