.Net: Making ContextVariables into a proper Dictionary. (#2852)

### Description
Simplifying ContextVariables by making it into an actual
Dictionary<string, string> instead of a reimplemenation.

### 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 😄
- BREAKING CHANGE - use normal Dictionary methods instead. Behavior
change: retrieving missing values via indexer [key] will throw if
argument is missing, instead of returning string.Empty.

---------

Co-authored-by: Roger Barreto <19890735+RogerBarreto@users.noreply.github.com>

dotnet/src/IntegrationTests/Fakes/EmailSkillFake.cs

@@ -11,7 +11,7 @@ internal sealed class EmailSkillFake
 {
     [SKFunction, Description("Given an email address and message body, send an email")]
     public Task<string> SendEmailAsync(
-        [Description("The body of the email message to send.")] string input,
+        [Description("The body of the email message to send.")] string input = "",
         [Description("The email address to send email to.")] string? email_address = "default@email.com")
     {
         email_address ??= string.Empty;
@@ -20,8 +20,8 @@ internal sealed class EmailSkillFake
 
     [SKFunction, Description("Lookup an email address for a person given a name")]
     public Task<string> GetEmailAddressAsync(
-        [Description("The name of the person to email.")] string input,
-        ILogger logger)
+        ILogger logger,
+        [Description("The name of the person to email.")] string? input = null)
     {
         if (string.IsNullOrEmpty(input))
         {

dotnet/src/IntegrationTests/TemplateLanguage/PromptTemplateEngineTests.cs

@@ -189,7 +189,7 @@ public string MyFunction(string input)
         }
 
         [SKFunction, Description("This is a test"), SKName("asis")]
-        public string MyFunction2(string input)
+        public string? MyFunction2(string? input = null)
         {
             return input;
         }

dotnet/src/Plugins/Plugins.UnitTests/MsGraph/CalendarPluginTests.cs

@@ -225,16 +225,16 @@ public async Task AddEventAsyncWithoutSubjectFailsAsync()
 
         CalendarPlugin target = new(connectorMock.Object);
 
-        // Act
-        var ex = await Assert.ThrowsAsync<ArgumentException>(() => FunctionHelpers.CallViaKernelAsync(target, "AddEvent",
+        // Act & Assert
+        var ex = await Assert.ThrowsAsync<SKException>(() => FunctionHelpers.CallViaKernelAsync(target, "AddEvent",
             ("start", anyStartTime.ToString(CultureInfo.InvariantCulture)),
             ("end", anyEndTime.ToString(CultureInfo.InvariantCulture)),
             ("location", anyLocation),
             ("content", anyContent),
             ("attendees", string.Join(";", anyAttendees)))
         );
 
-        // Assert
-        Assert.Equal("subject", ex.ParamName);
+        Assert.True(ex.InnerException is ArgumentException);
+        Assert.Equal("input", ((ArgumentException)ex.InnerException).ParamName);
     }
 }

dotnet/src/SemanticKernel.Abstractions/Orchestration/ContextVariables.cs

@@ -1,18 +1,11 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System;
-using System.Collections;
-using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using Microsoft.SemanticKernel.Diagnostics;
 
-#pragma warning disable CA1710 // ContextVariables doesn't end in Dictionary or Collection
-#pragma warning disable CA1725, RCS1168 // Uses "name" instead of "key" for some public APIs
-#pragma warning disable CS8767 // Reference type nullability doesn't match because netstandard2.0 surface area isn't nullable reference type annotated
-// TODO: support more complex data types, and plan for rendering these values into prompt templates.
-
 namespace Microsoft.SemanticKernel.Orchestration;
 
 /// <summary>
@@ -21,15 +14,16 @@ namespace Microsoft.SemanticKernel.Orchestration;
 /// </summary>
 [DebuggerDisplay("{DebuggerDisplay,nq}")]
 [DebuggerTypeProxy(typeof(ContextVariables.TypeProxy))]
-public sealed class ContextVariables : IDictionary<string, string>
+public sealed class ContextVariables : Dictionary<string, string>
 {
     /// <summary>
     /// Constructor for context variables.
     /// </summary>
     /// <param name="value">Optional value for the main variable of the context including trust information.</param>
     public ContextVariables(string? value = null)
+        : base(StringComparer.OrdinalIgnoreCase)
     {
-        this._variables[MainKey] = value ?? string.Empty;
+        this.Set(MainKey, value);
     }
 
     /// <summary>
@@ -39,7 +33,7 @@ public ContextVariables(string? value = null)
     public ContextVariables Clone()
     {
         var clone = new ContextVariables();
-        foreach (KeyValuePair<string, string> x in this._variables)
+        foreach (KeyValuePair<string, string> x in this)
         {
             clone.Set(x.Key, x.Value);
         }
@@ -49,7 +43,7 @@ public ContextVariables Clone()
 
