feat: make BooleanExpression Aliaseable (#307)

exp/bool.go

@@ -35,6 +35,10 @@ func (b boolean) Op() BooleanOperation {
 	return b.op
 }
 
+func (b boolean) As(val interface{}) AliasedExpression {
+	return NewAliasExpression(b, val)
+}
+
 // used internally to create an equality BooleanExpression
 func eq(lhs Expression, rhs interface{}) BooleanExpression {
 	return checkBoolExpType(EqOp, lhs, rhs, false)

exp/exp.go

@@ -209,6 +209,7 @@ type (
 	BooleanOperation  int
 	BooleanExpression interface {
 		Expression
+		Aliaseable
 		// Returns the operator for the expression
 		Op() BooleanOperation
 		// The left hand side of the expression (e.g. I("a")

sqlgen/expression_sql_generator_test.go

@@ -473,6 +473,16 @@ func (esgs *expressionSQLGeneratorSuite) TestGenerate_AliasedExpression() {
 	)
 }
 
+func (esgs *expressionSQLGeneratorSuite) TestGenerate_BooleanExpressionAliased() {
+	ident := exp.NewIdentifierExpression("", "", "a")
+
+	esgs.assertCases(
+		sqlgen.NewExpressionSQLGenerator("test", sqlgen.DefaultDialectOptions()),
+		expressionTestCase{val: ident.Eq(1).As("b"), sql: `("a" = 1) AS "b"`},
+		expressionTestCase{val: ident.Eq(1).As("b"), sql: `("a" = ?) AS "b"`,
+			isPrepared: true, args: []interface{}{int64(1)}},
+	)
+}
 func (esgs *expressionSQLGeneratorSuite) TestGenerate_BooleanExpression() {
 	ae := newTestAppendableExpression(`SELECT "id" FROM "test2"`, emptyArgs, nil, nil)
 	re := regexp.MustCompile("[ab]")

sqlgen/select_sql_generator_test.go

@@ -57,13 +57,32 @@ func (ssgs *selectSQLGeneratorSuite) TestGenerate() {
 	sc := exp.NewSelectClauses().SetFrom(exp.NewColumnListExpression("test"))
 	scWithCols := sc.SetSelect(exp.NewColumnListExpression("a", "b"))
 
+	ident := exp.NewIdentifierExpression("", "", "a")
+	scWithBooExpAliased := sc.SetSelect(
+		exp.NewColumnListExpression(
+			ident.Eq(1).As("x"),
+			ident.IsNull().As("y"),
+		),
+	)
+
 	ssgs.assertCases(
 		sqlgen.NewSelectSQLGenerator("test", opts),
 		selectTestCase{clause: sc, sql: `select # FROM "test"`},
 		selectTestCase{clause: sc, sql: `select # FROM "test"`, isPrepared: true},
 
 		selectTestCase{clause: scWithCols, sql: `select "a", "b" FROM "test"`},
 		selectTestCase{clause: scWithCols, sql: `select "a", "b" FROM "test"`, isPrepared: true},
+
+		selectTestCase{
+			clause: scWithBooExpAliased,
+			sql:    `select ("a" = 1) AS "x", ("a" IS NULL) AS "y" FROM "test"`,
+		},
+		selectTestCase{
+			clause:     scWithBooExpAliased,
+			sql:        `select ("a" = ?) AS "x", ("a" IS NULL) AS "y" FROM "test"`,
+			isPrepared: true,
+			args:       []interface{}{int64(1)},
+		},
 	)
 }