Add checker.ParseCheck func

Author: antonmedv

checker/checker.go

@@ -13,6 +13,45 @@ import (
 	"github.com/expr-lang/expr/parser"
 )
 
+// ParseCheck parses input expression and checks its types. Also, it applies
+// all provided patchers. In case of error, it returns error with a tree.
+func ParseCheck(input string, config *conf.Config) (*parser.Tree, error) {
+	tree, err := parser.ParseWithConfig(input, config)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(config.Visitors) > 0 {
+		for i := 0; i < 1000; i++ {
+			more := false
+			for _, v := range config.Visitors {
+				// We need to perform types check, because some visitors may rely on
+				// types information available in the tree.
+				_, _ = Check(tree, config)
+
+				ast.Walk(&tree.Node, v)
+
+				if v, ok := v.(interface {
+					ShouldRepeat() bool
+				}); ok {
+					more = more || v.ShouldRepeat()
+				}
+			}
+			if !more {
+				break
+			}
+		}
+	}
+	_, err = Check(tree, config)
+	if err != nil {
+		return tree, err
+	}
+
+	return tree, nil
+}
+
+// Check checks types of the expression tree. It returns type of the expression
+// and error if any. If config is nil, then default configuration will be used.
 func Check(tree *parser.Tree, config *conf.Config) (t reflect.Type, err error) {
 	if config == nil {
 		config = conf.New(nil)

expr.go

@@ -13,7 +13,6 @@ import (
 	"github.com/expr-lang/expr/conf"
 	"github.com/expr-lang/expr/file"
 	"github.com/expr-lang/expr/optimizer"
-	"github.com/expr-lang/expr/parser"
 	"github.com/expr-lang/expr/patcher"
 	"github.com/expr-lang/expr/vm"
 )
@@ -206,33 +205,7 @@ func Compile(input string, ops ...Option) (*vm.Program, error) {
 	}
 	config.Check()
 
-	tree, err := parser.ParseWithConfig(input, config)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(config.Visitors) > 0 {
-		for i := 0; i < 1000; i++ {
-			more := false
-			for _, v := range config.Visitors {
-				// We need to perform types check, because some visitors may rely on
-				// types information available in the tree.
-				_, _ = checker.Check(tree, config)
-
-				ast.Walk(&tree.Node, v)
-
-				if v, ok := v.(interface {
-					ShouldRepeat() bool
-				}); ok {
-					more = more || v.ShouldRepeat()
-				}
-			}
-			if !more {
-				break
-			}
-		}
-	}
-	_, err = checker.Check(tree, config)
+	tree, err := checker.ParseCheck(input, config)
 	if err != nil {
 		return nil, err
 	}