     /// <summary>Gets the main input string.</summary>
     /// <remarks>If the main input string was removed from the collection, an empty string will be returned.</remarks>
-    public string Input => this._variables.TryGetValue(MainKey, out string? value) ? value : string.Empty;
+    public string Input => this.TryGetValue(MainKey, out string? value) ? value : string.Empty;
 
     /// <summary>
     /// Updates the main input text with the new value after a function is complete.
@@ -59,30 +53,7 @@ public ContextVariables Clone()
     /// <returns>The current instance</returns>
     public ContextVariables Update(string? value)
     {
-        this._variables[MainKey] = value ?? string.Empty;
-        return this;
-    }
-
-    /// <summary>
-    /// Updates all the local data with new data, merging the two datasets.
-    /// Do not discard old data
-    /// </summary>
-    /// <param name="newData">New data to be merged</param>
-    /// <param name="merge">Whether to merge and keep old data, or replace. False == discard old data.</param>
-    /// <returns>The current instance</returns>
-    public ContextVariables Update(ContextVariables newData, bool merge = true)
-    {
-        if (!object.ReferenceEquals(this, newData))
-        {
-            // If requested, discard old data and keep only the new one.
-            if (!merge) { this._variables.Clear(); }
-
-            foreach (KeyValuePair<string, string> varData in newData._variables)
-            {
-                this._variables[varData.Key] = varData.Value;
-            }
-        }
-
+        this.Set(MainKey, value);
         return this;
     }
 
@@ -98,111 +69,38 @@ public void Set(string name, string? value)
         Verify.NotNullOrWhiteSpace(name);
         if (value != null)
         {
-            this._variables[name] = value;
+            this[name] = value;
         }
         else
         {
-            this._variables.TryRemove(name, out _);
-        }
-    }
-
-    /// <summary>
-    /// Gets the variable value associated with the specified name.
-    /// </summary>
-    /// <param name="name">The name of the variable to get.</param>
-    /// <param name="value">
-    /// When this method returns, contains the variable value associated with the specified name, if the variable is found;
-    /// otherwise, null.
-    /// </param>
-    /// <returns>true if the <see cref="ContextVariables"/> contains a variable with the specified name; otherwise, false.</returns>
-    public bool TryGetValue(string name, [NotNullWhen(true)] out string? value)
-    {
-        if (this._variables.TryGetValue(name, out value))
-        {
-            return true;
-        }
-
-        value = null;
-        return false;
-    }
-
-    /// <summary>
-    /// Array of all variables in the context variables.
-    /// </summary>
-    /// <param name="name">The name of the variable.</param>
-    /// <returns>The value of the variable.</returns>
-    public string this[string name]
-    {
-        get => this._variables[name];
-        set
-        {
-            this._variables[name] = value;
+            this.Remove(name);
         }
     }
 
-    /// <summary>
-    /// Determines whether the <see cref="ContextVariables"/> contains the specified variable.
-    /// </summary>
-    /// <param name="name">The name of the variable to locate.</param>
-    /// <returns>true if the <see cref="ContextVariables"/> contains a variable with the specified name; otherwise, false.</returns>
-    public bool ContainsKey(string name)
-    {
-        return this._variables.ContainsKey(name);
-    }
-
     /// <summary>
     /// Print the processed input, aka the current data after any processing occurred.
     /// </summary>
     /// <returns>Processed input, aka result</returns>
     public override string ToString() => this.Input;
 
-    /// <summary>
-    /// Get an enumerator that iterates through the context variables.
-    /// </summary>
-    /// <returns>An enumerator that iterates through the context variables</returns>
-    public IEnumerator<KeyValuePair<string, string>> GetEnumerator() => this._variables.GetEnumerator();
-
-    IEnumerator IEnumerable.GetEnumerator() => this._variables.GetEnumerator();
-    void IDictionary<string, string>.Add(string key, string value) => ((IDictionary<string, string>)this._variables).Add(key, value);
-    bool IDictionary<string, string>.Remove(string key) => ((IDictionary<string, string>)this._variables).Remove(key);
-    void ICollection<KeyValuePair<string, string>>.Add(KeyValuePair<string, string> item) => ((ICollection<KeyValuePair<string, string>>)this._variables).Add(item);
-    void ICollection<KeyValuePair<string, string>>.Clear() => ((ICollection<KeyValuePair<string, string>>)this._variables).Clear();
-    bool ICollection<KeyValuePair<string, string>>.Contains(KeyValuePair<string, string> item) => ((ICollection<KeyValuePair<string, string>>)this._variables).Contains(item);
-    void ICollection<KeyValuePair<string, string>>.CopyTo(KeyValuePair<string, string>[] array, int arrayIndex) => ((ICollection<KeyValuePair<string, string>>)this._variables).CopyTo(array, arrayIndex);
-    bool ICollection<KeyValuePair<string, string>>.Remove(KeyValuePair<string, string> item) => ((ICollection<KeyValuePair<string, string>>)this._variables).Remove(item);
-    ICollection<string> IDictionary<string, string>.Keys => ((IDictionary<string, string>)this._variables).Keys;
-    ICollection<string> IDictionary<string, string>.Values => ((IDictionary<string, string>)this._variables).Values;
-    int ICollection<KeyValuePair<string, string>>.Count => ((ICollection<KeyValuePair<string, string>>)this._variables).Count;
-    bool ICollection<KeyValuePair<string, string>>.IsReadOnly => ((ICollection<KeyValuePair<string, string>>)this._variables).IsReadOnly;
-    string IDictionary<string, string>.this[string key]
-    {
-        get => ((IDictionary<string, string>)this._variables)[key];
-        set => ((IDictionary<string, string>)this._variables)[key] = value;
-    }
-
     internal const string MainKey = "INPUT";
 
