Fix AddKeyValue logging parser errors for trailing dot in keyPath (#7327)

* Fix AddKeyValue logging parser errors for trailing dot in keyPath (#6207)

Normalize trailing dot in JsonPathMatcher constructor so that `$.` is
treated as `$`, preventing ANTLR from printing a parse error to stderr.

* Add @issue annotation to trailing dot test

Author: timtebeek

rewrite-json/src/main/java/org/openrewrite/json/AddKeyValue.java

@@ -39,7 +39,7 @@ public class AddKeyValue extends Recipe {
 
     @Option(displayName = "Key path",
             description = "A JsonPath expression to locate the *parent* JSON entry.",
-            example = "'$.subjects.*' or '$.' or '$.x[1].y.*' etc.")
+            example = "'$.subjects.*' or '$' or '$.x[1].y.*' etc.")
     String keyPath;
 
     @Option(displayName = "Key",

rewrite-json/src/main/java/org/openrewrite/json/JsonPathMatcher.java

@@ -52,7 +52,9 @@ public class JsonPathMatcher {
     private JsonPathParser.@Nullable JsonPathContext parsed;
 
     public JsonPathMatcher(String jsonPath) {
-        this.jsonPath = jsonPath;
+        this.jsonPath = jsonPath.endsWith(".") && jsonPath.length() > 1
+                ? jsonPath.substring(0, jsonPath.length() - 1)
+                : jsonPath;
     }
 
     public <T> Optional<T> find(Cursor cursor) {

rewrite-json/src/test/java/org/openrewrite/json/AddKeyValueTest.java

@@ -17,6 +17,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.openrewrite.DocumentExample;
+import org.openrewrite.Issue;
 import org.openrewrite.test.RewriteTest;
 
 import static org.openrewrite.json.Assertions.json;
@@ -105,6 +106,28 @@ void shouldAppendToNestedObjectInArray() {
         );
     }
 
+    @Issue("https://github.com/openrewrite/rewrite/issues/6207")
+    @Test
+    void shouldAppendSimpleValueWithTrailingDot() {
+        rewriteRun(
+          spec -> spec.recipe(new AddKeyValue("$.", "surname", "\"Doe\"", false)),
+          //language=json
+          json(
+            """
+              {
+                  "name": "John"
+              }
+              """,
+            """
+              {
+                  "name": "John",
+                  "surname": "Doe"
+              }
+              """
+          )
+        );
+    }
+
     @Test
     void shouldNotAppendIfExists() {
         rewriteRun(