feat: set SpecVersion when decoding from xml

`SpecVersion` as a field is only used in the json format, but when working with `BOM` instances it is useful to know what spec version one is dealing with.

Signed-off-by: nscuro <nscuro@protonmail.com>

decode.go

@@ -49,5 +49,17 @@ type xmlBOMDecoder struct {
 
 // Decode implements the BOMDecoder interface.
 func (x xmlBOMDecoder) Decode(bom *BOM) error {
-	return xml.NewDecoder(x.reader).Decode(bom)
+	err := xml.NewDecoder(x.reader).Decode(bom)
+	if err != nil {
+		return err
+	}
+
+	for specVersion, xmlNs := range xmlNamespaces {
+		if xmlNs == bom.XMLNS {
+			bom.SpecVersion = specVersion
+			break
+		}
+	}
+
+	return nil
 }

decode_test.go

@@ -18,12 +18,57 @@
 package cyclonedx
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestNewBOMDecoder(t *testing.T) {
 	assert.IsType(t, &jsonBOMDecoder{}, NewBOMDecoder(nil, BOMFileFormatJSON))
 	assert.IsType(t, &xmlBOMDecoder{}, NewBOMDecoder(nil, BOMFileFormatXML))
 }
+
+func TestXmlBOMDecoder_Decode(t *testing.T) {
+	t.Run("ShouldSetSpecVersion", func(t *testing.T) {
+		testCases := []struct {
+			bomContent  string
+			specVersion SpecVersion
+		}{
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/1.0"></bom>`,
+				specVersion: SpecVersion1_0,
+			},
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/1.1"></bom>`,
+				specVersion: SpecVersion1_1,
+			},
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/1.2"></bom>`,
+				specVersion: SpecVersion1_2,
+			},
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/1.3"></bom>`,
+				specVersion: SpecVersion1_3,
+			},
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/1.4"></bom>`,
+				specVersion: SpecVersion1_4,
+			},
+			{
+				bomContent:  `<?xml version="1.0"?><bom version="1" xmlns="http://cyclonedx.org/schema/bom/666"></bom>`,
+				specVersion: SpecVersion(0),
+			},
+		}
+
+		for _, tc := range testCases {
+			t.Run(tc.specVersion.String(), func(t *testing.T) {
+				var bom BOM
+				err := NewBOMDecoder(strings.NewReader(tc.bomContent), BOMFileFormatXML).Decode(&bom)
+				require.NoError(t, err)
+				require.Equal(t, tc.specVersion, bom.SpecVersion)
+			})
+		}
+	})
+}