Count query generation should handle missing alias.

In the event of a Hibernate query where the FROM clause has no alias, the query parser should use "__" as a stand-in alias.

Resolves spring-projects#2032.
Related: spring-projects#2220.

Author: gregturn

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/HqlQueryTransformer.java

@@ -243,6 +243,17 @@ public List<JpaQueryParsingToken> visitFromRoot(HqlParser.FromRootContext ctx) {
 				if (this.alias == null && !isSubquery(ctx)) {
 					this.alias = tokens.get(tokens.size() - 1).getToken();
 				}
+			} else {
+
+				if (countQuery) {
+
+					tokens.add(TOKEN_AS);
+					tokens.add(TOKEN_DOUBLE_UNDERSCORE);
+
+					if (this.alias == null && !isSubquery(ctx)) {
+						this.alias = TOKEN_DOUBLE_UNDERSCORE.getToken();
+					}
+				}
 			}
 		} else if (ctx.subquery() != null) {
 

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryParsingToken.java

@@ -17,7 +17,6 @@
 
 import java.util.List;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.tree.TerminalNode;
@@ -53,6 +52,10 @@ class JpaQueryParsingToken {
 	public static final JpaQueryParsingToken TOKEN_CLOSE_SQUARE_BRACKET_BRACE = new JpaQueryParsingToken("]}");
 	public static final JpaQueryParsingToken TOKEN_CLOSE_PAREN_BRACE = new JpaQueryParsingToken(")}");
 
+	public static final JpaQueryParsingToken TOKEN_DOUBLE_UNDERSCORE = new JpaQueryParsingToken("__");
+
+	public static final JpaQueryParsingToken TOKEN_AS = new JpaQueryParsingToken("AS");
+
 	public static final JpaQueryParsingToken TOKEN_DESC = new JpaQueryParsingToken("desc", false);
 
 	public static final JpaQueryParsingToken TOKEN_ASC = new JpaQueryParsingToken("asc", false);

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/query/HqlQueryTransformerTests.java

@@ -798,6 +798,16 @@ void queryParserPicksCorrectAliasAmidstMultipleAlises() {
 		assertThat(alias("select u from User as u left join  u.roles as r")).isEqualTo("u");
 	}
 
+	@Test // GH-2032
+	void countQueryShouldWorkEvenWithoutExplicitAlias() {
+
+		assertCountQuery("FROM BookError WHERE portal = :portal",
+				"select count(__) FROM BookError AS __ WHERE portal = :portal");
+
+		assertCountQuery("FROM BookError b WHERE portal = :portal",
+				"select count(b) FROM BookError b WHERE portal = :portal");
+	}
+
 	private void assertCountQuery(String originalQuery, String countQuery) {
 		assertThat(createCountQueryFor(originalQuery)).isEqualTo(countQuery);
 	}