vela: Move special error cases

Due to an issue with potential cyclical imports, especially when running
individual parts of vela standalone for example with pytest, the
specialised error functions are moved out of errors.py to their
respective locations.
The use of getattr over isinstance prevents the need to import the
tensor/operator class causing the cyclical import issue.

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: If8cee4b1a2562660c6a47e1c7aeb5d7fd4dd1fca

1 files changed, 30 insertions, 3 deletions

diff --git a/ethosu/vela/tensor.py b/ethosu/vela/tensor.py
index c1443b3b..69618d2c 100644
--- a/ethosu/vela/tensor.py
+++ b/ethosu/vela/tensor.py
@@ -31,10 +31,11 @@ from uuid import UUID
 
 import numpy as np
 
-from . import errors  # Import this way due to cyclic imports
 from . import numeric_util
 from .data_type import BaseType
 from .data_type import DataType
+from .errors import UnsupportedFeatureError
+from .errors import VelaError
 from .ethos_u55_regs.ethos_u55_regs import resampling_mode
 from .operation import Op
 from .operation import Operation
@@ -630,7 +631,7 @@ class Tensor:
 
         if end_coord[2] > crossing_x:
             addresses[1] = self.address_for_coordinate([start_coord[0], start_coord[1], crossing_x, start_coord[3]])
-            raise errors.UnsupportedFeatureError("Striping in vertical direction is not supported")
+            raise UnsupportedFeatureError("Striping in vertical direction is not supported")
         if end_coord[1] > crossing_y:
             addresses[2] = self.address_for_coordinate([start_coord[0], crossing_y, start_coord[2], start_coord[3]])
         if end_coord[1] > crossing_y and end_coord[2] > crossing_x:
@@ -737,7 +738,7 @@ class Tensor:
         if index < len(self.weight_compressed_offsets) - 1:
             # There are no half-way points in the weights
             if (depth % brick_depth) != 0:
-                raise errors.UnsupportedFeatureError("Offset into weights must be aligned to a brick")
+                raise UnsupportedFeatureError("Offset into weights must be aligned to a brick")
 
         return index
 
@@ -851,6 +852,32 @@ class Tensor:
 
     __repr__ = __str__
 
+    def error(self, msg):
+        """
+        Raises a VelaError exception for errors encountered when parsing a Tensor
+
+        :param self: Tensor object that resulted in the error
+        :param msg: str object that contains a description of the specific error encountered
+        """
+
+        def _print_operators(ops):
+            lines = []
+            for idx, op in enumerate(ops):
+                op_type = getattr(op, "type", "Not an Operation")
+                op_id = getattr(op, "op_index", "-")
+                lines.append(f"        {idx} = {op_type} ({op_id})")
+            return lines
+
+        lines = [f"Invalid {self.name} tensor. {msg}"]
+
+        lines += ["    Driving operators:"]
+        lines += _print_operators(self.ops)
+
+        lines += ["    Consuming operators:"]
+        lines += _print_operators(self.consumer_list)
+
+        raise VelaError("\n".join(lines))
+
 
 def check_quantized_tens_scaling_equal(tens_a: Tensor, tens_b: Tensor) -> bool:
     # checks that the scaling of two quantized tensors are equal