From dd3a6a10d4e835f4d2d442623b1d93123a4ae9bb Mon Sep 17 00:00:00 2001
From: Ilya <darpa@yandex.ru>
Date: Tue, 11 Oct 2022 23:50:16 +0500
Subject: [PATCH] Use source generator for `PSVersionInfo` to improve startup
 time (#15603)

---
 PowerShell.Common.props                       |   3 +
 .../PSVersionInfoGenerator.cs                 | 130 ++++++++++++++++++
 .../PSVersionInfoGenerator.csproj             |  18 +++
 .../System.Management.Automation.csproj       |  23 +++-
 .../engine/PSVersionInfo.cs                   |  58 +++-----
 5 files changed, 190 insertions(+), 42 deletions(-)
 create mode 100644 src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.cs
 create mode 100644 src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.csproj

diff --git a/PowerShell.Common.props b/PowerShell.Common.props
index 5e7e41f147..8f784ede51 100644
--- a/PowerShell.Common.props
+++ b/PowerShell.Common.props
@@ -104,6 +104,9 @@
 
     </PropertyGroup>
 
+    <!-- Remove existing generated files by source generators because new source code will soon be generated when the build starts -->
+    <RemoveDir Directories="gen\SourceGenerated" Condition="Exists('gen\SourceGenerated')" />
+
     <!-- Output For Debugging
       <WriteLinesToFile File="targetfile1.txt"
         Lines="ReleaseTag=$(ReleaseTag);
diff --git a/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.cs b/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.cs
new file mode 100644
index 0000000000..6f5b47cca0
--- /dev/null
+++ b/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.cs
@@ -0,0 +1,130 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System;
+using System.Globalization;
+using Microsoft.CodeAnalysis;
+
+namespace SMA
+{
+    /// <summary>
+    /// Source Code Generator to create partial PSVersionInfo class.
+    /// </summary>
+    [Generator]
+    public class PSVersionInfoGenerator : ISourceGenerator
+    {
+        /// <summary>
+        /// Generate output PSVersionInfo.g.cs file.
+        /// This allows to directly get ProductVersion and others without reflection.
+        /// </summary>
+        /// <param name="context">Generator execution context.</param>
+        public void Execute(GeneratorExecutionContext context)
+        {
+            var result = CreatePSVersionInfoPartialClass(context);
+
+            // We must use specific file name suffix (*.g.cs,*.g, *.i.cs, *.generated.cs, *.designer.cs)
+            // so that Roslyn analyzers skip the file.
+            context.AddSource("PSVersionInfo.g.cs", result);
+        }
+
+        /// <summary>
+        /// Not used.
+        /// </summary>
+        /// <param name="context">Generator initialization context.</param>
+        public void Initialize(GeneratorInitializationContext context)
+        {
+            // No initialization required for this one.
+        }
+
+        /// <summary>
+        /// Generate source code for the partial PSVersionInfo class.
+        /// </summary>
+        /// <param name="context">Generator execution context.</param>
+        /// <returns>A string with partial PSVersionInfo class.</returns>
+        private static string CreatePSVersionInfoPartialClass(GeneratorExecutionContext context)
+        {
+            // We must put "<auto-generated" on first line so that Roslyng analyzers skip the file.
+            const string SourceTemplate = @"// <auto-generated>
+// This file is auto-generated by PSVersionInfoGenerator.
+// </auto-generated>
+
+namespace System.Management.Automation
+{{
+    public static partial class PSVersionInfo
+    {{
+        // Defined in 'PowerShell.Common.props' as 'ProductVersion'
+        // Example:
+        //  - when built from a commit:              ProductVersion = '7.3.0-preview.8 Commits: 29 SHA: 52c6b...'
+        //  - when built from a preview release tag: ProductVersion = '7.3.0-preview.8 SHA: f1ec9...'
+        //  - when built from a stable release tag:  ProductVersion = '7.3.0 SHA: f1ec9...'
+        internal const string ProductVersion = ""{0}"";
+
+        // The git commit id that the build is based off.
+        // Defined in 'PowerShell.Common.props' as 'PowerShellVersion' or 'ReleaseTag',
+        // depending on whether the '-ReleaseTag' is specified when building.
+        // Example:
+        //  - when built from a commit:              GitCommitId = '7.3.0-preview.8-29-g52c6b...'
+        //  - when built from a preview release tag: GitCommitId = '7.3.0-preview.8'
+        //  - when built from a stable release tag:  GitCommitId = '7.3.0'
+        internal const string GitCommitId = ""{1}"";
+
+        // The PowerShell version components.
+        // The version string is defined in 'PowerShell.Common.props' as 'PSCoreBuildVersion',
+        // but we break it into components to save the overhead of parsing at runtime.
+        // Example:
+        //  - '7.3.0-preview.8' for preview release or private build
+        //  - '7.3.0' for stable release
+        private const int Version_Major = {2};
+        private const int Version_Minor = {3};
+        private const int Version_Patch = {4};
+        private const string Version_Label = ""{5}"";
+    }}
+}}";
+
+            context.AnalyzerConfigOptions.GlobalOptions.TryGetValue("build_property.ProductVersion", out var productVersion);
+            context.AnalyzerConfigOptions.GlobalOptions.TryGetValue("build_property.PSCoreBuildVersion", out var mainVersion);
