Reuse common JOIN traversal when discovering UPDATE tables

src/main/java/net/sf/jsqlparser/util/TablesNamesFinder.java

@@ -1393,11 +1393,7 @@ public <S> Void visit(Update update, S context) {
             visit(update.getTable(), context);
         }
 
-        if (update.getStartJoins() != null) {
-            for (Join join : update.getStartJoins()) {
-                join.getRightItem().accept(this, context);
-            }
-        }
+        visitJoins(update.getStartJoins(), context);
 
         if (update.getUpdateSets() != null) {
             for (UpdateSet updateSet : update.getUpdateSets()) {
@@ -1410,14 +1406,7 @@ public <S> Void visit(Update update, S context) {
             update.getFromItem().accept(this, context);
         }
 
-        if (update.getJoins() != null) {
-            for (Join join : update.getJoins()) {
-                join.getRightItem().accept(this, context);
-                for (Expression expression : join.getOnExpressions()) {
-                    expression.accept(this, context);
-                }
-            }
-        }
+        visitJoins(update.getJoins(), context);
 
         if (update.getWhere() != null) {
             update.getWhere().accept(this, context);

src/test/java/net/sf/jsqlparser/util/UpdateJoinTablesTest.java

@@ -0,0 +1,54 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2019 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import java.util.Set;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.schema.Table;
+import net.sf.jsqlparser.statement.update.Update;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class UpdateJoinTablesTest {
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "UPDATE target t JOIN source s ON s.id IN (SELECT id FROM hidden) SET t.a = 1",
+            "UPDATE target t LEFT JOIN source s ON EXISTS (SELECT 1 FROM hidden h WHERE h.id = s.id) SET t.a = 1",
+            "UPDATE target SET a = 1 FROM source s JOIN target t ON s.id IN (SELECT id FROM hidden)",
+            "WITH h AS (SELECT id FROM hidden) UPDATE target t JOIN source s ON s.id IN (SELECT id FROM h) SET t.a = 1"})
+    void includesTablesInsideJoinConditions(String sql) throws Exception {
+        assertEquals(Set.of("target", "source", "hidden"), TablesNamesFinder.findTables(sql));
+    }
+
+    @Test
+    void preservesContextAndVisitsEachSourceOnce() throws Exception {
+        Update update = (Update) CCJSqlParserUtil.parse(
+                "UPDATE target t JOIN source s ON s.id IN (SELECT id FROM hidden) SET t.a = 1");
+        Object context = new Object();
+        java.util.List<String> seen = new java.util.ArrayList<>();
+        TablesNamesFinder<Void> finder = new TablesNamesFinder<Void>() {
+            {
+                init(false);
+            }
+
+            @Override
+            public <S> Void visit(Table table, S actual) {
+                assertSame(context, actual);
+                seen.add(table.getName());
+                return null;
+            }
+        };
+        update.accept(finder, context);
+        assertEquals(java.util.List.of("target", "source", "hidden"), seen);
+    }
+}