Add [ScheduleEvent] annotation attribute and source generator support

.autover/changes/add-scheduleevent-annotation.json

@@ -0,0 +1,11 @@
+{
+  "Projects": [
+    {
+      "Name": "Amazon.Lambda.Annotations",
+      "Type": "Minor",
+      "ChangelogMessages": [
+        "Added [ScheduleEvent] annotation attribute for declaratively configuring schedule-triggered Lambda functions with support for rate and cron expressions, description, input, and enabled state."
+      ]
+    }
+  ]
+}

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Diagnostics/AnalyzerReleases.Unshipped.md

@@ -21,3 +21,4 @@ AWSLambda0133 | AWSLambdaCSharpGenerator | Error | ALB Listener Reference Not Fo
 AWSLambda0134 | AWSLambdaCSharpGenerator | Error | FromRoute not supported on ALB functions
 AWSLambda0135 | AWSLambdaCSharpGenerator | Error | Unmapped parameter on ALB function
 AWSLambda0136 | AWSLambdaCSharpGenerator | Error | Invalid S3EventAttribute
+AWSLambda0139 | AWSLambdaCSharpGenerator | Error | Invalid ScheduleEventAttribute

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Diagnostics/DiagnosticDescriptors.cs

@@ -281,5 +281,12 @@ public static class DiagnosticDescriptors
             category: "AWSLambdaCSharpGenerator",
             DiagnosticSeverity.Error,
             isEnabledByDefault: true);
+
+        public static readonly DiagnosticDescriptor InvalidScheduleEventAttribute = new DiagnosticDescriptor(id: "AWSLambda0139",
+            title: "Invalid ScheduleEventAttribute",
+            messageFormat: "Invalid ScheduleEventAttribute encountered: {0}",
+            category: "AWSLambdaCSharpGenerator",
+            DiagnosticSeverity.Error,
+            isEnabledByDefault: true);
     }
 }

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Models/Attributes/AttributeModelBuilder.cs

@@ -1,5 +1,6 @@
 using System;
 using Amazon.Lambda.Annotations.ALB;
+using Amazon.Lambda.Annotations.Schedule;
 using Amazon.Lambda.Annotations.APIGateway;
 using Amazon.Lambda.Annotations.S3;
 using Amazon.Lambda.Annotations.SQS;
@@ -101,6 +102,15 @@ public static AttributeModel Build(AttributeData att, GeneratorExecutionContext
                     Type = TypeModelBuilder.Build(att.AttributeClass, context)
                 };
             }
+            else if (att.AttributeClass.Equals(context.Compilation.GetTypeByMetadataName(TypeFullNames.ScheduleEventAttribute), SymbolEqualityComparer.Default))
+            {
+                var data = ScheduleEventAttributeBuilder.Build(att);
+                model = new AttributeModel<ScheduleEventAttribute>
+                {
+                    Data = data,
+                    Type = TypeModelBuilder.Build(att.AttributeClass, context)
+                };
+            }
             else if (att.AttributeClass.Equals(context.Compilation.GetTypeByMetadataName(TypeFullNames.HttpApiAuthorizerAttribute), SymbolEqualityComparer.Default))
             {
                 var data = HttpApiAuthorizerAttributeBuilder.Build(att);

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Models/Attributes/ScheduleEventAttributeBuilder.cs

@@ -0,0 +1,44 @@
+using Amazon.Lambda.Annotations.Schedule;
+using Microsoft.CodeAnalysis;
+using System;
+
+namespace Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes
+{
+    /// <summary>
+    /// Builder for <see cref="ScheduleEventAttribute"/>.
+    /// </summary>
+    public class ScheduleEventAttributeBuilder
+    {
+        public static ScheduleEventAttribute Build(AttributeData att)
+        {
+            if (att.ConstructorArguments.Length != 1)
+            {
+                throw new NotSupportedException($"{TypeFullNames.ScheduleEventAttribute} must have constructor with 1 argument.");
+            }
+            var schedule = att.ConstructorArguments[0].Value as string;
+            var data = new ScheduleEventAttribute(schedule);
+
+            foreach (var pair in att.NamedArguments)
+            {
+                if (pair.Key == nameof(data.ResourceName) && pair.Value.Value is string resourceName)
+                {
+                    data.ResourceName = resourceName;
+                }
+                else if (pair.Key == nameof(data.Description) && pair.Value.Value is string description)
+                {
+                    data.Description = description;
+                }
+                else if (pair.Key == nameof(data.Input) && pair.Value.Value is string input)
+                {
+                    data.Input = input;
+                }
+                else if (pair.Key == nameof(data.Enabled) && pair.Value.Value is bool enabled)
+                {
+                    data.Enabled = enabled;
+                }
+            }
+
+            return data;
+        }
+    }
+}

