Adding support for overriding the binding property name in function metadata (#1086)

* Add support for overriding the property name used when building binding entry for function metatdata generation.

* - Bit of cleanup
 - Version bump for Storage.Blobs extension

* Comments cleanup

* Update version of Worker.Extensions.Storage package.

* Clean up based on PR feedback

* Addressing some of PR feedback

* SDK package bump to preview2

* Rebased on main. Fixed release notes in sdk and blob extension

Author: kshyju

extensions/Worker.Extensions.Abstractions/src/BindingPropertyNameAttribute.cs

@@ -0,0 +1,29 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.Azure.Functions.Worker.Extensions.Abstractions
+{
+    /// <summary>
+    /// Specifies the binding property name that is used when generating function metadata.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property)]
+    public sealed class BindingPropertyNameAttribute : Attribute
+    {
+        /// <summary>
+        /// Initializes a new instance of <see cref="BindingPropertyNameAttribute"/> with the specified property name.
+        /// </summary>
+        /// <param name="bindingPropertyName">The name of the property to be used when generating function metadata.</param>
+        /// <exception cref="ArgumentNullException">Throws when bindingPropertyName is null.</exception>
+        public BindingPropertyNameAttribute(string bindingPropertyName)
+        {
+            BindingPropertyName = bindingPropertyName ?? throw new ArgumentNullException(nameof(bindingPropertyName));
+        }
+
+        /// <summary>
+        /// Gets the binding property name to be used for metadata generation.
+        /// </summary>
+        public string BindingPropertyName { get; }
+    }
+}

extensions/Worker.Extensions.Storage.Blobs/release_notes.md

@@ -2,3 +2,4 @@
 <!-- Please add your release notes in the following format:
 - My change description (#PR/#issue)
 -->
+- Overriding binding property name for "BlobPath" property of BlobTrigger (#1086)

extensions/Worker.Extensions.Storage.Blobs/src/BlobTriggerAttribute.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
-using System;
 using Microsoft.Azure.Functions.Worker.Extensions.Abstractions;
 
 namespace Microsoft.Azure.Functions.Worker
@@ -28,6 +27,7 @@ public BlobTriggerAttribute(string blobPath)
         /// The blob portion of the path can contain tokens in curly braces to indicate a pattern to match. The matched
         /// name can be used in other binding attributes to define the output name of a Job function.
         /// </remarks>
+        [BindingPropertyName("path")]
         public string BlobPath
         {
             get { return _blobPath; }

extensions/Worker.Extensions.Storage.Blobs/src/Worker.Extensions.Storage.Blobs.csproj

@@ -6,7 +6,7 @@
     <Description>Azure Blob Storage extensions for .NET isolated functions</Description>
 
     <!--Version information-->
-    <VersionPrefix>5.0.0</VersionPrefix>
+    <VersionPrefix>5.0.1</VersionPrefix>
 
     <!--Temporarily opting out of documentation. Pending documentation-->
     <GenerateDocumentationFile>false</GenerateDocumentationFile>

extensions/Worker.Extensions.Storage/src/Worker.Extensions.Storage.csproj

@@ -6,7 +6,7 @@
     <Description>Azure Storage extensions for .NET isolated functions</Description>
 
     <!--Version information-->
-    <VersionPrefix>5.0.0</VersionPrefix>
+    <VersionPrefix>5.0.1</VersionPrefix>
 
     <!--Temporarily opting out of documentation. Pending documentation-->
     <GenerateDocumentationFile>false</GenerateDocumentationFile>

sdk/Sdk/Constants.cs

@@ -14,6 +14,7 @@ internal static class Constants
         internal const string DefaultValueAttributeType = "Microsoft.Azure.Functions.Worker.Extensions.Abstractions.DefaultValueAttribute";
         internal const string FixedDelayRetryAttributeType = "Microsoft.Azure.Functions.Worker.FixedDelayRetryAttribute";
         internal const string ExponentialBackoffRetryAttributeType = "Microsoft.Azure.Functions.Worker.ExponentialBackoffRetryAttribute";
+        internal const string BindingPropertyNameAttributeType = "Microsoft.Azure.Functions.Worker.Extensions.Abstractions.BindingPropertyNameAttribute";
 
         // System types
         internal const string IEnumerableType = "System.Collections.IEnumerable";

sdk/Sdk/FunctionMetadataGenerator.cs

@@ -54,7 +54,7 @@ public IEnumerable<SdkFunctionMetadata> GenerateFunctionMetadata(string assembly
 
             var functions = new List<SdkFunctionMetadata>();
 
-            _logger.LogMessage($"Found { targetAssemblies.Count} assemblies to evaluate in '{sourcePath}':");
+            _logger.LogMessage($"Found {targetAssemblies.Count} assemblies to evaluate in '{sourcePath}':");
 
             foreach (var path in targetAssemblies)
             {
@@ -202,7 +202,7 @@ private bool TryCreateFunctionMetadata(MethodDefinition method, out SdkFunctionM
             // if a retry attribute is defined, add it to the function.
             if (retryOptions != null)
             {
-                function.Retry = retryOptions;   
+                function.Retry = retryOptions;
             }
 
             return true;
@@ -425,6 +425,54 @@ private static void AddBindingMetadata(IList<ExpandoObject> bindingMetadata, Cus
             bindingMetadata.Add(binding);
         }
 
