Polishing.

Resolve collation from template expression & update issue references + Javadoc.

Original Pull Request: #4131

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/CompoundIndex.java

@@ -22,6 +22,7 @@
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.data.mongodb.core.mapping.Document;
 /**
  * Mark a class to use compound indexes. <br />
  * <p>
@@ -166,17 +167,19 @@
 	String partialFilter() default "";
 
 	/**
-	 * The actual collation definition in JSON format or a {@link org.springframework.expression.spel.standard.SpelExpression
-	 * template expression} resolving to either a JSON String or a {@link org.bson.Document}. The keys of the JSON
-	 * document are configuration options for the collation (language-specific rules for string comparison).
-	 * <br><br>
-	 * TODO write code documentation & example!!!
-	 * <br>
+	 * The actual collation definition in JSON format or a
+	 * {@link org.springframework.expression.spel.standard.SpelExpression template expression} resolving to either a JSON
+	 * String or a {@link org.bson.Document}. The keys of the JSON document are configuration options for the collation
+	 * (language-specific rules for string comparison) to be applied on string properties being part of the index.
+	 * <p>
+	 * <strong>NOTE:</strong> Overrides {@link Document#collation()}.
+	 * <p>
+	 *
 	 *
 	 * @return empty String by default.
 	 * @see <a href=
-	 * "https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation/</a>
-	 * @since 3.4
+	 *      "https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation/</a>
+	 * @since 4.0
 	 */
 	String collation() default "";
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/Indexed.java

@@ -20,6 +20,7 @@
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.data.mongodb.core.mapping.Document;
 /**
  * Mark a field to be indexed using MongoDB's indexing feature.
  *
@@ -176,12 +177,16 @@
 	String partialFilter() default "";
 
 	/**
-	 * Apply collation configuration for field <br />
+	 * The actual collation definition in JSON format or a
+	 * {@link org.springframework.expression.spel.standard.SpelExpression template expression} resolving to either a JSON
+	 * String or a {@link org.bson.Document}. The keys of the JSON document are configuration options for the collation
+	 * (language-specific rules for string comparison) applied to the indexed based on the field value.
+	 * <p>
+	 * <strong>NOTE:</strong> Overrides {@link Document#collation()}.
 	 *
 	 * @return empty by default.
-	 * @see <a href=
-	 *      "https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation//</a>
-	 * @since 3.1
+	 * @see <a href="https://www.mongodb.com/docs/manual/reference/collation/">https://www.mongodb.com/docs/manual/reference/collation/</a>
+	 * @since 4.0
 	 */
 	String collation() default "";
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/MongoPersistentEntityIndexResolver.java

@@ -455,7 +455,7 @@ protected IndexDefinitionHolder createCompoundIndexDefinition(String dotPath, St
 		}
 
 		if (StringUtils.hasText(index.collation())) {
-			indexDefinition.collation(Collation.parse(index.collation()));
+			indexDefinition.collation(evaluateCollation(index.collation(), entity));
 		}
 
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
@@ -578,7 +578,7 @@ protected IndexDefinitionHolder createIndexDefinition(String dotPath, String col
 		}
 
 		if (StringUtils.hasText(index.collation())) {
-			indexDefinition.collation(Collation.parse(index.collation()));
+			indexDefinition.collation(evaluateCollation(index.collation(), persistentProperty.getOwner()));
 		}
 
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);

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

@@ -93,7 +93,7 @@ public void readsWildcardIndexProjectionCorrectly() {
 				.contains(new Document("fieldA", 0).append("fieldB.fieldC", 0));
 	}
 
-	@Test // DATAMONGO-2133
+	@Test // GH-3002
 	public void collationParsedCorrectly() {
 		assertThat(getIndexInfo(INDEX_WITH_COLLATION).getCollation())
 				.contains(Document.parse("{ \"locale\": \"en_US\", \"strength\": 2 }"));

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

@@ -700,7 +700,7 @@ public void singleIndexWithPartialFilter() {
 					org.bson.Document.parse("{'value': {'$exists': true}}"));
 		}
 
-		@Test // DATAMONGO-2133
+		@Test // GH-3002
 		public void compoundIndexWithCollation() {
 
 			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(
@@ -1419,7 +1419,7 @@ public void shouldSkipMapStructuresUnlessAnnotatedWithWildcardIndex() {
 			assertThat(indexDefinitions).hasSize(1);
 		}
 
-		@Test // DATAMONGO-2133
+		@Test // GH-3002
 		public void indexedWithCollation() {
 
 			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(