Add workaround for SOAP server XML decoding limitations.

soap/soap.go

@@ -10,6 +10,7 @@ import (
 	"net/http"
 	"net/url"
 	"reflect"
+	"regexp"
 )
 
 const (
@@ -126,14 +127,49 @@ func encodeRequestArgs(w *bytes.Buffer, inAction interface{}) error {
 		if value.Kind() != reflect.String {
 			return fmt.Errorf("goupnp: SOAP arg %q is not of type string, but of type %v", argName, value.Type())
 		}
-		if err := enc.EncodeElement(value.Interface(), xml.StartElement{xml.Name{"", argName}, nil}); err != nil {
-			return fmt.Errorf("goupnp: error encoding SOAP arg %q: %v", argName, err)
+		elem := xml.StartElement{xml.Name{"", argName}, nil}
+		if err := enc.EncodeToken(elem); err != nil {
+			return fmt.Errorf("goupnp: error encoding start element for SOAP arg %q: %v", argName, err)
+		}
+		if err := enc.Flush(); err != nil {
+			return fmt.Errorf("goupnp: error flushing start element for SOAP arg %q: %v", argName, err)
+		}
+		if _, err := w.Write([]byte(escapeXMLText(value.Interface().(string)))); err != nil {
+			return fmt.Errorf("goupnp: error writing value for SOAP arg %q: %v", argName, err)
+		}
+		if err := enc.EncodeToken(elem.End()); err != nil {
+			return fmt.Errorf("goupnp: error encoding end element for SOAP arg %q: %v", argName, err)
 		}
 	}
 	enc.Flush()
 	return nil
 }
 
+var xmlCharRx = regexp.MustCompile("[<>&]")
+
+// escapeXMLText is used by generated code to escape text in XML, but only
+// escaping the characters `<`, `>`, and `&`.
+//
+// This is provided in order to work around SOAP server implementations that
+// fail to decode XML correctly, specifically failing to decode `"`, `'`. Note
+// that this can only be safely used for injecting into XML text, but not into
+// attributes or other contexts.
+func escapeXMLText(s string) string {
+	return xmlCharRx.ReplaceAllStringFunc(s, replaceEntity)
+}
+
+func replaceEntity(s string) string {
+	switch s {
+	case "<":
+		return "&lt;"
+	case ">":
+		return "&gt;"
+	case "&":
+		return "&amp;"
+	}
+	return s
+}
+
 type soapEnvelope struct {
 	XMLName       xml.Name `xml:"http://schemas.xmlsoap.org/soap/envelope/ Envelope"`
 	EncodingStyle string   `xml:"http://schemas.xmlsoap.org/soap/envelope/ encodingStyle,attr"`

soap/soap_test.go

@@ -21,6 +21,7 @@ func (rt *capturingRoundTripper) RoundTrip(req *http.Request) (*http.Response, e
 }
 
 func TestActionInputs(t *testing.T) {
+	t.Parallel()
 	url, err := url.Parse("http://example.com/soap")
 	if err != nil {
 		t.Fatal(err)
@@ -51,12 +52,13 @@ func TestActionInputs(t *testing.T) {
 	type In struct {
 		Foo string
 		Bar string `soap:"bar"`
+		Baz string
 	}
 	type Out struct {
 		A string
 		B string
 	}
-	in := In{"foo", "bar"}
+	in := In{"foo", "bar", "quoted=\"baz\""}
 	gotOut := Out{}
 	err = client.PerformAction("mynamespace", "myaction", &in, &gotOut)
 	if err != nil {
@@ -67,6 +69,7 @@ func TestActionInputs(t *testing.T) {
 		`<u:myaction xmlns:u="mynamespace">` +
 		`<Foo>foo</Foo>` +
 		`<bar>bar</bar>` +
+		`<Baz>quoted="baz"</Baz>` +
 		`</u:myaction>` +
 		soapSuffix)
 	body, err := ioutil.ReadAll(rt.capturedReq.Body)
@@ -83,3 +86,26 @@ func TestActionInputs(t *testing.T) {
 		t.Errorf("Bad output\nwant: %+v\n got: %+v", wantOut, gotOut)
 	}
 }
+
+
+func TestEscapeXMLText(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		input string
+		want  string
+	}{
+		{"", ""},
+		{"abc123", "abc123"},
+		{"<foo>&", "&lt;foo&gt;&amp;"},
+		{"\"foo'", "\"foo'"},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.input, func(t *testing.T) {
+			got := escapeXMLText(test.input)
+			if got != test.want {
+				t.Errorf("want %q, got %q", test.want, got)
+			}
+		})
+	}
+}