go-chi-route-shadow-mount

Answer

Two independent defects were blocking the /trees feature: a chi radix-tree route collision and a stale Postgres CHECK constraint. Both are fixed below.

1. Route shadowing — remount the subrouter at a deeper path

Root cause: chi (go-chi/chi/v5) stores routes in a radix tree per method. r.Mount("/trees/{tree_id}", subrouter) splices the subrouter's handlers into the tree at the same pattern node where the parent's bare GET/PATCH/DELETE /trees/{tree_id} handlers live. The mount owns that wildcard node for all methods, so the parent's bare handlers become unreachable (shadowed). Requests to GET /trees/42 never reach the tree handler → persisted tree never appeared in selects; the UI mockups that depended on it (2 and 4) timed out.

Fix: mount the feature subrouter at a distinct, more specific prefix /trees/{tree_id}/topic-detection so the bare {tree_id} endpoint node stays intact and the subrouter gets its own subtree.

// routes.go
r := chi.NewRouter()
r.Route("/trees", func(r chi.Router) {
    r.Use(middleware.Logger, middleware.Recoverer)

    // Bare CRUD on a single tree — these were SHADOWED by the old mount.
    r.Get("/", TreeHandler.List)
    r.Post("/", TreeHandler.Create)
    r.Get("/{tree_id}", TreeHandler.Get)      // was unreachable
    r.Patch("/{tree_id}", TreeHandler.Patch)  // was unreachable
    r.Delete("/{tree_id}", TreeHandler.Delete) // was unreachable

    // FIX: mount below the {tree_id} endpoint node instead of ON it.
    // Before: r.Mount("/{tree_id}", topicDetectionRouter())  ← bug
    r.Mount("/{tree_id}/topic-detection", topicDetectionRouter())
})

The subrouter itself is unchanged — only its mount prefix moves:

func topicDetectionRouter() http.Handler {
    sr := chi.NewRouter()
    sr.Get("/", TopicDetectionHandler.Get)
    sr.Put("/", TopicDetectionHandler.Upsert)
    sr.Post("/sync", TopicDetectionHandler.Sync) // yjs update sync (204)
    sr.Delete("/{topic_id}", TopicDetectionHandler.Delete)
    return sr
}

Callers that hit the old full path must be updated to the new one:

// client (before)  POST /trees/{tree_id}/sync
// client (after)   POST /trees/{tree_id}/topic-detection/sync
func (c *Client) SyncTopicDetection(ctx context.Context, treeID string, doc []byte) error {
    req, _ := http.NewRequestWithContext(ctx, http.MethodPost,
        c.base+"/trees/"+url.PathEscape(treeID)+"/topic-detection/sync",
        bytes.NewReader(doc))
    ...
}

2. CHECK constraint — migration 000031 drop + re-add

Root cause: the events table carries CONSTRAINT chk_event_type CHECK (event_type IN (...)) that enumerates allowed event types. The codebase started emitting yjs_update events from the sync endpoint, but the constraint never listed yjs_update, so every insert aborted with a check-violation → POST .../sync returned 500.

Fix: migration 000031 drops and re-creates the constraint with the new type included, and the Go enum constant is added.

-- migrations/000031_add_yjs_update_event_type.up.sql
ALTER TABLE events DROP CONSTRAINT chk_event_type;

ALTER TABLE events ADD CONSTRAINT chk_event_type
    CHECK (event_type IN (
        'tree_created',
        'tree_updated',
        'tree_deleted',
        'topic_added',
        'topic_updated',
        'topic_deleted',
        'yjs_update'            -- NEW event type
    ));

-- migrations/000031_add_yjs_update_event_type.down.sql
ALTER TABLE events DROP CONSTRAINT chk_event_type;

ALTER TABLE events ADD CONSTRAINT chk_event_type
    CHECK (event_type IN (
        'tree_created',
        'tree_updated',
        'tree_deleted',
        'topic_added',
        'topic_updated',
        'topic_deleted'
    ));

// events.go — keep the Go enum in lockstep with the DB constraint
type EventType string

const (
    EventTypeTreeCreated  EventType = "tree_created"
    EventTypeTreeUpdated  EventType = "tree_updated"
    EventTypeTreeDeleted  EventType = "tree_deleted"
    EventTypeTopicAdded   EventType = "topic_added"
    EventTypeTopicUpdated EventType = "topic_updated"
    EventTypeTopicDeleted EventType = "topic_deleted"
    EventTypeYjsUpdate    EventType = "yjs_update" // NEW
)

Apply with the project's migrator (e.g. golang-migrate): migrate -path migrations -database "$DATABASE_URL" up (or on startup via migrate.Up()), then verify the constraint definition.