Fix bug in ValidateInput

When reading from a stream reader that consumes input as it reads, validation
would fail because it would attempt to read the stream twice.

etree.go

@@ -358,9 +358,14 @@ func (d *Document) SetRoot(e *Element) {
 // returns the number of bytes read and any error encountered.
 func (d *Document) ReadFrom(r io.Reader) (n int64, err error) {
 	if d.ReadSettings.ValidateInput {
-		if err := validateXML(r, d.ReadSettings); err != nil {
+		b, err := io.ReadAll(r)
+		if err != nil {
 			return 0, err
 		}
+		if err := validateXML(bytes.NewReader(b), d.ReadSettings); err != nil {
+			return 0, err
+		}
+		r = bytes.NewReader(b)
 	}
 	return d.Element.readFrom(r, d.ReadSettings)
 }
@@ -373,19 +378,30 @@ func (d *Document) ReadFromFile(filepath string) error {
 		return err
 	}
 	defer f.Close()
+
 	_, err = d.ReadFrom(f)
 	return err
 }
 
 // ReadFromBytes reads XML from the byte slice 'b' into the this document.
 func (d *Document) ReadFromBytes(b []byte) error {
-	_, err := d.ReadFrom(bytes.NewReader(b))
+	if d.ReadSettings.ValidateInput {
+		if err := validateXML(bytes.NewReader(b), d.ReadSettings); err != nil {
+			return err
+		}
+	}
+	_, err := d.Element.readFrom(bytes.NewReader(b), d.ReadSettings)
 	return err
 }
 
 // ReadFromString reads XML from the string 's' into this document.
 func (d *Document) ReadFromString(s string) error {
-	_, err := d.ReadFrom(strings.NewReader(s))
+	if d.ReadSettings.ValidateInput {
+		if err := validateXML(strings.NewReader(s), d.ReadSettings); err != nil {
+			return err
+		}
+	}
+	_, err := d.Element.readFrom(strings.NewReader(s), d.ReadSettings)
 	return err
 }
 

etree_test.go

@@ -7,8 +7,12 @@ package etree
 import (
 	"bytes"
 	"encoding/xml"
+	"errors"
 	"io"
+	"io/fs"
 	"math/rand"
+	"os"
+	"path"
 	"strings"
 	"testing"
 )
@@ -1540,19 +1544,46 @@ func TestValidateInput(t *testing.T) {
 		{`<root><child>x</child></root1>`, `XML syntax error on line 1: element <root> closed by </root1>`},
 	}
 
-	for i, test := range tests {
-		doc := NewDocument()
-		doc.ReadSettings.ValidateInput = true
-		err := doc.ReadFromString(test.s)
-		if err == nil {
-			if test.err != "" {
-				t.Errorf("etree: test #%d:\nExpected error:\n  %s\nReceived error:\n  nil", i, test.err)
-			}
-		} else {
-			te := err.Error()
-			if te != test.err {
-				t.Errorf("etree: test #%d:\nExpected error;\n  %s\nReceived error:\n  %s", i, test.err, te)
+	type readFunc func(doc *Document, s string) error
+	runTests := func(t *testing.T, read readFunc) {
+		for i, test := range tests {
+			doc := NewDocument()
+			doc.ReadSettings.ValidateInput = true
+			err := read(doc, test.s)
+			if err == nil {
+				if test.err != "" {
+					t.Errorf("etree: test #%d:\nExpected error:\n  %s\nReceived error:\n  nil", i, test.err)
+				}
+				root := doc.Root()
+				if root == nil || root.Tag != "root" {
+					t.Errorf("etree: test #%d: failed to read document after input validation", i)
+				}
+			} else {
+				te := err.Error()
+				if te != test.err {
+					t.Errorf("etree: test #%d:\nExpected error;\n  %s\nReceived error:\n  %s", i, test.err, te)
+				}
 			}
 		}
 	}
+
+	readFromString := func(doc *Document, s string) error {
+		return doc.ReadFromString(s)
+	}
+	t.Run("ReadFromString", func(t *testing.T) { runTests(t, readFromString) })
+
+	readFromBytes := func(doc *Document, s string) error {
+		return doc.ReadFromBytes([]byte(s))
+	}
+	t.Run("ReadFromBytes", func(t *testing.T) { runTests(t, readFromBytes) })
+
+	readFromFile := func(doc *Document, s string) error {
+		pathtmp := path.Join(t.TempDir(), "etree-test")
+		err := os.WriteFile(pathtmp, []byte(s), fs.ModePerm)
+		if err != nil {
+			return errors.New("unable to write tmp file for input validation")
+		}
+		return doc.ReadFromFile(pathtmp)
+	}
+	t.Run("ReadFromFile", func(t *testing.T) { runTests(t, readFromFile) })
 }