0003. Route directories are Go packages, with Go-safe names

• Status: Accepted
• Date: 2026-11-09

#Context

SvelteKit colocates server code with routes (blog/[slug]/+page.server.ts). We want the same with Go, so a route's Load sits next to its +page.svelte.

We tested what Go accepts:

Name	Result
directories [slug], (app)	malformed import path. Worse, go build ./..., go vet ./... and go test ./... fail for the whole module, and gopls cannot load the package.
directories ~slug, +slug, -slug	invalid input directory name
directory _slug	builds, but ./... patterns silently skip it, so its tests and vet never run
directories slug.param, slug-x, slug_x	work everywhere
file +page.server.go	invalid input file name

Mirroring route packages into a generated tree with //line directives would fix compiler errors but not go test ./... or editor support for the original files, because the original directories would still be malformed packages.

#Decision

1. Directory names use suffixes, which are valid Go import path elements:

   SvelteKit	Tern
   [slug]	slug.param
   [id=integer]	id.param.integer
   [[lang]]	lang.optional
   [...path]	path.rest
   (app)	app.group

   Segments that mix text and parameters ([slug].json) are not supported; an endpoint can do the same job. The scanner rejects SvelteKit names with an error that gives the Tern name.

2. A route directory's Go code is an ordinary Go package. File names are free; page.server.go, layout.server.go and server.go are the convention. Roles come from exported names:

   Export	Role
   func Load	page data
   var Actions	page form actions
   func LayoutLoad	layout data
   func GET, POST, PUT, PATCH, DELETE, OPTIONS, HEAD	endpoint

3. Wiring is generated. tern gen writes tern.gen.go into the app's root package. It imports each route package directly and registers its functions with the runtime.

#Consequences

• go build ./..., go test ./..., go vet ./..., gopls and golangci-lint all work on route code with no special setup.
• Compiler errors point at the user's own files.
• Page and layout loads in one directory share a package, which is why the layout's function is named LayoutLoad.
• Route URLs look different on disk from SvelteKit's. Patterns are still displayed in bracket notation (/blog/[slug]) wherever Tern prints them.