Swagger plugins support

README.md

@@ -1302,13 +1302,17 @@ app.UseSwaggerUI(c =>
     c.MaxDisplayedTags(5);
     c.ShowExtensions();
     c.ShowCommonExtensions();
+    c.Plugins = ["myCustomPlugin"];
     c.EnableValidator();
     c.SupportedSubmitMethods(SubmitMethod.Get, SubmitMethod.Head);
     c.UseRequestInterceptor("(request) => { return request; }");
     c.UseResponseInterceptor("(response) => { return response; }");
 });
 ```
 
+ > [!NOTE]
+ > When adding custom plugins, make sure you add any custom `js` files that define the plugin function(s).
+
 ### Inject Custom JavaScript ###
 
 To tweak the behavior, you can inject additional JavaScript files by adding them to your `wwwroot` folder and specifying the relative paths in the middleware options:

src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/PublicAPI.Unshipped.txt

@@ -0,0 +1,2 @@
+Swashbuckle.AspNetCore.SwaggerUI.ConfigObject.Plugins.get -> System.Collections.Generic.IList<string>
+Swashbuckle.AspNetCore.SwaggerUI.ConfigObject.Plugins.set -> void

src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIOptions.cs

@@ -190,6 +190,12 @@ public class ConfigObject
         [JsonPropertyName("validatorUrl")]
         public string ValidatorUrl { get; set; } = null;
 
+        /// <summary>
+        /// Any custom plugins' function names.
+        /// </summary>
+        [JsonPropertyName("plugins")]
+        public IList<string>  Plugins { get; set; } = null;
+
         [JsonExtensionData]
         public Dictionary<string, object> AdditionalItems { get; set; } = [];
     }

src/Swashbuckle.AspNetCore.SwaggerUI/index.js

@@ -57,6 +57,10 @@ window.onload = function () {
     if (interceptors.ResponseInterceptorFunction)
         configObject.responseInterceptor = parseFunction(interceptors.ResponseInterceptorFunction);
 
+    if (configObject.plugins) {
+        configObject.plugins = configObject.plugins.map(eval);
+    }
+
     // Begin Swagger UI call region
 
     const ui = SwaggerUIBundle(configObject);

test/Swashbuckle.AspNetCore.IntegrationTests/SwaggerUIIntegrationTests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using System.Net;
 using System.Threading.Tasks;
 using Xunit;
@@ -74,6 +75,29 @@ public async Task SwaggerUIMiddleware_ReturnsInitializerScript(
             Assert.DoesNotContain("%(Interceptors)", jsContent);
         }
 
+        [Fact]
+        public async Task IndexUrl_DefinesPlugins()
+        {
+            var client = new TestSite(typeof(CustomUIConfig.Startup)).BuildClient();
+
+            var jsResponse = await client.GetAsync("/swagger/index.js");
+            Assert.Equal(HttpStatusCode.OK, jsResponse.StatusCode);
+
+            var jsContent = await jsResponse.Content.ReadAsStringAsync();
+            Assert.Contains("\"plugins\":[\"customPlugin1\",\"customPlugin2\"]", jsContent);
+        }
+
+        [Fact]
+        public async Task IndexUrl_DoesntDefinePlugins()
+        {
+            var client = new TestSite(typeof(Basic.Startup)).BuildClient();
+
+            var jsResponse = await client.GetAsync("/index.js");
+            Assert.Equal(HttpStatusCode.OK, jsResponse.StatusCode);
+            var jsContent = await jsResponse.Content.ReadAsStringAsync();
+            Assert.DoesNotContain("\"plugins\"", jsContent);
+        }
+
         [Fact]
         public async Task IndexUrl_ReturnsCustomPageTitleAndStylesheets_IfConfigured()
         {

test/WebSites/CustomUIConfig/Startup.cs

@@ -73,14 +73,18 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
                 // Other
                 c.DocumentTitle = "CustomUIConfig";
                 c.StylesPath = "/ext/custom-stylesheet.css";
+                c.InjectStylesheet("/ext/custom-stylesheet.css");
                 c.ScriptBundlePath = "/ext/custom-javascript.js";
                 c.ScriptPresetsPath = "/ext/custom-javascript.js";
-                c.InjectStylesheet("/ext/custom-stylesheet.css");
                 c.InjectJavascript("/ext/custom-javascript.js");
+                c.InjectJavascript("/ext/custom-plugin1.js");
+                c.InjectJavascript("/ext/custom-plugin2.js");
                 c.UseRequestInterceptor("(req) => { req.headers['x-my-custom-header'] = 'MyCustomValue'; return req; }");
                 c.UseResponseInterceptor("(res) => { console.log('Custom interceptor intercepted response from:', res.url); return res; }");
                 c.EnablePersistAuthorization();
 
+                c.ConfigObject.Plugins = ["customPlugin1", "customPlugin2"];
+
                 c.ConfigObject.AdditionalItems.Add("syntaxHighlight", false);
                 c.ConfigObject.AdditionalItems.Add("charProperty", 'c');
                 c.ConfigObject.AdditionalItems.Add("stringProperty", "value");

test/WebSites/CustomUIConfig/wwwroot/ext/custom-plugin1.js

@@ -0,0 +1,9 @@
+const customPlugin1 = function (system) {
+    var elem = document.createElement("div");
+    elem.innerHTML =
+        "<div style=\"text-align: center; font-family: Titillium Web,sans-serif; margin: 16px;\">This text was injected via /ext/custom-plugin1.js, using the SwaggerUIOptions.Plugins method.</div>";
+
+    document.body.insertBefore(elem, document.body.firstChild);
+    return {
+    };
+};

test/WebSites/CustomUIConfig/wwwroot/ext/custom-plugin2.js

@@ -0,0 +1,9 @@
+const customPlugin2 = function (system) {
+    var elem = document.createElement("div");
+    elem.innerHTML =
+        "<div style=\"text-align: center; font-family: Titillium Web,sans-serif; margin: 16px;\">This text was injected via /ext/custom-plugin2.js, using the SwaggerUIOptions.Plugins method.</div>";
+
+    document.body.insertBefore(elem, document.body.firstChild);
+    return {
+    };
+};