Ensure receiver and global matches cost estimates agree

Author: TristonianJones

checker/cost.go

@@ -791,18 +791,26 @@ func (c *coster) functionCost(e ast.Expr, function, overloadID string, target *A
 			return CallEstimate{CostEstimate: c.sizeOrUnknown(args[1]).MultiplyByCostFactor(1).Add(argCostSum())}
 		}
 	// O(nm) functions
-	case overloads.MatchesString:
+	case overloads.Matches, overloads.MatchesString:
 		// https://swtch.com/~rsc/regexp/regexp1.html applies to RE2 implementation supported by CEL
-		if target != nil && len(args) == 1 {
+		var strNode, regexNode AstNode
+		if overloadID == overloads.MatchesString && target != nil && len(args) == 1 {
+			strNode = *target
+			regexNode = args[0]
+		} else if overloadID == overloads.Matches && target == nil && len(args) == 2 {
+			strNode = args[0]
+			regexNode = args[1]
+		}
+		if strNode != nil && regexNode != nil {
 			// Add one to string length for purposes of cost calculation to prevent product of string and regex to be 0
 			// in case where string is empty but regex is still expensive.
-			strCost := c.sizeOrUnknown(*target).Add(SizeEstimate{Min: 1, Max: 1}).MultiplyByCostFactor(common.StringTraversalCostFactor)
+			strCost := c.sizeOrUnknown(strNode).Add(SizeEstimate{Min: 1, Max: 1}).MultiplyByCostFactor(common.StringTraversalCostFactor)
 			// We don't know how many expressions are in the regex, just the string length (a huge
 			// improvement here would be to somehow get a count the number of expressions in the regex or
 			// how many states are in the regex state machine and use that to measure regex cost).
 			// For now, we're making a guess that each expression in a regex is typically at least 4 chars
 			// in length.
-			regexCost := c.sizeOrUnknown(args[0]).MultiplyByCostFactor(common.RegexStringLengthCostFactor)
+			regexCost := c.sizeOrUnknown(regexNode).MultiplyByCostFactor(common.RegexStringLengthCostFactor)
 			return CallEstimate{CostEstimate: strCost.Multiply(regexCost).Add(argCostSum())}
 		}
 	case overloads.ContainsString:

checker/cost_test.go

@@ -314,6 +314,15 @@ func TestCost(t *testing.T) {
 			hints:  map[string]uint64{"input": 500},
 			wanted: CostEstimate{Min: 3, Max: 103},
 		},
+		{
+			name: "matches global",
+			expr: `matches(input, '\\d+a\\d+b')`,
+			vars: []*decls.VariableDecl{
+				decls.NewVariable("input", types.StringType),
+			},
+			hints:  map[string]uint64{"input": 500},
+			wanted: CostEstimate{Min: 3, Max: 103},
+		},
 		{
 			name: "startsWith",
 			expr: `input.startsWith(arg1)`,

interpreter/runtimecost.go

@@ -285,7 +285,7 @@ func (c *CostTracker) costCall(call InterpretableCall, args []ref.Val, result re
 		// In the worst case scenario, we would need to reallocate a new backing store and copy both operands over.
 		cost += uint64(math.Ceil(float64(actualSize(args[0])+actualSize(args[1])) * common.StringTraversalCostFactor))
 	// O(nm) functions
-	case overloads.MatchesString:
+	case overloads.Matches, overloads.MatchesString:
 		// https://swtch.com/~rsc/regexp/regexp1.html applies to RE2 implementation supported by CEL
 		// Add one to string length for purposes of cost calculation to prevent product of string and regex to be 0
 		// in case where string is empty but regex is still expensive.

interpreter/runtimecost_test.go

@@ -606,6 +606,15 @@ func TestRuntimeCost(t *testing.T) {
 			want: 103,
 			in:   map[string]any{"input": string(randSeq(500)), "arg1": string(randSeq(500))},
 		},
+		{
+			name: "matches global",
+			expr: `matches(input, '\\d+a\\d+b')`,
+			vars: []*decls.VariableDecl{
+				decls.NewVariable("input", types.StringType),
+			},
+			want: 103,
+			in:   map[string]any{"input": string(randSeq(500))},
+		},
 		{
 			name: "startsWith",
 			expr: `input.startsWith(arg1)`,