Add callbacks for variable creation.

docs/cypher-parser/cypher-parser.adoc

@@ -232,4 +232,25 @@ include::../../neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/main
 ----
 <.> The condition that only people born later than 1980 is hard coded in the service.
     An arbitrary String is than parsed into a condition and attached via `AND`.
-    Thus only valid cypher can go in there and with filters and callbacks, preconditions of that Cypher can be asserted.
+    Thus, only valid cypher can go in there and with filters and callbacks, preconditions of that Cypher can be asserted.
+
+The downside to the above solution is that the query fragment passed to the service and eventually the repository must
+know the root node (which is `n` in case of SDN 6) and the caller code might look like this:
+
+[source,java,indent=0,tabsize=4]
+----
+include::../../neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/test/java/org/neo4j/cypherdsl/examples/sdn6/ApplicationIT.java[tag=exchange1]
+----
+
+Notice `n.name` etc.
+We could change the service method slightly and apply a callback like this:
+
+[source,java,indent=0,tabsize=4]
+----
+include::../../neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/main/java/org/neo4j/cypherdsl/examples/sdn6/movies/PeopleService.java[tag=using-parser-with-spring2]
+----
+<.> Create a function that takes the value of a variable created in the fragment and use it to look up a property on the
+    SDN root node.
+<.> Create an instance of parsing options. It's probably a good idea todo this once and store them away in an instance variable.
+    Options are thread safe.
+<.> Apply them when calling the corresponding parse method

neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/main/java/org/neo4j/cypherdsl/examples/sdn6/movies/PeopleController.java

@@ -54,9 +54,15 @@ Iterable<Person> findPeopleBornInThe70tiesOr(@RequestParam(name = "name") Option
 		return peopleService.findPeopleBornInThe70tiesOr(optionalName);
 	}
 
-	@GetMapping("/findPeopleBornAfterThe70ties")
+	@GetMapping("/v1/findPeopleBornAfterThe70ties")
 	Iterable<Person> findPeopleBornAfterThe70ties(@RequestParam(name = "conditions") String additionalConditions) {
 
 		return peopleService.findPeopleBornAfterThe70tiesAnd(additionalConditions);
 	}
+
+	@GetMapping("/v2/findPeopleBornAfterThe70ties")
+	Iterable<Person> findPeopleBornAfterThe70tiesV2(@RequestParam(name = "conditions") String additionalConditions) {
+
+		return peopleService.findPeopleBornAfterThe70tiesAndV2(additionalConditions);
+	}
 }

neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/main/java/org/neo4j/cypherdsl/examples/sdn6/movies/PeopleService.java

@@ -20,14 +20,20 @@
 
 // tag::using-person-repo[]
 import java.util.Optional;
+import java.util.function.Function;
 
 import org.neo4j.cypherdsl.core.Conditions;
 import org.neo4j.cypherdsl.core.Cypher;
+import org.neo4j.cypherdsl.core.Expression;
 import org.neo4j.cypherdsl.core.Functions;
 // end::using-person-repo[]
+import org.neo4j.cypherdsl.core.SymbolicName;
 import org.neo4j.cypherdsl.parser.CypherParser;
+import org.neo4j.cypherdsl.parser.ExpressionCreatedEventType;
+import org.neo4j.cypherdsl.parser.Options;
 import org.springframework.data.domain.Example;
 // tag::using-person-repo[]
+import org.springframework.data.neo4j.core.mapping.Constants;
 import org.springframework.stereotype.Service;
 
 // end::using-person-repo[]
@@ -63,6 +69,30 @@ Iterable<Person> findPeopleBornAfterThe70tiesAnd(String additionalConditions) {
 	}
 	// end::using-parser-with-spring[]
 
+	// tag::using-parser-with-spring2[]
+	Iterable<Person> findPeopleBornAfterThe70tiesAndV2(String additionalConditions) {
+
+		Function<Expression, Expression> enforceReference =
+			e -> Constants.NAME_OF_ROOT_NODE.property(((SymbolicName) e).getValue()); // <.>
+		var parserOptions = Options.newOptions()
+			.withCallback(
+				ExpressionCreatedEventType.ON_NEW_VARIABLE,
+				Expression.class,
+				enforceReference
+			) // <.>
+			.build();
+
+		return peopleRepository.findAll(
+			PERSON.BORN.gte(Cypher.literalOf(1980)).and(
+				CypherParser.parseExpression(
+					additionalConditions,
+					parserOptions // <.>
+				).asCondition()
+			)
+		);
+	}
+	// end::using-parser-with-spring2[]
+
 	// tag::using-person-repo[]
 	Iterable<Person> findPeopleBornInThe70tiesOr(Optional<String> optionalName) {
 

neo4j-cypher-dsl-examples/neo4j-cypher-dsl-examples-sdn6/src/test/java/org/neo4j/cypherdsl/examples/sdn6/ApplicationIT.java

@@ -179,9 +179,26 @@ void findPeopleBornInThe70tiesOrShouldWork2(@Autowired TestRestTemplate restTemp
 	@DisplayName("Using conditions pt3.")
 	void findPeopleBornAfterThe70tiesShouldWork(@Autowired TestRestTemplate restTemplate) {
 
+		// tag::exchange1[]
+		var exchange = restTemplate.exchange(
+			"/api/people/v1/findPeopleBornAfterThe70ties?conditions={conditions}",
+			HttpMethod.GET,
+			null, new ParameterizedTypeReference<List<Person>>() { },
+			"n.name contains \"Ricci\" OR n.name ends with 'Hirsch'"
+		);
+		// end::exchange1[]
+		assertThat(exchange.getStatusCode()).isEqualTo(HttpStatus.OK);
+		var people = exchange.getBody();
+		assertThat(people).hasSize(2);
+	}
+
+	@Test
+	@DisplayName("Using conditions pt4.")
+	void findPeopleBornAfterThe70tiesV2ShouldWork(@Autowired TestRestTemplate restTemplate) {
+
 		var exchange = restTemplate
-			.exchange("/api/people/findPeopleBornAfterThe70ties?conditions={conditions}", HttpMethod.GET, null, new ParameterizedTypeReference<List<Person>>() {
-			}, "n.name contains \"Ricci\" OR n.name ends with 'Hirsch'");
+			.exchange("/api/people/v2/findPeopleBornAfterThe70ties?conditions={conditions}", HttpMethod.GET, null, new ParameterizedTypeReference<List<Person>>() {
+			}, "name contains \"Ricci\" OR name ends with 'Hirsch'");
 		assertThat(exchange.getStatusCode()).isEqualTo(HttpStatus.OK);
 		var people = exchange.getBody();
 		assertThat(people).hasSize(2);