Add Nav Menu

Author: andrewlock

BlazorPreRender/BlazorApp1/BlazorApp1/Pages/Counter.razor

@@ -1,4 +1,5 @@
 @page "/counter"
+@attribute [System.ComponentModel.Description("Counter")]
 
 <h1>Counter</h1>
 

BlazorPreRender/BlazorApp1/BlazorApp1/Pages/Example.razor

@@ -0,0 +1,4 @@
+@page "/Example"
+@attribute [System.ComponentModel.Description("Example")]
+
+<h3>Example</h3>

BlazorPreRender/BlazorApp1/BlazorApp1/Pages/Index.razor

@@ -1,4 +1,5 @@
 @page "/"
+@attribute [System.ComponentModel.Description("Home")]
 
 <h1>Hello, world!</h1>
 

BlazorPreRender/BlazorApp1/BlazorApp1/Shared/NavMenu.razor

@@ -7,21 +7,14 @@
 
 <div class="@NavMenuCssClass" @onclick="ToggleNavMenu">
     <ul class="nav flex-column">
-        <li class="nav-item px-3">
-            <NavLink class="nav-link" href="" Match="NavLinkMatch.All">
-                <span class="oi oi-home" aria-hidden="true"></span> Home
-            </NavLink>
-        </li>
-        <li class="nav-item px-3">
-            <NavLink class="nav-link" href="counter">
-                <span class="oi oi-plus" aria-hidden="true"></span> Counter
-            </NavLink>
-        </li>
-        <li class="nav-item px-3">
-            <NavLink class="nav-link" href="fetchdata">
-                <span class="oi oi-list-rich" aria-hidden="true"></span> Fetch data
-            </NavLink>
-        </li>
+        @foreach (var pageDetail in PageDetails.MenuPages)
+        {
+            <li class="nav-item px-3">
+                <NavLink class="nav-link" href="@pageDetail.Route" Match="NavLinkMatch.All">
+                    @pageDetail.Title
+                </NavLink>
+            </li>    
+        }
     </ul>
 </div>
 

BlazorPreRender/BlazorApp1/SourceGenerators/PageDetailsGenerator.cs

@@ -0,0 +1,96 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Text;
+
+namespace SourceGenerators
+{
+    [Generator]
+    public class PageDetailsGenerator : ISourceGenerator
+    {
+        private const string RouteAttributeName = "Microsoft.AspNetCore.Components.RouteAttribute";
+        private const string DescriptionAttributeName = "System.ComponentModel.Description";
+        
+        public void Execute(GeneratorExecutionContext context)
+        {
+            try
+            {
+                // Debugger.Launch();
+                
+                IEnumerable<RouteableComponent> menuComponents = GetMenuComponents(context.Compilation);
+
+                context.AddSource("PageDetail", SourceText.From(Templates.PageDetail(), Encoding.UTF8));
+                var pageDetailsSource = SourceText.From(Templates.MenuPages(menuComponents), Encoding.UTF8);
+                context.AddSource("PageDetails", pageDetailsSource);
+            }
+            catch (Exception)
+            {
+                Debugger.Launch();
+            }
+        }
+
+        public void Initialize(GeneratorInitializationContext context)
+        {
+            //Debugger.Launch();
+        }
+
+        private static ImmutableArray<RouteableComponent> GetMenuComponents(Compilation compilation)
+        {
+            // Get all classes
+            IEnumerable<SyntaxNode> allNodes = compilation.SyntaxTrees.SelectMany(s => s.GetRoot().DescendantNodes());
+            IEnumerable<ClassDeclarationSyntax> allClasses = allNodes
+                .Where(d => d.IsKind(SyntaxKind.ClassDeclaration))
+                .OfType<ClassDeclarationSyntax>();
+            
+            return allClasses
+                .Select(component => TryGetMenuComponent(compilation, component))
+                .Where(page => page is not null)
+                .Cast<RouteableComponent>()// stops the nullable lies
+                .ToImmutableArray();
+        }
+        
+        private static RouteableComponent? TryGetMenuComponent(Compilation compilation, ClassDeclarationSyntax component)
+        {
+            var attributes = component.AttributeLists
+                .SelectMany(x => x.Attributes)
+                .Where(attr => 
+                    attr.Name.ToString() == RouteAttributeName
+                    || attr.Name.ToString() == DescriptionAttributeName)
+                .ToList();
+
+            var routeAttribute = attributes.FirstOrDefault(attr => attr.Name.ToString() == RouteAttributeName);
+            var descriptionAttribute = attributes.FirstOrDefault(attr => attr.Name.ToString() == DescriptionAttributeName);
+
+            if (routeAttribute is null || descriptionAttribute is null)
+            {
+                return null;
+            }
+                
+            if (
+                routeAttribute.ArgumentList?.Arguments.Count != 1 ||
+                descriptionAttribute.ArgumentList?.Arguments.Count != 1)
+            {
+                // no route path or description value
+                return null;
+            }
+                
+            var semanticModel = compilation.GetSemanticModel(component.SyntaxTree);
+
+            var routeArg = routeAttribute.ArgumentList.Arguments[0];
+            var routeExpr = routeArg.Expression;
+            var routeTemplate = semanticModel.GetConstantValue(routeExpr).ToString();
+            
+            var descriptionArg = descriptionAttribute.ArgumentList.Arguments[0];
+            var descriptionExpr = descriptionArg.Expression;
+            var title = semanticModel.GetConstantValue(descriptionExpr).ToString();
+
+            return new RouteableComponent(routeTemplate, title);
+        }
+    }
+}

BlazorPreRender/BlazorApp1/SourceGenerators/RouteableComponent.cs

@@ -0,0 +1,14 @@
+namespace SourceGenerators
+{
+    public class RouteableComponent
+    {
+        public string Route { get; }
+        public string Title { get; }
+
+        public RouteableComponent(string route, string title)
+        {
+            Title = title;
+            Route = route;
+        }
+    }
+}

BlazorPreRender/BlazorApp1/SourceGenerators/Templates.cs

@@ -25,6 +25,46 @@ public static class AppRoutes
             {
                 sb.AppendLine($"\"{route}\",");
             }
+
+            sb.Append(@"
+                }
+            );
+    }
+}");
+            return sb.ToString();
+        }
+
+        public static string PageDetail()
+        {
+            return @"
+namespace BlazorApp1
+{
+    public record PageDetail(string Route, string Title);
+}
+";
+        }
+
+        public static string MenuPages(IEnumerable<RouteableComponent> pages)
+        {
+            // hard code the namespace for now
+            var sb = new StringBuilder(@"
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+
+namespace BlazorApp1
+{
+    public static class PageDetails
+    {
+        public static ReadOnlyCollection<PageDetail> MenuPages { get; } = 
+            new ReadOnlyCollection<PageDetail>(
+                new List<PageDetail>
+                {
+");
+            foreach (var page in pages)
+            {
+                sb.AppendLine($"new PageDetail(\"{page.Route}\", \"{page.Title}\"),");
+            }
+
             sb.Append(@"
                 }
             );