🔥 feat: Add OpenAPI middleware

app.go

@@ -706,6 +706,30 @@ func (app *App) Name(name string) Router {
 	return app
 }
 
+// Summary assigns a short summary to the most recently added route.
+func (app *App) Summary(sum string) Router {
+	app.mutex.Lock()
+	app.latestRoute.Summary = sum
+	app.mutex.Unlock()
+	return app
+}
+
+// Description assigns a description to the most recently added route.
+func (app *App) Description(desc string) Router {
+	app.mutex.Lock()
+	app.latestRoute.Description = desc
+	app.mutex.Unlock()
+	return app
+}
+
+// MediaType assigns a response media type to the most recently added route.
+func (app *App) MediaType(typ string) Router {
+	app.mutex.Lock()
+	app.latestRoute.MediaType = typ
+	app.mutex.Unlock()
+	return app
+}
+
 // GetRoute Get route by name
 func (app *App) GetRoute(name string) Route {
 	for _, routes := range app.stack {

docs/middleware/openapi.md

@@ -0,0 +1,103 @@
+---
+id: openapi
+---
+
+# OpenAPI
+
+OpenAPI middleware for [Fiber](https://github.com/gofiber/fiber) that generates an OpenAPI specification based on the routes registered in your application.
+
+## Signatures
+
+```go
+func New(config ...Config) fiber.Handler
+```
+
+## Examples
+
+Import the middleware package that is part of the Fiber web framework
+
+```go
+import (
+    "github.com/gofiber/fiber/v3"
+    "github.com/gofiber/fiber/v3/middleware/openapi"
+)
+```
+
+After you initiate your Fiber app, you can use the following possibilities:
+
+```go
+// Initialize default config. Register the middleware *after* all routes
+// so that the spec includes every handler.
+app.Use(openapi.New())
+
+// Or extend your config for customization
+app.Use(openapi.New(openapi.Config{
+    Title:   "My API",
+    Version: "1.0.0",
+    ServerURL: "https://example.com",
+}))
+
+// Customize metadata for specific operations
+app.Use(openapi.New(openapi.Config{
+    Operations: map[string]openapi.Operation{
+        "GET /users": {
+            Summary:     "List users",
+            Description: "Returns all users",
+            MediaType:   fiber.MIMEApplicationJSON,
+        },
+    },
+}))
+
+// Routes may optionally document themselves using Summary, Description and MediaType
+app.Get("/users", listUsers).
+    Summary("List users").
+    Description("List all users").
+    MediaType(fiber.MIMEApplicationJSON)
+
+// If not specified, routes default to an empty summary and description and a
+// "text/plain" response media type.
+```
+
+Each documented route automatically includes a `200` response with the description `OK` to satisfy the minimum OpenAPI requirements.
+
+`CONNECT` routes are ignored because the OpenAPI specification does not define a `connect` operation.
+
+## Config
+
+| Property    | Type                    | Description                                                     | Default            |
+|:------------|:------------------------|:----------------------------------------------------------------|:------------------:|
+| Next        | `func(fiber.Ctx) bool`  | Next defines a function to skip this middleware when returned true. | `nil` |
+| Title       | `string`                | Title is the title for the generated OpenAPI specification.     | `"Fiber API"`     |
+| Version     | `string`                | Version is the version for the generated OpenAPI specification. | `"1.0.0"`         |
+| Description | `string`                | Description is the description for the generated specification. | `""`             |
+| ServerURL   | `string`                | ServerURL is the server URL used in the generated specification.| `""`             |
+| Path        | `string`                | Path is the route where the specification will be served.       | `"/openapi.json"` |
+| Operations  | `map[string]Operation`  | Per-route metadata keyed by `METHOD /path`.                     | `nil`             |
+
+## Default Config
+
+```go
+var ConfigDefault = Config{
+    Next:        nil,
+    Title:       "Fiber API",
+    Version:     "1.0.0",
+    Description: "",
+    ServerURL:   "",
+    Path:        "/openapi.json",
+    Operations:         nil,
+}
+```
+
+### Operation
+
+```go
+type Operation struct {
+    OperationID string
+    Summary     string
+    Description string
+    Tags        []string
+    Deprecated  bool
+    MediaType   string
+}
+```
+

docs/whats_new.md

@@ -1288,6 +1288,10 @@ Deprecated fields `Duration`, `Store`, and `Key` have been removed in v3. Use `E
 
 Monitor middleware is migrated to the [Contrib package](https://github.com/gofiber/contrib/tree/main/monitor) with [PR #1172](https://github.com/gofiber/contrib/pull/1172).
 