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
     internal string DebuggerDisplay =>
         this.TryGetValue(MainKey, out string? input) && !string.IsNullOrEmpty(input)
-            ? $"Variables = {this._variables.Count}, Input = {input}"
-            : $"Variables = {this._variables.Count}";
+            ? $"Variables = {this.Count}, Input = {input}"
+            : $"Variables = {this.Count}";
 
     #region private ================================================================================
 
-    /// <summary>
-    /// Important: names are case insensitive
-    /// </summary>
-    private readonly ConcurrentDictionary<string, string> _variables = new(StringComparer.OrdinalIgnoreCase);
-
     private sealed class TypeProxy
     {
         private readonly ContextVariables _variables;
 
         public TypeProxy(ContextVariables variables) => this._variables = variables;
 
         [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
-        public KeyValuePair<string, string>[] Items => this._variables._variables.ToArray();
+        public KeyValuePair<string, string>[] Items => this._variables.ToArray();
     }
 
     #endregion

dotnet/src/SemanticKernel.UnitTests/Orchestration/ContextVariablesConverterTests.cs

@@ -26,7 +26,8 @@ public void ReadFromJsonSucceeds()
 
         // Assert
         Assert.Equal("b", result!["a"]);
-        Assert.Equal(string.Empty, result!["INPUT"]);
+        Assert.Throws<KeyNotFoundException>(() => result!["INPUT"]);
+        Assert.Equal(string.Empty, result!.Input);
     }
 
     [Fact]
@@ -60,10 +61,6 @@ public void ReadFromJsonSucceedsWithInput()
     // input value
     // params key/value
     [Theory]
-    [InlineData(null, new[] { "a", "b" }, new[]
-    {
-        /*lang=json,strict*/ @"{""Key"":""INPUT"",""Value"":""""}", /*lang=json,strict*/ @"{""Key"":""a"",""Value"":""b""}"
-    })]
     [InlineData("", new[] { "a", "b" }, new[]
     {
         /*lang=json,strict*/ @"{""Key"":""INPUT"",""Value"":""""}", /*lang=json,strict*/ @"{""Key"":""a"",""Value"":""b""}"
@@ -157,7 +154,8 @@ public void ReadFromJsonReturnsDefaultWithEmpty()
 
         // Assert
         Assert.NotNull(result);
-        Assert.Equal(string.Empty, result!["INPUT"]);
+        Assert.Throws<KeyNotFoundException>(() => result!["INPUT"]);
+        Assert.Equal(string.Empty, result!.Input);
     }
 
     [Fact]

dotnet/src/SemanticKernel.UnitTests/Orchestration/ContextVariablesTests.cs

@@ -248,14 +248,13 @@ public void UpdateOriginalDoesNotAffectClonedSucceeds()
         string anyContent = Guid.NewGuid().ToString();
         string someOtherMainContent = Guid.NewGuid().ToString();
         string someOtherContent = Guid.NewGuid().ToString();
-        ContextVariables target = new();
-        ContextVariables original = new(mainContent);
 
+        ContextVariables original = new(mainContent);
         original.Set(anyName, anyContent);
 
         // Act
         // Clone original into target
-        target.Update(original);
+        ContextVariables target = original.Clone();
         // Update original
         original.Update(someOtherMainContent);
         original.Set(anyName, someOtherContent);

dotnet/src/SemanticKernel/Planning/Plan.cs

@@ -499,7 +499,7 @@ private ContextVariables GetNextStepVariables(ContextVariables variables, Plan s
         var input = string.Empty;
         if (!string.IsNullOrEmpty(step.Parameters.Input))
         {
-            input = this.ExpandFromVariables(variables, step.Parameters.Input);
+            input = this.ExpandFromVariables(variables, step.Parameters.Input!);
         }
         else if (!string.IsNullOrEmpty(variables.Input))
         {

dotnet/src/SemanticKernel/SkillDefinition/NativeFunction.cs

@@ -481,9 +481,10 @@ Task<SKContext> function(ITextCompletion? text, AIRequestSettings? requestSettin
                 }
 
                 // 4. Otherwise, fail.
-                throw new SKException($"Missing value for parameter '{name}'");
+                throw new SKException($"Missing value for parameter '{name}'",
+                    new ArgumentException("Missing value function parameter", name));
 
-                object? Process(string value)
+                object ? Process(string value)
                 {
                     if (type == typeof(string))
                     {