Auto-remove manual NuGet.* version pins on future major versions

src/Fallout.Migrate/Migration.cs

@@ -27,6 +27,8 @@ internal sealed class Migration(AbsolutePath rootDirectory, bool dryRun, TextWri
         new VerifyBuildTargetFrameworkStep(),
         new ConfirmMigrationStep(),
         new RewriteCsprojsStep(),
+        new RemoveNugetFrameworkPinStep(),
+        new RemoveRelatedNugetPinsStep(),
         new BumpDotNetVersionStep(),
         new RewriteCsFilesStep(),
         new RewriteBootstrapScriptsStep(),

src/Fallout.Migrate/Steps/RemoveNugetFrameworkPinStep.cs

@@ -0,0 +1,113 @@
+using System;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using Fallout.Migrate.Common;
+
+namespace Fallout.Migrate.Steps;
+
+/// <summary>
+/// Removes explicit <c>NuGet.Frameworks</c> package pins from project files. The pins are no longer needed.
+/// </summary>
+internal sealed class RemoveNugetFrameworkPinStep : IMigrationStep
+{
+    /// <summary>
+    /// Matches an entire single-line, self-closing
+    /// <c>PackageReference</c> element for <c>NuGet.Frameworks</c>
+    /// that explicitly declares a non-empty <c>Version</c> attribute,
+    /// including its indentation and trailing line ending.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Intended for removing explicitly versioned
+    /// <c>NuGet.Frameworks</c> package references from MSBuild XML
+    /// files such as <c>.csproj</c>, <c>.props</c>, and <c>.targets</c>.
+    /// </para>
+    /// <para>
+    /// The <c>Include</c> and <c>Version</c> attributes may appear
+    /// in any order. Additional attributes, such as
+    /// <c>PrivateAssets</c>, are allowed before, between, or after
+    /// the required attributes.
+    /// </para>
+    /// <para>
+    /// Matching requirements:
+    /// </para>
+    /// <list type="bullet">
+    ///   <item>
+    ///     <description>
+    ///       The element must begin on a line containing only optional
+    ///       leading spaces or tabs.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must contain
+    ///       <c>Include="NuGet.Frameworks"</c>.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must contain a non-empty
+    ///       <c>Version="..."</c> attribute.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must be self-closing and contained on one line.
+    ///     </description>
+    ///   </item>
+    /// </list>
+    /// <para>
+    /// The expression consumes the entire matching line, including
+    /// its indentation, optional trailing whitespace, and line
+    /// ending (if present). Replacing matches with an empty string
+    /// therefore removes the package reference without leaving
+    /// an empty line.
+    /// </para>
+    /// <para>
+    /// <b>Example:</b>
+    /// </para>
+    /// <code>
+    /// &lt;PackageReference Version="7.9.0" PrivateAssets="all" Include="NuGet.Frameworks" /&gt;
+    /// </code>
+    /// <para>
+    /// <b>Limitations:</b>
+    /// The expression is case-sensitive, supports double-quoted
+    /// attributes only, and does not match multiline elements.
+    /// It does not validate XML structure or NuGet version syntax
+    /// and may match package references inside XML comments.
+    /// </para>
+    /// </remarks>
+    private static readonly Regex explicitPinPattern = new(
+        @"^[ \t]*<PackageReference\b(?=[^\r\n>]*[ \t]Include=""NuGet\.Frameworks"")(?=[^\r\n>]*[ \t]Version=""[^""]+"")[^\r\n>]*?/>[ \t]*(?:\r?\n|$)",
+        RegexOptions.Compiled | RegexOptions.Multiline);
+
+    /// <inheritdoc />
+    public Task ExecuteAsync(MigrationContext context, Summary summary)
+    {
+        Version.TryParse(context.FalloutVersion, out var versionGate);
+
+        if (versionGate < Version.Parse("10.5.0"))
+        {
+            return Task.CompletedTask;
+        }
+
+        foreach (var path in MigrationFileOperations.EnumerateFiles(context.RootDirectory, "_build.csproj"))
+        {
+            MigrationFileOperations.ApplyRewrite(context, path, Rewrite, summary);
+        }
+
+        return Task.CompletedTask;
+    }
+
+    private static RewriteResult Rewrite(string original)
+    {
+        var edits = 0;
+        var content = explicitPinPattern.Replace(original, _ =>
+        {
+            edits++;
+            return string.Empty;
+        });
+
+        return new RewriteResult(content, edits);
+    }
+}

