datatable-java: Empty cell are not converted to `null`'s for `String` class

Summary

The empty cell is not converted to (Double)null in Cucumber 4.3.0, as it happened in Cucumber 1.2.5

In Cucumber 1.2.5 empty cell was converted to null of type Double, when performing asMap(String,Double) table conversion. This no longer happens in Cucumber 4.3.0. I also couldn’t find the way to override this behavior because just adding new DataTableType definition results in io.cucumber.datatable.DublicateTypeException.

typeRegistry.defineDataTableType(
    new DataTableType(
        Double.class,
        (TableCellTransformer<Double>) value ->
            (!value.isEmpty()) ? (Double.parseDouble(value)) : (null)));

Expected Behavior

Empty cell is converted to null by default for nullable number types (Double, Float, Int etc.). So that the table in the following step

Then the marker values are
  | M1   | 1.7988 |
  | M2   |        |
  | M3   | 1.5312 |
  | M4   | 1.7720 |
  | M5   | 1.6840 |
  | M6   | 0.0000 |
  | M9   |        |
  | M12 | 1.7002 |

is transformed to

{
    "M1": 1.7988,
    "M2": null,
    "M3": 1.5312,
    "M4": 1.7720,
    "M5": 1.6840,
    "M6": 0.0,
    "M9": null,
    "M12": 1.7002,
}

Current Behavior

Exception is thrown: io.cucumber.datatable.CucumberDataTableException: ‘java.util.List<java.util.List<java.lang.Double>>’ could not transform

Possible Solution

Convert empty cells to null values, or allow to override default build-in type transformations.

Steps to Reproduce (for bugs)

1. The table in the following step:

   Then the marker values are

   | M1 | 1.7988 | | M2 | | | M3 | 1.5312 | | M4 | 1.7720 | | M5 | 1.6840 | | M6 | 0.0000 | | M9 | | | M12 | 1.7002 |

2. Is trasformed to a Map

   @Then(“Then the marker values are”) public void theMarkerValuesAre(DataTable expectedValues) { Map<String, Double> expected = expectedValues.asMap(String.class, Double.class); }

3. CucumberDataTableException is thrown with message: ‘java.util.List<java.util.List<java.lang.Double>>’ could not transform

Context & Motivation

It could be useful to represent the clearing of the input value in the form where user can enter/update several similar values in one go.

Your Environment

• Version used: 4.3.0
• Operating System and version: Windows 10
• Link to your project: N/A

[mpkorstanje]

@hsynkrtl you’re replying to a closed issue which means that chances of anybody reading this are absolutely terrible. I happened to see this by sheer chance.

I would suggest that you make empty strings explicit by using the text [empty] and then prior to converting the entry to an object replace the "[empty]" strings with "".

[hsynkrtl]

how can i now pass an empty string to a datatable.

  | street | houseNumber | city         | zip | country | state | type            |
  |      |           | Trololotown2 |     | AZ           | WY    | ADDRESS |

with the last update of datatable street and housNumber get [null] instead of an empty string “” which is valid for a string value to be empty.