Fix XML deserialization for over-consumption (#29)

We read a token too much in `unmarshalXxx` functions. The bug went
unnoticed as all our examples used indented XML, which eclipsed the
over-consumption.

In this patch, we remove the `unmarshalXxx`, as they turn out to be
redundant, and use `readXxxWithLookahead` to appropriately read the
tokens without over-consumption.

Fixes #24.

testdata/DeserializationError/Xml/ContainedInEnvironment/Unexpected/TypeViolation/embeddedDataSpecification/dataSpecificationContent.xml.error

@@ -1 +1 @@
-assetAdministrationShells/*[0]/embeddedDataSpecifications/*[0]/dataSpecificationContent: Expected a start element, but got an end element dataSpecificationContent in namespace https://admin-shell.io/aas/3/0
+assetAdministrationShells/*[0]/embeddedDataSpecifications/*[0]/dataSpecificationContent: Expected a start element, but got text Unexpected string value

testdata/DeserializationError/Xml/ContainedInEnvironment/Unexpected/TypeViolation/operationVariable/value.xml.error

@@ -1 +1 @@
-submodels/*[0]/submodelElements/*[0]/inputVariables/*[0]/value: Expected a start element, but got an end element value in namespace https://admin-shell.io/aas/3/0
+submodels/*[0]/submodelElements/*[0]/inputVariables/*[0]/value: Expected a start element, but got text Unexpected string value

xmlization/test/edge_cases_test.go

@@ -0,0 +1,176 @@
+package xmlization_test
+
+import (
+	"bytes"
+	"encoding/xml"
+	aastypes "github.com/aas-core-works/aas-core3.0-golang/types"
+	aasxmlization "github.com/aas-core-works/aas-core3.0-golang/xmlization"
+	"strings"
+	"testing"
+)
+
+func TestRobustToNewline(t *testing.T) {
+	// See:
+	// https://github.com/aas-core-works/aas-core3.0-golang/issues/24
+	//
+	// We relied erroneously on whitespace between the elements which eclipsed the bug
+	// where we read into the content of a class property instead of letting the called
+	// function move the cursor.
+	text := ("<environment xmlns=\"https://admin-shell.io/aas/3/0\">" +
+		"<submodels>" +
+		"<submodel><id>some-unique-global-identifier</id></submodel>" +
+		"</submodels>" +
+		"</environment>")
+
+	reader := strings.NewReader(text)
+	decoder := xml.NewDecoder(reader)
+
+	deserialized, deseriaErr := aasxmlization.Unmarshal(decoder)
+
+	source := "Minimal example to reproduce robustness to newlines"
+
+	ok := assertNoDeserializationError(t, deseriaErr, source)
+	if !ok {
+		return
+	}
+
+	if _, ok := deserialized.(aastypes.IEnvironment); !ok {
+		t.Fatalf(
+			"Expected an instance of IEnvironment, "+
+				"but got %T: %v",
+			deserialized, deserialized,
+		)
+		return
+	}
+
+	buf := &bytes.Buffer{}
+	encoder := xml.NewEncoder(buf)
+	encoder.Indent("", "\t")
+
+	seriaErr := aasxmlization.Marshal(encoder, deserialized, true)
+	ok = assertNoSerializationError(t, seriaErr, source)
+	if !ok {
+		return
+	}
+
+	roundTrip := string(buf.Bytes())
+
+	expected := `<environment xmlns="https://admin-shell.io/aas/3/0">
+	<submodels>
+		<submodel>
+			<id>some-unique-global-identifier</id>
+		</submodel>
+	</submodels>
+</environment>`
+	if roundTrip != expected {
+		t.Fatalf(
+			"Expected round-trip serialization to be `%v`, but got `%v`",
+			expected, roundTrip,
+		)
+	}
+}
+
+func TestRobustToNewlineOnDispatch(t *testing.T) {
+	// See:
+	// https://github.com/aas-core-works/aas-core3.0-golang/issues/24
+	//
+	// Note that both `dataSpecificationContent` and `dataSpecificationIec61360` are
+	// on the same line (right in the middle).
+	text := `<environment xmlns="https://admin-shell.io/aas/3/0">
+  <conceptDescriptions>
+    <conceptDescription>
+      <id>0173-1#02-AAR529#004</id>
+      <embeddedDataSpecifications>
+        <embeddedDataSpecification>
+          <dataSpecification>
+            <type>ExternalReference</type>
+            <keys>
+              <key>
+                <type>GlobalReference</type>
+                <value>https://admin-shell.io/DataSpecificationTemplates/DataSpecificationIEC61360/3/0</value>
+              </key>
+            </keys>
+          </dataSpecification>
+          <dataSpecificationContent><dataSpecificationIec61360>
+              <preferredName>
+                <langStringPreferredNameTypeIec61360>
+                  <language>en</language>
+                  <text>kilogram</text>
+                </langStringPreferredNameTypeIec61360>
+              </preferredName>
+            </dataSpecificationIec61360>
+          </dataSpecificationContent>
+        </embeddedDataSpecification>
+      </embeddedDataSpecifications>
+    </conceptDescription>
+  </conceptDescriptions>
+</environment>`
+
+	reader := strings.NewReader(text)
+	decoder := xml.NewDecoder(reader)
+
+	deserialized, deseriaErr := aasxmlization.Unmarshal(decoder)
+
+	pth := "Issue #24"
+
+	ok := assertNoDeserializationError(t, deseriaErr, pth)
+	if !ok {
+		return
+	}
+
+	if _, ok := deserialized.(aastypes.IEnvironment); !ok {
+		t.Fatalf(
+			"Expected an instance of IEnvironment, "+
+				"but got %T: %v",
+			deserialized, deserialized,
+		)
+		return
+	}
+
+	buf := &bytes.Buffer{}
+	encoder := xml.NewEncoder(buf)
+	encoder.Indent("", "\t")
+
+	seriaErr := aasxmlization.Marshal(encoder, deserialized, true)
+	ok = assertNoSerializationError(t, seriaErr, pth)
+	if !ok {
+		return
+	}
+
+	roundTrip := string(buf.Bytes())
+
+	expected := `<environment xmlns="https://admin-shell.io/aas/3/0">
+	<conceptDescriptions>
+		<conceptDescription>
+			<id>0173-1#02-AAR529#004</id>
+			<embeddedDataSpecifications>
+				<embeddedDataSpecification>
+					<dataSpecificationContent>
+						<dataSpecificationIec61360>
+							<preferredName>
+								<langStringPreferredNameTypeIec61360>
+									<language>en</language>
+									<text>kilogram</text>
+								</langStringPreferredNameTypeIec61360>
+							</preferredName>
+						</dataSpecificationIec61360>
+					</dataSpecificationContent>
+					<dataSpecification>
+						<type>ExternalReference</type>
+						<keys>
+							<key>
+								<type>GlobalReference</type>
+								<value>https://admin-shell.io/DataSpecificationTemplates/DataSpecificationIEC61360/3/0</value>
+							</key>
+						</keys>
+					</dataSpecification>
+				</embeddedDataSpecification>
+			</embeddedDataSpecifications>
+		</conceptDescription>
+	</conceptDescriptions>
+</environment>`
+
+	if expected != roundTrip {
+		t.Fatalf("Expected `%v`, got `%v`", expected, roundTrip)
+	}
+}