Projection expressions with single arguments e.g. {"$size": "$source"} #1150
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This fixes the case where a single argument expression such as {$size: “$source”} generates an arg array
containing a string rather than a DBObject. The current behaviour would try to unwrap the “$source” and cast it to
a DBObject, which caused a ClassCastException.
By moving the check for single arguments to the toDBObject method, it’s possible to preserve the existing behaviour
where DBObjects are unwrapped and used as the argument while also correctly handling string arguments.
kothar
changed the title
|
rebased and merged. |
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After #667 was merged, expressions could be composed such as
Projection.expression("$size", Projection.projection("field"))Which would be translated to:
{"$size": ["$field"]}Though
$sizeonly accepts a single argument, an array containing a single string is also accepted.After @e95cdc3271408000bc57cf8f94c9468de55f1c43 (Location of change) a check was added to unwrap single-argument expressions, but it assumes that the type of the argument is a
DBObject. This fails in the above case, where the argument is a projection reference string.This PR adds a helper method for
$sizeprojection expressions, and a corresponding test to make sure the argument is unwrapped correctly from the arguments list.The fix for the
ClassCastExceptionmoves the unwrapping check to the caller oftoExpressionArgsso that the string value can be handled without a cast to DBObject causing an exception.