+            context.AnalyzerConfigOptions.GlobalOptions.TryGetValue("build_property.PowerShellVersion", out var gitDescribe);
+            context.AnalyzerConfigOptions.GlobalOptions.TryGetValue("build_property.ReleaseTag", out var releaseTag);
+
+            string gitCommitId = string.IsNullOrEmpty(releaseTag) ? gitDescribe : releaseTag;
+            if (gitCommitId.StartsWith("v"))
+            {
+                gitCommitId = gitCommitId.Substring(1);
+            }
+
+            var result = ParsePSVersion(mainVersion);
+
+            return string.Format(
+                CultureInfo.InvariantCulture,
+                SourceTemplate,
+                productVersion,
+                gitCommitId,
+                result.major,
+                result.minor,
+                result.patch,
+                result.preReleaseLabel);
+        }
+
+        private static (int major, int minor, int patch, string preReleaseLabel) ParsePSVersion(string mainVersion)
+        {
+            // We only handle the pre-defined PSVersion format here, e.g. 7.x.x or 7.x.x-preview.x
+            int dashIndex = mainVersion.IndexOf('-');
+            bool hasLabel = dashIndex != -1;
+            string preReleaseLabel = hasLabel ? mainVersion.Substring(dashIndex + 1) : string.Empty;
+
+            if (hasLabel)
+            {
+                mainVersion = mainVersion.Substring(0, dashIndex);
+            }
+
+            int majorEnd = mainVersion.IndexOf('.');
+            int minorEnd = mainVersion.LastIndexOf('.');
+
+            int major = int.Parse(mainVersion.Substring(0, majorEnd), NumberStyles.Integer, CultureInfo.InvariantCulture);
+            int minor = int.Parse(mainVersion.Substring(majorEnd + 1, minorEnd - majorEnd - 1), NumberStyles.Integer, CultureInfo.InvariantCulture);
+            int patch = int.Parse(mainVersion.Substring(minorEnd + 1), NumberStyles.Integer, CultureInfo.InvariantCulture);
+
+            return (major, minor, patch, preReleaseLabel);
+        }
+    }
+}
diff --git a/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.csproj b/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.csproj
new file mode 100644
index 0000000000..5b9c4cffff
--- /dev/null
+++ b/src/System.Management.Automation/SourceGenerators/PSVersionInfoGenerator/PSVersionInfoGenerator.csproj
@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
+  <PropertyGroup>
+    <Description>Generate code for SMA using source generator</Description>
+    <AssemblyName>SMA.Generator</AssemblyName>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <!-- source generator project needs to target 'netstandard2.0' -->
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <LangVersion>10.0</LangVersion>
+    <SuppressNETCoreSdkPreviewMessage>true</SuppressNETCoreSdkPreviewMessage>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.3.1" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.3" PrivateAssets="all" />
+  </ItemGroup>
+</Project>
diff --git a/src/System.Management.Automation/System.Management.Automation.csproj b/src/System.Management.Automation/System.Management.Automation.csproj
index 75deb301ba..17938e9294 100644
--- a/src/System.Management.Automation/System.Management.Automation.csproj
+++ b/src/System.Management.Automation/System.Management.Automation.csproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
+<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <Import Project="..\..\PowerShell.Common.props" />
   <PropertyGroup>
     <Description>PowerShell's System.Management.Automation project</Description>
@@ -6,6 +6,24 @@
     <AssemblyName>System.Management.Automation</AssemblyName>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <!-- we persist source generator files under 'gen' folder so that they are visible to IDEs -->
+    <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
+    <CompilerGeneratedFilesOutputPath>gen\SourceGenerated</CompilerGeneratedFilesOutputPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- these properties are declared in 'PowerShell.Common.props' and used by source generator -->
+    <CompilerVisibleProperty Include="ProductVersion" />
+    <CompilerVisibleProperty Include="PSCoreBuildVersion" />
+    <CompilerVisibleProperty Include="PowerShellVersion" />
+    <CompilerVisibleProperty Include="ReleaseTag" />
+
+    <ProjectReference Include="SourceGenerators\PSVersionInfoGenerator\PSVersionInfoGenerator.csproj"
+                      OutputItemType="Analyzer"
+                      ReferenceOutputAssembly="false" />
+  </ItemGroup>
+
   <ItemGroup Condition=" '$(IsWindows)' == 'true' ">
     <ProjectReference Include="..\Microsoft.PowerShell.CoreCLR.Eventing\Microsoft.PowerShell.CoreCLR.Eventing.csproj" />
   </ItemGroup>
@@ -38,6 +56,9 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <!-- exclude code of source generators from compilation and IDEs (e.g. vscode and visual studio) -->
+    <Compile Remove="SourceGenerators\**\*.cs" />
+
     <Compile Remove="cimSupport\cmdletization\xml\cmdlets-over-objects.objectModel.autogen.cs" />
     <Compile Remove="cimSupport\cmdletization\xml\cmdlets-over-objects.xmlSerializer.autogen.cs" />
     <Compile Remove="engine\TransactedString.cs" />
diff --git a/src/System.Management.Automation/engine/PSVersionInfo.cs b/src/System.Management.Automation/engine/PSVersionInfo.cs
index 169024508e..620577d8d4 100644
--- a/src/System.Management.Automation/engine/PSVersionInfo.cs
+++ b/src/System.Management.Automation/engine/PSVersionInfo.cs
@@ -3,7 +3,6 @@
 
