FLUID-5970: top-level "undefined" values in transforms result in an empty object....

Description

There is still some work to be done around the handling of "undefined" values in the model transformation API. If an input value or the result of a transform is "undefined", we have made a design decision to strip it out. This is reasonable enough, but is specifically a problem when we expect to use the "" convention to pass through the original data type, as in the following examples:

fluid.model.transformWithRules(new Date(), { "": ""}) // Returns today's date

fluid.model.transformWithRules("", { "": ""}) // Returns ""

fluid.model.transformWithRules(null, { "": ""}) // Returns null

fluid.model.transformWithRules({}, { "": ""}) // Returns {}

fluid.model.transformWithRules(undefined, { "": ""}) // Returns {}

The last two are obviously not equivalent, and yet produce the same results. also, the last is the only case in which the simplest "passthrough" transformation rule returns a different type of data altogether.

I believe I can work around this behavior in a number of ways, but I wanted to point it out for further discussion. If this is truly the intended behavior, at a minimum the special handling of undefined values should finally be documented.

Comments

• Tony Atkins [RtF] commented 2016-09-27T05:10:58.401-0400

  The previous discussion around this can be found here:

  https://issues.fluidproject.org/browse/FLUID-5703

  The examples given here demonstrate that it's not simply a problem with transformation functions. In the examples I gave, I cannot "opt out" of the input handling. I would have to supply my own transformation function that closely mirrors fluid.transforms.value, but which does not extend standardInputTransformFunction.