=concat() causes a validation error

[benbrown]

Describe the bug

Composer throws a validation error if an expression is using concat as the returned value.

For example, use =concat('foo','bar') a field that expects a string.

Version

1.1.1

To Reproduce

1. Add an HTTP request step
2. In the URL field, set the type to expression
3. Set the value to =concat('foo','bar')

you will see a validation error

expected response

this should be a valid value since concat returns a string.

[LouisEugeneMSFT]

I investigated this issue a couple days ago. My hypothesis is that this is coming from the adaptive-expressions library. Validation is made under packages/lib/indexers/src/validations/expressionValidation/validation.ts. Specifically returnType = Expression.parse(exp). Expression.parse calls the adaptive-expressions library. We can see with the example of concat that returnType yields 24 when the enum has valid properties only up to 16.

[cwhitten]

Transferring to botbuilder-js

[Danieladu]

@cwhitten The concat returns 24 is because Expression library uses "bit field" of enum. (Something like IntFlag in python).
Using this feature, the built-in function can support multiple return types.
For example:
The return type of concat is String or Array, corresponding to the return type enum is 24 (8 + 16), 8 presents String, and 16 presents Array.

So, maybe should adjust the validation of returntype in Composer?

[cwhitten]

Thank you @Danieladu

@boydc2014 @lei9444 should this return type instead be exported from adaptive-expressions?

[lei9444]

Thank you @Danieladu

@boydc2014 @lei9444 should this return type instead be exported from adaptive-expressions?

hi, @cwhitten I am working on the return type in composer last week, and I will have a PR to fix it today.