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[typescript-fetch] Remove returns in oneOf serialization code which short circuit additional type checks #21886

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[typescript-fetch] Remove returns in oneOf serialization code which short circuit additional type checks #21886

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7f18701
Remove returns from array blocks in typescript-fetch serialization/de…
cgual-omnidian Sep 4, 2025
9dad8af
Update samples
cgual-omnidian Sep 4, 2025
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26 changes: 12 additions & 14 deletions modules/openapi-generator/src/main/resources/typescript-fetch/modelOneOf.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -56,12 +56,11 @@ export function {{classname}}FromJSONTyped(json: any, ignoreDiscriminator: boole
if (Array.isArray(json)) {
if (json.every(item => typeof item === 'object')) {
{{/-first}}
if (json.every(item => instanceOf{{{.}}}(item))) {
return json.map(value => {{{.}}}FromJSONTyped(value, true));
if (json.every(item => instanceOf{{{.}}}(item as object))) {
return json.map(item => {{{.}}}FromJSONTyped(item, true));
}
{{#-last}}
}
return json;
}
{{/-last}}
{{/oneOfArrays}}
Expand All @@ -70,15 +69,15 @@ export function {{classname}}FromJSONTyped(json: any, ignoreDiscriminator: boole
{{#items}}
{{#isDateType}}
if (Array.isArray(json)) {
if (json.every(item => !(isNaN(new Date(json).getTime()))) {
return json.map(value => new Date(json);
if (json.every(item => !(isNaN(new Date(item).getTime())))) {
return json.map(item => new Date(item));
}
}
{{/isDateType}}
{{#isDateTimeType}}
if (Array.isArray(json)) {
if (json.every(item => !(isNaN(new Date(json).getTime()))) {
return json.map(value => new Date(json);
if (json.every(item => !(isNaN(new Date(item).getTime())))) {
return json.map(item => new Date(item));
}
}
{{/isDateTimeType}}
Expand Down Expand Up @@ -161,12 +160,11 @@ export function {{classname}}ToJSONTyped(value?: {{classname}} | null, ignoreDis
if (Array.isArray(value)) {
if (value.every(item => typeof item === 'object')) {
{{/-first}}
if (value.every(item => instanceOf{{{.}}}(item))) {
return value.map(value => {{{.}}}ToJSON(value as {{{.}}}));
if (value.every(item => instanceOf{{{.}}}(item as object))) {
return value.map(item => {{{.}}}ToJSON(item as {{{.}}}));
}
{{#-last}}
}
return value;
}
{{/-last}}
{{/oneOfArrays}}
Expand All @@ -175,15 +173,15 @@ export function {{classname}}ToJSONTyped(value?: {{classname}} | null, ignoreDis
{{#items}}
{{#isDateType}}
if (Array.isArray(value)) {
if (value.every(item => item instanceof Date) {
return value.map(value => value.toISOString().substring(0,10)));
if (value.every(item => item instanceof Date)) {
return value.map(item => item.toISOString().substring(0,10));
}
}
{{/isDateType}}
{{#isDateTimeType}}
if (Array.isArray(value)) {
if (value.every(item => item instanceof Date) {
return value.map(value => value.toISOString();
if (value.every(item => item instanceof Date)) {
return value.map(item => item.toISOString());
}
}
{{/isDateTimeType}}
Expand Down
18 changes: 8 additions & 10 deletions samples/client/petstore/typescript-fetch/builds/oneOf/models/TestArrayResponse.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -44,14 +44,13 @@ export function TestArrayResponseFromJSONTyped(json: any, ignoreDiscriminator: b
}
if (Array.isArray(json)) {
if (json.every(item => typeof item === 'object')) {
if (json.every(item => instanceOfTestA(item))) {
return json.map(value => TestAFromJSONTyped(value, true));
if (json.every(item => instanceOfTestA(item as object))) {
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Instead of using item as object we could also tell typescript that json is object[] if the condition that checks that every item is object is true:

if (json.every((item): item is object => typeof item === 'object')) {
    if (json.every(item => instanceOfTestA(item))) {
      // ...
    }
}

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Another thing: The check, that every item in the array is an object should also check that the item is not null, because typeof null also returns 'object'.

if (json.every((item): item is object => item !== null && typeof item === 'object')) {
// ...
}

Otherwise instanceOfTestA will be called with null if json contains [null], and that will cause a TypeError because the in operator cannot be used with null.

export function instanceOfTestA(value: object): value is TestA {
    if (!('foo' in value) || value['foo'] === undefined) return false;
    return true;
}

return json.map(item => TestAFromJSONTyped(item, true));
}
if (json.every(item => instanceOfTestB(item))) {
return json.map(value => TestBFromJSONTyped(value, true));
if (json.every(item => instanceOfTestB(item as object))) {
return json.map(item => TestBFromJSONTyped(item, true));
}
}
return json;
}
if (Array.isArray(json)) {
if (json.every(item => typeof item === 'string')) {
Expand All @@ -71,14 +70,13 @@ export function TestArrayResponseToJSONTyped(value?: TestArrayResponse | null, i
}
if (Array.isArray(value)) {
if (value.every(item => typeof item === 'object')) {
if (value.every(item => instanceOfTestA(item))) {
return value.map(value => TestAToJSON(value as TestA));
if (value.every(item => instanceOfTestA(item as object))) {
return value.map(item => TestAToJSON(item as TestA));
}
if (value.every(item => instanceOfTestB(item))) {
return value.map(value => TestBToJSON(value as TestB));
if (value.every(item => instanceOfTestB(item as object))) {
return value.map(item => TestBToJSON(item as TestB));
}
}
return value;
}
if (Array.isArray(value)) {
if (value.every(item => typeof item === 'string')) {
Expand Down
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