Expected `json` string interpolator from io.circe.literal to be able to interpolate variable inside of value strings

[César Enrique Ramírez]

I'm having some issues with the behaviour of the json string interpolator.

I was expecting this to compile:

//> using toolkit typelevel:0.1.25
//> using dep io.circe::circe-literal::0.14.6
//> using scala 3.3.3

import io.circe.literal.*

val value = 5
val json = json"""{
  "a": "something with value: $value"
}"""

But, instead I had to resort to extracting the whole string from the right hand side of a and use regular string interpolation there:

//> using toolkit typelevel:0.1.25
//> using dep io.circe::circe-literal::0.14.6
//> using scala 3.3.3

import io.circe.literal.*

val value = 5
val valueString = s"something with value: $value"
val json = json"""{
  "a": $valueString
}"""

Is this expected behaviour? I think this wasn't the case in scala 2

[César Enrique Ramírez]

This seems to work:

//> using toolkit typelevel:0.1.25
//> using dep io.circe::circe-literal::0.14.6
//> using scala 3.3.3

import io.circe.literal._

val value = 5
val json = json"""{
  "a": ${s"something with value: $value"}
}"""

I've check using scala 2.13 and the behaviour is the same, so I was wrong about that. I'm curious to know if this is a bug, a technical limitation or a design decision though 😄

[CJ Smith]

I think that they way this works is the macro replacements happen before parsing the string into the io.circe.Json AST. So the macro turns this

val value = "5"
val json = json"""{
  "a": "something with value: $value"
}"""

into this

val jsonString = """{
  "a": "something with value: "5""
}"""

The inner "5" doesn't have the " escaped, so it's not valid json. The parsing fails at this point.