Crash in [@ java.lang.IllegalArgumentException: at android.app.DownloadManager.validateArgumentIsNonEmpty(DownloadManager.java)]

[kbrosnan]

Crash report: https://crash-stats.mozilla.org/report/index/160819c3-1b57-4902-917a-4bd130210301

Java stack trace:

java.lang.IllegalArgumentException
	at android.app.DownloadManager.validateArgumentIsNonEmpty(DownloadManager.java:1430)
	at android.app.DownloadManager.addCompletedDownload(DownloadManager.java:1388)
	at android.app.DownloadManager.addCompletedDownload(DownloadManager.java:1368)
	at mozilla.components.feature.downloads.AbstractFetchDownloadService.updateDownloadNotification$feature_downloads_release(AbstractFetchDownloadService.kt:21)
	at mozilla.components.feature.downloads.AbstractFetchDownloadService.access$updateDownloadNotification(AbstractFetchDownloadService.kt:5)
	at mozilla.components.feature.downloads.AbstractFetchDownloadService$onStartCommand$2.invokeSuspend(AbstractFetchDownloadService.kt:7)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:3)
	at kotlinx.coroutines.AwaitKt.resume(Await.kt:7)
	at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:18)
	at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:6)
	at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:3)
	at kotlinx.coroutines.android.HandlerContext$scheduleResumeAfterDelay$$inlined$Runnable$1.run(Runnable.kt:1)
	at android.os.Handler.handleCallback(Handler.java:809)
	at android.os.Handler.dispatchMessage(Handler.java:102)
	at android.os.Looper.loop(Looper.java:166)
	at android.app.ActivityThread.main(ActivityThread.java:7377)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:469)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:963)

┆Issue is synchronized with this Jira Task

[Mugurell]

Based on the stacktraces I saw the exception being thrown because of this DownloadManager check for even an empty mime type.

This seems to be a general issue, not tied to a specific device or Android version but I could not reproduce it.
Haven't saw anything immediately wrong with our current implementation of inferring the mimeType and given that the code in AC is pretty tight about nullability I think that in specific cases the mime type gets to be empty.

As a speculative fix (without actually having a broken download to verify) we can treat the cases of empty mime types the same as we treat the null ones -> replace them with a default */* one.

[Mugurell]

And since the exception is thrown in AC without a STRs in Fenix I'll move the ticket to AC and fix it there.

[Mugurell]

This were quite a lot of crashes, it should be easy to see a decline now that a patch for this was merged.