.Net: Obsolete the useless SetDefaultFunctionCollection (microsoft#3183)

### Description

`ISKFunction` exposes a `SetDefaultFunctionCollection`. On all
implementations it's either a nop or just delegates to the same
interface method on a wrapped object. The one exception to that is
`SemanticFunction`, which stores the argument into a field _that then is
never used_.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>

dotnet/src/Functions/Functions.Semantic/Extensions/KernelSemanticFunctionExtensions.cs

@@ -286,10 +286,6 @@ private static ISKFunction CreateSemanticFunction(
             kernel.LoggerFactory
         );
 
-        // Connect the function to the current kernel function collection, in case the function
-        // is invoked manually without a context and without a way to find other functions.
-        func.SetDefaultFunctionCollection(kernel.Functions);
-
         func.SetAIConfiguration(promptTemplateConfig.GetDefaultRequestSettings());
 
         // Note: the service is instantiated using the kernel configuration state when the function is invoked

dotnet/src/Functions/Functions.Semantic/SemanticFunction.cs

@@ -96,13 +96,6 @@ public async Task<FunctionResult> InvokeAsync(
         return await this.RunPromptAsync(this._aiService?.Value, requestSettings ?? this.RequestSettings, context, cancellationToken).ConfigureAwait(false);
     }
 
-    /// <inheritdoc/>
-    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions)
-    {
-        this._functionCollection = functions;
-        return this;
-    }
-
     /// <inheritdoc/>
     public ISKFunction SetAIService(Func<ITextCompletion> serviceFactory)
     {
@@ -169,7 +162,6 @@ internal SemanticFunction(
     private static readonly JsonSerializerOptions s_toStringStandardSerialization = new();
     private static readonly JsonSerializerOptions s_toStringIndentedSerialization = new() { WriteIndented = true };
     private readonly ILogger _logger;
-    private IReadOnlyFunctionCollection? _functionCollection;
     private Lazy<ITextCompletion>? _aiService;
     private readonly Lazy<FunctionView> _view;
     public IPromptTemplate _promptTemplate { get; }
@@ -244,9 +236,14 @@ private async Task<FunctionResult> RunPromptAsync(
     public bool IsSemantic => true;
 
     /// <inheritdoc/>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this;
+
+    /// <inheritdoc/>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this.SetDefaultFunctionCollection(skills);
+    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) => this;
 
     #endregion
 }

dotnet/src/SemanticKernel.Abstractions/Functions/ISKFunction.cs

@@ -56,14 +56,6 @@ Task<FunctionResult> InvokeAsync(
         AIRequestSettings? requestSettings = null,
         CancellationToken cancellationToken = default);
 
-    /// <summary>
-    /// Set the default function collection to use when the function is invoked
-    /// without a context or with a context that doesn't have a collection.
-    /// </summary>
-    /// <param name="functions">Kernel's function collection</param>
-    /// <returns>Self instance</returns>
-    ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions);
-
     /// <summary>
     /// Set the AI service used by the semantic function, passing a factory method.
     /// The factory allows to lazily instantiate the client and to properly handle its disposal.
@@ -94,10 +86,20 @@ Task<FunctionResult> InvokeAsync(
     /// </summary>
     /// <param name="skills">Kernel's function collection</param>
     /// <returns>Self instance</returns>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
     ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills);
 
+    /// <summary>
+    /// Set the default function collection to use when the function is invoked
+    /// without a context or with a context that doesn't have a collection.
+    /// </summary>
+    /// <param name="functions">Kernel's function collection</param>
+    /// <returns>Self instance</returns>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions);
+
     /// <summary>
     /// Whether the function is defined using a prompt template.
     /// IMPORTANT: native functions might use semantic functions internally,

dotnet/src/SemanticKernel.Core/Functions/InstrumentedSKFunction.cs

@@ -86,10 +86,6 @@ public ISKFunction SetAIConfiguration(AIRequestSettings? requestSettings) =>
     public ISKFunction SetAIService(Func<ITextCompletion> serviceFactory) =>
         this._function.SetAIService(serviceFactory);
 
