Add more tests and comments

Author: antonmedv

conf/config.go

@@ -11,10 +11,10 @@ import (
 )
 
 var (
-	// DefaultMemoryBudget represents an upper limit of memory usage
+	// DefaultMemoryBudget represents default maximum allowed memory usage by the vm.VM.
 	DefaultMemoryBudget uint = 1e6
 
-	// DefaultMaxNodes represents an upper limit of AST nodes
+	// DefaultMaxNodes represents default maximum allowed AST nodes by the compiler.
 	DefaultMaxNodes uint = 1e4
 )
 

expr.go

@@ -197,6 +197,7 @@ func Timezone(name string) Option {
 
 // MaxNodes sets the maximum number of nodes allowed in the expression.
 // By default, the maximum number of nodes is conf.DefaultMaxNodes.
+// If MaxNodes is set to 0, the node budget check is disabled.
 func MaxNodes(n uint) Option {
 	return func(c *conf.Config) {
 		c.MaxNodes = n

expr_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/expr-lang/expr/conf"
 	"github.com/expr-lang/expr/internal/testify/assert"
 	"github.com/expr-lang/expr/internal/testify/require"
 	"github.com/expr-lang/expr/types"
@@ -2729,6 +2730,16 @@ func TestMaxNodes(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestMaxNodesDisabled(t *testing.T) {
+	code := ""
+	for i := 0; i < 2*int(conf.DefaultMaxNodes); i++ {
+		code += "1; "
+	}
+
+	_, err := expr.Compile(code, expr.MaxNodes(0))
+	require.NoError(t, err)
+}
+
 func TestMemoryBudget(t *testing.T) {
 	tests := []struct {
 		code string