[edge-config] Changeset for major release (#577)

* [edge-config] Changeset for major release * Update changeset * Add newlines * Update wording * Apply suggestions from code review Co-authored-by: Dominik Ferber <[email protected]> * Fix indentation * Update example * Wording * Order * Wording * Fix wording * Update .changeset/lemon-phones-sort.md Co-authored-by: Dominik Ferber <[email protected]> * Update .changeset/lemon-phones-sort.md Co-authored-by: Dominik Ferber <[email protected]> --------- Co-authored-by: Dominik Ferber <[email protected]>
vercel · Feb 12, 2024 · fcdc55e · fcdc55e
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+---
+"@vercel/edge-config": major
+---
+
+ - **BREAKING CHANGE** Return values are now read-only to improve in-memory caching
+
+   It used to be possible to change the returned value as shown in this example:
+
+   ```typescript
+    import { get } from '@vercel/edge-config';
+    const countries = await get('allowedCountryCodes');
+    countries.DE = true; // Will now cause TypeScript to error
+   ```
+
+   Moving forward, modifications like the above will cause a type error.
+
+   If there is a need to modify the value, then the `clone` function can be used to clone the data and make it modifiable.
+
+   ```typescript
+    import { get, clone } from '@vercel/edge-config';
+
+    const myArray = await get('listOfAllowedIPs');
+    const myArrayClone = clone(myArray); // Clones the data to make it modifiable
+    myArrayClone.push('127.0.0.1'); // The `push` operation will work now
+   ```
+
+ - **BREAKING CHANGE** SDK now throws underlying errors
+
+   Previous versions of the `@vercel/edge-config` package would catch most errors thrown by native functions and throw a generic network error instead - even if the underlying issue wasn't a network error. The new version will throw the original errors.
+
+   **Note** applications which rely on the `@vercel/edge-config: Unexpected error` and `@vercel/edge-config: Network error` errors must adapt to the new implementation by ensuring other types of errors are handled as well.
+
+ - The SDK now uses stale-while-revalidate semantics during development
+
+   When `@vercel/edge-config` is used during development, with `NODE_ENV` being set to `development`, any read operation will fetch the entire Edge Config once and keep it in-memory to quickly resolve all other read operations for other keys, without waiting for the network. Subsequent reads will update the in-memory data in the background.
+
+   This behaviour can be disabled by setting the environment variable `EDGE_CONFIG_DISABLE_DEVELOPMENT_SWR` to `1`, or by using the `disableDevelopmentCache` option on the `createClient` function.