read_json not being determined as a Map

I’m using read_json to read the contents of a file with a json output, and then immediately trying to access a property on this (through the following minimal example):

version development
task readjson {

  command <<<
      echo '{"out": "Hello, WDL!"}' > out.txt
  >>>

  output {
    String out = read_json('out.txt')["out"]
  }
}

This validates and runs correctly in Cromwell, but in miniWDL I get the following error:

miniwdl run --verbose codetool.wdl
(codetool.wdl Ln 10 Col 18) Not an array
        String out = read_json('out.txt')["out"]
                     ^^^^^^^^^^^^^^^^^^^^

I’ve noticed that you can coerce it to the correct type which will then validate, eg:

version development
task readjson {

  command <<<
      echo '{"out": "Hello, WDL!"}' > out.txt
  >>>

  output {
    Map[String, String] coercedmap = read_json('out.txt')
    String out = coercedmap["out"]
  }
}

But this has the disadvantage that it returns more than what’s required.

---

Versions:

• v0.6.3 (through Pip)
• Latest on Git: miniwdl v0.6.4.dev14

[mlin]

@illusional the solution in just-released v0.7.1 is very much along the lines you suggested, but exapts some type unification logic that had existed elsewhere for other purposes. There will probably still be some weird corner cases like non-homogeneity in lists and object value types, as you mention – let us know if you hit anything that clearly ought to work even given that JSON isn’t 100% embeddable in WDL values. Thanks!

[mlin]

Thanks – yea, looks like I punted on this case previously. Will take another look