Enable creating C# projections based on multiple input winmd's and docs

Directory.Build.props

@@ -28,8 +28,9 @@
     <IncludeSymbols Condition=" '$(DebugType)' != 'embedded' ">true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
 
-    <MetadataVersion>10.2.163-preview</MetadataVersion>
-    <ApiDocsVersion>0.1.4-alpha</ApiDocsVersion>
+    <MetadataVersion>10.2.185-preview</MetadataVersion>
+    <!-- <DiaMetadataVersion>0.2.185-preview-g7e1e6a442c</DiaMetadataVersion> -->
+    <ApiDocsVersion>0.1.6-alpha</ApiDocsVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/Microsoft.Windows.CsWin32/AnalyzerReleases.Unshipped.md

@@ -9,4 +9,6 @@ PInvoke001 | Functionality | Warning | SourceGenerator
 PInvoke002 | Functionality | Warning | SourceGenerator
 PInvoke003 | Functionality | Warning | SourceGenerator
 PInvoke004 | Functionality | Warning | SourceGenerator
-PInvoke005 | Functionality | Warning | SourceGenerator
+PInvoke005 | Functionality | Warning | SourceGenerator
+PInvoke006 | Configuration | Warning | SourceGenerator
+PInvoke007 | Functionality | Error | SourceGenerator

src/Microsoft.Windows.CsWin32/Docs.cs

@@ -7,11 +7,14 @@ namespace Microsoft.Windows.CsWin32
     using System.Collections.Generic;
     using System.Diagnostics.CodeAnalysis;
     using System.IO;
-    using System.Reflection;
+    using System.Linq;
     using MessagePack;
     using Microsoft.Windows.SDK.Win32Docs;
 
-    internal class Docs
+    /// <summary>
+    /// An in-memory representation of API documentation.
+    /// </summary>
+    public class Docs
     {
         private static readonly Dictionary<string, Docs> DocsByPath = new Dictionary<string, Docs>(StringComparer.OrdinalIgnoreCase);
 
@@ -22,7 +25,12 @@ private Docs(Dictionary<string, ApiDetails> apisAndDocs)
             this.apisAndDocs = apisAndDocs;
         }
 
-        internal static Docs Get(string docsPath)
+        /// <summary>
+        /// Loads docs from a file.
+        /// </summary>
+        /// <param name="docsPath">The messagepack docs file to read from.</param>
+        /// <returns>An instance of <see cref="Docs"/> that accesses the documentation in the file specified by <paramref name="docsPath"/>.</returns>
+        public static Docs Get(string docsPath)
         {
             lock (DocsByPath)
             {
@@ -48,6 +56,35 @@ internal static Docs Get(string docsPath)
             }
         }
 
+        /// <summary>
+        /// Returns a <see cref="Docs"/> instance that contains all the merged documentation from a list of docs.
+        /// </summary>
+        /// <param name="docs">The docs to be merged. When API documentation is provided by multiple docs in this list, the first one appearing in this list is taken.</param>
+        /// <returns>An instance that contains all the docs provided. When <paramref name="docs"/> contains exactly one element, that element is returned.</returns>
+        public static Docs Merge(IReadOnlyList<Docs> docs)
+        {
+            if (docs.Count == 1)
+            {
+                // Nothing to merge.
+                return docs[0];
+            }
+
+            Dictionary<string, ApiDetails> mergedDocs = new(docs.Sum(d => d.apisAndDocs.Count), StringComparer.OrdinalIgnoreCase);
+            foreach (Docs doc in docs)
+            {
+                foreach (KeyValuePair<string, ApiDetails> api in doc.apisAndDocs)
+                {
+                    // We want a first one wins policy.
+                    if (!mergedDocs.ContainsKey(api.Key))
+                    {
+                        mergedDocs.Add(api.Key, api.Value);
+                    }
+                }
+            }
+
+            return new Docs(mergedDocs);
+        }
+
         internal bool TryGetApiDocs(string apiName, [NotNullWhen(true)] out ApiDetails? docs) => this.apisAndDocs.TryGetValue(apiName, out docs);
     }
 }

src/Microsoft.Windows.CsWin32/GeneratorOptions.cs

@@ -23,12 +23,6 @@ public record GeneratorOptions
         /// <value>The default value is "PInvoke".</value>
         public string? ClassName { get; init; } = "PInvoke";
 
-        /// <summary>
-        /// Gets the namespace for generated code.
-        /// </summary>
-        /// <value>The default value is "Windows.Win32". Must be non-empty.</value>
-        public string Namespace { get; init; } = "Windows.Win32";
-
         /// <summary>
         /// Gets a value indicating whether to emit a single source file as opposed to types spread across many files.
         /// </summary>
@@ -57,10 +51,6 @@ public record GeneratorOptions
         /// <exception cref="InvalidOperationException">Thrown when some setting is invalid.</exception>
         public void Validate()
         {
-            if (string.IsNullOrWhiteSpace(this.Namespace))
-            {
-                throw new InvalidOperationException("The namespace must be set.");
-            }
         }
 
         /// <summary>