Never resolve tokens after evaluating a text-field or icon-image expression

[jfirebaugh]

We want to deprecate and remove {} token interpolation in favor of string expressions like concat, so we should avoid setting the precedent that interpolation is supported in combination with expressions. A text-field or icon-image expression that evaluates to a string containing { and } characters should always treat those characters literally, and never do interpolation, regardless of whether the expression is feature-constant or not.

cc @anandthakker

[jfirebaugh]

Note that this implies that any auto-conversion of stop-based functions to expressions needs to convert {}-interpolation to equivalent get and concat expressions.

[dpieri]

It took me a while to figure out what this change was. Am I correct in concluding that my existing styles that use tokens like this will still work?

"icon-image": "{shield}-{reflen}",

[jfirebaugh]

Yes, correct, the change affects only expressions, not constant string values.