Enable resolution of an alias to its function definition (#1662)

Two caveats:

1. The alias must be set in the runspace, which means the script needs
   to have been executed.
2. The definition is the function itself, not the `Set-Alias` command.

Author: andyleejordan

src/PowerShellEditorServices/Services/PowerShell/Utility/CommandHelpers.cs

@@ -51,8 +51,8 @@ internal static class CommandHelpers
 
         private static readonly ConcurrentDictionary<string, CommandInfo> s_commandInfoCache = new();
         private static readonly ConcurrentDictionary<string, string> s_synopsisCache = new();
-        private static readonly ConcurrentDictionary<string, List<string>> s_cmdletToAliasCache = new(System.StringComparer.OrdinalIgnoreCase);
-        private static readonly ConcurrentDictionary<string, string> s_aliasToCmdletCache = new(System.StringComparer.OrdinalIgnoreCase);
+        internal static readonly ConcurrentDictionary<string, List<string>> s_cmdletToAliasCache = new(System.StringComparer.OrdinalIgnoreCase);
+        internal static readonly ConcurrentDictionary<string, string> s_aliasToCmdletCache = new(System.StringComparer.OrdinalIgnoreCase);
 
         /// <summary>
         /// Gets the CommandInfo instance for a command with a particular name.

src/PowerShellEditorServices/Services/Symbols/SymbolsService.cs

@@ -405,6 +405,20 @@ public async Task<SymbolReference> GetDefinitionOfSymbolAsync(
             Validate.IsNotNull(nameof(sourceFile), sourceFile);
             Validate.IsNotNull(nameof(foundSymbol), foundSymbol);
 
+            // If symbol is an alias, resolve it.
+            (Dictionary<string, List<string>> _, Dictionary<string, string> aliasToCmdlets) =
+                await CommandHelpers.GetAliasesAsync(_executionService).ConfigureAwait(false);
+
+            if (aliasToCmdlets.ContainsKey(foundSymbol.SymbolName))
+            {
+                foundSymbol = new SymbolReference(
+                    foundSymbol.SymbolType,
+                    aliasToCmdlets[foundSymbol.SymbolName],
+                    foundSymbol.ScriptRegion,
+                    foundSymbol.FilePath,
+                    foundSymbol.SourceLine);
+            }
+
             ScriptFile[] referencedFiles =
                 _workspaceService.ExpandScriptReferences(
                     sourceFile);

src/PowerShellEditorServices/Services/Symbols/Vistors/FindDeclarationVisitor.cs

@@ -52,8 +52,10 @@ public override AstVisitAction VisitFunctionDefinition(FunctionDefinitionAst fun
                 File = functionDefinitionAst.Extent.File
             };
 
+            // We compare to the SymbolName instead of its text because it may have been resolved
+            // from an alias.
             if (symbolRef.SymbolType.Equals(SymbolType.Function) &&
-                nameExtent.Text.Equals(symbolRef.ScriptRegion.Text, StringComparison.CurrentCultureIgnoreCase))
+                nameExtent.Text.Equals(symbolRef.SymbolName, StringComparison.CurrentCultureIgnoreCase))
             {
                 this.FoundDeclaration =
                     new SymbolReference(

test/PowerShellEditorServices.Test.Shared/Definition/FindsFunctionDefinitionOfAlias.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.PowerShell.EditorServices.Services.TextDocument;
+
+namespace Microsoft.PowerShell.EditorServices.Test.Shared.Definition
+{
+    public static class FindsFunctionDefinitionOfAliasData
+    {
+        public static readonly ScriptRegion SourceDetails = new(
+            file: TestUtilities.NormalizePath("References/SimpleFile.ps1"),
+            text: string.Empty,
+            startLineNumber: 20,
+            startColumnNumber: 4,
+            startOffset: 0,
+            endLineNumber: 0,
+            endColumnNumber: 0,
+            endOffset: 0);
+    }
+}

test/PowerShellEditorServices.Test.Shared/References/SimpleFile.ps1

@@ -16,3 +16,5 @@ gci
 dir
 Write-Host
 Get-ChildItem
+
+My-Alias

test/PowerShellEditorServices.Test/Language/SymbolsServiceTests.cs

@@ -5,10 +5,13 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Management.Automation;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.PowerShell.EditorServices.Services;
 using Microsoft.PowerShell.EditorServices.Services.PowerShell.Host;
+using Microsoft.PowerShell.EditorServices.Services.PowerShell.Utility;
 using Microsoft.PowerShell.EditorServices.Services.Symbols;
 using Microsoft.PowerShell.EditorServices.Services.TextDocument;
 using Microsoft.PowerShell.EditorServices.Test.Shared;
@@ -44,6 +47,8 @@ public SymbolsServiceTests()
         public void Dispose()
         {
             psesHost.StopAsync().GetAwaiter().GetResult();
+            CommandHelpers.s_cmdletToAliasCache.Clear();
+            CommandHelpers.s_aliasToCmdletCache.Clear();
             GC.SuppressFinalize(this);
         }
 
@@ -126,14 +131,43 @@ public async Task FindsFunctionDefinition()
         }
 
         [Fact]
-         public async Task FindsReferencesOnFunction()
+        public async Task FindsFunctionDefinitionForAlias()
+        {
+            // TODO: Eventually we should get the alises through the AST instead of relying on them
+            // being defined in the runspace.
+            await psesHost.ExecutePSCommandAsync(
+                new PSCommand().AddScript("Set-Alias -Name My-Alias -Value My-Function"),
+                CancellationToken.None).ConfigureAwait(true);
+
+            SymbolReference definitionResult = await GetDefinition(FindsFunctionDefinitionOfAliasData.SourceDetails).ConfigureAwait(true);
+            Assert.Equal(1, definitionResult.ScriptRegion.StartLineNumber);
+            Assert.Equal(10, definitionResult.ScriptRegion.StartColumnNumber);
+            Assert.Equal("My-Function", definitionResult.SymbolName);
+        }
+
+        [Fact]
+        public async Task FindsReferencesOnFunction()
         {
             List<SymbolReference> referencesResult = await GetReferences(FindsReferencesOnFunctionData.SourceDetails).ConfigureAwait(true);
             Assert.Equal(3, referencesResult.Count);
             Assert.Equal(1, referencesResult[0].ScriptRegion.StartLineNumber);
             Assert.Equal(10, referencesResult[0].ScriptRegion.StartColumnNumber);
         }
 
+        [Fact]
+        public async Task FindsReferencesOnFunctionIncludingAliases()
+        {
+            // TODO: Same as in FindsFunctionDefinitionForAlias.
+            await psesHost.ExecutePSCommandAsync(
+                new PSCommand().AddScript("Set-Alias -Name My-Alias -Value My-Function"),
+                CancellationToken.None).ConfigureAwait(true);
+
+            List<SymbolReference> referencesResult = await GetReferences(FindsReferencesOnFunctionData.SourceDetails).ConfigureAwait(true);
+            Assert.Equal(4, referencesResult.Count);
+            Assert.Equal(1, referencesResult[0].ScriptRegion.StartLineNumber);
+            Assert.Equal(10, referencesResult[0].ScriptRegion.StartColumnNumber);
+        }
+
         [Fact]
         public async Task FindsFunctionDefinitionInDotSourceReference()
         {