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 source is a nonempty address block with a nonempty country label. Accept LF and CRLF line breaks; reject a lone CR. Split into addressLines without trimming or removing blank lines, and retain sourceBlock. Country labels are opaque source text, not a geographical validation result.
| Case | Input record (JSON) | Expected output (JSON) |
|---|---|---|
| Split supplied address block | {"block":"Demo Tower\nUnit 7","countryLabel":"Example"} | {"ok":true,"value":{"addressLines":["Demo Tower","Unit 7"],"countryLabel":"Example","sourceBlock":"Demo Tower\nUnit 7"}} |
| Reject absent address | {"block":"","countryLabel":"Example"} | {"ok":false,"error":"ADDRESS_EMPTY"} |
| Preserve interior blank line | {"block":"Demo Tower\n\nUnit 7","countryLabel":"Example"} | {"ok":true,"value":{"addressLines":["Demo Tower","","Unit 7"],"countryLabel":"Example","sourceBlock":"Demo Tower\n\nUnit 7"}} |
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 addressLines(i){
const fail=error=>({ok:false,error});if(!i||typeof i.block!=='string'||!i.block||typeof i.countryLabel!=='string'||!i.countryLabel)return fail('ADDRESS_EMPTY');
if(/\r(?!\n)/.test(i.block))return fail('ADDRESS_BREAK');
return {ok:true,value:{addressLines:i.block.split(/\r?\n/),countryLabel:i.countryLabel,sourceBlock:i.block}};
}
// Original synthetic cases; expected outputs are literal records.
const cases = [
{
"label": "Split supplied address block",
"input": {
"block": "Demo Tower\nUnit 7",
"countryLabel": "Example"
},
"expected": {
"ok": true,
"value": {
"addressLines": [
"Demo Tower",
"Unit 7"
],
"countryLabel": "Example",
"sourceBlock": "Demo Tower\nUnit 7"
}
}
},
{
"label": "Reject absent address",
"input": {
"block": "",
"countryLabel": "Example"
},
"expected": {
"ok": false,
"error": "ADDRESS_EMPTY"
}
},
{
"label": "Preserve interior blank line",
"input": {
"block": "Demo Tower\n\nUnit 7",
"countryLabel": "Example"
},
"expected": {
"ok": true,
"value": {
"addressLines": [
"Demo Tower",
"",
"Unit 7"
],
"countryLabel": "Example",
"sourceBlock": "Demo Tower\n\nUnit 7"
}
}
}
];
for (const sample of cases) {
const actual = addressLines(sample.input);
assert.deepEqual(actual, sample.expected);
console.log(sample.label, JSON.stringify(actual));
}
Work through the boundary
Why is the blank line between Demo Tower and Unit 7 retained?
Show the worked answer
It is part of the supplied layout. The output has three lines, with an empty second string; sourceBlock retains the original breaks for reconstruction.