Bug: Fallback not working if top Ad Elements returns empty Vast or fails in case of multiple Ad Elements

[shubham-si]

https://github.com/dailymotion/vast-client-js/blob/master/src/parser/vast_parser.js#L461C25-L461C25

const resolvedAds = util.flatten(unwrappedAds); default to [] Link

if (!resolvedAds && this.remainingAds.length > 0) {

There seems to be a issue here !resolvedAds. Since !Array<T> gives false always, thus the code within if will not be executed at all.

So If any Ad element (going from top to bottom) fails to fetch xml or return empty vast, it will not fallback to next Ad Element.

<VAST xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="vast.xsd" version="3.0">
<Ad>
<Wrapper fallbackOnNoAd="true">
<AdSystem/>
<Error>
<![CDATA[ https://error-pixel?[ERRORCODE] ]]>
</Error>
<VASTAdTagURI>
<![CDATA[ ]]>
</VASTAdTagURI>
<Extensions>
<Extension type="waterfall" fallback_index="0"/>
</Extensions>
</Wrapper>
</Ad>
<Ad>
<Wrapper fallbackOnNoAd="true">
<AdSystem/>
<Error>
<![CDATA[ https://error-pixel?[ERRORCODE] ]]>
</Error>
<VASTAdTagURI>
<![CDATA[ does-not-exist ]]>
</VASTAdTagURI>
<Extensions>
<Extension type="waterfall" fallback_index="1"/>
</Extensions>
</Wrapper>
</Ad>
<Ad>
<Wrapper>
<AdSystem/>
<Error>
<![CDATA[ https://error-pixel?[ERRORCODE] ]]>
</Error>
<VASTAdTagURI>
<![CDATA[ https://glomex.github.io/vast-ima-player/linear-ad.xml ]]>
</VASTAdTagURI>
<Extensions>
<Extension type="waterfall" fallback_index="2"/>
</Extensions>
</Wrapper>
</Ad>
</VAST>

Fix: if (resolvedAds.length === 0 && this.remainingAds.length > 0) {

so that if resolvedAds fails and we have remainingAds, can be proceeded with them.

[Rapha0511]

Hello !
thank you for reporting this issue, we will take a look at it asap !

[shubham-si]

@Rapha0511 is the bug fixed ?