Trim BindlableMongoExpression input.

Trim the given source so that wrapping checks still work for text blocks.
Fix a typo in Javadoc.

Resolves: #4821
Original Pull Request: #4822

Author: gbaso

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/BindableMongoExpression.java

@@ -23,13 +23,14 @@
 import org.springframework.data.mongodb.util.json.ParameterBindingDocumentCodec;
 import org.springframework.data.util.Lazy;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
  * A {@link MongoExpression} using the {@link ParameterBindingDocumentCodec} for parsing a raw ({@literal json})
  * expression. The expression will be wrapped within <code>{ ... }</code> if necessary. The actual parsing and parameter
- * binding of placeholders like {@code ?0} is delayed upon first call on the the target {@link Document} via
+ * binding of placeholders like {@code ?0} is delayed upon first call on the target {@link Document} via
  * {@link #toDocument()}.
  * <br />
  *
@@ -45,6 +46,7 @@
  * containing the required {@link org.bson.codecs.Codec codec} via {@link #withCodecRegistry(CodecRegistry)}.
  *
  * @author Christoph Strobl
+ * @author Giacomo Baso
  * @since 3.2
  */
 public class BindableMongoExpression implements MongoExpression {
@@ -77,7 +79,9 @@ public BindableMongoExpression(String expression, @Nullable Object[] args) {
 	public BindableMongoExpression(String expression, @Nullable CodecRegistryProvider codecRegistryProvider,
 			@Nullable Object[] args) {
 
-		this.expressionString = expression;
+		Assert.notNull(expression, "Expression must not be null");
+
+		this.expressionString = expression.trim();
 		this.codecRegistryProvider = codecRegistryProvider;
 		this.args = args;
 		this.target = Lazy.of(this::parse);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoTemplateFieldProjectionTests.java

@@ -42,6 +42,7 @@
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Giacomo Baso
  */
 @ExtendWith(MongoTemplateExtension.class)
 @EnableIfMongoServerVersion(isGreaterThanEqual = "4.4")
@@ -89,6 +90,21 @@ void usesMongoExpressionWithPlaceholdersAsIs() {
 		assertThat(result).isEqualTo(luke.upperCaseLastnameClone());
 	}
 
+	@Test // GH-4821
+	void usesMongoExpressionWithLineBreaksAsIs() {
+
+		Person result = findLuke(fields -> {
+			fields.include("firstname").project(MongoExpression.create("""
+							{
+							  '$toUpper' : '$last_name'
+							}
+							"""))
+					.as("last_name");
+		});
+
+		assertThat(result).isEqualTo(luke.upperCaseLastnameClone());
+	}
+
 	@Test // GH-3583
 	void mapsAggregationExpressionToDomainType() {