Collect crashes when trying to download media file with path as `filename`

[seadowg]

Originally reported on the forum.

This only happens with "custom" server implementations as Central won't return filename with a hierarchical path.

Software and hardware versions

Collect v2021.3, custom server

Problem description

Collect crashes when trying to copy a downloaded media file to the form's media directory if the filename attribute in the manifest is a path (dir1/dir2/file.extension) instead of a file name (file.extension).

Steps to reproduce the problem

1. Set up Collect with a server that returns paths in filename
2. Attempt to download a form

Expected behavior

Off the top of my head, there are three options we could go for here:

1. Collect could copy the file into the specified path relative to the media dir (<media dir>/dir1/dir2/file.extension)
2. Collect could ignore everything other than the file name and just copy the file into the media dir directly (<media dir>/file.extension)
3. Collect could throw a FormSourceException.ParseError when the manifest is fetched - this would probably mean us also updating the spec to make it stricter.

Other information

Stack trace of crash:

java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:354)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)
Caused by: java.lang.RuntimeException: Could not copy '/storage/emulated/0/Android/data/org.odk.collect.android/files/projects/ac2d95cd-c319-4f58-9a90-3a2f91ccaefc/.cache/download-b7854eef-0a51-4477-9172-47a2677450ac/tag.xml3517133847896120566.tempDownload' over '/storage/emulated/0/Android/data/org.odk.collect.android/files/projects/ac2d95cd-c319-4f58-9a90-3a2f91ccaefc/.cache/download-b7854eef-0a51-4477-9172-47a2677450ac/media/example/terms/tag.xml'. Reason: /storage/emulated/0/Android/data/org.odk.collect.android/files/projects/ac2d95cd-c319-4f58-9a90-3a2f91ccaefc/.cache/download-b7854eef-0a51-4477-9172-47a2677450ac/media/example/terms/tag.xml (No such file or directory)
at org.odk.collect.android.formmanagement.ServerFormDownloader.writeFile(SourceFile:368)
at org.odk.collect.android.formmanagement.ServerFormDownloader.downloadMediaFiles(SourceFile:389)
at org.odk.collect.android.formmanagement.ServerFormDownloader.processOneForm(SourceFile:109)
at org.odk.collect.android.formmanagement.ServerFormDownloader.downloadForm(SourceFile:81)
at org.odk.collect.android.tasks.DownloadFormsTask.doInBackground(SourceFile:62)
at org.odk.collect.android.tasks.DownloadFormsTask.doInBackground(SourceFile:41)
at android.os.AsyncTask$2.call(AsyncTask.java:333)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)