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Models/EventTypeBuilder.cs

@@ -30,6 +30,10 @@ public static HashSet<EventType> Build(IMethodSymbol lambdaMethodSymbol,
                 {
                     events.Add(EventType.S3);
                 }
+                else if (attribute.AttributeClass.ToDisplayString() == TypeFullNames.ScheduleEventAttribute)
+                {
+                    events.Add(EventType.Schedule);
+                }
                 else if (attribute.AttributeClass.ToDisplayString() == TypeFullNames.HttpApiAuthorizerAttribute
                     || attribute.AttributeClass.ToDisplayString() == TypeFullNames.RestApiAuthorizerAttribute)
                 {

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/SyntaxReceiver.cs

@@ -23,7 +23,8 @@ internal class SyntaxReceiver : ISyntaxContextReceiver
             { "RestApiAttribute", "RestApi" },
             { "SQSEventAttribute", "SQSEvent" },
             { "ALBApiAttribute", "ALBApi" },
-            { "S3EventAttribute", "S3Event" }
+            { "S3EventAttribute", "S3Event" },
+            { "ScheduleEventAttribute", "ScheduleEvent" }
         };
 
         public List<MethodDeclarationSyntax> LambdaMethods { get; } = new List<MethodDeclarationSyntax>();

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/TypeFullNames.cs

@@ -56,6 +56,9 @@ public static class TypeFullNames
         public const string S3Event = "Amazon.Lambda.S3Events.S3Event";
         public const string S3EventAttribute = "Amazon.Lambda.Annotations.S3.S3EventAttribute";
 
+        public const string ScheduledEvent = "Amazon.Lambda.CloudWatchEvents.ScheduledEvents.ScheduledEvent";
+        public const string ScheduleEventAttribute = "Amazon.Lambda.Annotations.Schedule.ScheduleEventAttribute";
+
         public const string LambdaSerializerAttribute = "Amazon.Lambda.Core.LambdaSerializerAttribute";
         public const string DefaultLambdaSerializer = "Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer";
 
@@ -84,7 +87,8 @@ public static class TypeFullNames
             HttpApiAttribute,
             SQSEventAttribute,
             ALBApiAttribute,
-            S3EventAttribute
+            S3EventAttribute,
+            ScheduleEventAttribute
         };
     }
 }

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Validation/LambdaFunctionValidator.cs

@@ -4,6 +4,7 @@
 using Amazon.Lambda.Annotations.SourceGenerator.Extensions;
 using Amazon.Lambda.Annotations.SourceGenerator.Models;
 using Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes;
+using Amazon.Lambda.Annotations.Schedule;
 using Amazon.Lambda.Annotations.SQS;
 using Microsoft.CodeAnalysis;
 using System.Collections.Generic;
@@ -61,6 +62,7 @@ internal static bool ValidateFunction(GeneratorExecutionContext context, IMethod
             // Validate Events
             ValidateApiGatewayEvents(lambdaFunctionModel, methodLocation, diagnostics);
             ValidateSqsEvents(lambdaFunctionModel, methodLocation, diagnostics);
+            ValidateScheduleEvents(lambdaFunctionModel, methodLocation, diagnostics);
             ValidateAlbEvents(lambdaFunctionModel, methodLocation, diagnostics);
             ValidateS3Events(lambdaFunctionModel, methodLocation, diagnostics);
 
@@ -110,6 +112,16 @@ internal static bool ValidateDependencies(GeneratorExecutionContext context, IMe
                 }
             }
 
+            // Check for references to "Amazon.Lambda.CloudWatchEvents" if the Lambda method is annotated with ScheduleEvent attribute.
+            if (lambdaMethodSymbol.HasAttribute(context, TypeFullNames.ScheduleEventAttribute))
+            {
+                if (context.Compilation.ReferencedAssemblyNames.FirstOrDefault(x => x.Name == "Amazon.Lambda.CloudWatchEvents") == null)
+                {
+                    diagnosticReporter.Report(Diagnostic.Create(DiagnosticDescriptors.MissingDependencies, methodLocation, "Amazon.Lambda.CloudWatchEvents"));
+                    return false;
+                }
+            }
+
             return true;
         }
 
