XmlUtils.newPullParser: enable FEATURE_RELAXED if available (#44)

* XmlUtils.newPullParser: enable FEATURE_RELAXED if available * Added KDoc
bitfireAT · Apr 17, 2024 · b87d772 · b87d772
1 parent 6a0b597
commit b87d772
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Showing 2 changed files with 38 additions and 9 deletions.
diff --git a/src/main/kotlin/at/bitfire/dav4jvm/Property.kt b/src/main/kotlin/at/bitfire/dav4jvm/Property.kt
@@ -55,6 +55,7 @@ interface Property {
                         log.log(Level.WARNING, "Ignoring invalid property", e)
                     }
                 }
+
                 eventType = parser.next()
             }
 

diff --git a/src/main/kotlin/at/bitfire/dav4jvm/XmlUtils.kt b/src/main/kotlin/at/bitfire/dav4jvm/XmlUtils.kt
@@ -6,6 +6,7 @@
 
 package at.bitfire.dav4jvm
 
+import at.bitfire.dav4jvm.exception.DavException
 import at.bitfire.dav4jvm.exception.InvalidPropertyException
 import org.xmlpull.v1.XmlPullParser
 import org.xmlpull.v1.XmlPullParserException
@@ -15,18 +16,45 @@ import java.io.IOException
 
 object XmlUtils {
 
-    private val factory: XmlPullParserFactory
-    init {
+    /**
+     * Requests the parser to be as lenient as possible when parsing invalid XML.
+     *
+     * See [https://www.xmlpull.org/](xmlpull.org) and specific implementations, for instance
+     * [Android XML](https://developer.android.com/reference/android/util/Xml#FEATURE_RELAXED)
+     */
+    private const val FEATURE_RELAXED = "http://xmlpull.org/v1/doc/features.html#relaxed"
+
+    /** [XmlPullParserFactory] that is namespace-aware and does relaxed parsing */
+    private val relaxedFactory =
+        XmlPullParserFactory.newInstance().apply {
+            isNamespaceAware = true
+            setFeature(FEATURE_RELAXED, true)
+        }
+
+    /** [XmlPullParserFactory] that is namespace-aware */
+    private val standardFactory: XmlPullParserFactory =
+        XmlPullParserFactory.newInstance().apply {
+            isNamespaceAware = true
+        }
+
+    /**
+     * Creates a new [XmlPullParser].
+     *
+     * First tries to create a namespace-aware parser that supports [FEATURE_RELAXED]. If that
+     * fails, it falls back to a namespace-aware parser without relaxed parsing.
+     */
+    fun newPullParser(): XmlPullParser =
         try {
-            factory = XmlPullParserFactory.newInstance()
-            factory.isNamespaceAware = true
-        } catch (e: XmlPullParserException) {
-            throw RuntimeException("Couldn't create XmlPullParserFactory", e)
+            relaxedFactory.newPullParser()
+        } catch (_: XmlPullParserException) {
+            // FEATURE_RELAXED may not be supported, try without it
+            null
         }
-    }
+        ?: standardFactory.newPullParser()
+        ?: throw DavException("Couldn't create XML parser")
 
-    fun newPullParser() = factory.newPullParser()!!
-    fun newSerializer() = factory.newSerializer()!!
+    fun newSerializer(): XmlSerializer = standardFactory.newSerializer()
+        ?: throw DavException("Couldn't create XML serializer")
 
 
     @Throws(IOException::class, XmlPullParserException::class)