[BUG] Always NullReferenceException in FileStorage.Find()

[rickguedes]

Version
Using version 5.0.2

Describe the bug
Find always returns a System.NullReferenceException in any path or database we try. The same code works perfectly and was in production on Version 4.1.4.
We know there are file because Exists() and Download() is working correctly with the same paths

Code to Reproduce

    public List<string> GetFilesInPath(string path)
    {
        List<string> foundFiles = new List<string>();
        // Returns all the files in this path
        var files = db.FileStorage.Find("$" + path);
        foreach (var lf in files)
        {
            foundFiles.Add(lf.Id);
        }
        return foundFiles;
    }

Expected behavior
Should return a list with all the file ids

Screenshots/Stacktrace
Result StackTrace:
at LiteDB.BsonExpressionParser.TryParseFunction(Tokenizer tokenizer, ExpressionContext context, Boolean isRoot)
at LiteDB.BsonExpressionParser.ParseSingleExpression(Tokenizer tokenizer, ExpressionContext context, Boolean isRoot)
at LiteDB.BsonExpressionParser.ParseFullExpression(Tokenizer tokenizer, ExpressionContext context, Boolean isRoot)
at LiteDB.BsonExpression.Parse(Tokenizer tokenizer, BsonExpressionParserMode mode, Boolean isRoot)
at LiteDB.BsonExpression.Create(String expression)
at LiteDB.BsonExpression.Create(String expression, BsonValue[] args)
at LiteDB.LiteStorage`1.Find(String predicate, BsonValue[] args)
at ....
Result Message:
Method threw exception:
System.NullReferenceException: Object reference not set to an instance of an object.

[deje07]

FileStorage.FindAll() is also affected...

[mbdavid]

Hi @duduric,

FileStorage works a bit different in v5. There is no more restriction about _id type in _files collection. In v4, _id is the filename with path. In v5, is any unique _id (with any data type you what, like string, int, ...). So, the Find() method change to implement any type of query over _files. You can write like:

fs.Find("_id LIKE @0", path + "%")

or

fs.Find("_id = @0", path);

or

fs.Find("filename = @0", filename)

[mbdavid]

@deje07, yes, it's a bug. I'm fixing this. For now you can use some like fs.Find("1 =1")

[rickguedes]

Thanks, we have been able to fix this part of the code

[CodeWithMichal]

Hi @mbdavid , could you change FileStorage section on https://www.litedb.org/docs/filestorage/ ?
Example provided doesnt work anymore

// Find all files references in a "directory"
var files = fs.Find("$/photos/2014/");