fix(nextjs-config): warn when withPostHogConfig is wrapped by another Next config wrapper#3611
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cat-ph wants to merge 1 commit into
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fix(nextjs-config): warn when withPostHogConfig is wrapped by another Next config wrapper#3611cat-ph wants to merge 1 commit into
cat-ph wants to merge 1 commit into
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… Next config wrapper
When withPostHogConfig is not the outermost wrapper in next.config (e.g.
withNextIntl(withPostHogConfig(...))), some outer wrappers silently drop
the function-form config that withPostHogConfig returns. The result is
that the webpack/compiler hooks are never installed, no source maps are
generated or uploaded, and no errors or logs surface.
This change registers a process.on('exit') handler that emits a clear
warning if the inner Next.js config function was never invoked while
sourcemaps are enabled, pointing the user to the correct wrapper order.
It also documents the recommended order in the README.
Generated-By: PostHog Code
Task-Id: 689c4895-349a-4139-98c6-4ac93b522ae9
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Summary
withPostHogConfigis called but its inner config function is never invoked (the failure mode when another Next.js config wrapper is applied around it and silently drops the function-form return value).withPostHogConfigshould be the outermost wrapper.Context — the bug
User report:
Root cause:
withPostHogConfigreturns a function-form Next.js config ((phase, opts) => Promise<NextConfig>). When another wrapper likewithNextIntl(withPostHogConfig(...))does{ ...result }on it, spreading a function yields{}— silently dropping the PostHog hooks. Next.js itself supports function-form configs, so whenwithPostHogConfigis the outermost wrapper it works correctly.Approach
This PR implements the "warn + document" mitigation discussed in chat. A complementary follow-up would be to make
withPostHogConfigpreserve the input shape (return an object when given an object) so it composes correctly as an inner wrapper too — that would be the full fix. This PR is intentionally smaller-scope: it makes the silent failure loud.What the warning looks like
Test plan
pnpm lintpassespnpm test:unitpasses (3 new tests, all green)pnpm buildpasses (CJS + ESM bundles + declaration files)withNextIntl(withPostHogConfig(...))to confirm the warning fires at the end ofnext buildNotes / open questions
process.on('exit')so the warning surfaces at the very end ofnext build. That's late, butnext buildexits cleanly so it does still show up. Earlier detection would require a timer-based heuristic that's noisier.withPostHogConfigis essentially only called once per process.Generated-By: PostHog Code
Task-Id: 689c4895-349a-4139-98c6-4ac93b522ae9