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Fixing an issue that type 'null' is not assignable to validateStatus … #8

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Fixing an issue that type 'null' is not assignable to validateStatus … #8

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2 changes: 1 addition & 1 deletion index.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -62,8 +62,8 @@ export interface AxiosRequestConfig {
onUploadProgress?: (progressEvent: ProgressEvent) => void;
onDownloadProgress?: (progressEvent: ProgressEvent) => void;
maxContentLength?: number;
validateStatus?: ((status: number) => boolean | null);
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@coderabbitai coderabbitai bot Jan 29, 2026

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⚠️ Potential issue | 🟠 Major

LGTM! Type signature correctly allows null return value.

The change properly expands the return type to boolean | null, which fixes the type error when users return null from their validateStatus implementation. The parentheses correctly scope the union type to the return value.Important: The type signature should be ((status: number) => boolean) | null rather than ((status: number) => boolean | null). The current implementation parses as a function that returns boolean | null, but the intended fix should allow the entire property to be set to null.

According to Axios documentation, validateStatus can be assigned a function, undefined, or null to the property itself. When set to null or undefined, all status codes resolve the promise.

🐛 Proposed fix for the type signature 
-  validateStatus?: ((status: number) => boolean | null);
+  validateStatus?: ((status: number) => boolean) | null;

This was also noted in the original Axios PR discussion where the same mistake was made and later corrected in PR #3200.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
validateStatus?: ((status: number) => boolean | null);
validateStatus?: ((status: number) => boolean) | null;
🤖 Prompt for AI Agents 
In `@index.d.ts` at line 65, The type for validateStatus is wrong: it currently
defines a function that returns boolean|null but should allow the entire
property to be null; change the signature for validateStatus so the union
applies to the property (i.e., ((status: number) => boolean) | null) instead of
((status: number) => boolean | null), updating the declaration named
validateStatus in index.d.ts so callers can assign null to the property itself.

maxBodyLength?: number;
validateStatus?: (status: number) => boolean;
maxRedirects?: number;
socketPath?: string | null;
httpAgent?: any;
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