-    /// <inheritdoc/>
-    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) =>
-        this._function.SetDefaultFunctionCollection(functions);
-
     #region private ================================================================================
 
     private readonly ISKFunction _function;
@@ -189,9 +185,14 @@ private async Task<FunctionResult> InvokeWithInstrumentationAsync(Func<Task<Func
     public bool IsSemantic => this._function.IsSemantic;
 
     /// <inheritdoc/>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this;
+
+    /// <inheritdoc/>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this._function.SetDefaultFunctionCollection(skills);
+    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) => this;
 
     #endregion
 }

dotnet/src/SemanticKernel.Core/Functions/NativeFunction.cs

@@ -150,14 +150,6 @@ public async Task<FunctionResult> InvokeAsync(
         }
     }
 
-    /// <inheritdoc/>
-    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions)
-    {
-        // No-op for native functions; do not throw, as both Plan and PromptFunctions use this,
-        // and we don't have a way to distinguish between a native function and a Plan.
-        return this;
-    }
-
     /// <inheritdoc/>
     public ISKFunction SetAIService(Func<ITextCompletion> serviceFactory)
     {
@@ -892,9 +884,14 @@ private static string SanitizeMetadataName(string methodName) =>
     public bool IsSemantic => true;
 
     /// <inheritdoc/>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this;
+
+    /// <inheritdoc/>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this.SetDefaultFunctionCollection(skills);
+    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) => this;
 
     #endregion
 }

dotnet/src/SemanticKernel.Core/Kernel.cs

@@ -90,7 +90,6 @@ public ISKFunction RegisterCustomFunction(ISKFunction customFunction)
     {
         Verify.NotNull(customFunction);
 
-        customFunction.SetDefaultFunctionCollection(this.Functions);
         this._functionCollection.AddFunction(customFunction);
 
         return customFunction;

dotnet/src/SemanticKernel.Core/Planning/InstrumentedPlan.cs

@@ -68,10 +68,6 @@ public ISKFunction SetAIConfiguration(AIRequestSettings? requestSettings) =>
     public ISKFunction SetAIService(Func<ITextCompletion> serviceFactory) =>
         this._plan.SetAIService(serviceFactory);
 
-    /// <inheritdoc/>
-    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) =>
-        this._plan.SetDefaultFunctionCollection(functions);
-
     #region private ================================================================================
 
     private readonly IPlan _plan;
@@ -170,9 +166,14 @@ private async Task<FunctionResult> InvokeWithInstrumentationAsync(Func<Task<Func
     public bool IsSemantic => this._plan.IsSemantic;
 
     /// <inheritdoc/>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this;
+
+    /// <inheritdoc/>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this._plan.SetDefaultFunctionCollection(skills);
+    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) => this;
 
     #endregion
 }

dotnet/src/SemanticKernel.Core/Planning/Plan.cs

@@ -359,12 +359,6 @@ public async Task<FunctionResult> InvokeAsync(
         return result;
     }
 
-    /// <inheritdoc/>
-    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions)
-    {
-        return this.Function is not null ? this.Function.SetDefaultFunctionCollection(functions) : this;
-    }
-
     /// <inheritdoc/>
     public ISKFunction SetAIService(Func<ITextCompletion> serviceFactory)
     {
@@ -656,9 +650,14 @@ private string DebuggerDisplay
     public bool IsSemantic { get; private set; }
 
     /// <inheritdoc/>
-    [Obsolete("Methods, properties and classes which include Skill in the name have been renamed. Use ISKFunction.SetDefaultFunctionCollection instead. This will be removed in a future release.")]
+    [Obsolete("This method is a nop and will be removed in a future release.")]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this;
+
+    /// <inheritdoc/>
+    [Obsolete("This method is a nop and will be removed in a future release.")]
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public ISKFunction SetDefaultSkillCollection(IReadOnlyFunctionCollection skills) => this.SetDefaultFunctionCollection(skills);
+    public ISKFunction SetDefaultFunctionCollection(IReadOnlyFunctionCollection functions) => this;
 
     #endregion
 }