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fix: coerce undefined values like null when serializing #893

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fix: coerce undefined values like null when serializing #893

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ff8d519
fix: coerce undefined values like null when serializing
cpruijsen Oct 10, 2026
63c9bc0
test: cover undefined in multi-type, tuple and const positions
cpruijsen Oct 10, 2026
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28 changes: 14 additions & 14 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -818,7 +818,7 @@ function buildObject (context, location, input) {
// ${asComment(schemaRef)}
function ${functionName} (input) {
const obj = ${toJSON('input')}
if (obj === null) return ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_OBJECT'}
if (obj == null) return ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_OBJECT'}
let json = ''

${buildInnerObject(context, location, 'obj')}
Expand All @@ -834,7 +834,7 @@ function buildObject (context, location, input) {
const objVar = `obj_${context.uid++}`
const code = `
const ${objVar} = ${toJSON(input)}
if (${objVar} === null) {
if (${objVar} == null) {
json += ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_OBJECT'}
} else {
${buildInnerObject(context, location, objVar)}
Expand Down Expand Up @@ -880,7 +880,7 @@ function buildArray (context, location, input) {
`

functionCode += `
if (obj === null) return ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_ARRAY'}
if (obj == null) return ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_ARRAY'}
if (!Array.isArray(obj)) {
throw new TypeError(${JSON.stringify(`The value of '${schemaRef}' does not match schema definition.`)})
}
Expand Down Expand Up @@ -964,7 +964,7 @@ function buildArray (context, location, input) {
const objVar = `obj_${context.uid++}`
let inlinedCode = `
const ${objVar} = ${input}
if (${objVar} === null) {
if (${objVar} == null) {
json += ${nullable ? 'JSON_STR_NULL' : 'JSON_STR_EMPTY_ARRAY'}
} else if (!Array.isArray(${objVar})) {
throw new TypeError(${JSON.stringify(`The value of '${safeSchemaRef}' does not match schema definition.`)})
Expand Down Expand Up @@ -1051,11 +1051,11 @@ function buildArrayTypeCondition (type, accessor) {
let condition
switch (type) {
case 'null':
condition = `${accessor} === null`
condition = `${accessor} == null`
break
case 'string':
condition = `typeof ${accessor} === 'string' ||
${accessor} === null ||
${accessor} == null ||
${accessor} instanceof Date ||
${accessor} instanceof RegExp ||
(
Expand Down Expand Up @@ -1108,7 +1108,7 @@ function buildMultiTypeSerializer (context, location, input) {
switch (type) {
case 'null':
code += `
${statement} (${input} === null) {
${statement} (${input} == null) {
${nestedResult}
}
`
Expand All @@ -1117,7 +1117,7 @@ function buildMultiTypeSerializer (context, location, input) {
code += `
${statement}(
typeof ${input} === "string" ||
${input} === null ||
${input} == null ||
${input} instanceof Date ||
${input} instanceof RegExp ||
(
Expand All @@ -1141,7 +1141,7 @@ function buildMultiTypeSerializer (context, location, input) {
}
case 'integer': {
code += `
${statement}(Number.isInteger(${input}) || ${input} === null) {
${statement}(Number.isInteger(${input}) || ${input} == null) {
${nestedResult}
}
`
Expand All @@ -1152,15 +1152,15 @@ function buildMultiTypeSerializer (context, location, input) {
// by this branch and serialized as an object (dropping its items). Exclude
// arrays here so a sibling `array` type in the same `type` list can match.
code += `
${statement}((typeof ${input} === "object" && !Array.isArray(${input})) || ${input} === null) {
${statement}((typeof ${input} === "object" && !Array.isArray(${input})) || ${input} == null) {
${nestedResult}
}
`
break
}
default: {
code += `
${statement}(typeof ${input} === "${type}" || ${input} === null) {
${statement}(typeof ${input} === "${type}" || ${input} == null) {
${nestedResult}
}
`
Expand Down Expand Up @@ -1193,7 +1193,7 @@ function buildSingleTypeSerializer (context, location, input) {
} else {
return `
if (typeof ${input} !== 'string') {
if (${input} === null) {
if (${input} == null) {
json += JSON_STR_EMPTY_STRING
} else if (${input} instanceof Date) {
json += JSON_STR_QUOTE + ${input}.toISOString() + JSON_STR_QUOTE
Expand Down Expand Up @@ -1328,7 +1328,7 @@ function buildConstSerializer (location, input) {

if (hasNullType) {
code += `
if (${input} === null) {
if (${input} == null) {
json += JSON_STR_NULL
} else {
`
Expand Down Expand Up @@ -1538,7 +1538,7 @@ function buildValue (context, location, input) {
const nullable = schema.nullable === true
if (nullable) {
code += `
if (${input} === null) {
if (${input} == null) {
json += JSON_STR_NULL
} else {
`
Expand Down
12 changes: 9 additions & 3 deletions lib/serializer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,9 @@ module.exports = class Serializer {
} else if (typeof i === 'bigint') {
return i.toString()
}
if (i == null) {
return '0'
}
/* eslint no-undef: "off" */
const integer = this.parseInteger(i)
// check if number is Infinity or NaN
Expand All @@ -77,6 +80,9 @@ module.exports = class Serializer {
}

