[Bug]: Runtime NPE with elvis operator and filter() function about ballerina-lang HOT 3 CLOSED

As a workaround, we can explicitly specify a type for the list constructor (e.g., <int[]>[]) within the nil conditional (elvis) expression.

int[] x2 = (x ?: <int[]>[]).filter(n => n > 2);

Also reproducible with

public function main() {
    var x = [];
    anydata[] y = x;
    anydata[] _ = y.filter(v => v is int);
}

The execution path of the original example may change with ballerina-platform/ballerina-spec#1050. Therefore, we need to also add a test with the second sample when this issue is being fixed.

from ballerina-lang.

This seems to happen because in org.ballerinalang.langlib.array.utils.ArrayUtils#createEmptyArrayFromTuple (at https://github.com/ballerina-platform/ballerina-lang/blob/v2201.8.4/langlib/lang.array/src/main/java/org/ballerinalang/langlib/array/utils/ArrayUtils.java#L118), via https://github.com/ballerina-platform/ballerina-lang/blob/v2201.8.4/langlib/lang.array/src/main/java/org/ballerinalang/langlib/array/Filter.java#L58, the flow seems to have assumed that there will be at least be one member in a tuple, which is not correct.

[] (tuple with no members) is equivalent to never[] (also empty list since there can't be a never member). Therefore, we should be able to handle this by creating a never[] to correspond to empty tuples.

from ballerina-lang.

This issue is NOT closed with a proper Reason/ label. Make sure to add proper reason label before closing. Please add or leave a comment with the proper reason label now.

      - Reason/EngineeringMistake - The issue occurred due to a mistake made in the past.
      - Reason/Regression - The issue has introduced a regression.
      - Reason/MultipleComponentInteraction - Issue occured due to interactions in multiple components.
      - Reason/Complex - Issue occurred due to complex scenario.
      - Reason/Invalid - Issue is invalid.
      - Reason/Other - None of the above cases.

from ballerina-lang.