@@ -420,6 +432,43 @@ private static void ValidateS3Events(LambdaFunctionModel lambdaFunctionModel, Lo
             }
         }
 
+        private static void ValidateScheduleEvents(LambdaFunctionModel lambdaFunctionModel, Location methodLocation, List<Diagnostic> diagnostics)
+        {
+            if (!lambdaFunctionModel.LambdaMethod.Events.Contains(EventType.Schedule))
+            {
+                return;
+            }
+
+            foreach (var att in lambdaFunctionModel.Attributes)
+            {
+                if (att.Type.FullName != TypeFullNames.ScheduleEventAttribute)
+                    continue;
+
+                var scheduleEventAttribute = ((AttributeModel<ScheduleEventAttribute>)att).Data;
+                var validationErrors = scheduleEventAttribute.Validate();
+                validationErrors.ForEach(errorMessage => diagnostics.Add(Diagnostic.Create(DiagnosticDescriptors.InvalidScheduleEventAttribute, methodLocation, errorMessage)));
+            }
+
+            // Validate method parameters
+            var parameters = lambdaFunctionModel.LambdaMethod.Parameters;
+            if (parameters.Count > 2 ||
+                (parameters.Count >= 1 && parameters[0].Type.FullName != TypeFullNames.ScheduledEvent) ||
+                (parameters.Count == 2 && parameters[1].Type.FullName != TypeFullNames.ILambdaContext))
+            {
+                var errorMessage = $"When using the {nameof(ScheduleEventAttribute)}, the Lambda method can accept at most 2 parameters. " +
+                    $"The first parameter must be of type {TypeFullNames.ScheduledEvent}. " +
+                    $"The second parameter is optional and must be of type {TypeFullNames.ILambdaContext}.";
+                diagnostics.Add(Diagnostic.Create(DiagnosticDescriptors.InvalidLambdaMethodSignature, methodLocation, errorMessage));
+            }
+
+            // Validate return type - must be void or Task
+            if (!lambdaFunctionModel.LambdaMethod.ReturnsVoid && !lambdaFunctionModel.LambdaMethod.ReturnsVoidTask)
+            {
+                var errorMessage = $"When using the {nameof(ScheduleEventAttribute)}, the Lambda method can return either void or {TypeFullNames.Task}";
+                diagnostics.Add(Diagnostic.Create(DiagnosticDescriptors.InvalidLambdaMethodSignature, methodLocation, errorMessage));
+            }
+        }
+
         private static bool ReportDiagnostics(DiagnosticReporter diagnosticReporter, List<Diagnostic> diagnostics)
         {
             var isValid = true;

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Writers/CloudFormationWriter.cs

@@ -3,6 +3,7 @@
 using Amazon.Lambda.Annotations.SourceGenerator.Diagnostics;
 using Amazon.Lambda.Annotations.SourceGenerator.FileIO;
 using Amazon.Lambda.Annotations.SourceGenerator.Models;
+using Amazon.Lambda.Annotations.Schedule;
 using Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes;
 using Amazon.Lambda.Annotations.S3;
 using Amazon.Lambda.Annotations.SQS;
@@ -232,6 +233,10 @@ private void ProcessLambdaFunctionEventAttributes(ILambdaFunctionSerializable la
                         eventName = ProcessS3Attribute(lambdaFunction, s3AttributeModel.Data, currentSyncedEventProperties);
                         currentSyncedEvents.Add(eventName);
                         break;
+                    case AttributeModel<ScheduleEventAttribute> scheduleAttributeModel:
+                        eventName = ProcessScheduleAttribute(lambdaFunction, scheduleAttributeModel.Data, currentSyncedEventProperties);
+                        currentSyncedEvents.Add(eventName);
+                        break;
                 }
             }
 
@@ -608,6 +613,40 @@ private string ProcessSqsAttribute(ILambdaFunctionSerializable lambdaFunction, S
             return att.ResourceName;
         }
 
