[pkg/ottl] Make LambdaExpression arguments pointers

Author: evan-bradley

.chloggen/ottl-lambda-pointers.yaml

@@ -0,0 +1,29 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Switch `LambdaExpression` arguments to be pointers.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: []
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  These values are intended to be mutable and are passed by reference in normal use,
+  so this keeps symmetry between the argument declaration and their use by the function.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

pkg/ottl/functions.go

@@ -460,6 +460,8 @@ func (p *parseContext[K]) buildArgs(ed editor, argsVal reflect.Value) error {
 			val = StandardFunctionGetter[K]{FCtx: FunctionContext{Set: p.telemetrySettings}, Fact: f}
 		case fieldType.Kind() == reflect.Slice:
 			val, err = p.buildSliceArg(arg.Value, fieldType)
+		case fieldType.Kind() == reflect.Pointer:
+			val, err = p.buildArg(arg.Value, fieldType.Elem())
 		default:
 			val, err = p.buildArg(arg.Value, fieldType)
 		}
@@ -736,7 +738,7 @@ func (p *parseContext[K]) buildArg(argVal value, argType reflect.Type) (any, err
 		if err != nil {
 			return nil, err
 		}
-		return *lambExpr, nil
+		return lambExpr, nil
 	default:
 		return nil, fmt.Errorf("unsupported argument type: %s", name)
 	}

pkg/ottl/functions_test.go

@@ -91,6 +91,11 @@ func Test_NewFunctionCall_invalid(t *testing.T) {
 			&optionalArgsArguments{},
 			functionWithOptionalArgs,
 		),
+		createFactory[any](
+			"testing_non_pointer_lambda",
+			&nonPointerLambdaArguments{},
+			functionWithNonPointerLambda,
+		),
 	)
 
 	p, _ := NewParser(
@@ -588,6 +593,28 @@ func Test_NewFunctionCall_invalid(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "lambda expression argument that is not a pointer",
+			inv: editor{
+				Function: "testing_non_pointer_lambda",
+				Arguments: []argument{
+					{
+						Value: value{
+							Lambda: &lambdaExpr{
+								Params: []localIdentifierDecl{"value"},
+								Body: lambdaBody{
+									Value: &value{
+										Literal: &mathExprLiteral{
+											Path: &path{Fields: []field{{Name: "value"}}},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -2531,13 +2558,23 @@ func functionWithFunctionGetter(FunctionGetter[any]) (ExprFunc[any], error) {
 	}, nil
 }
 
+type nonPointerLambdaArguments struct {
+	Expr LambdaExpression[any]
+}
+
+func functionWithNonPointerLambda(LambdaExpression[any]) (ExprFunc[any], error) {
+	return func(context.Context, any) (any, error) {
+		return nil, nil
+	}, nil
+}
+
 type evalLambdaArguments[K any] struct {
-	Expr LambdaExpression[K]
+	Expr *LambdaExpression[K]
 	Args []Getter[K]
 }
 
 //nolint:unparam // returning (ExprFunc[K], error) is required by this local test framework
-func evalLambdaFunction[K any](expr LambdaExpression[any], args []Getter[K]) (ExprFunc[K], error) {
+func evalLambdaFunction[K any](expr *LambdaExpression[any], args []Getter[K]) (ExprFunc[K], error) {
 	return func(ctx context.Context, tCtx K) (any, error) {
 		lambda, err := expr.Activate(ctx, len(args))
 		if err != nil {

pkg/ottl/parser_collection_test.go

@@ -924,7 +924,7 @@ func mockParser(t *testing.T, options ...Option[any]) *Parser[any] {
 			}, nil
 		})
 
-	mockLambdaFactory := NewFactory("Lambda", &struct{ Expr LambdaExpression[any] }{},
+	mockLambdaFactory := NewFactory("Lambda", &struct{ Expr *LambdaExpression[any] }{},
 		func(FunctionContext, Arguments) (ExprFunc[any], error) {
 			return nil, nil
 		})