Fix empty array encoding crash

[FredericRuaudel]

Hi!

I recently stubble upon a crash when creating a SQLite schema model with an Array type member like so:

struct MyModel: SQLiteModel {
    var id: Int?
    var values: [String]
}

if I submit a JSON with an empty array, I got a crash back here.
So I update my Fluent* libs to the last rc4 version and investigate for this bug.

The reason of the crash is that when the _UnkeyedEncodingContainer get an empty array, none of its methods get called and as a consequence, no data is returned to the encoder and it doesn't throw any _DoJSONError() either.

I'm not sure this is the right way to fix this, but after adding some test to check the encoding/decoding of an empty and non empty array, I've added a guard let statement on the encoder.data value and throw the _DoJSONError in case it's nil
But maybe it would be better to move the fix directly inside the _UnkeyedEncodingContainer to be sure we are dealing with an array but I didn't find a clean solution at this location.

To reproduce the bug from a real vapor project, run this sample project:

bugEmptyArray.zip

Then run this cUrl command:

curl -X "POST" "http://localhost:8080/todos" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "titles": []
}'

And you should got the crash with the last SQLite release.

Hope it will help!

Have a great day!

[tanner0101]

Great, thanks!

[penny-coin]

Hey @FredericRuaudel, you just merged a pull request, have a coin!

You now have 1 coins.