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fix: count duplicate keys independently of prototype names #318

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fix: count duplicate keys independently of prototype names #318

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3 changes: 2 additions & 1 deletion lib/ini.js
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Original file line number Diff line number Diff line change
Expand Up @@ -111,7 +111,8 @@ const decode = (str, opt = {}) => {
// section |key = value
const re = /^\[([^\]]*)\]\s*$|^([^=]+)(=(.*))?$/i
const lines = str.split(/[\r\n]+/g)
const duplicates = {}
// 2026-10-11: Count only keys from the input, including prototype member names.
const duplicates = Object.create(null)

for (const line of lines) {
if (!line || line.match(/^\s*[;#]/) || line.match(/^\s*$/)) {
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11 changes: 11 additions & 0 deletions test/duplicate-properties.js
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Expand Up @@ -38,3 +38,14 @@ test('encode duplicate properties with bracketedArray=false', function (t) {
t.matchSnapshot(e)
t.end()
})

// 2026-10-11: Prototype member names are ordinary duplicate keys in INI data.
test('decode duplicate keys named after prototype properties', function (t) {
for (const key of ['constructor', 'toString', 'valueOf', 'hasOwnProperty']) {
const input = `${key}=first\n${key}=second\n${key}=third`
t.same(i.decode(input, { bracketedArray: false })[key], ['first', 'second', 'third'], key)
t.same(i.decode(`${key}=single`, { bracketedArray: false })[key], 'single', `${key} stays scalar`)
t.same(i.decode(input)[key], 'third', `${key} follows default last-value behavior`)
}
t.end()
})