Parse ASTInfo to determine which of a set of GraphQL fields that have been requested

getRequestedFields.js

/* Given a list of fields, such as [ 'a', 'b', 'c' ] and ASTInfo, return an object
on the form {a: true, b: false, c: true } where a property is true if the field is requested through the ASTInfo */
const getRequestedFields = (fieldNames, info) => {
  let { fieldNodes, fragments } = info;
  let result = {};
  for (let i = 0; i < fieldNodes.length; i++) {
    if (!fieldNodes[i].selectionSet) {
      continue;
    }
    for (let j = 0; j < fieldNodes[i].selectionSet.selections.length; j++) {
      if (fieldNodes[i].selectionSet.selections[j].kind === "InlineFragment") {
        result = {
          ...result,
          ...getRequestedFields(fieldNames, {
            fieldNodes: fieldNodes[i].selectionSet.selections,
            fragments,
          }),
        };
      } else if (
        fieldNodes[i].selectionSet.selections[j].kind === "FragmentSpread"
      ) {
        let fragmentName = fieldNodes[i].selectionSet.selections[j].name.value;
        result = {
          ...result,
          ...getRequestedFields(fieldNames, {
            fieldNodes: [fragments[fragmentName]],
            fragments,
          }),
        };
      }
      for (let k = 0; k < fieldNames.length; k++) {
        if (
          fieldNodes[i].selectionSet.selections[j].kind === "Field" &&
          fieldNodes[i].selectionSet.selections[j].name.value === fieldNames[k]
        ) {
          result[fieldNames[k]] = true;
          fieldNames.splice(k, 1);
          if (fieldNames.length === 0) {
            return result;
          }
          break;
        }
      }
    }
  }
  for (let i = 0; i < fieldNames.length; i++) {
    result[fieldNames[i]] = false;
  }
  return result;
};