BindingGenerator - Syntax Error when building

Issue

I am trying to build a Binding Library (.AAR binding) and keep getting error as listed below:

1>BINDINGSGENERATOR : error (37: 14): Syntax error, expected: #PCDATA, , , , , {@code, {@docRoot}, {@inheritDoc}, {@link, {@linkplain, {@literal, {@value}, {@value, UnknownHtmlElementStart, @author, @apiSince, @deprecated, @deprecatedSince, @exception, @param, @return, @see, @serialData, @serialField, @since, @throws, @[unknown], @version

To replicate the issue follow the steps Binding an .AAR.

The .AAR file, doc and sources are coming from Gecko Nightly Build geckoview-nightly-90.0.20210420095122.aar, geckoview-nightly-90.0.20210420095122-javadoc.jar and geckoview-nightly-90.0.20210420095122-sources.jar

Target Framework: Android 10.0(Q) (I've tried against 9.0 as well, no luck)

*Here's a screenshot of the error's I am getting, nothing other than the BINDINGSGENERATOR errors.

Has anyone else came across such issues when building a Bindings Library from a .AAR file?

---

EDIT PER COMMENT

Version Information

• VS Version: 16.10.4
• Xamarin.Android.SDK Version: 11.3.0.4
• Xamarin Version: 16.10.000.234

Steps To Reproduce

1. Create a new project (Android Bindings Library Xamarin C#)
2. Navigate to Mozilla Maven and download geckoview-nightly-93.0.20210823092315.aar, geckoview-nightly-93.0.20210823092315-sources.jar and geckoview-nightly-93.0.20210823092315-javadoc.jar files.
3. Move the 3 files to the Jars directory and include them in the project (you may need to unblock the files through the files properties). Here's what my Jars directory looks like:
4. Set Build Action for files as follows: javadoc.jar => JavaDocJar sources.jar => JavaSourceJar and .aar => LibraryProjectZip
5. Rebuild Solution (you should see at least 5 errors) for example: BINDINGSGENERATOR : Syntax error along those lines.

Solution

So I spent some time getting the binding working for this. I added the following to the Metadata.xml file to make it bind.

<metadata>
    <remove-node path="/api/package[contains(@name,'org.mozilla.thirdparty')]" />
    <remove-node path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/field[@name='mWindow']" />
    <remove-node path="/api/package[@name='org.mozilla.geckoview']/class[@name='RuntimeSettings.Builder']/method[@name='newSettings' and count(parameter)=1 and parameter[1]]" />

    <!-- Because of interfaces contain const fields Xamarin generate abstract classes, which clash with property name. Renaming properties -->
    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='getHistoryDelegate' and count(parameter)=0]" name="propertyName">SessionHistoryDelegate</attr>
    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='setHistoryDelegate' and count(parameter)=1 and parameter[1][@type='org.mozilla.geckoview.GeckoSession.HistoryDelegate']]" name="propertyName">SessionHistoryDelegate</attr>

    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='getNavigationDelegate' and count(parameter)=0]" name="propertyName">SessionNavigationDelegate</attr>
    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='setNavigationDelegate' and count(parameter)=1 and parameter[1][@type='org.mozilla.geckoview.GeckoSession.NavigationDelegate']]" name="propertyName">SessionNavigationDelegate</attr>

    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='getPermissionDelegate' and count(parameter)=0]" name="propertyName">SessionPermissionDelegate</attr>
    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='setPermissionDelegate' and count(parameter)=1 and parameter[1][@type='org.mozilla.geckoview.GeckoSession.PermissionDelegate']]" name="propertyName">SessionPermissionDelegate</attr>

    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='getSelectionActionDelegate' and count(parameter)=0]" name="propertyName">SessionSelectionActionDelegate</attr>
    <attr path="/api/package[@name='org.mozilla.geckoview']/class[@name='GeckoSession']/method[@name='setSelectionActionDelegate' and count(parameter)=1 and parameter[1][@type='org.mozilla.geckoview.GeckoSession.SelectionActionDelegate']]" name="propertyName">SessionSelectionActionDelegate</attr>
</metadata>

The remove-node can be explained as:

1. First remove-node removes some internals that you won't use anyways. So no need to create bindings for that.
2. Second one remove the field mWindow that for some reason was exposed publicly. I just removed it, we could also change visibility.
3. Third one I was not 100% sure how to fix. The RuntimeSettings class contains a NewSettings method that differened between RuntimeSettings and the builder in the generated code. I just opted to remove it.
4. The renaming of generated property names is due to a Java 8 feature where you can have static fields in a Interface in Java. This will generate an abstract class in the generated code. This class name clashed with the property name generated for the Setter/Getter for these delegates.

This makes the bindings build. I then added a simple sample project with the following code in the MainActivity to just show something on the screen:

public class MainActivity : AppCompatActivity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
            
        var geckoView = new GeckoView(this);
        geckoView.LayoutParameters = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.MatchParent);
        SetContentView(geckoView);

        var session = new GeckoSession();
        GeckoRuntime runtime = GeckoRuntime.Create(this);
        session.Open(runtime);

        geckoView.Session = session;

        session.LoadUri("https://blog.ostebaronen.dk");
    }
}

Everything builds but now it crashes at runtime claiming to be missing org.yaml.snakeyaml.constructor.Constructor. Not sure if this aar needs some additional dependencies, which need to be added when binding.

EDIT:

I checked the POM of the version of GeckoView you linked to, no traces of SnakeYAML. However, the latest version found (93.0.20210825095400) does have it:

<dependency>
  <groupId>org.yaml</groupId>
  <artifactId>snakeyaml</artifactId>
  <version>1.24</version>
</dependency>

It also has some other dependencies it will need at runtime. Install the following NuGet packages in the binding project:

• Xamarin.AndroidX.Annotation
• Xamarin.AndroidX.Legacy.Support.V4
• Xamarin.AndroidX.Lifecycle.Extensions

Additionally, download the .jar file for SnakeYAML 1.24 (the android one) and add as a EmbeddedReferenceJar: https://repo1.maven.org/maven2/org/yaml/snakeyaml/1.24/

After you've done this it runs!

Answered By - Cheesebaron