Adding hx-headers-* server-side processing to hx-headers

src/Htmx.TagHelpers/HtmxHeadersTagHelper.cs

@@ -0,0 +1,43 @@
+using JetBrains.Annotations;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using System.Collections.Generic;
+using System;
+using System.Text.Json;
+using System.Linq;
+
+namespace Htmx.TagHelpers
+{
+    /// <summary>
+    /// Targets any element that has hx-get, hx-post, hx-put, hx-patch, and hx-delete.
+    /// https://htmx.org/attributes/hx-headers/
+    /// </summary>
+    [PublicAPI]
+    [HtmlTargetElement("*", Attributes = "[hx-get]")]
+    [HtmlTargetElement("*", Attributes = "[hx-post]")]
+    [HtmlTargetElement("*", Attributes = "[hx-put]")]
+    [HtmlTargetElement("*", Attributes = "[hx-delete]")]
+    [HtmlTargetElement("*", Attributes = "[hx-patch]")]
+    public class HtmxHeadersTagHelper : TagHelper
+    {
+        /// <summary>
+        /// Dictionary of hx-headers
+        /// </summary>
+        [HtmlAttributeName(DictionaryAttributePrefix = "hx-headers-")]
+        public IDictionary<string, string?> HeaderAttributes { get; set; } = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase);
+
+        /// <inheritdoc />
+        public override void Process(TagHelperContext context, TagHelperOutput output)
+        {
+            var existingHxHeaders = output.Attributes["hx-headers"]?.Value;
+            if (existingHxHeaders != null || !HeaderAttributes.Any())
+            {
+                return;
+            }
+
+            // serialize
+            var json = JsonSerializer.Serialize(HeaderAttributes);
+
+            output.Attributes.Add("hx-headers", json);
+        }
+    }
+}

test/Htmx.Tests/Htmx.Tests.csproj

@@ -25,6 +25,7 @@
     </ItemGroup>
 
     <ItemGroup>
+      <ProjectReference Include="..\..\src\Htmx.TagHelpers\Htmx.TagHelpers.csproj" />
       <ProjectReference Include="..\..\src\Htmx\Htmx.csproj" />
     </ItemGroup>
 

test/Htmx.Tests/TagHelpers/HtmxHeadersTagHelperTests.cs

@@ -0,0 +1,92 @@
+using Htmx.TagHelpers;
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Htmx.Tests.TagHelpers
+{
+    public class HtmxHeadersTagHelperTests
+    {
+        private readonly HtmxHeadersTagHelper _tagHelper;
+        private readonly TagHelperContext _context;
+        private readonly TagHelperOutput _output;
+
+        public HtmxHeadersTagHelperTests()
+        {
+            _tagHelper = new HtmxHeadersTagHelper();
+
+            _context = new TagHelperContext(
+                new TagHelperAttributeList(),
+                new Dictionary<object, object>(),
+                "test_unique_id");
+
+            _output = new TagHelperOutput(
+                "div",
+                new TagHelperAttributeList(),
+                (useCachedResult, encoder) =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    var tagBuilder = new TagBuilder("div");
+                    tagBuilder.Attributes.Add("hx-post", "url");
+                    tagHelperContent.SetHtmlContent(tagBuilder);
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
+        }
+
+        [Fact]
+        public void Is_HeaderAttributes_NotNull()
+        {
+            Assert.NotNull(_tagHelper.HeaderAttributes);
+            Assert.Empty(_tagHelper.HeaderAttributes);
+        }
+
+        [Fact]
+        public void Process_AddsHeadersAttribute_WhenNoExistingHeadersAndHeaderAttributesPresent()
+        {
+            // Arrange
+            _tagHelper.HeaderAttributes.Add("Key1", "Value1");
+            _tagHelper.HeaderAttributes.Add("Key2", "Value2");
+
+            // Act
+            _tagHelper.Process(_context, _output);
+
+            // Assert
+            Assert.True(_output.Attributes.TryGetAttribute("hx-headers", out var headersAttribute));
+            Assert.NotNull(headersAttribute);
+
+            var json = JsonSerializer.Deserialize<JsonObject>(headersAttribute.Value.ToString()!)!;
+            Assert.Equal("Value1", json["Key1"]!.GetValue<string>());
+            Assert.Equal("Value2", json["Key2"]!.GetValue<string>());
+        }
+
+        [Fact]
+        public void Process_DoesNotAddHeadersAttribute_WhenExistingHeadersPresent()
+        {
+            // Arrange
+            var existingHeaders = new TagHelperAttribute("hx-headers", "{\"ExistingKey1\":\"ExistingValue1\"}");
+            _output.Attributes.Add(existingHeaders);
+
+            // Act
+            _tagHelper.Process(_context, _output);
+
+            // Assert
+            var json = JsonSerializer.Deserialize<JsonObject>(_output.Attributes["hx-headers"].Value.ToString()!)!;
+            Assert.Equal("ExistingValue1", json["ExistingKey1"]!.GetValue<string>());
+        }
+
+        [Fact]
+        public void Process_DoesNotAddHeadersAttribute_WhenNoHeaderAttributes()
+        {
+            // Act
+            _tagHelper.Process(_context, _output);
+
+            // Assert
+            Assert.False(_output.Attributes.TryGetAttribute("hx-headers", out _));
+        }
+    }
+
+}

