Source contract and expected records
This is an original, fully synthetic mapping example. Inputs are plain, acyclic JSON-shaped records with the fields shown; the canonical shape and rejection codes belong to this example. Adapt the contract before using a different source.
Every parcel has a unique positive safe integer number and a contents array. Contents require sku text and nonnegative safe whole units. Map number to parcelNo, copy its lines, and sort parcels numerically. Empty parcels remain; an empty source yields an empty consignment.
| Case | Input record (JSON) | Expected output (JSON) |
|---|---|---|
| Retain nested parcel contents | {"parcels":[{"number":2,"contents":[{"sku":"A","units":1}]},{"number":1,"contents":[]}]} | {"ok":true,"value":{"consignment":[{"parcelNo":1,"lines":[]},{"parcelNo":2,"lines":[{"sku":"A","units":1}]}]}} |
| Reject repeated parcel number | {"parcels":[{"number":1,"contents":[]},{"number":1,"contents":[]}]} | {"ok":false,"error":"PARCEL_NUMBER"} |
| Preserve empty consignment | {"parcels":[]} | {"ok":true,"value":{"consignment":[]}} |
Run the local transformation
Run the complete example as a JavaScript module in Node.js. It contains the pure mapping function, all three inputs and literal expected outputs; assertions stop on a mismatch. A rejected case returns ok=false with an error code, rather than a partial canonical record.
import assert from 'node:assert/strict';
function parcelContents(i){
const fail=error=>({ok:false,error});if(!i||!Array.isArray(i.parcels))return fail('PARCEL_LIST');
const seen=new Set(),consignment=[];
for(const p of i.parcels){
if(!p||!Number.isSafeInteger(p.number)||p.number<1||seen.has(p.number)||!Array.isArray(p.contents))return fail('PARCEL_NUMBER');seen.add(p.number);
if(p.contents.some(c=>!c||typeof c.sku!=='string'||!c.sku||!Number.isSafeInteger(c.units)||c.units<0))return fail('PARCEL_CONTENT');
consignment.push({parcelNo:p.number,lines:p.contents.map(c=>({sku:c.sku,units:c.units}))});
}
consignment.sort((a,b)=>a.parcelNo-b.parcelNo);return {ok:true,value:{consignment}};
}
// Original synthetic cases; expected outputs are literal records.
const cases = [
{
"label": "Retain nested parcel contents",
"input": {
"parcels": [
{
"number": 2,
"contents": [
{
"sku": "A",
"units": 1
}
]
},
{
"number": 1,
"contents": []
}
]
},
"expected": {
"ok": true,
"value": {
"consignment": [
{
"parcelNo": 1,
"lines": []
},
{
"parcelNo": 2,
"lines": [
{
"sku": "A",
"units": 1
}
]
}
]
}
}
},
{
"label": "Reject repeated parcel number",
"input": {
"parcels": [
{
"number": 1,
"contents": []
},
{
"number": 1,
"contents": []
}
]
},
"expected": {
"ok": false,
"error": "PARCEL_NUMBER"
}
},
{
"label": "Preserve empty consignment",
"input": {
"parcels": []
},
"expected": {
"ok": true,
"value": {
"consignment": []
}
}
}
];
for (const sample of cases) {
const actual = parcelContents(sample.input);
assert.deepEqual(actual, sample.expected);
console.log(sample.label, JSON.stringify(actual));
}
Work through the boundary
Does sorting parcel 1 before parcel 2 move A into parcel 1?
Show the worked answer
No. Parcel 1 retains lines=[] and parcel 2 retains A=1. Sorting changes record order, not membership; the mapped record does not establish dispatch.