Separate ALTER key definitions from column drop targets

Signed-off-by: minleejae <mmj9808@gmail.com>

Author: minleejae

src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java

@@ -57,9 +57,7 @@ public enum TableRenameKeyword {
     private List<ColumnSetDefault> columnSetDefaultList;
     private List<ColumnSetVisibility> columnSetVisibilityList;
 
-    private List<String> pkColumns;
-    private List<String> ukColumns;
-    private String ukName;
+    private List<String> dropColumns;
     private Index index = null;
     private Index oldIndex = null;
     private NamedConstraint constraint;
@@ -94,8 +92,6 @@ public enum TableRenameKeyword {
      */
     @Deprecated
     private List<String> fkSourceColumns;
-    private boolean uk;
-    private boolean ukTypeSpecified;
     private boolean useEqual;
 
     private List<String> partitions;
@@ -551,75 +547,144 @@ public void setUsingIfExists(boolean usingIfExists) {
     }
 
     /**
-     * Returns a snapshot of the rendered key elements for a structured PRIMARY_KEY, or the legacy
-     * list otherwise. Changing the snapshot does not change the constraint; use
-     * {@link #setPkColumns(List)} to replace its keys, or {@link KeyConstraint#getColumns()} for
-     * structured edits.
+     * Returns the stored key definition, or null for another definition. The returned object is
+     * shared with {@link #getConstraint()} and can be edited directly.
+     */
+    public KeyConstraint getKeyConstraint() {
+        return constraint instanceof KeyConstraint ? (KeyConstraint) constraint : null;
+    }
+
+    /**
+     * Returns the owned mutable column targets for parenthesized DROP, DROP UNIQUE or DROP FOREIGN
+     * KEY syntax, or null when omitted. Stored targets are independent of any ADD definition.
+     */
+    public List<String> getDropColumns() {
+        return dropColumns;
+    }
+
+    /** Copies the supplied targets without changing the operation or any stored definition. */
+    public void setDropColumns(List<String> dropColumns) {
+        this.dropColumns = dropColumns == null ? null : new ArrayList<>(dropColumns);
+    }
+
+    public AlterExpression withDropColumns(List<String> dropColumns) {
+        setDropColumns(dropColumns);
+        return this;
+    }
+
+    public AlterExpression addDropColumns(String... columns) {
+        return addDropColumns(Arrays.asList(columns));
+    }
+
+    public AlterExpression addDropColumns(Collection<String> columns) {
+        if (dropColumns == null) {
+            dropColumns = new ArrayList<>();
+        }
+        dropColumns.addAll(columns);
+        return this;
+    }
+
+    /**
+     * Returns a rendered snapshot of the stored PRIMARY KEY's elements, or null when absent. For
+     * DROP, DROP UNIQUE and DROP FOREIGN KEY operations this legacy accessor instead returns a
+     * snapshot of {@link #getDropColumns()}. Snapshot edits never change the AST. New code should
+     * use {@link #getKeyConstraint()} or {@link #getDropColumns()} explicitly.
      */
     public List<String> getPkColumns() {
+        if (usesLegacyDropColumns()) {
+            return dropColumns == null ? null : new ArrayList<>(dropColumns);
+        }
         return hasKeyConstraint(ConstraintKind.PRIMARY_KEY)
                 ? ((KeyConstraint) constraint).getColumnsNames()
-                : pkColumns;
+                : null;
     }
 
     /**
-     * Replaces a structured PRIMARY_KEY's elements using
-     * {@link KeyConstraint#setColumnsNames(List)}. The strings are not parsed and existing element
-     * attributes are not retained, even when the rendered SQL is unchanged. Use
-     * {@link KeyConstraint#setColumns(List)} to preserve structured elements. Without a matching
-     * constraint, stores the legacy list.
+     * Replaces PRIMARY KEY elements with opaque names, without parsing or retaining element
+     * attributes. A non-null list creates a definition when none exists; a competing definition
+     * must be replaced explicitly using {@link #setConstraint(NamedConstraint)}. Null clears only
+     * an existing PRIMARY KEY's elements and does not create a definition. With DROP, DROP UNIQUE
+     * or DROP FOREIGN KEY already selected, delegates to {@link #setDropColumns(List)} instead. Set
+     * the operation first for this legacy DROP alias; new builders should use setDropColumns.
+     *
+     * @throws IllegalStateException if a non-null list would replace another definition
      */
     public void setPkColumns(List<String> pkColumns) {
-        if (hasKeyConstraint(ConstraintKind.PRIMARY_KEY)) {
-            ((KeyConstraint) constraint).setColumnsNames(pkColumns);
-            this.pkColumns = null;
-        } else {
-            this.pkColumns = pkColumns;
+        if (usesLegacyDropColumns()) {
+            setDropColumns(pkColumns);
+            return;
+        }
+        KeyConstraint key = keyForUpdate(ConstraintKind.PRIMARY_KEY, pkColumns != null);
+        if (key != null) {
+            key.setColumnsNames(pkColumns);
         }
     }
 
