fix: use lazy promise on getCartCount to defer cookies() execution

[fikrikarim]

What/Why?

This fixes 500 error:

needs to bail out of prerendering at this point because it used cookies()

Without the lazy promise, the getCartCount() is immediately executed, and calls cookies() on the Header.

With lazy promise, the getCartCount() execution is deferred, until await/then is used.

Testing

This bug was only reproducible if we reverted the temporary fix commit on the soul/makeswift/integration branch. See this deployment.

Makeswift pages are PPRed correctly instead of being server-rendered

@bigcommerce/catalyst-core:build: ├ ◐ /[locale]                                  1.8 kB          441 kB
@bigcommerce/catalyst-core:build: ├   ├ /[locale]
@bigcommerce/catalyst-core:build: ├   └ /en
@bigcommerce/catalyst-core:build: ├ ◐ /[locale]/[...rest]                        1.8 kB          441 kB
@bigcommerce/catalyst-core:build: ├   ├ /[locale]/[...rest]
@bigcommerce/catalyst-core:build: ├   ├ /en/[...rest]
@bigcommerce/catalyst-core:build: ├   ├ /en/blog
@bigcommerce/catalyst-core:build: ├   └ [+5 more paths]

No 500 error logs:

[linear]

VIB-1052 Calling `cookies()` in a streamed function results in a 500 error

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Name	Status	Preview	Comments	Updated (UTC)
catalyst-latest	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 9, 2025 3:17pm
catalyst-soul	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 9, 2025 3:17pm

3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
catalyst	⬜️ Ignored (Inspect)			Jan 9, 2025 3:17pm
catalyst-au	⬜️ Ignored (Inspect)			Jan 9, 2025 3:17pm
catalyst-uk	⬜️ Ignored (Inspect)			Jan 9, 2025 3:17pm

[migueloller]

Thanks!

Looking at this makes me wonder if we should handle this in VIBES at some point, where we take the approach of accepting functions and we turn them into lazy promises 🤔