unify the usage of lazy in ClientProvider (#5469)

Fixes #5470

Author: ArcturusZhang

packages/http-client-csharp/generator/Microsoft.Generator.CSharp.ClientModel/src/Providers/ClientProvider.cs

@@ -41,13 +41,12 @@ private record OAuth2Fields(FieldProvider AuthField, FieldProvider Authorization
 
         private FieldProvider? _apiVersionField;
         private readonly Lazy<IReadOnlyList<ParameterProvider>> _subClientInternalConstructorParams;
-        private IReadOnlyList<Lazy<ClientProvider>>? _subClients;
+        private readonly Lazy<IReadOnlyList<ClientProvider>> _subClients;
         private RestClientProvider? _restClient;
-        private readonly InputParameter[] _allClientParameters;
-        private Lazy<List<FieldProvider>> _additionalClientFields;
+        private readonly IReadOnlyList<InputParameter> _allClientParameters;
+        private Lazy<IReadOnlyList<FieldProvider>> _additionalClientFields;
 
         private Lazy<ParameterProvider?> ClientOptionsParameter { get; }
-        private IReadOnlyList<Lazy<ClientProvider>> SubClients => _subClients ??= GetSubClients();
 
         // for mocking
 #pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
@@ -141,6 +140,7 @@ public ClientProvider(InputClient inputClient)
             _allClientParameters = _inputClient.Parameters.Concat(_inputClient.Operations.SelectMany(op => op.Parameters).Where(p => p.Kind == InputOperationParameterKind.Client)).DistinctBy(p => p.Name).ToArray();
             _subClientInternalConstructorParams = new(GetSubClientInternalConstructorParameters);
             _clientParameters = new(GetClientParameters);
+            _subClients = new(GetSubClients);
         }
 
         private IReadOnlyList<ParameterProvider> GetSubClientInternalConstructorParameters()
@@ -225,18 +225,18 @@ protected override FieldProvider[] BuildFields()
             fields.AddRange(_additionalClientFields.Value);
 
             // add sub-client caching fields
-            foreach (var subClient in SubClients)
+            foreach (var subClient in _subClients.Value)
             {
-                if (subClient.Value.Methods.Count != 0 && subClient.Value._clientCachingField != null)
+                if (subClient.Methods.Count != 0 && subClient._clientCachingField != null)
                 {
-                    fields.Add(subClient.Value._clientCachingField);
+                    fields.Add(subClient._clientCachingField);
                 }
             }
 
             return [.. fields];
         }
 
-        private List<FieldProvider> BuildAdditionalClientFields()
+        private IReadOnlyList<FieldProvider> BuildAdditionalClientFields()
         {
             var fields = new List<FieldProvider>();
             // Add optional client parameters as fields
@@ -452,7 +452,8 @@ [.. primaryCtorOrderedParams.Select(p => p.InitializationValue ?? p)
 
         protected override MethodProvider[] BuildMethods()
         {
-            var subClientCount = SubClients.Count;
+            var subClients = _subClients.Value;
+            var subClientCount = subClients.Count;
             List<MethodProvider> methods = new List<MethodProvider>((_inputClient.Operations.Count * 4) + subClientCount);
 
             // Build methods for all the operations
@@ -474,19 +475,18 @@ protected override MethodProvider[] BuildMethods()
             var parentClientFields = Fields.ToDictionary(f => f.Name.ToVariableName());
 
             // Build factory accessor methods for the sub-clients
-            foreach (var subClient in SubClients)
+            foreach (var subClient in subClients)
             {
-                var subClientInstance = subClient.Value;
-                if (subClientInstance._clientCachingField is null || subClientInstance.Methods.Count == 0)
+                if (subClient._clientCachingField is null || subClient.Methods.Count == 0)
                 {
                     continue;
                 }
 
-                var cachedClientFieldVar = new VariableExpression(subClientInstance.Type, subClientInstance._clientCachingField.Declaration, IsRef: true);
+                var cachedClientFieldVar = new VariableExpression(subClient.Type, subClient._clientCachingField.Declaration, IsRef: true);
                 List<ValueExpression> subClientConstructorArgs = new(3);
 
                 // Populate constructor arguments
-                foreach (var param in subClientInstance._subClientInternalConstructorParams.Value)
+                foreach (var param in subClient._subClientInternalConstructorParams.Value)
                 {
                     if (parentClientProperties.TryGetValue(param.Name, out var parentProperty))
                     {
@@ -501,23 +501,23 @@ protected override MethodProvider[] BuildMethods()
                 // Create the interlocked compare exchange expression for the body
                 var interlockedCompareExchange = Static(typeof(Interlocked)).Invoke(
                     nameof(Interlocked.CompareExchange),
-                    [cachedClientFieldVar, New.Instance(subClientInstance.Type, subClientConstructorArgs), Null]);
-                var factoryMethodName = subClient.Value.Name.EndsWith(ClientSuffix, StringComparison.OrdinalIgnoreCase)
-                    ? $"Get{subClient.Value.Name}"
-                    : $"Get{subClient.Value.Name}{ClientSuffix}";
+                    [cachedClientFieldVar, New.Instance(subClient.Type, subClientConstructorArgs), Null]);
+                var factoryMethodName = subClient.Name.EndsWith(ClientSuffix, StringComparison.OrdinalIgnoreCase)
+                    ? $"Get{subClient.Name}"
+                    : $"Get{subClient.Name}{ClientSuffix}";
 
                 var factoryMethod = new MethodProvider(
                     new(
                         factoryMethodName,
-                        $"Initializes a new instance of {subClientInstance.Type.Name}",
+                        $"Initializes a new instance of {subClient.Type.Name}",
                         MethodSignatureModifiers.Public | MethodSignatureModifiers.Virtual,
-                        subClientInstance.Type,
+                        subClient.Type,
                         null,
                         []),
                     // return Volatile.Read(ref _cachedClient) ?? Interlocked.CompareExchange(ref _cachedClient, new Client(_pipeline, _keyCredential, _endpoint), null) ?? _cachedClient;
                     Return(
                         Static(typeof(Volatile)).Invoke(nameof(Volatile.Read), cachedClientFieldVar)
-                        .NullCoalesce(interlockedCompareExchange.NullCoalesce(subClientInstance._clientCachingField))),
+                        .NullCoalesce(interlockedCompareExchange.NullCoalesce(subClient._clientCachingField))),
                     this);
                 methods.Add(factoryMethod);
             }
@@ -545,18 +545,17 @@ private ParameterProvider BuildClientEndpointParameter()
             };
         }
 
-        // TODO: Update method to be more efficient
-        private IReadOnlyList<Lazy<ClientProvider>> GetSubClients()
+        private IReadOnlyList<ClientProvider> GetSubClients()
         {
             var inputClients = ClientModelPlugin.Instance.InputLibrary.InputNamespace.Clients;
-            var subClients = new List<Lazy<ClientProvider>>(inputClients.Count);
+            var subClients = new List<ClientProvider>(inputClients.Count);
 
             foreach (var client in inputClients)
             {
                 // add direct child clients
                 if (client.Parent != null && client.Parent == _inputClient.Key)
                 {
-                    subClients.Add(new(() => ClientModelPlugin.Instance.TypeFactory.CreateClient(client)));
+                    subClients.Add(ClientModelPlugin.Instance.TypeFactory.CreateClient(client));
                 }
             }