Addressing @obi1kenobi's comments

Author: jmeulemans

graphql_compiler/compiler/emit_sql.py

@@ -219,8 +219,8 @@ def _transform_binary_composition_to_expression(expression, node, context):
         right.expanding = True
         clause = getattr(left, sql_operator.name)(right)
         return clause
-    else:
-        raise AssertionError(u'Unknown operator cardinality {}'.format(sql_operator.cardinality))
+    raise AssertionError(u'Unreachable, operator cardinality {} for compiler expression {} is '
+                         u'unknown'.format(sql_operator.cardinality, expression))
 
 
 def _get_column_and_bindparam(left, right, operator):
@@ -230,11 +230,11 @@ def _get_column_and_bindparam(left, right, operator):
     if not isinstance(left, Column):
         raise AssertionError(
             u'SQLAlchemy operator {} expects Column as left side the of expression, got {} '
-            u'of type {}'.format(operator, left, type(left)))
+            u'of type {} instead.'.format(operator, left, type(left)))
     if not isinstance(right, BindParameter):
         raise AssertionError(
-            u'SQLAlchemy operator {} expects BindParameter as the right side of the expression, got'
-            u' {} of type {}'.format(operator, right, type(right)))
+            u'SQLAlchemy operator {} expects BindParameter as the right side of the expression, '
+            u'got {} of type {} instead.'.format(operator, right, type(right)))
     return left, right
 
 

graphql_compiler/compiler/ir_lowering_sql/__init__.py

@@ -240,7 +240,8 @@ def visitor_fn(expression):
         if not isinstance(expression, expressions.UnaryTransformation):
             return expression
         raise NotImplementedError(
-            u'UnaryTransformation expression "{}" is unsupported by SQL backend.'.format(expression)
+            u'UnaryTransformation expression "{}" encountered with IR blocks {} is unsupported by '
+            u'the SQL backend.'.format(expression, ir_blocks)
         )
 
     new_ir_blocks = [

graphql_compiler/tests/integration_tests/integration_test_helpers.py

@@ -31,14 +31,14 @@ def try_convert_decimal_to_string(value):
     """Return Decimals as string if value is a Decimal, return value otherwise."""
     if isinstance(value, list):
         return [try_convert_decimal_to_string(subvalue) for subvalue in value]
-    if not isinstance(value, Decimal):
-        return value
-    return str(value)
+    if isinstance(value, Decimal):
+        return str(value)
+    return value
 
 
 def compile_and_run_match_query(schema, graphql_query, parameters, graph_client):
     """Compiles and runs a MATCH query against the supplied graph client."""
-    # OrientDB expects decimals to be passed as their string representation
+    # MATCH code emitted by the compiler expects Decimals to be passed in as strings
     converted_parameters = {
         name: try_convert_decimal_to_string(value)
         for name, value in six.iteritems(parameters)