asNumber (i) {
if (i == null) {
return '0'
}
// fast cast to number
const num = Number(i)
// check if number is NaN
Expand All @@ -95,7 +101,7 @@ module.exports = class Serializer {
}

asDateTime (date) {
if (date === null) return '""'
if (date == null) return '""'
if (date instanceof Date) {
return '"' + date.toISOString() + '"'
}
Expand All @@ -106,7 +112,7 @@ module.exports = class Serializer {
}

asDate (date) {
if (date === null) return '""'
if (date == null) return '""'
if (date instanceof Date) {
return '"' + new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString().slice(0, 10) + '"'
}
Expand All @@ -117,7 +123,7 @@ module.exports = class Serializer {
}

asTime (date) {
if (date === null) return '""'
if (date == null) return '""'
if (date instanceof Date) {
return '"' + new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString().slice(11, 19) + '"'
}
Expand Down
206 changes: 206 additions & 0 deletions test/missing-values.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -86,3 +86,209 @@ test('handle null when value should be boolean', (t) => {

t.assert.equal('{"bool":false}', stringify({ bool: null }))
})

test('handle undefined when value should be string', (t) => {
t.plan(1)

const stringify = build({
type: 'string'
})

t.assert.equal('""', stringify(undefined))
})

test('handle undefined in array of strings', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'string'
}
})

t.assert.equal('["test1","test2","test3",""]', stringify(['test1', 'test2', 'test3', undefined]))
})

test('handle undefined in array of integers', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'integer'
}
})

t.assert.equal('[1,2,0]', stringify([1, 2, undefined]))
})

test('handle undefined in array of numbers', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'number'
}
})

t.assert.equal('[1.5,0]', stringify([1.5, undefined]))
})

test('handle undefined in array of booleans', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'boolean'
}
})

t.assert.equal('[true,false]', stringify([true, undefined]))
})

test('handle undefined in array of objects', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'object',
properties: {
str: {
type: 'string'
}
}
}
})

t.assert.equal('[{"str":"test"},{}]', stringify([{ str: 'test' }, undefined]))
})

test('handle undefined in array of date-time strings', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'string',
format: 'date-time'
}
})

t.assert.equal('["2020-01-01T00:00:00.000Z",""]', stringify(['2020-01-01T00:00:00.000Z', undefined]))
})

test('handle undefined in array of date strings', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'string',
format: 'date'
}
})

t.assert.equal('["2020-01-01",""]', stringify(['2020-01-01', undefined]))
})

test('handle undefined in array of time strings', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'string',
format: 'time'
}
})

t.assert.equal('["00:00:00",""]', stringify(['00:00:00', undefined]))
})

test('handle undefined when value is nullable', (t) => {
t.plan(1)

const stringify = build({
type: 'string',
nullable: true
})

t.assert.equal('null', stringify(undefined))
})

test('handle undefined in tuple of strings', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: [
{
type: 'string'
},
{
type: 'string'
}
]
})

t.assert.equal('["test",""]', stringify(['test', undefined]))
})

test('handle undefined in array with multiple item types', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: ['string', 'integer']
}
})

t.assert.equal('["test",""]', stringify(['test', undefined]))
})

test('handle undefined in nested arrays', (t) => {
t.plan(1)

const stringify = build({
type: 'array',
items: {
type: 'array',
items: {
type: 'string'
}
}
})

t.assert.equal('[["test"],[]]', stringify([['test'], undefined]))
})

test('undefined object properties are still skipped', (t) => {
t.plan(1)

const stringify = build({
type: 'object',
properties: {
str: {
type: 'string'
}
}
})

t.assert.equal('{}', stringify({ str: undefined }))
})

test('handle undefined in multi-type, tuple and const positions', (t) => {
t.plan(6)

t.assert.equal('["a",null]', build({ type: 'array', items: { type: ['null', 'string'] } })(['a', undefined]))
t.assert.equal('[1,0]', build({ type: 'array', items: { type: ['integer', 'string'] } })([1, undefined]))
t.assert.equal('[{},{}]', build({ type: 'array', items: { type: ['object', 'string'] } })([{}, undefined]))
t.assert.equal('[true,false]', build({ type: 'array', items: { type: ['boolean', 'string'] } })([true, undefined]))
t.assert.equal('[null]', build({ type: 'array', items: [{ type: 'null' }] })([undefined]))
t.assert.equal('["x",null]', build({ type: 'array', items: { type: ['string', 'null'], const: 'x' } })(['x', undefined]))
})
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