+### OpenAPI
+
+Introduces an `openapi` middleware that inspects registered routes and serves a generated OpenAPI 3.0 specification. Each operation includes a summary and default `200` response. Routes may attach descriptions and return media types directly or configure them globally.
+
 ### Proxy
 
 The proxy middleware has been updated to improve consistency with Go naming conventions. The `TlsConfig` field in the configuration struct has been renamed to `TLSConfig`. Additionally, the `WithTlsConfig` method has been removed; you should now configure TLS directly via the `TLSConfig` property within the `Config` struct.

group.go

@@ -45,6 +45,24 @@ func (grp *Group) Name(name string) Router {
 	return grp
 }
 
+// Summary assigns a short summary to the most recently added route in the group.
+func (grp *Group) Summary(sum string) Router {
+	grp.app.Summary(sum)
+	return grp
+}
+
+// Description assigns a description to the most recently added route in the group.
+func (grp *Group) Description(desc string) Router {
+	grp.app.Description(desc)
+	return grp
+}
+
+// MediaType assigns a response media type to the most recently added route in the group.
+func (grp *Group) MediaType(typ string) Router {
+	grp.app.MediaType(typ)
+	return grp
+}
+
 // Use registers a middleware route that will match requests
 // with the provided prefix (which is optional and defaults to "/").
 // Also, you can pass another app instance as a sub-router along a routing path.

middleware/openapi/config.go

@@ -0,0 +1,98 @@
+package openapi
+
+import (
+	"github.com/gofiber/fiber/v3"
+)
+
+// Config defines the config for middleware.
+type Config struct {
+	// Next defines a function to skip this middleware when returned true.
+	//
+	// Optional. Default: nil
+	Next func(c fiber.Ctx) bool
+
+	// Title is the title for the generated OpenAPI specification.
+	//
+	// Optional. Default: "Fiber API"
+	Title string
+
+	// Version is the version for the generated OpenAPI specification.
+	//
+	// Optional. Default: "1.0.0"
+	Version string
+
+	// Description is the description for the generated OpenAPI specification.
+	//
+	// Optional. Default: ""
+	Description string
+
+	// ServerURL is the server URL used in the generated specification.
+	//
+	// Optional. Default: ""
+	ServerURL string
+
+	// Path is the route where the specification will be served.
+	//
+	// Optional. Default: "/openapi.json"
+	Path string
+
+	// Operations allows providing per-route metadata keyed by
+	// "METHOD /path" (e.g. "GET /users").
+	//
+	// Optional. Default: nil
+	Operations map[string]Operation
+}
+
+// ConfigDefault is the default config.
+var ConfigDefault = Config{
+	Next:        nil,
+	Title:       "Fiber API",
+	Version:     "1.0.0",
+	Description: "",
+	ServerURL:   "",
+	Path:        "/openapi.json",
+	Operations:  nil,
+}
+
+func configDefault(config ...Config) Config {
+	if len(config) < 1 {
+		return ConfigDefault
+	}
+
+	cfg := config[0]
+
+	if cfg.Next == nil {
+		cfg.Next = ConfigDefault.Next
+	}
+	if cfg.Title == "" {
+		cfg.Title = ConfigDefault.Title
+	}
+	if cfg.Version == "" {
+		cfg.Version = ConfigDefault.Version
+	}
+	if cfg.Description == "" {
+		cfg.Description = ConfigDefault.Description
+	}
+	if cfg.ServerURL == "" {
+		cfg.ServerURL = ConfigDefault.ServerURL
+	}
+	if cfg.Path == "" {
+		cfg.Path = ConfigDefault.Path
+	}
+	if cfg.Operations == nil {
+		cfg.Operations = ConfigDefault.Operations
+	}
+
+	return cfg
+}
+
+// Operation configures metadata for a single route in the generated spec.
+type Operation struct {
+	OperationID string
+	Summary     string
+	Description string
+	Tags        []string
+	Deprecated  bool
+	// MediaType defines the media type for the 200 response.
+	MediaType string
+}