How to handle NSExtensionActivationRule is truepredicate?

You have to specify every data type you want to use in Info.plist of your App Extension.

See the documentation for the available keys. Look for NSExtensionActivationRule.

//UPDATE:

<key>NSExtensionActivationRule</key>
            <dict>
                <key>NSExtensionActivationSupportsImageWithMaxCount</key>
                <integer>1</integer>
                <key>NSExtensionActivationSupportsMovieWithMaxCount</key>
                <integer>1</integer>
                <key>NSExtensionActivationSupportsWebURLWithMaxCount</key>
                <integer>1</integer>
            </dict>

I wanted my app to accept text only. This is what works:

...
<key>NSExtensionAttributes</key>
    <dict>
        <key>NSExtensionActivationUsesStrictMatching</key>
        <integer>2</integer>
        <key>NSExtensionActivationRule</key>
        <dict>
            <key>NSExtensionActivationDictionaryVersion</key>
            <integer>2</integer>
            <key>NSExtensionActivationSupportsText</key>
            <true/>
        </dict>
    </dict>
...