avoid printing full error during development

[dferber90]

When developing locally it is common to create a feature flag in code before actually creating it in the feature flag provider, and to then use Flags Explorer to override this flag and continue development.

This works fine when a defaultValue is declared. However the feature flag provider will - expectedly - not find the feature flag yet, and usually emit an error. This has the negative effect that we currently print the whole error the flag provider emits to the console, even though this is expected. This is quite distracting.

This PR reduces the log level by downgrading the log to a console.info, and by omitting the error itself from the log.

Before

@vercel/flags: Flag "example-flag" is falling back to the defaultValue after catching the following error Error: test
    at Object.decide (app/concepts/identify/basic/flags.ts:21:10)
    at decide (../../packages/flags/src/next/index.ts:173:24)
    at run (../../packages/flags/src/next/index.ts:286:8)
    at async Page (app/concepts/identify/basic/page.tsx:5:16)

After

@vercel/flags: Flag "example-flag" is falling back to its defaultValue

For preview and production environments we continue to show the full error, as you would expect the feature flag to be declared in those environments.

To see the full error during development you can temporarily remove the defaultValue from the declaration, which will make the flag function throw the actual error.

Alternatives considered

• Using console.groupCollapsed to log the warning and show the full error in a collapsed state during development.
• Allowing customers to handle errors manually as shown in Allow intercepting evaluations #58

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
flags-sdk-snippets	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Feb 5, 2025 3:40pm
summer-sale	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Feb 5, 2025 3:40pm