parser: check invalid column define option for generated columns (pin…

…gcap#201)

* parser: add check on column options

* add related tests

* add more tests

* fix ident problems

* fix bug

* Code refine according to reviewer's opinion

ast/ddl.go

@@ -354,6 +354,14 @@ const (
 	ColumnOptionCollate
 )
 
+var (
+	invalidOptionForGeneratedColumn = map[ColumnOptionType]struct{}{
+		ColumnOptionAutoIncrement: {},
+		ColumnOptionOnUpdate:      {},
+		ColumnOptionDefaultValue:  {},
+	}
+)
+
 // ColumnOption is used for parsing column constraint info from SQL.
 type ColumnOption struct {
 	node
@@ -672,6 +680,23 @@ func (n *ColumnDef) Accept(v Visitor) (Node, bool) {
 	return v.Leave(n)
 }
 
+// Validate checks if a column definition is legal.
+// For example, generated column definitions that contain such
+// column options as `ON UPDATE`, `AUTO_INCREMENT`, `DEFAULT`
+// are illegal.
+func (n *ColumnDef) Validate() bool {
+	generatedCol := false
+	illegalOpt4gc := false
+	for _, opt := range n.Options {
+		if opt.Tp == ColumnOptionGenerated {
+			generatedCol = true
+		}
+		_, found := invalidOptionForGeneratedColumn[opt.Tp]
+		illegalOpt4gc = illegalOpt4gc || found
+	}
+	return !(generatedCol && illegalOpt4gc)
+}
+
 // CreateTableStmt is a statement to create a table.
 // See https://dev.mysql.com/doc/refman/5.7/en/create-table.html
 type CreateTableStmt struct {

parser.y

@@ -1550,7 +1550,12 @@ ColumnDefList:
 ColumnDef:
 	ColumnName Type ColumnOptionListOpt
 	{
-		$$ = &ast.ColumnDef{Name: $1.(*ast.ColumnName), Tp: $2.(*types.FieldType), Options: $3.([]*ast.ColumnOption)}
+		colDef := &ast.ColumnDef{Name: $1.(*ast.ColumnName), Tp: $2.(*types.FieldType), Options: $3.([]*ast.ColumnOption)}
+		if !colDef.Validate() {
+			yylex.AppendError(yylex.Errorf("Invalid column definition"))
+			return 1
+		}
+        $$ = colDef
 	}
 
 ColumnName: