[jackielii]

What

An interface-typed parameter on Props, ServeHTTP, Init or Middlewares is now filled by the single WithArgs registration that implements it. A page can then declare a narrow consumer-side interface, and a unit test can call Props directly with a fake.

type userLister interface{ ListUsers(context.Context) ([]User, error) }

func (usersPage) Props(r *http.Request, users userLister) (UsersProps, error) { … }
// Mount(…, WithArgs(&PostgresStore{})) fills users; a test passes fakeUsers{}.

Matching rules

1. The per-request values (writer, request, RenderTarget, *PageNode) fill a parameter first.
2. Otherwise, an interface parameter takes the one registration implementing it. Registrations are keyed by their dynamic type, so there is no "register under an interface" form; a concrete parameter matches as before.
3. If two or more registrations implement it, that's an error naming them: X is implemented by more than one registered value (A, B); declare the parameter as the concrete type, or narrow the interface.

Startup check

Mount checks every Props and extended ServeHTTP parameter for ambiguity (checkInjection), so the ambiguity fails startup with the page named instead of failing a request. Parse skips the check.

A missing dependency is deliberately not checked at Mount and stays a request-time error, as before. Apps such as eos mount pages in configurations, and tests, that don't register those pages' services.

Behaviour changes

• Interface parameters that used to fail every request with "not found" are now filled when exactly one registration implements them.
• An app with an interface parameter implemented by two registrations now fails Mount. Before, every request to that page failed.
• Nothing else changes: per-request injection is untouched.

Verification

• go test ./... and golangci-lint are clean.
• Every example passes go vet and its tests.
• The full eos suite against this branch, via go.work: 338 packages ok, 0 failures.
• New tests are in di_interface_test.go. The args_test/generics_injection_test cases were updated for interface filling.

Docs updated: docs/dependency-injection.md, skills/structpages/SKILL.md §7, reference.md, CLAUDE.md.

https://claude.ai/code/session_01Dp3Jmu2ePyCME2yG9yd672

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.21%. Comparing base (a296d69) to head (756af74).

Files with missing lines	Patch %	Lines
parse.go	87.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   95.16%   95.21%   +0.04%     
==========================================
  Files          16       16              
  Lines        1490     1547      +57     
==========================================
+ Hits         1418     1473      +55     
- Misses         43       44       +1     
- Partials       29       30       +1     

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