Add test cases for pattern matching against optional inputs (#1890)

I updated the pattern matcher to support matching against optional
inputs. The change was accidentally pushed into the main branch (not a
sub-branch as I thought) ... guess the branch protections were not good
enough, changed it now.

Adding test-cases now to test it in this PR.

---------

Signed-off-by: Ganesan Ramalingam <[email protected]>

onnxscript/rewriter/pattern.py

@@ -592,10 +592,12 @@ def producer(self) -> NodePattern:
 
 Var = ValuePattern
 
+
 def _is_pattern_variable(x: Any) -> bool:
     # The derived classes of ValuePattern represent constant patterns and node-output patterns.
     return type(x) is ValuePattern
 
+
 class Constant(ValuePattern):
     """Represents a pattern that matches against a scalar constant value."""
 
@@ -988,16 +990,16 @@ def _bind_value(self, pattern_value: ValuePattern, value: ir.Value | None) -> bo
 
     def _match_value(self, pattern_value: ValuePattern, value: ir.Value | None) -> bool:
         """Match an IR value against a ValuePattern instance."""
-        if value is None:
-            if not _is_pattern_variable(pattern_value):
-                return self.fail("Mismatch: input value is None, but pattern value is not a variable.")
-
         if not self._bind_value(pattern_value, value):
             return False
 
         if isinstance(pattern_value, NodeOutputPattern):
+            if value is None:
+                return self.fail("Mismatch: Computed node pattern does not match None.")
             return self._match_node_output(pattern_value, value)
         if isinstance(pattern_value, Constant):
+            if value is None:
+                return self.fail("Mismatch: Constant pattern does not match None.")
             return self._match_constant(pattern_value, value)
         return True
 

onnxscript/rewriter/pattern_test.py

@@ -8,7 +8,8 @@
 import onnx.checker
 import onnx.parser
 
-from onnxscript import ir
+from onnxscript import FLOAT, ir, script
+from onnxscript import opset17 as op
 from onnxscript.rewriter import _ir_utils, cast_constant_of_shape, pattern
 
 logger = logging.getLogger(__name__)
@@ -420,6 +421,62 @@ def concat(op, x, y, result: ir.Value):
         self.assertEqual(model.graph[0].op_type, "Concat")
         self.assertNotIn("axis", model.graph[0].attributes)
 
+    def test_match_none_input(self):
+        def none_pattern(op, x):
+            # match against a call to Original where the first input is None
+            return op.Original(None, x)
+
+        def replacement(op, x):
+            return op.Replaced(x)
+
+        rule = pattern.RewriteRule(none_pattern, replacement)
+
+        @script()
+        def test_model(x: FLOAT[1024]) -> FLOAT[1024]:
+            # Pattern should match following call
+            t1 = op.Original(None, x)
+            # Pattern should not match following call
+            z = op.Original(t1, x)
+            return z
+
+        model_proto = test_model.to_model_proto()
+        model = ir.serde.deserialize_model(model_proto)
+
+        count = rule.apply_to_model(model)
+        self.assertEqual(count, 1)
+        self.assertEqual(len(model.graph), 2)
+        self.assertEqual(model.graph.node(0).op_type, "Replaced")
+        self.assertEqual(model.graph.node(1).op_type, "Original")
+
+    def test_match_optional_input(self):
+        def none_pattern(op, optional_input, x):
+            # match against a call to Original where the first input may or may not be None
+            return op.Original(optional_input, x)
+
+        def replacement(op, optional_input, x):
+            if optional_input is None:
+                return op.ReplacedNone(x)
+            return op.ReplacedNotNone(x)
+
+        rule = pattern.RewriteRule(none_pattern, replacement)
+
+        @script()
+        def test_model(x: FLOAT[1024]) -> FLOAT[1024]:
+            # Pattern should match following call
+            t1 = op.Original(None, x)
+            # as well as this one
+            z = op.Original(t1, x)
+            return z
+
+        model_proto = test_model.to_model_proto()
+        model = ir.serde.deserialize_model(model_proto)
+
+        count = rule.apply_to_model(model)
+        self.assertEqual(count, 2)
+        self.assertEqual(len(model.graph), 2)
+        self.assertEqual(model.graph.node(0).op_type, "ReplacedNone")
+        self.assertEqual(model.graph.node(1).op_type, "ReplacedNotNone")
+
 
 class PatternBuilderTest(unittest.TestCase):
     def test_pattern_builder_context(self):