Add ServerRequest.pathVariableOrNull Kotlin extension

Closes spring-projectsgh-32738

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensions.kt

@@ -35,7 +35,7 @@ import kotlin.reflect.KClass
  * Extension for [ServerRequest.bodyToMono] providing a `bodyToMono<Foo>()` variant
  * leveraging Kotlin reified type parameters. This extension is not subject to type
  * erasure and retains actual generic type arguments.
- * 
+ *
  * @author Sebastien Deleuze
  * @since 5.0
  */
@@ -192,3 +192,13 @@ fun ServerRequest.Headers.contentLengthOrNull(): Long? =
  */
 fun ServerRequest.Headers.contentTypeOrNull(): MediaType? =
 		contentType().orElse(null)
+
+/**
+ * Nullable variant of [ServerRequest.pathVariable].
+ *
+ * @author George Papadopoulos
+ * @since 6.2
+ */
+fun ServerRequest.pathVariableOrNull(name: String): String? {
+	return pathVariables()[name]
+}

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensionsTests.kt

@@ -222,5 +222,19 @@ class ServerRequestExtensionsTests {
 		verify { headers.contentType() }
 	}
 
+	@Test
+	fun `pathVariableOrNull with value`() {
+		every { request.pathVariables() } returns hashMapOf("name" to "123")
+		assert(request.pathVariableOrNull("name") == "123")
+		verify { request.pathVariables() }
+	}
+
+	@Test
+	fun `pathVariableOrNull with null`() {
+		every { request.pathVariables() } returns emptyMap()
+		assert(request.pathVariableOrNull("name") == null)
+		verify { request.pathVariables() }
+	}
+
 	class Foo
 }