Add support for IS NULL and IS NOT NULL syntax

compose/internal/repository/ql/ast_nodes.go

@@ -20,6 +20,8 @@ type (
 
 	Columns []Column
 
+	Null struct{}
+
 	String struct {
 		Value string
 		Args  []interface{}
@@ -51,12 +53,16 @@ type (
 		Expr  ASTNodes
 		Alias string
 	}
+
 	Function struct {
 		Name      string
 		Arguments ASTSet
 	}
 )
 
+func (n Null) Validate() (err error) { return }
+func (n Null) String() string        { return "NULL" }
+
 func (n String) Validate() (err error) { return }
 func (n String) String() string        { return fmt.Sprintf("%q", n.Value) }
 

compose/internal/repository/ql/ast_parser.go

@@ -166,6 +166,8 @@ checkToken:
 			list = append(list, ident)
 			goto next
 		}
+	case NULL:
+		list = append(list, Null{})
 	case OPERATOR:
 		if len(list) > 0 {
 			// Merge with previous operator node

compose/internal/repository/ql/ast_parser_test.go

@@ -156,6 +156,33 @@ func TestAstParser_Parser(t *testing.T) {
 				String{Value: "bar%"},
 			},
 		},
+		{
+			parser: NewParser().ParseExpression,
+			in:     `foo = NULL`,
+			tree: ASTNodes{
+				Ident{Value: "foo"},
+				Operator{Kind: "="},
+				Null{},
+			},
+		},
+		{
+			parser: NewParser().ParseExpression,
+			in:     `foo IS NOT NULL`,
+			tree: ASTNodes{
+				Ident{Value: "foo"},
+				Operator{Kind: "IS NOT"},
+				Null{},
+			},
+		},
+		{
+			parser: NewParser().ParseExpression,
+			in:     `foo IS NULL`,
+			tree: ASTNodes{
+				Ident{Value: "foo"},
+				Operator{Kind: "IS"},
+				Null{},
+			},
+		},
 	}
 
 	for i, test := range tests {

compose/internal/repository/ql/squirrel.go

@@ -62,6 +62,10 @@ func (n Ident) ToSql() (string, []interface{}, error) {
 	return n.Value, n.Args, nil
 }
 
+func (n Null) ToSql() (string, []interface{}, error) {
+	return "NULL", nil, nil
+}
+
 func (n Function) ToSql() (string, []interface{}, error) {
 	if paramsSql, args, err := n.Arguments.ToSql(); err != nil {
 		return "", nil, err

compose/internal/repository/ql/token_codes.go

@@ -23,4 +23,5 @@ const (
 	PARENTHESIS_OPEN
 	PARENTHESIS_CLOSE
 	KEYWORD
+	NULL
 )

compose/internal/repository/ql/token_consumers.go

@@ -85,7 +85,9 @@ func (TokenConsumerIdent) Consume(s RuneReader) Token {
 	lit := strings.ToUpper(buf.String())
 
 	switch lit {
-	case "LIKE", "NOT", "AND", "OR", "XOR":
+	case "NULL":
+		return Token{code: NULL}
+	case "IS", "LIKE", "NOT", "AND", "OR", "XOR":
 		return Token{code: OPERATOR, literal: lit}
 	case "DESC", "ASC", "INTERVAL":
 		return Token{code: KEYWORD, literal: lit}