allow to delete a selective property (#45)

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- TODO

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Author: dirkbolte

README.md

@@ -271,6 +271,7 @@ wiremock/wiremock:3x \
 The state is recorded in `serveEventListeners` of a stub. The following functionalities are provided:
 
 - `state` : stores a state in a context. Storing the state multiple times can be used to selectively overwrite existing properties.
+  - to delete a selective property, set it to `null` (as string).
 - `list` : stores a state in a list. Can be used to prepend/append new states to an existing list. List elements cannot be modified (only read/deleted).
 
 `state` and `list` can be used in the same `ServeEventListener` (would count as two updates). Adding multiple `recordState` `ServeEventListener` is supported.
@@ -392,6 +393,28 @@ To record a complete response body, use:
 }
 ```
 
+To delete a selective property, ensure that the field has the value `null` as string, e.g. by specifying `default='null` for `jsonpath`:
+
+```json
+{
+  "request": {},
+  "response": {},
+  "serveEventListeners": [
+    {
+      "name": "recordState",
+      "parameters": {
+        "context": "{{jsonPath response.body '$.id'}}",
+        "state": {
+          "id": "{{jsonPath response.body '$.id'}}",
+          "firstName": "{{jsonPath request.body '$.firstName' default='null'}}",
+          "lastName": "{{jsonPath request.body '$.lastName' default='null'}}"
+        }
+      }
+    }
+  ]
+}
+```
+
 To append a state to a list:
 
 ```json

src/main/java/org/wiremock/extensions/state/internal/ContextManager.java

@@ -62,7 +62,13 @@ public Long createOrUpdateContextState(String contextName, Map<String, String> p
                     it.incUpdateCount();
                     return it;
                 }).orElseGet(() -> new Context(contextName));
-            context.getProperties().putAll(properties);
+            properties.forEach((k, v) -> {
+                if(v.equals("null")) {
+                    context.getProperties().remove(k);
+                } else {
+                    context.getProperties().put(k, v);
+                }
+            });
             store.put(contextName, context);
             return context.getUpdateCount();
         }

src/test/java/org/wiremock/extensions/state/functionality/StateRequestMatcherTest.java

@@ -28,6 +28,7 @@
 import org.junit.jupiter.api.Test;
 
 import java.net.URI;
+import java.util.HashMap;
 import java.util.Map;
 
 import static com.github.tomakehurst.wiremock.client.WireMock.delete;
@@ -173,7 +174,7 @@ private void createPostStub() throws JsonProcessingException {
                         Map.of(
                             "context", "{{jsonPath response.body '$.id'}}",
                             "state", Map.of(
-                                "stateValue", "{{jsonPath request.body '$.contextValue'}}"
+                                "stateValue", "{{jsonPath request.body '$.contextValue' default='null'}}"
                             ),
                             "list", Map.of(
                                 "addLast", Map.of(
@@ -228,7 +229,10 @@ private String postAndAssertContextValue(String contextValue) {
     private String postAndAssertContextValue(String contextName, String contextValue) {
         var context = given()
             .accept(ContentType.JSON)
-            .body(Map.of("contextValue", contextValue, "id", contextName))
+            .body(new HashMap<String, String>() {{
+                put("contextValue", contextValue);
+                put("id", contextName);
+            }})
             .post(assertDoesNotThrow(() -> new URI(wm.getRuntimeInfo().getHttpBaseUrl() + TEST_URL + "/" + contextName)))
             .then()
             .statusCode(HttpStatus.SC_OK)
@@ -303,6 +307,16 @@ void test_hasProperty_propertyExists_ok() {
                 getAndAssertContextMatcher(context, "hasProperty/stateValue", HttpStatus.SC_OK, "context found", "2", "1");
             }
 
+            @Test
+            void test_hasProperty_propertyGotDeleted_fail() {
+                var contextValue = RandomStringUtils.randomAlphabetic(5);
+
+                var context = postAndAssertContextValue(contextValue);
+                postAndAssertContextValue(contextValue);
+                postAndAssertContextValue(context, null);
+                getAndAssertContextMatcher(context, "hasProperty/stateValue", HttpStatus.SC_NOT_FOUND);
+            }
+
             @Test
             void test_hasNotProperty_propertyExists_fail() {
                 var contextValue = RandomStringUtils.randomAlphabetic(5);