If I have one db dbtest and two collections example,

1) NameColletion with 10 documents (1KB for document)
2) nameCollection with 0 documents

when execute the mongodump of dbtest, in the folder dump i found olny this result:

NameCollection.bson 0KB
nameCollection.metadata.json 1KB

instead:

NameCollection.bson 10KB
NameCollection.metadata.json 1KB

nameCollection.bson 0KB
nameCollection.metadata.json 1KB

I repeated the dump operation and i receive the same result.

If execute the dump of only collection, the dump is correct.

I found this bug while execute the migration process from windows to linux environment.