Add [SNSEvent] annotation attribute and source generator support

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

@@ -16,3 +16,4 @@ AWSLambda0128 | AWSLambdaCSharpGenerator | Error | Authorizer Payload Version Mi
 AWSLambda0129 | AWSLambdaCSharpGenerator | Error | Missing LambdaFunction Attribute
 AWSLambda0130 | AWSLambdaCSharpGenerator | Error | Invalid return type IAuthorizerResult
 AWSLambda0131 | AWSLambdaCSharpGenerator | Error | FromBody not supported on Authorizer functions
+AWSLambda0134 | AWSLambdaCSharpGenerator | Error | Invalid SNSEventAttribute

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

@@ -242,5 +242,12 @@ public static class DiagnosticDescriptors
             category: "AWSLambdaCSharpGenerator",
             DiagnosticSeverity.Error,
             isEnabledByDefault: true);
+
+        public static readonly DiagnosticDescriptor InvalidSnsEventAttribute = new DiagnosticDescriptor(id: "AWSLambda0134",
+            title: "Invalid SNSEventAttribute",
+            messageFormat: "Invalid SNSEventAttribute 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.APIGateway;
+using Amazon.Lambda.Annotations.SNS;
 using Amazon.Lambda.Annotations.SQS;
 using Microsoft.CodeAnalysis;
 
@@ -90,6 +91,15 @@ public static AttributeModel Build(AttributeData att, GeneratorExecutionContext
                     Type = TypeModelBuilder.Build(att.AttributeClass, context)
                 };
             }
+            else if (att.AttributeClass.Equals(context.Compilation.GetTypeByMetadataName(TypeFullNames.SNSEventAttribute), SymbolEqualityComparer.Default))
+            {
+                var data = SNSEventAttributeBuilder.Build(att);
+                model = new AttributeModel<Amazon.Lambda.Annotations.SNS.SNSEventAttribute>
+                {
+                    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/SNSEventAttributeBuilder.cs

@@ -0,0 +1,40 @@
+using Amazon.Lambda.Annotations.SNS;
+using Microsoft.CodeAnalysis;
+using System;
+
+namespace Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes
+{
+    /// <summary>
+    /// Builder for <see cref="SNSEventAttribute"/>.
+    /// </summary>
+    public class SNSEventAttributeBuilder
+    {
+        public static SNSEventAttribute Build(AttributeData att)
+        {
+            if (att.ConstructorArguments.Length != 1)
+            {
+                throw new NotSupportedException($"{TypeFullNames.SNSEventAttribute} must have constructor with 1 argument.");
+            }
+            var topic = att.ConstructorArguments[0].Value as string;
+            var data = new SNSEventAttribute(topic);
+
+            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.FilterPolicy) && pair.Value.Value is string filterPolicy)
+                {
+                    data.FilterPolicy = filterPolicy;
+                }
+                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/EventType.cs

@@ -9,6 +9,7 @@ public enum EventType
         API,
         S3,
         SQS,
+        SNS,
         DynamoDB,
         Schedule,
         Authorizer

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

@@ -26,6 +26,10 @@ public static HashSet<EventType> Build(IMethodSymbol lambdaMethodSymbol,
                 {
                     events.Add(EventType.SQS);
                 }
+                else if (attribute.AttributeClass.ToDisplayString() == TypeFullNames.SNSEventAttribute)
+                {
+                    events.Add(EventType.SNS);
+                }
                 else if (attribute.AttributeClass.ToDisplayString() == TypeFullNames.HttpApiAuthorizerAttribute
                     || attribute.AttributeClass.ToDisplayString() == TypeFullNames.RestApiAuthorizerAttribute)
                 {

