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fix(RequestInit): restrict body type based on method to improve type safety #1953

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fix(RequestInit): restrict body type based on method to improve type safety #1953

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5febfea
fix(RequestInit): restrict body type based on method to improve type …
Bashamega Mar 30, 2025
f60b054
Merge branch 'microsoft:main' into 1678
Bashamega Mar 31, 2025
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2 changes: 1 addition & 1 deletion baselines/dom.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1953,7 +1953,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
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This won't work if method is a general string, e.g.:

function download(url: URL, method: string, body: any) {
  return fetch(url, { method, body });
}

Or method is lowercased or something weird like "gET" (this still works in browsers as the browser internally makes it uppercase). Actually not sure this would work even if method is GET/HEAD, can you add a unit test?

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Actually, when I think about it more, it seems that this is a missing feature in TypeScript. TS needs to have a Template Literal Type for case-insensitive matching.

/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/serviceworker.generated.d.ts
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Expand Up @@ -560,7 +560,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/sharedworker.generated.d.ts
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Expand Up @@ -494,7 +494,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/ts5.5/dom.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1953,7 +1953,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/ts5.5/serviceworker.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -560,7 +560,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/ts5.5/sharedworker.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -494,7 +494,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/ts5.5/webworker.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -702,7 +702,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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2 changes: 1 addition & 1 deletion baselines/webworker.generated.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -702,7 +702,7 @@ interface ReportingObserverOptions {

interface RequestInit {
/** A BodyInit object or null to set request's body. */
body?: BodyInit | null;
body?: 'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null | null;
/** A string indicating how the request will interact with the browser's cache to set request's cache. */
cache?: RequestCache;
/** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
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3 changes: 3 additions & 0 deletions inputfiles/overridingTypes.jsonc
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Expand Up @@ -3924,6 +3924,9 @@
"member": {
"window": {
"overrideType": "null"
},
"body": {
"overrideType": "'GET' | 'HEAD' extends this['method'] ? never : BodyInit | null"
}
}
}
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