Youโve probably already noticed this, but I should note for whoever else might be following along that both the label and the description of the โNull-safe accessโ checkbox are confusing. What itโs meant to address is data that missing from the input, not data thatโs present but whose value is null โ you donโt need to check this checkbox just to map a present-but-null value to the output.
The description (tool tip) for this setting is a bit more accurate:
Enable this to ignore missing data when accessing the source path, such as $a but a does not exist in the source data
The problem with that description is that โignoreโ implies it will simply omit any value from the output. Instead, it maps it to a null value. What weโre looking for here is a way to actually do what this says โ if a mapped value is missing from the input, donโt put anything in the output for it.
So, yes, there are a number of ways to approach a solution, depending on how flexible you want to get. A simple way would be to replace the โNull-safe accessโ checkbox with a 3-way choice:
Missing Data Policy:
- Error (equivalent to โNull-safe accessโ = false now)
- Map to null (equivalent to โNull-safe accessโ = true now)
- Omit (not possible now)
What I like about this approach is its simplicity. But itโs lacking some flexibility:
- One setting applies to all of the mappings for that Mapper. What if you want different policies for different mappings within the same Mapper?
- The only condition where this will omit data from the output is when the value is missing from the input. What if you want to omit for other reasons, such as when the value is present but is a blank string? For that, I think youโd need some sort of support in the expression language. Something like $.get(โpathโ, omit()) or $.getOrOmit(โpathโ). That adds more flexibility at the cost of relying on EL tricks that some users might find somewhat intimidating.