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

@@ -21,7 +21,8 @@ internal class SyntaxReceiver : ISyntaxContextReceiver
             { "RestApiAuthorizerAttribute", "RestApiAuthorizer" },
             { "HttpApiAttribute", "HttpApi" },
             { "RestApiAttribute", "RestApi" },
-            { "SQSEventAttribute", "SQSEvent" }
+            { "SQSEventAttribute", "SQSEvent" },
+            { "SNSEventAttribute", "SNSEvent" }
         };
 
         public List<MethodDeclarationSyntax> LambdaMethods { get; } = new List<MethodDeclarationSyntax>();

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

@@ -46,6 +46,9 @@ public static class TypeFullNames
         public const string SQSBatchResponse = "Amazon.Lambda.SQSEvents.SQSBatchResponse";
         public const string SQSEventAttribute = "Amazon.Lambda.Annotations.SQS.SQSEventAttribute";
 
+        public const string SNSEvent = "Amazon.Lambda.SNSEvents.SNSEvent";
+        public const string SNSEventAttribute = "Amazon.Lambda.Annotations.SNS.SNSEventAttribute";
+
         public const string LambdaSerializerAttribute = "Amazon.Lambda.Core.LambdaSerializerAttribute";
         public const string DefaultLambdaSerializer = "Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer";
 
@@ -67,7 +70,8 @@ public static class TypeFullNames
         {
             RestApiAttribute,
             HttpApiAttribute,
-            SQSEventAttribute
+            SQSEventAttribute,
+            SNSEventAttribute
         };
     }
 }

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

@@ -2,6 +2,7 @@
 using Amazon.Lambda.Annotations.SourceGenerator.Extensions;
 using Amazon.Lambda.Annotations.SourceGenerator.Models;
 using Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes;
+using Amazon.Lambda.Annotations.SNS;
 using Amazon.Lambda.Annotations.SQS;
 using Microsoft.CodeAnalysis;
 using System.Collections.Generic;
@@ -59,6 +60,7 @@ internal static bool ValidateFunction(GeneratorExecutionContext context, IMethod
             // Validate Events
             ValidateApiGatewayEvents(lambdaFunctionModel, methodLocation, diagnostics);
             ValidateSqsEvents(lambdaFunctionModel, methodLocation, diagnostics);
+            ValidateSnsEvents(lambdaFunctionModel, methodLocation, diagnostics);
 
             return ReportDiagnostics(diagnosticReporter, diagnostics);
         }
@@ -86,6 +88,16 @@ internal static bool ValidateDependencies(GeneratorExecutionContext context, IMe
                 }
             }
 
+            // Check for references to "Amazon.Lambda.SNSEvents" if the Lambda method is annotated with SNSEvent attribute.
+            if (lambdaMethodSymbol.HasAttribute(context, TypeFullNames.SNSEventAttribute))
+            {
+                if (context.Compilation.ReferencedAssemblyNames.FirstOrDefault(x => x.Name == "Amazon.Lambda.SNSEvents") == null)
+                {
+                    diagnosticReporter.Report(Diagnostic.Create(DiagnosticDescriptors.MissingDependencies, methodLocation, "Amazon.Lambda.SNSEvents"));
+                    return false;
+                }
+            }
+
             return true;
         }
 
@@ -268,6 +280,45 @@ private static void ValidateSqsEvents(LambdaFunctionModel lambdaFunctionModel, L
             }
         }
 
