Fix Slice that is Identity (#1476)

Signed-off-by: Tom Wildenhain <[email protected]>

Author: TomWildenhain-Microsoft

tests/test_backend.py

@@ -2540,6 +2540,16 @@ def func2(x):
         x_val = np.arange(np.prod(shape)).astype("float32").reshape(shape)
         self._run_test_case(func2, [_OUTPUT], {_INPUT: x_val})
 
+    @check_opset_min_version(10, "Slice")
+    @skip_tflite("not supported in tflite")
+    def test_strided_slice_only_ellipsis(self):
+        def func1(x):
+            x_ = x[...]
+            return tf.identity(x_, name=_TFOUTPUT)
+        shape = [1, 8, 64]
+        x_val = np.arange(np.prod(shape)).astype("float32").reshape(shape)
+        self._run_test_case(func1, [_OUTPUT], {_INPUT: x_val})
+
     @check_opset_min_version(7, "batchnorm")
     def test_fused_batchnorm(self):
         x_shape = [1, 28, 28, 2]

tf2onnx/onnx_opset/tensor.py

@@ -849,8 +849,11 @@ def version_1(cls, ctx, node, **kwargs):
         attr = {"starts": new_begin, "ends": new_end, "axes": axes}
         inputs_map = {"data": node.input[0], **attr}
         kwargs = {**inputs_map, "outputs": node.output}
-        node = GraphBuilder(ctx).make_slice(
-            kwargs, name=node.name, dtypes=out_dtypes, shapes=out_shapes, return_node=True)
+        if len(axes) > 0:
+            node = GraphBuilder(ctx).make_slice(
+                kwargs, name=node.name, dtypes=out_dtypes, shapes=out_shapes, return_node=True)
+        else:
+            node = ctx.make_node("Identity", [node.input[0]], name=node.name, dtypes=out_dtypes, shapes=out_shapes)
         nodes = [node]
         if needs_squeeze:
             # insert_new_node_on_output(self, op_type, output_name=None, name=None, inputs=None, domain=None, **kwargs)