test/Sample/Pages/Headers.cshtml

@@ -0,0 +1,63 @@
+@page
+@using Microsoft.AspNetCore.Antiforgery;
+@inject IAntiforgery antiforgery;
+@model HxRequestsModel
+
+<div>
+    <button type="button"
+            hx-post
+            hx-page="./Headers"
+            hx-headers-New-Key1="NewValue1"
+            hx-headers-New-Key2="NewValue2"
+            hx-swap="innerHTML"
+            hx-target="#post-result">
+        Click me (using hx-headers-key="value")
+    </button>
+</div>
+
+<div>
+    <button type="button"
+            hx-post
+            hx-page="./Headers"
+            hx-headers='{ "Existing-Key1": "ExistingValue1", "Existing-Key2": "ExistingValue1" }'
+            hx-headers-New-Key1="NewValue1"
+            hx-headers-New-Key2="NewValue2"
+            hx-swap="innerHTML"
+            hx-target="#post-result">
+        Click me (with existing hx-headers)
+    </button>
+</div>
+
+<div>
+    Testing: https://en.wikipedia.org/wiki/List_of_HTTP_header_fields
+    <br/>
+    <button type="button"
+            hx-post
+            hx-page="./Headers"
+            hx-headers-X-Forwarded-Host="en.wikipedia.org:8080"
+            hx-headers-X-Front-End-Https="on"
+            hx-headers-X-Forwarded-For="client1, proxy1, proxy2"
+            hx-headers-Upgrade-Insecure-Requests="1"
+            hx-headers-X-LongCustom-Header="Stuff"
+            hx-swap="innerHTML"
+            hx-target="#post-result">
+        Click me (List_of_HTTP_header_fields)
+    </button>
+</div>
+
+<div class="mt-2">
+    <code>requestConfig.headers</code>
+    <textarea class="w-100" id="post-result" rows="10"></textarea>
+</div>
+
+@section Scripts {
+    <script type="text/javascript">
+        window.addEventListener("htmx:afterRequest", evt => {
+            let headers = evt.detail.requestConfig.headers;
+            let json = JSON.stringify(headers, null, 2);
+
+            document.querySelector('#post-result').innerHTML = json;
+        });
+    </script>
+}
+

test/Sample/Pages/Headers.cshtml.cs

@@ -0,0 +1,20 @@
+using Htmx;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using System.Text.Json;
+
+namespace Sample.Pages
+{
+    [ValidateAntiForgeryToken]
+    public class HxRequestsModel : PageModel
+    {
+        public IActionResult OnPost()
+        {
+            // list of headers
+            var headers = Request.Headers.ToList();
+            var html = "<pre>" + JsonSerializer.Serialize(headers, new JsonSerializerOptions { WriteIndented = true }) + "</pre>";
+
+            return Content(html, "text/html");
+        }
+    }
+}

test/Sample/Pages/Shared/_Layout.cshtml

@@ -37,6 +37,9 @@
                     <li class="nav-item">
                         <a class="nav-link text-dark" asp-area="" asp-page="/Response">Response.Htmx()</a>
                     </li>
+                    <li class="nav-item">
+                        <a class="nav-link text-dark" asp-area="" asp-page="/Headers"><code>hx-headers</code></a>
+                    </li>
                     <li class="nav-item">
                         <a class="nav-link text-dark" asp-area="" asp-page="/Privacy">Privacy</a>
                     </li>