     /**
-     * Returns a snapshot of the rendered key elements for a structured UNIQUE, or the legacy list
-     * otherwise. Changing the snapshot does not change the constraint; use
-     * {@link #setUkColumns(List)} to replace its keys, or {@link KeyConstraint#getColumns()} for
-     * structured edits.
+     * Returns a snapshot of the stored UNIQUE's elements, or null when absent. Changing the
+     * snapshot does not change the constraint; use {@link #setUkColumns(List)} to replace its keys,
+     * or {@link KeyConstraint#getColumns()} for structured edits.
      */
     public List<String> getUkColumns() {
         return hasKeyConstraint(ConstraintKind.UNIQUE)
                 ? ((KeyConstraint) constraint).getColumnsNames()
-                : ukColumns;
+                : null;
     }
 
     /**
      * Replaces a structured UNIQUE's elements using {@link KeyConstraint#setColumnsNames(List)}.
      * The strings are not parsed and existing element attributes are not retained, even when the
      * rendered SQL is unchanged. Use {@link KeyConstraint#setColumns(List)} to preserve structured
-     * elements. Without a matching constraint, stores the legacy list.
+     * elements. A non-null list creates a UNIQUE definition only when none exists; a competing
+     * definition must be replaced explicitly. Null clears only an existing UNIQUE's elements.
+     *
+     * @throws IllegalStateException if a non-null list would replace another definition
      */
     public void setUkColumns(List<String> ukColumns) {
-        if (hasKeyConstraint(ConstraintKind.UNIQUE)) {
-            ((KeyConstraint) constraint).setColumnsNames(ukColumns);
-            this.ukColumns = null;
-        } else {
-            this.ukColumns = ukColumns;
+        KeyConstraint key = keyForUpdate(ConstraintKind.UNIQUE, ukColumns != null);
+        if (key != null) {
+            key.setColumnsNames(ukColumns);
         }
     }
 
+    private boolean usesLegacyDropColumns() {
+        return operation == AlterOperation.DROP || operation == AlterOperation.DROP_UNIQUE
+                || operation == AlterOperation.DROP_FOREIGN_KEY;
+    }
+
     private boolean hasKeyConstraint(ConstraintKind kind) {
         return constraint instanceof KeyConstraint && constraint.getKind() == kind;
     }
 
+    private KeyConstraint keyForUpdate(ConstraintKind kind, boolean create) {
+        if (hasKeyConstraint(kind)) {
+            return (KeyConstraint) constraint;
+        }
+        if (!create) {
+            return null;
+        }
+        if (constraint != null || index != null || getFkColumns() != null) {
+            throw new IllegalStateException(
+                    "Key setters cannot replace an existing definition; use setConstraint");
+        }
+        KeyConstraint key = new KeyConstraint()
+                .withType(kind == ConstraintKind.PRIMARY_KEY ? "PRIMARY KEY" : "UNIQUE");
+        setConstraint(key);
+        return key;
+    }
+
     public String getUkName() {
         return hasKeyConstraint(ConstraintKind.UNIQUE)
                 ? ((KeyConstraint) constraint).getIndexName()
-                : ukName;
+                : null;
     }
 
+    /** Uses the creation and replacement policy of {@link #setUkColumns(List)}. */
     public void setUkName(String ukName) {
-        if (hasKeyConstraint(ConstraintKind.UNIQUE)) {
-            ((KeyConstraint) constraint).setIndexName(ukName);
+        KeyConstraint key = keyForUpdate(ConstraintKind.UNIQUE, ukName != null);
+        if (key != null) {
+            key.setIndexName(ukName);
         }
-        this.ukName = ukName;
     }
 
     public Index getIndex() {
@@ -671,12 +736,6 @@ private ConstraintKind getAddedConstraintKind() {
         if (index != null) {
             return ConstraintKind.OTHER;
         }
-        if (pkColumns != null) {
-            return ConstraintKind.PRIMARY_KEY;
-        }
-        if (ukColumns != null) {
-            return ConstraintKind.UNIQUE;
-        }
         return fkColumns != null ? ConstraintKind.FOREIGN_KEY : ConstraintKind.OTHER;
     }
 
@@ -838,20 +897,53 @@ public void setUseEqual(boolean useEqual) {
     }
 
     public boolean getUk() {
-        return uk;
+        return "KEY".equalsIgnoreCase(getUniqueIndexKeyword());
     }
 
