feat(atomic): add request transformer support to MSW endpoint harness

[alexprudhomme]

Problem

Multiple MSW draft PRs (msw-commerce-facets, msw-facets, msw-navigation, msw-search-controls, msw-commerce-pagination, msw-commerce-query-status) each duplicate a large 490-540 line custom handler file to support interactive mocking (facet selections, pagination, facet search). This is architecturally misaligned with the existing EndpointHarness pattern and creates maintenance burden.

Solution

Extend EndpointHarness with a requestTransformer concept — a function that takes the request body + resolved response and returns a modified response. This keeps the harness pattern intact while enabling dynamic, request-aware mocking.

New transformer modules:

• commerce/facet-transformer.ts — facet selections, hierarchical navigation, range facets, show-more, facet search
• commerce/pagination-transformer.ts — reflects page/perPage from requests
• search/facet-transformer.ts — dynamic facet building, sorting (alphanumeric, natural, occurrences), numeric ranges, facet search

Transformers are wired into MockCommerceApi and MockSearchApi so all MSW-based stories get interactive behavior automatically without needing custom handler files.

How it works

// Before: each story had its own 500+ line handler
// After: transformers are registered on the harness
this.searchEndpoint.withRequestTransformer((body, response) => {
  let result = commerceFacetTransformer(body, response);
  result = commercePaginationTransformer(body, result);
  return result;
});

Migration path

The other MSW draft branches should rebase on this branch and delete their custom facet-aware-handler.ts / dynamic-handler.ts files.

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Latest commit: bd28220

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[chromatic-com]

Tip

All tests passed and all changes approved!

🟢 UI Tests: 367 tests unchanged
🟢 UI Review: 367 stories published -- no changes
Storybook Publish: 367 stories published

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commit: bd28220

[Copilot]

Pull request overview

Extends the EndpointHarness MSW mocking infrastructure in packages/atomic/storybook-utils to support request-aware response shaping via a requestTransformer, and wires new “interactive facets/pagination” behavior into the Atomic search and commerce mock APIs for Storybook.

Changes:

• Add RequestTransformer + withRequestTransformer() support to EndpointHarness and apply it during handler execution.
• Introduce new transformer modules for Search facet building/facet search, and Commerce facet selection + pagination + facet search.
• Wire interactive transformers into MockSearchApi and MockCommerceApi, and register transformer modules as Knip entry points.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
packages/atomic/storybook-utils/api/_base.ts	Adds RequestTransformer and applies it in generateHandler() via request body parsing.
packages/atomic/storybook-utils/api/search/mock.ts	Adds enableInteractiveFacets() and registers search/facet-search transformers.
packages/atomic/storybook-utils/api/search/facet-transformer.ts	New search transformers for dynamic facet responses and facet search filtering.
packages/atomic/storybook-utils/api/commerce/mock.ts	Adds commerce facet-search endpoint and enableInteractiveFacets() wiring (facet + pagination + facet search).
packages/atomic/storybook-utils/api/commerce/facet-transformer.ts	New commerce facet transformer + facet-search transformer factory.
packages/atomic/storybook-utils/api/commerce/pagination-transformer.ts	New pagination transformer reflecting request page/perPage into responses.
knip.js	Registers *-transformer.ts modules as entry points for Knip tracing.