+        /// <summary>
+        /// Writes all properties associated with <see cref="ScheduleEventAttribute"/> to the serverless template.
+        /// </summary>
+        private string ProcessScheduleAttribute(ILambdaFunctionSerializable lambdaFunction, ScheduleEventAttribute att, Dictionary<string, List<string>> syncedEventProperties)
+        {
+            var eventName = att.ResourceName;
+            var eventPath = $"Resources.{lambdaFunction.ResourceName}.Properties.Events.{eventName}";
+
+            _templateWriter.SetToken($"{eventPath}.Type", "Schedule");
+
+            // Schedule expression
+            SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Schedule", att.Schedule);
+
+            // Description
+            if (att.IsDescriptionSet)
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Description", att.Description);
+            }
+
+            // Input
+            if (att.IsInputSet)
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Input", att.Input);
+            }
+
+            // Enabled
+            if (att.IsEnabledSet)
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Enabled", att.Enabled);
+            }
+
+            return att.ResourceName;
+        }
+
         /// <summary>
         /// Writes all properties associated with <see cref="S3EventAttribute"/> to the serverless template.
         /// </summary>

Libraries/src/Amazon.Lambda.Annotations/README.md

@@ -19,6 +19,7 @@ Topics:
   - [Amazon API Gateway example](#amazon-api-gateway-example)
   - [Amazon S3 example](#amazon-s3-example)
   - [SQS Event Example](#sqs-event-example)
+  - [Schedule Event Example](#schedule-event-example)
   - [Application Load Balancer (ALB) Example](#application-load-balancer-alb-example)
   - [Custom Lambda Authorizer Example](#custom-lambda-authorizer-example)
     - [HTTP API Authorizer](#http-api-authorizer)
@@ -1073,6 +1074,25 @@ The `ALBApi` attribute requires an existing ALB listener. Here is a minimal exam
 
 Then your Lambda function references `@MyListener` in the `ALBApi` attribute.
 
+## Schedule Event Example
+This example shows how to use the `ScheduleEvent` attribute to trigger a Lambda function on a schedule using EventBridge.
+
+The `ScheduleEvent` attribute contains the following properties:
+* **Schedule** (Required) - The schedule expression. Supports `rate()` and `cron()` expressions (e.g. `rate(5 minutes)`, `cron(0 12 * * ? *)`).
+* **ResourceName** (Optional) - The CloudFormation resource name for the schedule event.
+* **Description** (Optional) - A description for the schedule rule.
+* **Input** (Optional) - A JSON string to pass as input to the Lambda function.
+* **Enabled** (Optional) - If false, the schedule rule is disabled. Default is true.
+
+```csharp
+[LambdaFunction(ResourceName = "ScheduledHandler", Policies = "AWSLambdaBasicExecutionRole")]
+[ScheduleEvent("rate(5 minutes)", ResourceName = "FiveMinuteSchedule", Description = "Runs every 5 minutes")]
+public void HandleSchedule(ScheduledEvent evnt, ILambdaContext lambdaContext)
+{
+    lambdaContext.Logger.Log($"Scheduled event received at {evnt.Time}");
+}
+```
+
 ## Custom Lambda Authorizer Example
 
 Lambda Annotations supports defining custom Lambda authorizers using attributes. Custom authorizers let you control access to your API Gateway endpoints by running a Lambda function that validates tokens or request parameters before the target function is invoked. The source generator automatically wires up the authorizer resources and references in the CloudFormation template.
@@ -1420,6 +1440,8 @@ parameter to the `LambdaFunction` must be the event object and the event source
     * Marks a Lambda function as a REST API (API Gateway V1) custom authorizer. The authorizer name is automatically derived from the method name. Other functions reference it via `RestApi.Authorizer` using `nameof()`. Use the `Type` property to choose between `Token` and `Request` authorizer types.
 * SQSEvent
     * Sets up event source mapping between the Lambda function and SQS queues. The SQS queue ARN is required to be set on the attribute. If users want to pass a reference to an existing SQS queue resource defined in their CloudFormation template, they can pass the SQS queue resource name prefixed with the '@' symbol.
+* ScheduleEvent
+    * Triggers the Lambda function on a schedule using EventBridge. Supports rate and cron expressions.
 * ALBApi
     * Configures the Lambda function to be called from an Application Load Balancer. The listener ARN (or `@ResourceName` template reference), path pattern, and priority are required. The source generator creates standalone CloudFormation resources (TargetGroup, ListenerRule, Lambda Permission) rather than SAM event types.