read_json

Union read_json(File)

Reads a JSON file into a WDL value whose type depends on the file's contents. The mapping of JSON type to WDL type is:

The return value is of type Union and must be used in a context where it can be coerced to the expected type, or an error is raised. For example, if the JSON file contains null, then the return value will be None, meaning the value can only be used in a context where an optional type is expected.

If the JSON file contains an array, then all the elements of the array must be coercible to the same type, or an error is raised.

The read_json function does not have access to any WDL type information, so it cannot return an instance of a specific Struct type. Instead, it returns a generic Object value that must be coerced to the desired Struct type.

Note that an empty file is not valid according to the JSON specification, and so calling read_json on an empty file raises an error.

Parameters

1. File: Path of the JSON file to read.

Returns: A value whose type is dependent on the contents of the JSON file.

Example: read_person.wdl

version 1.2

struct Person {
  String name
  Int age
}

workflow read_person {
  input {
    File json_file
  }

  output {
    Person p = read_json(json_file)
  }
}

{
  "read_person.json_file": "data/person.json"
}

{
  "read_person.p": {
    "name": "John",
    "age": 42
  }
}