Add NamespaceModifier.PreserveOriginalPrefixes

to preserve original namespace binding prefixes
and not introduce potentially shorter aliases.
Duplicate prefixes (prefixes binding to the same
namespace) will still be cleaned-up.

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
           fail_on_error: true
       - run: |
           gofmt -l . && test -z $(gofmt -l .)
-          go vet -unsafeptr=false .
+          go vet .
           go install github.com/mgechev/revive@latest
           revive -config revive.toml .
       - run: go build -v .

combined_test.go

@@ -319,6 +319,36 @@ soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
 		"</a:Envelope>", w.String())
 }
 
+func TestAttributesWithPrefixesPreserve(t *testing.T) {
+	// given
+	input := `
+<ns1:a xmlns:ns1="http://ns1" ns1:attr1="val1" ns2:attr2="val2" xmlns:ns2="http://ns2">
+<ns1:b>
+  <b:c xmlns:b="http://ns2" ns2:attr3="val3">
+    <b:d ns1:attr4="val4">Test</b:d>
+  </b:c>
+</ns1:b>
+</ns1:a>`
+	dec := gosaxml.NewDecoder(strings.NewReader(input))
+	w := &bytes.Buffer{}
+	namespaceModifier := gosaxml.NewNamespaceModifier()
+	namespaceModifier.PreserveOriginalPrefixes = true
+	enc := gosaxml.NewEncoder(w, namespaceModifier)
+	var tk gosaxml.Token
+
+	// when
+	decodeEncode(t, dec, enc, &tk)
+
+	// then
+	assert.Equal(t, "<ns1:a xmlns:ns1=\"http://ns1\" ns1:attr1=\"val1\" ns2:attr2=\"val2\" xmlns:ns2=\"http://ns2\">"+
+		"<ns1:b>"+
+		"<ns2:c ns2:attr3=\"val3\">"+
+		"<ns2:d ns1:attr4=\"val4\">Test</ns2:d>"+
+		"</ns2:c>"+
+		"</ns1:b>"+
+		"</ns1:a>", w.String())
+}
+
 func TestAttributesWithPrefixes(t *testing.T) {
 	// given
 	input := `

namespaceModifier.go

@@ -14,6 +14,8 @@ type NamespaceModifier struct {
 	prefixAliases [][]byte
 
 	top byte
+
+	PreserveOriginalPrefixes bool
 }
 
 // NewNamespaceModifier creates a new NamespaceModifier and returns a pointer to it.
@@ -148,13 +150,17 @@ func (thiz *NamespaceModifier) processNamespaces(t *Token) {
 				// we don't need the attribute anymore because we already had a prefix
 				continue
 			}
-			// wo don't know the prefix, but we want to rewrite it
-			nextPrefixAlias := len(thiz.prefixAliases) / 2
-			c := namespaceAliases[nextPrefixAlias : nextPrefixAlias+1]
-			bsc := bs(c)
-			thiz.addPrefixRewrite(attr.Name.Local, bsc)
-			thiz.addNamespaceBinding(bsc, attr.Value)
-			attr.Name.Local = bsc
+			if !thiz.PreserveOriginalPrefixes {
+				// wo don't know the prefix, but we want to rewrite it
+				nextPrefixAlias := len(thiz.prefixAliases) / 2
+				c := namespaceAliases[nextPrefixAlias : nextPrefixAlias+1]
+				bsc := bs(c)
+				thiz.addPrefixRewrite(attr.Name.Local, bsc)
+				thiz.addNamespaceBinding(bsc, attr.Value)
+				attr.Name.Local = bsc
+			} else {
+				thiz.addNamespaceBinding(attr.Name.Local, attr.Value)
+			}
 		} else if attr.Name.Prefix == nil && bytes.Equal(attr.Name.Local, bs("xmlns")) {
 			// check if the element is already in that namespace, in which case
 			// we can simply omit the namespace.