feat: sql expressions always return a value, along with the correct error types

Signed-off-by: Calum Murray <cmurray@redhat.com>

sql/v2/expression/function_invocation_expression.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 
 	cesql "github.com/cloudevents/sdk-go/sql/v2"
+	sqlerrors "github.com/cloudevents/sdk-go/sql/v2/errors"
 	"github.com/cloudevents/sdk-go/sql/v2/runtime"
 	"github.com/cloudevents/sdk-go/sql/v2/utils"
 	cloudevents "github.com/cloudevents/sdk-go/v2"
@@ -22,7 +23,7 @@ type functionInvocationExpression struct {
 func (expr functionInvocationExpression) Evaluate(event cloudevents.Event) (interface{}, error) {
 	fn := runtime.ResolveFunction(expr.name, len(expr.argumentsExpression))
 	if fn == nil {
-		return false, fmt.Errorf("cannot resolve function %s", expr.name)
+		return false, sqlerrors.NewMissingFunctionError(expr.name)
 	}
 
 	args := make([]interface{}, len(expr.argumentsExpression))
@@ -37,7 +38,7 @@ func (expr functionInvocationExpression) Evaluate(event cloudevents.Event) (inte
 
 		argType := fn.ArgType(i)
 		if argType == nil {
-			return defaultVal, fmt.Errorf("cannot resolve arg type at index %d", i)
+			return defaultVal, sqlerrors.NewFunctionEvaluationError(fmt.Errorf("cannot resolve arg type at index %d for function %s", i, fn.Name()))
 		}
 
 		arg, err = utils.Cast(arg, *argType)
@@ -50,8 +51,15 @@ func (expr functionInvocationExpression) Evaluate(event cloudevents.Event) (inte
 
 	result, err := fn.Run(event, args)
 	if result == nil {
+		if err != nil {
+			err = sqlerrors.NewFunctionEvaluationError(fmt.Errorf("function %s encountered error %w and did not return any value, defaulting to the default value for the function", fn.Name(), err))
+		} else {
+			err = sqlerrors.NewFunctionEvaluationError(fmt.Errorf("function %s did not return any value, defaulting to the default value for the function", fn.Name()))
+		}
+
 		return defaultVal, err
 	}
+
 	return result, err
 }
 

sql/v2/expression/identifier_expression.go

@@ -6,9 +6,8 @@
 package expression
 
 import (
-	"fmt"
-
 	cesql "github.com/cloudevents/sdk-go/sql/v2"
+	sqlerrors "github.com/cloudevents/sdk-go/sql/v2/errors"
 	"github.com/cloudevents/sdk-go/sql/v2/utils"
 	cloudevents "github.com/cloudevents/sdk-go/v2"
 )
@@ -20,7 +19,7 @@ type identifierExpression struct {
 func (l identifierExpression) Evaluate(event cloudevents.Event) (interface{}, error) {
 	value := utils.GetAttribute(event, l.identifier)
 	if value == nil {
-		return nil, fmt.Errorf("missing attribute '%s'", l.identifier)
+		return false, sqlerrors.NewMissingAttributeError(l.identifier)
 	}
 
 	return value, nil

sql/v2/expression/math_expressions.go

@@ -6,9 +6,8 @@
 package expression
 
 import (
-	"errors"
-
 	cesql "github.com/cloudevents/sdk-go/sql/v2"
+	sqlerrors "github.com/cloudevents/sdk-go/sql/v2/errors"
 	"github.com/cloudevents/sdk-go/sql/v2/utils"
 	cloudevents "github.com/cloudevents/sdk-go/v2"
 )
@@ -21,22 +20,22 @@ type mathExpression struct {
 func (s mathExpression) Evaluate(event cloudevents.Event) (interface{}, error) {
 	leftVal, err := s.left.Evaluate(event)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	rightVal, err := s.right.Evaluate(event)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	leftVal, err = utils.Cast(leftVal, cesql.IntegerType)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	rightVal, err = utils.Cast(rightVal, cesql.IntegerType)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	return s.fn(leftVal.(int32), rightVal.(int32))
@@ -86,7 +85,7 @@ func NewModuleExpression(left cesql.Expression, right cesql.Expression) cesql.Ex
 		},
 		fn: func(x, y int32) (int32, error) {
 			if y == 0 {
-				return 0, errors.New("math error: division by zero")
+				return 0, sqlerrors.NewMathError("division by zero")
 			}
 			return x % y, nil
 		},
@@ -101,7 +100,7 @@ func NewDivisionExpression(left cesql.Expression, right cesql.Expression) cesql.
 		},
 		fn: func(x, y int32) (int32, error) {
 			if y == 0 {
-				return 0, errors.New("math error: division by zero")
+				return 0, sqlerrors.NewMathError("division by zero")
 			}
 			return x / y, nil
 		},

sql/v2/expression/negate_expression.go

@@ -16,12 +16,12 @@ type negateExpression baseUnaryExpression
 func (l negateExpression) Evaluate(event cloudevents.Event) (interface{}, error) {
 	val, err := l.child.Evaluate(event)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	val, err = utils.Cast(val, cesql.IntegerType)
 	if err != nil {
-		return 0, err
+		return int32(0), err
 	}
 
 	return -(val.(int32)), nil