src/Fallout.Migrate/Steps/RemoveRelatedNugetPinsStep.cs

@@ -0,0 +1,151 @@
+using System.Globalization;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using Fallout.Migrate.Common;
+
+namespace Fallout.Migrate.Steps;
+
+/// <summary>
+/// Removes explicit <c>NuGet.Protocol</c>, <c>NuGet.Packaging</c>, and <c>NuGet.Resolver</c>
+/// package pins from project files when migrating to Fallout 11 or later.
+/// </summary>
+internal sealed class RemoveRelatedNugetPinsStep : IMigrationStep
+{
+    /// <summary>
+    /// The minimum Fallout major version that requires this step. On migrations below that version ths step is skipped.
+    /// </summary>
+    private const int MinimumFalloutMajor = 11;
+
+    /// <summary>
+    /// Matches an entire single-line, self-closing
+    /// <c>PackageReference</c> element for <c>NuGet.Protocol</c>,
+    /// <c>NuGet.Packaging</c>, or <c>NuGet.Resolver</c> that explicitly
+    /// declares a non-empty <c>Version</c> attribute, including its
+    /// indentation and trailing line ending.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Intended for removing explicitly versioned NuGet package
+    /// references from MSBuild XML files such as <c>.csproj</c>,
+    /// <c>.props</c>, and <c>.targets</c>.
+    /// </para>
+    /// <para>
+    /// The <c>Include</c> and <c>Version</c> attributes may appear
+    /// in any order. Additional attributes, such as
+    /// <c>PrivateAssets</c>, are allowed before, between, or after
+    /// the required attributes.
+    /// </para>
+    /// <para>
+    /// Matching requirements:
+    /// </para>
+    /// <list type="bullet">
+    ///   <item>
+    ///     <description>
+    ///       The element must begin on a line containing only optional
+    ///       leading spaces or tabs.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must contain an <c>Include</c> attribute
+    ///       identifying one of the following packages:
+    ///       <c>NuGet.Protocol</c>, <c>NuGet.Packaging</c>,
+    ///       or <c>NuGet.Resolver</c>.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must contain a non-empty
+    ///       <c>Version="..."</c> attribute.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <description>
+    ///       The element must be self-closing and contained on one line.
+    ///     </description>
+    ///   </item>
+    /// </list>
+    /// <para>
+    /// Two positive lookaheads independently verify the package name
+    /// and version attribute. Their positions allow either attribute
+    /// to appear first, with arbitrary additional attributes between
+    /// them.
+    /// </para>
+    /// <para>
+    /// The expression consumes the entire matching line, including
+    /// its indentation, optional trailing whitespace, and line
+    /// ending (if present). Replacing matches with an empty string
+    /// therefore removes the package reference without leaving
+    /// an empty line.
+    /// </para>
+    /// <para>
+    /// <b>Matching examples:</b>
+    /// </para>
+    /// <code>
+    /// &lt;PackageReference Include="NuGet.Protocol" Version="6.0.0" /&gt;
+    /// &lt;PackageReference Version="7.9.0" Include="NuGet.Packaging" /&gt;
+    /// &lt;PackageReference Version="7.9.0" PrivateAssets="all" Include="NuGet.Resolver" /&gt;
+    /// &lt;PackageReference Include="NuGet.Protocol" PrivateAssets="all" Version="6.0.0" /&gt;
+    /// </code>
+    /// <para>
+    /// <b>Limitations:</b>
+    /// Matching is case-sensitive and supports double-quoted
+    /// attributes only. Multiline elements are not supported.
+    /// The expression does not validate XML structure or NuGet
+    /// version syntax and may match elements inside XML comments.
+    /// </para>
+    /// </remarks>
+    private static readonly Regex explicitPinPattern = new(
+        @"^[ \t]*<PackageReference\b(?=[^\r\n>]*[ \t]Include=""NuGet\.(?:Protocol|Packaging|Resolver)"")(?=[^\r\n>]*[ \t]Version=""[^""]+"")[^\r\n>]*?/>[ \t]*(?:\r?\n|$)",
+        RegexOptions.Compiled | RegexOptions.Multiline);
+
+    /// <inheritdoc />
+    public Task ExecuteAsync(MigrationContext context, Summary summary)
+    {
+        if (!RunsForMinimumRequiredVersion(context.FalloutVersion))
+        {
+            return Task.CompletedTask;
+        }
+
+        foreach (var path in MigrationFileOperations.EnumerateFiles(context.RootDirectory, "_build.csproj"))
+        {
+            MigrationFileOperations.ApplyRewrite(context, path, Rewrite, summary);
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <returns>
+    /// <see langword="true"/> if the major version can be parsed as a
+    /// non-negative integer and is greater than or equal to
+    /// <see cref="MinimumFalloutMajor"/>; otherwise, <see langword="false"/>.
+    /// Returns <see langword="false"/> for <see langword="null"/>,
+    /// empty, or unparseable version strings.
+    /// </returns>
+    /// <remarks>
+    /// The major version is parsed using <see cref="NumberStyles.None"/>
+    /// and <see cref="CultureInfo.InvariantCulture"/>.
+    /// Minor, patch, and subsequent version segments are ignored and
+    /// are not validated.
+    /// </remarks>
+    private static bool RunsForMinimumRequiredVersion(string version)
+    {
+        int separatorIndex = version?.IndexOf('.') ?? -1;
+        string majorSegment = separatorIndex == -1 ? version : version[..separatorIndex];
+
+        return int.TryParse(majorSegment, NumberStyles.None, CultureInfo.InvariantCulture, out int major) &&
+               major >= MinimumFalloutMajor;
+    }
+
+    private static RewriteResult Rewrite(string original)
+    {
+        var edits = 0;
+        var content = explicitPinPattern.Replace(original, _ =>
+        {
+            edits++;
+            return string.Empty;
+        });
+
+        return new RewriteResult(content, edits);
+    }
+}