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.
The original flags object must contain exactly setup, training and export, each a Boolean. Return true keys in that fixed order and retain all three flags. Missing, unknown or non-Boolean flags reject the mapping. All false is a complete selection record with an empty selected list.
| Case | Input record (JSON) | Expected output (JSON) |
|---|---|---|
| Decode selected flag fields | {"flags":{"setup":true,"training":false,"export":true}} | {"ok":true,"value":{"selected":["setup","export"],"sourceFlags":{"setup":true,"training":false,"export":true}}} |
| Reject missing flag | {"flags":{"setup":true,"training":false}} | {"ok":false,"error":"FLAG_MISSING"} |
| Preserve all-false selection | {"flags":{"setup":false,"training":false,"export":false}} | {"ok":true,"value":{"selected":[],"sourceFlags":{"setup":false,"training":false,"export":false}}} |
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 serviceFlags(i){
const fail=error=>({ok:false,error});if(!i||!i.flags||typeof i.flags!=='object'||Array.isArray(i.flags))return fail('FLAG_OBJECT');
const keys=['setup','training','export'];
if(Object.keys(i.flags).some(k=>!keys.includes(k)))return fail('FLAG_UNKNOWN');
if(keys.some(k=>!Object.hasOwn(i.flags,k)))return fail('FLAG_MISSING');
if(keys.some(k=>typeof i.flags[k]!=='boolean'))return fail('FLAG_VALUE');
return {ok:true,value:{selected:keys.filter(k=>i.flags[k]),sourceFlags:{setup:i.flags.setup,training:i.flags.training,export:i.flags.export}}};
}
// Original synthetic cases; expected outputs are literal records.
const cases = [
{
"label": "Decode selected flag fields",
"input": {
"flags": {
"setup": true,
"training": false,
"export": true
}
},
"expected": {
"ok": true,
"value": {
"selected": [
"setup",
"export"
],
"sourceFlags": {
"setup": true,
"training": false,
"export": true
}
}
}
},
{
"label": "Reject missing flag",
"input": {
"flags": {
"setup": true,
"training": false
}
},
"expected": {
"ok": false,
"error": "FLAG_MISSING"
}
},
{
"label": "Preserve all-false selection",
"input": {
"flags": {
"setup": false,
"training": false,
"export": false
}
},
"expected": {
"ok": true,
"value": {
"selected": [],
"sourceFlags": {
"setup": false,
"training": false,
"export": false
}
}
}
}
];
for (const sample of cases) {
const actual = serviceFlags(sample.input);
assert.deepEqual(actual, sample.expected);
console.log(sample.label, JSON.stringify(actual));
}
Work through the boundary
Why must a missing export flag fail while export=false is valid?
Show the worked answer
Missing supplies no answer; false explicitly supplies an unselected answer. The first case selects setup and export while retaining training=false; it does not place a service order.