feat(parser): turn on the dialect's lexer feature preset in withDialect

src/main/java/net/sf/jsqlparser/parser/AbstractJSqlParser.java

@@ -13,7 +13,10 @@
 import net.sf.jsqlparser.parser.feature.FeatureConfiguration;
 
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.EnumSet;
 import java.util.List;
+import java.util.Set;
 
 public abstract class AbstractJSqlParser<P> {
 
@@ -22,7 +25,21 @@ public abstract class AbstractJSqlParser<P> {
     protected List<ParseException> parseErrors = new ArrayList<>();
 
     public enum Dialect {
-        ORACLE, EXASOL
+        ANSI_SQL, ORACLE, MYSQL(Feature.allowBackslashEscapeCharacter,
+                Feature.allowHashLineComments), MARIADB(Feature.allowBackslashEscapeCharacter,
+                        Feature.allowHashLineComments), SQLSERVER(
+                                Feature.allowSquareBracketQuotation), POSTGRESQL, H2, EXASOL;
+
+        private final Set<Feature> lexerFeatures;
+
+        Dialect(Feature... lexerFeatures) {
+            this.lexerFeatures = lexerFeatures.length == 0 ? EnumSet.noneOf(Feature.class)
+                    : EnumSet.copyOf(Arrays.asList(lexerFeatures));
+        }
+
+        public Set<Feature> getLexerFeatures() {
+            return lexerFeatures;
+        }
     }
 
     public P withSquareBracketQuotation() {
@@ -62,7 +79,11 @@ public P withTimeOut(long timeOutMillSeconds) {
     }
 
     public P withDialect(Dialect dialect) {
-        return withFeature(Feature.dialect, dialect.name());
+        withFeature(Feature.dialect, dialect.name());
+        for (Feature lexerFeature : dialect.getLexerFeatures()) {
+            withFeature(lexerFeature, true);
+        }
+        return me();
     }
 
     public P withAllowedNestingDepth(int allowedNestingDepth) {

src/site/sphinx/usage.rst

@@ -317,4 +317,16 @@ Additionally there are Features to control the Parser's effort at the cost of th
             sqlStr
             , parser -> parser
                 .withBackslashEscapeCharacter(true)
-    );
+    );
+
+Instead of turning the individual Parser Features on one by one, a ``Dialect`` preset selects the features of that database dialect: ``withDialect(Dialect.MYSQL)`` turns on ``withBackslashEscapeCharacter`` and ``withHashLineComments`` (both MySQL and MariaDB syntax), ``withDialect(Dialect.SQLSERVER)`` turns on ``withSquareBracketQuotation``. Features set explicitly after the dialect preset win over the preset.
+
+.. code-block:: java
+
+    // Select the Database Dialect: turns on that dialect's parser features
+    sqlStr="SELECT `col` FROM t WHERE a = 'x\\'yz' AND b = 42#24";
+    Statement stmt3 = CCJSqlParserUtil.parse(
+            sqlStr
+            , parser -> parser
+                .withDialect(Dialect.MYSQL)
+    );

src/test/java/net/sf/jsqlparser/parser/CCJSqlParserUtilTest.java

@@ -564,4 +564,51 @@ public void testHashLineCommentsMySQLStatementSemantics() throws Exception {
         assertEquals("SELECT 1 # comment",
                 CCJSqlParserUtil.parse("SELECT 1 # comment").toString());
     }
+
+    @Test
+    public void testDialectPresets() throws Exception {
+        // MYSQL and MARIADB: backslash escapes and # line comments (MySQL 8
+        // manual "Comments" and "String Literals", MariaDB KB "Comment Syntax"
+        // and "String Literals"); backticks are always on, brackets are not
+        // MySQL syntax
+        for (AbstractJSqlParser.Dialect dialect : new AbstractJSqlParser.Dialect[] {
+                AbstractJSqlParser.Dialect.MYSQL, AbstractJSqlParser.Dialect.MARIADB}) {
+            assertEquals("SELECT `col` FROM t WHERE a = 'x\\'yz' AND b = 42", CCJSqlParserUtil
+                    .parse("SELECT `col` FROM t WHERE a = 'x\\'yz' AND b = 42#24",
+                            p -> p.withDialect(dialect))
+                    .toString());
+        }
+        // SQLSERVER: bracket quotation only (Microsoft Learn "Database
+        // Identifiers"), `#` stays available for identifiers (temp tables)
+        assertEquals("SELECT [my column] FROM t",
+                CCJSqlParserUtil.parse("SELECT [my column] FROM t",
+                        p -> p.withDialect(AbstractJSqlParser.Dialect.SQLSERVER)).toString());
+        // empty presets keep the defaults: the #2507 operator, no backslash
+        // escapes
+        for (AbstractJSqlParser.Dialect dialect : new AbstractJSqlParser.Dialect[] {
+                AbstractJSqlParser.Dialect.ANSI_SQL, AbstractJSqlParser.Dialect.ORACLE,
+                AbstractJSqlParser.Dialect.POSTGRESQL, AbstractJSqlParser.Dialect.H2,
+                AbstractJSqlParser.Dialect.EXASOL}) {
+            assertEquals("SELECT 42 # 24",
+                    CCJSqlParserUtil.parse("SELECT 42 # 24", p -> p.withDialect(dialect))
+                            .toString());
+            assertThrows(JSQLParserException.class, () -> CCJSqlParserUtil
+                    .parse("SELECT 'a\\'b'", p -> p.withDialect(dialect)));
+        }
+    }
+
+    @Test
+    public void testDialectPresetSwitchOverrides() throws Exception {
+        // an explicit switch after the preset wins: `#` is the #2507
+        // operator again
+        assertEquals("SELECT 1 # comment", CCJSqlParserUtil.parse("SELECT 1 # comment",
+                p -> p.withDialect(AbstractJSqlParser.Dialect.MYSQL).withHashLineComments(false))
+                .toString());
+        // the preset never turns a previously enabled switch off
+        assertEquals("SELECT [my column] FROM mytable",
+                CCJSqlParserUtil.parse("SELECT [my column] FROM mytable",
+                        p -> p.withSquareBracketQuotation(true)
+                                .withDialect(AbstractJSqlParser.Dialect.MYSQL))
+                        .toString());
+    }
 }