+        private static void ValidateSnsEvents(LambdaFunctionModel lambdaFunctionModel, Location methodLocation, List<Diagnostic> diagnostics)
+        {
+            if (!lambdaFunctionModel.LambdaMethod.Events.Contains(EventType.SNS))
+            {
+                return;
+            }
+
+            // Validate SNSEventAttributes
+            foreach (var att in lambdaFunctionModel.Attributes)
+            {
+                if (att.Type.FullName != TypeFullNames.SNSEventAttribute)
+                    continue;
+
+                var snsEventAttribute = ((AttributeModel<SNSEventAttribute>)att).Data;
+                var validationErrors = snsEventAttribute.Validate();
+                validationErrors.ForEach(errorMessage => diagnostics.Add(Diagnostic.Create(DiagnosticDescriptors.InvalidSnsEventAttribute, methodLocation, errorMessage)));
+            }
+
+            // Validate method parameters - When using SNSEventAttribute, the method signature must be (SNSEvent snsEvent) or (SNSEvent snsEvent, ILambdaContext context)
+            var parameters = lambdaFunctionModel.LambdaMethod.Parameters;
+            if (parameters.Count == 0 ||
+                parameters.Count > 2 ||
+                (parameters.Count == 1 && parameters[0].Type.FullName != TypeFullNames.SNSEvent) ||
+                (parameters.Count == 2 && (parameters[0].Type.FullName != TypeFullNames.SNSEvent || parameters[1].Type.FullName != TypeFullNames.ILambdaContext)))
+            {
+                var errorMessage = $"When using the {nameof(SNSEventAttribute)}, the Lambda method can accept at most 2 parameters. " +
+                    $"The first parameter is required and must be of type {TypeFullNames.SNSEvent}. " +
+                    $"The second parameter is optional and must be of type {TypeFullNames.ILambdaContext}.";
+                diagnostics.Add(Diagnostic.Create(DiagnosticDescriptors.InvalidLambdaMethodSignature, methodLocation, errorMessage));
+            }
+
+            // Validate method return type - When using SNSEventAttribute, the return type must be either void or Task
+            if (!lambdaFunctionModel.LambdaMethod.ReturnsVoid && !lambdaFunctionModel.LambdaMethod.ReturnsVoidTask)
+            {
+                var errorMessage = $"When using the {nameof(SNSEventAttribute)}, 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.FileIO;
 using Amazon.Lambda.Annotations.SourceGenerator.Models;
 using Amazon.Lambda.Annotations.SourceGenerator.Models.Attributes;
+using Amazon.Lambda.Annotations.SNS;
 using Amazon.Lambda.Annotations.SQS;
 using Microsoft.CodeAnalysis;
 using System;
@@ -221,6 +222,10 @@ private void ProcessLambdaFunctionEventAttributes(ILambdaFunctionSerializable la
                         eventName = ProcessSqsAttribute(lambdaFunction, sqsAttributeModel.Data, currentSyncedEventProperties);
                         currentSyncedEvents.Add(eventName);
                         break;
+                    case AttributeModel<SNSEventAttribute> snsAttributeModel:
+                        eventName = ProcessSnsAttribute(lambdaFunction, snsAttributeModel.Data, currentSyncedEventProperties);
+                        currentSyncedEvents.Add(eventName);
+                        break;
                 }
             }
 
@@ -596,6 +601,46 @@ private string ProcessSqsAttribute(ILambdaFunctionSerializable lambdaFunction, S
             return att.ResourceName;
         }
 
+        /// <summary>
+        /// Writes all properties associated with <see cref="SNSEventAttribute"/> to the serverless template.
+        /// </summary>
+        private string ProcessSnsAttribute(ILambdaFunctionSerializable lambdaFunction, SNSEventAttribute att, Dictionary<string, List<string>> syncedEventProperties)
+        {
+            var eventName = att.ResourceName;
+            var eventPath = $"Resources.{lambdaFunction.ResourceName}.Properties.Events.{eventName}";
+
+            _templateWriter.SetToken($"{eventPath}.Type", "SNS");
+
+            // Topic - SNS topics use Ref to get the ARN
+            _templateWriter.RemoveToken($"{eventPath}.Properties.Topic");
+            if (!att.Topic.StartsWith("@"))
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Topic", att.Topic);
+            }
+            else
+            {
+                var topic = att.Topic.Substring(1);
+                if (_templateWriter.Exists($"{PARAMETERS}.{topic}"))
+                    SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, $"Topic.{REF}", topic);
+                else
+                    SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, $"Topic.{REF}", topic);
+            }
+
+            // FilterPolicy
+            if (att.IsFilterPolicySet)
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "FilterPolicy", att.FilterPolicy);
+            }
+
+            // Enabled
+            if (att.IsEnabledSet)
+            {
+                SetEventProperty(syncedEventProperties, lambdaFunction.ResourceName, eventName, "Enabled", att.Enabled);
+            }
+
+            return att.ResourceName;
+        }
+
         /// <summary>
         /// Writes all properties associated with <see cref="LambdaFunctionRoleAttribute"/> to the serverless template.
         /// </summary>