+        /// <summary>
+        /// Creates a map of property names and its binding property names, if specified from the attribute passed in.
+        /// </summary>
+        /// <remarks>
+        /// Example output generated from BlobTriggerAttribute.
+        ///     {
+        ///         "BlobPath" : "path"
+        ///     }
+        /// 
+        /// In BlobTriggerAttribute type, the "BlobPath" property is decorated with "MetadataBindingPropertyName" attribute
+        /// where "path" is provided as the value to be used when generating metadata binding data, as shown below.
+        ///
+        ///     [MetadataBindingPropertyName("path")]
+        ///     public string BlobPath { get; set; }
+        /// 
+        /// </remarks>
+        /// <param name="attribute">The CustomAttribute instance to use for building the map. This will be a binding attribute
+        /// used to decorate the function parameter. Ex: BlobTrigger</param>
+        /// <returns>A dictionary containing the mapping.</returns>
+        private static IDictionary<string, string> GetPropertyNameAliasMapping(CustomAttribute attribute)
+        {
+            var bindingNameAliasMap = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+            TypeDefinition typeDefinition = attribute.AttributeType.Resolve();
+
+            foreach (var prop in typeDefinition.Properties)
+            {
+                var bindingPropAttr = prop.CustomAttributes.FirstOrDefault(a =>
+                                                    a.AttributeType.FullName.Equals(Constants.BindingPropertyNameAttributeType));
+
+                // The "MetadataBindingPropertyName" attribute has only one constructor which takes the name to be used.
+                var firstArgument = bindingPropAttr?.ConstructorArguments.Single();
+                if (firstArgument?.Value is null)
+                {
+                    continue;
+                }
+
+                if (firstArgument.Value.Value is not string bindingNameArgumentValue)
+                {
+                    throw new ArgumentException(
+                        $"The type {Constants.BindingPropertyNameAttributeType} is expected to have a single constructor with a parameter of type {nameof(String)}");
+                }
+
+                bindingNameAliasMap[prop.Name] = bindingNameArgumentValue;
+            }
+
+            return bindingNameAliasMap;
+        }
+
         private static ExpandoObject BuildBindingMetadataFromAttribute(CustomAttribute attribute, string bindingType, TypeReference parameterType, string? parameterName)
         {
             ExpandoObject binding = new ExpandoObject();
@@ -450,9 +498,18 @@ private static ExpandoObject BuildBindingMetadataFromAttribute(CustomAttribute a
                 bindingDict["DataType"] = "Binary";
             }
 
+            var bindingNameAliasDict = GetPropertyNameAliasMapping(attribute);
+
             foreach (var property in attribute.GetAllDefinedProperties())
             {
-                bindingDict.Add(property.Key, property.Value);
+                var propName = property.Key;
+
+
+                var propertyName = bindingNameAliasDict.TryGetValue(property.Key, out var overriddenPropertyName)
+                    ? overriddenPropertyName
+                    : property.Key;
+
+                bindingDict.Add(propertyName, property.Value);
             }
 
             // Determine if we should set the "Cardinality" property based on
@@ -493,7 +550,7 @@ private static ExpandoObject BuildBindingMetadataFromAttribute(CustomAttribute a
                     else
                     {
                         throw new FunctionsMetadataGenerationException("Function is configured to process events in batches but parameter type is not iterable. " +
-                            $"Change parameter named '{ parameterName }' to be an IEnumerable type or set 'IsBatched' to false on your '{attribute.AttributeType.Name.Replace("Attribute", "")}' attribute.");
+                            $"Change parameter named '{parameterName}' to be an IEnumerable type or set 'IsBatched' to false on your '{attribute.AttributeType.Name.Replace("Attribute", "")}' attribute.");
                     }
                 }
                 // Batching set to false

sdk/Sdk/Sdk.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <MinorProductVersion>8</MinorProductVersion>
-    <VersionSuffix>-preview1</VersionSuffix>
+    <VersionSuffix>-preview2</VersionSuffix>
     <TargetFrameworks>netstandard2.0;net472</TargetFrameworks>
     <PackageId>Microsoft.Azure.Functions.Worker.Sdk</PackageId>
     <Description>This package provides development time support for the Azure Functions .NET Worker.</Description>

sdk/release_notes.md

@@ -2,4 +2,5 @@
 <!-- Please add your release notes in the following format:
 - My change description (#PR/#issue)
 -->
-- Improvements to WebJobsAttributesNotSupported analyzer. (#1092)
+- Improvements to WebJobsAttributesNotSupported analyzer. (#1092)
+- Adding support for overriding the binding property name in function metadata (#1086)

test/DotNetWorkerTests/BindingNameAttributeTest.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using Microsoft.Azure.Functions.Worker.Extensions.Abstractions;
+using Xunit;
+
+namespace Microsoft.Azure.Functions.Worker.Tests
+{
+    public class BindingNameAttributeTest
+    {
+        [Fact]
+        public void Ensure_BindingPropertyNameAttribute_Has_Single_Constructor()
+        {
+            // This test is to ensure that the BindingPropertyNameAttribute constructors are not modified
+            // as our metadata generation code makes the assumption that this type has only one
+            // constructor which accepts the binding property name which is of string type.
+
+            var allConstructors = typeof(BindingPropertyNameAttribute).GetConstructors();
+
+            Assert.Single(allConstructors);
+
+            var constructorParameters = allConstructors[0].GetParameters();
+            Assert.Single(constructorParameters);
+            Assert.Equal(typeof(string), constructorParameters[0].ParameterType);
+        }
+    }
+}