+    /** Selects KEY when true or INDEX when false on the stored UNIQUE definition. */
     public void setUk(boolean uk) {
-        this.uk = uk;
-        this.ukTypeSpecified = true;
+        setUniqueIndexKeyword(keyForUpdate(ConstraintKind.UNIQUE, true), uk ? "KEY" : "INDEX");
     }
 
     public boolean isUkTypeSpecified() {
-        return ukTypeSpecified;
+        return getUniqueIndexKeyword() != null;
     }
 
+    /**
+     * Removes the explicit KEY/INDEX spelling when false. When true, retains an existing spelling
+     * or selects INDEX. Clearing an absent UNIQUE definition does not create one.
+     */
     public void setUkTypeSpecified(boolean ukTypeSpecified) {
-        this.ukTypeSpecified = ukTypeSpecified;
+        KeyConstraint key = keyForUpdate(ConstraintKind.UNIQUE, ukTypeSpecified);
+        if (key != null) {
+            String keyword = getUniqueIndexKeyword();
+            setUniqueIndexKeyword(key,
+                    ukTypeSpecified ? keyword == null ? "INDEX" : keyword : null);
+        }
+    }
+
+    private String getUniqueIndexKeyword() {
+        KeyConstraint key = keyForUpdate(ConstraintKind.UNIQUE, false);
+        if (key == null) {
+            return null;
+        }
+        if (key.getIndexKeyword() != null) {
+            return key.getIndexKeyword();
+        }
+        if ("UNIQUE KEY".equalsIgnoreCase(key.getType())) {
+            return "KEY";
+        }
+        return "UNIQUE INDEX".equalsIgnoreCase(key.getType()) ? "INDEX" : null;
+    }
+
+    private void setUniqueIndexKeyword(KeyConstraint key, String keyword) {
+        if (hasLegacyKeyConstraint() || "UNIQUE KEY".equalsIgnoreCase(key.getType())
+                || "UNIQUE INDEX".equalsIgnoreCase(key.getType())) {
+            key.setType("UNIQUE" + (keyword == null ? "" : " " + keyword));
+            key.setIndexKeyword(null);
+        } else {
+            key.setIndexKeyword(keyword);
+        }
     }
 
     public boolean isUseIfNotExists() {
@@ -1059,7 +1151,7 @@ protected boolean isDropSpecialOperation() {
             case DROP_CHECK:
                 return true;
             case DROP:
-                return columnName == null && pkColumns != null && !pkColumns.isEmpty();
+                return columnName == null && dropColumns != null && !dropColumns.isEmpty();
             default:
                 return false;
         }
@@ -1220,22 +1312,23 @@ protected void toStringDropSpecial(StringBuilder b) {
                 b.append("DROP PRIMARY KEY ");
                 break;
             case DROP_UNIQUE:
-                b.append("DROP UNIQUE (").append(PlainSelect.getStringList(pkColumns)).append(')');
+                b.append("DROP UNIQUE (").append(PlainSelect.getStringList(dropColumns))
+                        .append(')');
                 break;
             case DROP_FOREIGN_KEY:
                 b.append("DROP FOREIGN KEY ");
                 if (constraintName != null) {
                     b.append(constraintName);
                 } else {
-                    b.append('(').append(PlainSelect.getStringList(pkColumns)).append(')');
+                    b.append('(').append(PlainSelect.getStringList(dropColumns)).append(')');
                 }
                 break;
             case DROP_CHECK:
                 b.append("DROP CHECK ").append(constraintName);
                 break;
             default:
                 // Oracle Multi Column Drop
-                b.append("DROP (").append(PlainSelect.getStringList(pkColumns)).append(')');
+                b.append("DROP (").append(PlainSelect.getStringList(dropColumns)).append(')');
                 break;
         }
     }
@@ -1451,26 +1544,7 @@ private void toStringGeneral(StringBuilder b, Consumer<ColumnDataType> columnPri
         } else if (constraint != null) {
             b.append(constraint);
         } else if (index != null) {
-            // The structured index is canonical. Legacy PK/UK/FK fields may also be populated for
-            // source compatibility, but cannot represent names, expressions, or index options.
             b.append(index);
-        } else if (pkColumns != null) {
-            b.append("PRIMARY KEY (").append(PlainSelect.getStringList(pkColumns)).append(')');
-        } else if (ukColumns != null) {
-            b.append("UNIQUE");
-            if (ukName != null) {
-                if (isUkTypeSpecified()) {
-                    if (getUk()) {
-                        b.append(" KEY ");
-                    } else {
-                        b.append(" INDEX ");
-                    }
-                } else {
-                    b.append(" ");
-                }
-                b.append(ukName);
-            }
-            b.append(" (").append(PlainSelect.getStringList(ukColumns)).append(")");
         } else if (fkColumns != null) {
             // @deprecated path - kept for backward compatibility when ForeignKeyConstraint is not
             // set