Provide ability to conditionally append key-value pair in amp-analytics

[britice]

In some analytics platforms, when a parameter is empty the expected behavior is to not include that parameter in the request. For example, if there was an optional user-defined authors variable and the user left the value undefined, the request would not contain an authors parameter.

[rudygalfi]

Is this blocking for your integration?

[britice]

Is this blocking for your integration?

No. We've tested our systems with empty query params and everything is working as expected. At this time, this issue is not a high priority from Chartbeat's perspective.

[jmadler]

@cramforce @avimehta LMK if this works:

I intend to implement this as a new boolean config option, skipEmptyUrlParams, which, when true, will omit "vars" and "extraUrlParams" if the value is anything other than a non-empty string.

[avimehta]

vars can't be omitted like that. For example, lets say this is my config:

{
  "requests": { "foo": "/foo?bar=${baz}" },
  "vars": { "baz" = "" }
}

In this case, regardless of the value of `baz`, the parameter `bar` will always be there. It's value will be empty if `baz` is empty but it will still be sent over wire. 

[rudygalfi]

This hasn't been discussed in awhile. Closing since it's pretty low in priority but we can reopen if anyone has a specific need for this.