Libraries/src/Amazon.Lambda.Annotations/SNS/SNSEventAttribute.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace Amazon.Lambda.Annotations.SNS
+{
+    /// <summary>
+    /// This attribute defines the SNS event source configuration for a Lambda function.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    public class SNSEventAttribute : Attribute
+    {
+        private static readonly Regex _resourceNameRegex = new Regex("^[a-zA-Z0-9]+$");
+
+        /// <summary>
+        /// The SNS topic that will act as the event trigger for the Lambda function.
+        /// This can either be the topic ARN or reference to the SNS topic resource that is already defined in the serverless template.
+        /// To reference an SNS topic resource in the serverless template, prefix the resource name with "@" symbol.
+        /// </summary>
+        public string Topic { get; set; }
+
+        /// <summary>
+        /// The CloudFormation resource name for the SNS event. By default this is set to the SNS topic name if the <see cref="Topic"/> is set to an SNS topic ARN.
+        /// If <see cref="Topic"/> is set to an existing CloudFormation resource, than that is used as the default value without the "@" prefix.
+        /// </summary>
+        public string ResourceName
+        {
+            get
+            {
+                if (IsResourceNameSet)
+                {
+                    return resourceName;
+                }
+                if (Topic.StartsWith("@"))
+                {
+                    return Topic.Substring(1);
+                }
+
+                var arnTokens = Topic.Split(new char[] { ':' }, 6);
+                var topicName = arnTokens[5];
+                var sanitizedTopicName = string.Join(string.Empty, topicName.Where(char.IsLetterOrDigit));
+                return sanitizedTopicName;
+            }
+            set => resourceName = value;
+        }
+
+        private string resourceName { get; set; } = null;
+        internal bool IsResourceNameSet => resourceName != null;
+
+        /// <summary>
+        /// A JSON filter policy that is applied to the SNS subscription.
+        /// Only messages matching the filter policy will be delivered to the Lambda function.
+        /// </summary>
+        public string FilterPolicy { get; set; } = null;
+        internal bool IsFilterPolicySet => FilterPolicy != null;
+
+        /// <summary>
+        /// If set to false, the event source will be disabled.
+        /// Default value is true.
+        /// </summary>
+        public bool Enabled
+        {
+            get => enabled.GetValueOrDefault();
+            set => enabled = value;
+        }
+        private bool? enabled { get; set; }
+        internal bool IsEnabledSet => enabled.HasValue;
+
+        /// <summary>
+        /// Creates an instance of the <see cref="SNSEventAttribute"/> class.
+        /// </summary>
+        /// <param name="topic"><see cref="Topic"/> property</param>
+        public SNSEventAttribute(string topic)
+        {
+            Topic = topic;
+        }
+
+        internal List<string> Validate()
+        {
+            var validationErrors = new List<string>();
+
+            if (!Topic.StartsWith("@"))
+            {
+                var arnTokens = Topic.Split(new char[] { ':' }, 6);
+                if (arnTokens.Length != 6)
+                {
+                    validationErrors.Add($"{nameof(SNSEventAttribute.Topic)} = {Topic}. The SNS topic ARN is invalid. The ARN format is 'arn:<partition>:sns:<region>:<account-id>:<topic-name>'");
+                }
+            }
+            if (IsResourceNameSet && !_resourceNameRegex.IsMatch(ResourceName))
+            {
+                validationErrors.Add($"{nameof(SNSEventAttribute.ResourceName)} = {ResourceName}. It must only contain alphanumeric characters and must not be an empty string");
+            }
+
+            return validationErrors;
+        }
+    }
+}