Description:

Currently, Axios passes the parseReviver configuration option directly to the native JSON.parse function under the hood (e.g., return JSON.parse(data, own(this, 'parseReviver'));). However, there are two issues regarding its discoverability and TypeScript support:

1. Missing from Documentation: The parseReviver option is completely absent from the Request Config documentation.
2. Outdated TypeScript Definitions: The type definition for parseReviver does not support the ES2023/ES14 standard, which introduces a third context argument to the reviver function (specifically for context.source).

Expected Behavior:

1. Documentation:
parseReviver should be listed in the Request Config docs alongside transformResponse, explaining that it allows users to provide a custom reviver function to JSON.parse.

2. TypeScript Definitions:
The index.d.ts file should be updated to reflect modern JavaScript engine capabilities. The third argument allows developers to access the raw JSON source, which is critical for parsing large integers (BigInt) without precision loss or properly hydrating strict date types (like Temporal).

Current Type:

parseReviver?: (this: any, key: string, value: any) => any;

Proposed Type:

parseReviver?: (this: any, key: string, value: any, context?: { source: string }) => any;

Steps To Reproduce / Motivation:

When attempting to use modern ES2023 features to hydrate data at the network edge, TypeScript throws an error because the Axios types do not recognize the third argument.

const apiClient = axios.create({
  baseURL: '/api',
  parseReviver: (key, value, context) => { // TS Error: Expected 2 arguments, but got 3.
    // Use case: Prevent BigInt precision loss from backend systems
    if (typeof value === 'number' && context?.source && context.source.length > 15) {
       return BigInt(context.source);
    }
    return value;
  }
});

Currently, developers have to manually cast the function to bypass the Axios type definitions, even though the native JS engine executes the code perfectly.

Environment:

• Axios Version: 1.15.1
• Node.js/Browser: Node 20+ / Chrome 114+ / Modern Browsers (ES2023 support)
• TypeScript Version: 5.9.3

Proposed Solution:

• Add a brief entry for parseReviver in docs/req_config.md.
• Update the parseReviver signature in index.d.ts to include the optional context parameter.

Summary by cubic

Adds ES2023 context.source support to the parseReviver TypeScript type and documents safe usage (BigInt and optional Temporal). No runtime changes to axios.

Description

• Summary of changes
  • Types: update index.d.ts and index.d.cts to parseReviver?: (this: any, key: string, value: any, context?: { source: string }) => any.
  • Docs: add a parseReviver section to /docs/pages/advanced/request-config.md with precision-safe BigInt parsing and guarded Temporal hydration; fix a minor formatting issue (trailing comma in examples).
  • README: add a parseReviver example showing precision-safe BigInt parsing.
• Reasoning
  • Aligns with ES2023 JSON.parse reviver context and surfaces safe parsing patterns.
• Additional context
  • parseReviver is passed to native JSON.parse by the default transformResponse.

Docs

Update the docs site in /docs/ to include the new parseReviver section and examples, and ensure the README references remain consistent.

Testing

• No tests added.
• Recommend adding tsd/dtslint assertions for (key, value, context?) and context.source: string in both .d.ts and .d.cts. No runtime tests needed.

Semantic version impact

Patch: types and docs only; no runtime behavior changes.

^{Written for commit 8df2d9e. Summary will update on new commits. Review in cubic}