 using System.Collections;
 using System.Globalization;
-using System.Reflection;
 using System.Text;
 using System.Text.RegularExpressions;
 
@@ -27,7 +26,7 @@ namespace System.Management.Automation
     /// The above statement retrieves the PowerShell edition.
     /// </para>
     /// </summary>
-    public static class PSVersionInfo
+    public static partial class PSVersionInfo
     {
         internal const string PSVersionTableName = "PSVersionTable";
         internal const string PSRemotingProtocolVersionName = "PSRemotingProtocolVersion";
@@ -42,6 +41,18 @@ namespace System.Management.Automation
 
         private static readonly PSVersionHashTable s_psVersionTable;
 
+        /*
+            The following constants are generated by the source generator 'PSVersionInfoGenerator':
+
+                internal const string ProductVersion;
+                internal const string GitCommitId;
+
+                private const int Version_Major
+                private const int Version_Minor;
+                private const int Version_Patch;
+                private const string Version_Label;
+        */
+
         /// <summary>
         /// A constant to track current PowerShell Version.
         /// </summary>
@@ -78,39 +89,14 @@ namespace System.Management.Automation
         {
             s_psVersionTable = new PSVersionHashTable(StringComparer.OrdinalIgnoreCase);
 
-            Assembly currentAssembly = typeof(PSVersionInfo).Assembly;
-            ProductVersion = currentAssembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion;
-
-            // Get 'GitCommitId' and 'PSVersion' from the 'productVersion' assembly attribute.
-            //
-            // The strings can be one of the following format examples:
-            //    when powershell is built from a commit:
-            //      productVersion = '6.0.0-beta.7 Commits: 29 SHA: 52c6b...' convert to GitCommitId = 'v6.0.0-beta.7-29-g52c6b...'
-            //                                                                           PSVersion   = '6.0.0-beta.7'
-            //    when powershell is built from a release tag:
-            //      productVersion = '6.0.0-beta.7 SHA: f1ec9...'             convert to GitCommitId = 'v6.0.0-beta.7'
-            //                                                                           PSVersion   = '6.0.0-beta.7'
-            //    when powershell is built from a release tag for RTM:
-            //      productVersion = '6.0.0 SHA: f1ec9...'                    convert to GitCommitId = 'v6.0.0'
-            //                                                                           PSVersion   = '6.0.0'
-            string rawGitCommitId;
-            string mainVersion = ProductVersion.Substring(0, ProductVersion.IndexOf(' '));
-
-            if (ProductVersion.Contains(" Commits: "))
-            {
-                rawGitCommitId = ProductVersion.Replace(" Commits: ", "-").Replace(" SHA: ", "-g");
-            }
-            else
-            {
-                rawGitCommitId = mainVersion;
-            }
-
-            s_psSemVersion = new SemanticVersion(mainVersion);
+            s_psSemVersion = Version_Label == string.Empty
+                ? new SemanticVersion(Version_Major, Version_Minor, Version_Patch)
+                : new SemanticVersion(Version_Major, Version_Minor, Version_Patch, Version_Label, buildLabel: null);
             s_psVersion = (Version)s_psSemVersion;
 
             s_psVersionTable[PSVersionName] = s_psSemVersion;
             s_psVersionTable[PSEditionName] = PSEditionValue;
-            s_psVersionTable[PSGitCommitIdName] = rawGitCommitId;
+            s_psVersionTable[PSGitCommitIdName] = GitCommitId;
             s_psVersionTable[PSCompatibleVersionsName] = new Version[] { s_psV1Version, s_psV2Version, s_psV3Version, s_psV4Version, s_psV5Version, s_psV51Version, s_psV6Version, s_psV61Version, s_psV62Version, s_psV7Version, s_psV71Version, s_psV72Version, s_psVersion };
             s_psVersionTable[SerializationVersionName] = new Version(InternalSerializer.DefaultVersion);
             s_psVersionTable[PSRemotingProtocolVersionName] = RemotingConstants.ProtocolVersion;
@@ -183,16 +169,6 @@ namespace System.Management.Automation
             }
         }
 
-        internal static string ProductVersion { get; }
-
-        internal static string GitCommitId
-        {
-            get
-            {
-                return (string)s_psVersionTable[PSGitCommitIdName];
-            }
-        }
-
         /// <summary>
         /// Gets the edition of PowerShell.
         /// </summary>