Add pathAppending

README.md

@@ -52,10 +52,7 @@ func getUser(id: Int) -> RequestMiddleware {
 }
 ```
 
-Note that the order inside the builder does not matter and middleware are applied
-in the order they are defined. If the same middleware is defined multiple times,
-the last one will be used. If you're defining custom middleware, try to make them idempotent so as to
-avoid unexpected behavior.
+Note that the order inside the builder only matters for middleware that are not idempotent, such as the built-in `pathAppending`.
 
 Once you have an endpoint defined, you can use it to create a request for Foundation.
 
@@ -112,6 +109,25 @@ let createGame = games/"create"
 let featuredGames = games/"featured"
 ```
 
+You can also compose paths using the built-in `pathAppending` middleware.
+
+```swift
+import HTTPRequestBuilder
+
+@RequestBuilder
+var userEndpoints: RequestMiddleware = {
+  path("/users")
+}
+
+@RequestBuilder
+func editUser(id: Int) -> RequestMiddleware {
+  userEndpoints
+  pathAppending("/edit")
+  pathAppending(id)
+  Method.put
+}
+```
+
 ## Authentication Middleware
 
 This library comes with a couple middleware functions to help with authentication.

Sources/HTTPRequestBuilder/RequestMiddleware.swift

@@ -19,6 +19,32 @@ public func path(
   }
 }
 
+/// Append to the path of the request.
+///  - Parameter component: The path component to append.
+///  - Returns: A request middleware.
+public func pathAppending(
+  _ component: CustomStringConvertible
+) -> RequestMiddleware {
+  { request in
+    var newRequest = request
+    newRequest.path = request.path / component
+    return newRequest
+  }
+}
+
+/// Append to the path of the request.
+///  - Parameter component: The path component to append.
+///  - Returns: A request middleware.
+public func pathAppending<T: RawRepresentable>(
+  _ component: T
+) -> RequestMiddleware where T.RawValue == String {
+  { request in
+    var newRequest = request
+    newRequest.path = request.path / component
+    return newRequest
+  }
+}
+
 /// Add headers to the request.
 /// - Parameters:
 ///  - key: The header key.

Tests/HTTPRequestBuilderTests/HTTPRequestBuilderTests.swift

@@ -92,4 +92,24 @@ final class HTTPRequestBuilderTests: XCTestCase {
     XCTAssertEqual(urlRequest.url, URL(string: "https://api.example.com/users/12"))
   }
 
+  func testPathAppending() throws {
+    enum Action: String {
+      case edit
+      case view
+    }
+
+    @RequestBuilder
+    var example: RequestMiddleware {
+      path("/users")
+      pathAppending("12")
+      pathAppending(Action.edit)
+      pathAppending(3)
+    }
+
+    let request = try example(
+      Request()
+    )
+
+    XCTAssertEqual(request.path.fragments, ["users", "12", "edit", "3"])
+  }
 }