active-svelte/docs/conventions.md

# Active conventions

This document captures the **mandatory naming and structure
conventions** for the Active framework codebase. Every new module,
type, constant, and file must comply. Existing code that drifts from
these rules is treated as audit debt and migrated module by module.

The goal is single-rule homogeneity: a developer learns the convention
once and applies it everywhere. No exceptions without an explicit
decision recorded here.

---

## 1. Module identifier — 4-letter alias

Every artifact and lib that pairs with one is identified by a stable
**4-letter alias** that already lives in `svelte.config.js` as a
bundler alias (`$buss`, `$conn`, `$sess`, …).

The same alias is the canonical module identifier across the codebase:

- **Path scoping in string values** (already enforced after audit
  section 2): `'buss.event.published'`, `'conn.auth_failed'`,
  `'sess.lifecycle.adopted'`, `'perm.client.remote_check_failed'`.
- **Constant name prefix**: `BUSS_*`, `CONN_*`, `SESS_*`, `PERM_*`,
  `TIMR_*`, `LOGR_*`, `CACH_*`, `STOR_*`, `FMTS_*`, `FEND_*`, `ADOM_*`,
  `AAPP_*`, `AUTH_*`, `LANG_*`, `HTTP_*`, `SIUM_*`, `ERRS_*`.

Forbidden: full English words like `BUS_*`, `CONNECTION_*`, `SESSION_*`,
`PERMISSION_*`, `TIMER_*`, `LOGGER_*`, `CACHE_*`, `STORAGE_*`,
`FORMATS_*`, `FRONTEND_*`. Drift on this axis is being closed in a
dedicated audit pass.

---

## 2. Constant naming — `<MOD>_<CATEGORY>_<NAME>`

Every categorical module-level constant follows the pattern:

```
<MOD>_<CATEGORY>_<NAME>
```

- **`<MOD>`** — the module's 4-letter alias in caps (rule 1).
- **`<CATEGORY>`** — what kind of constant it is. Picked from the
  fixed vocabulary in section 3.
- **`<NAME>`** — the specific value's identifier in
  `UPPER_SNAKE_CASE`.

### Examples

```ts
// good
BUSS_DIAGNOSTIC_EVENTS
BUSS_DEFAULT_MAX_LISTENERS_PER_EVENT
BUSS_ERR_DISPOSED
SESS_EVENT_LIFECYCLE_ADOPTED
PERM_METHOD_CHECK
TIMR_STATE_PENDING
CONN_REASON_AUTH_FAILED
CACH_LIMIT_DEFAULT_MAX_ENTRIES
STOR_MODULE

// bad (will be flagged in audit)
BUS_DIAGNOSTIC_EVENTS              // wrong module prefix (rule 1)
DEFAULT_TIMER_SCOPE_SEPARATOR      // category before module (rule 2)
PERMISSION_METHOD_CHECK            // wrong module prefix (rule 1)
AUTO_REAUTH_USER_IDENTITY_CHANGE   // missing module prefix (rule 1)
```

### Sub-categories

When a category needs internal hierarchy, append additional segments
in the `<NAME>` part, not in `<CATEGORY>`:

```ts
// good
BUSS_LISTENER_ERROR_MODE_THROW
SESS_EVENT_LIFECYCLE_ADOPTED
SESS_EVENT_LIFECYCLE_REVOKED
PERM_DEFAULT_REMOTE_FAILURE_BACKOFF_MS

// bad
BUSS_LISTENER_ERR_MODE_THROW       // category split across underscores
```

---

## 3. Category vocabulary — fixed list

Only these category tokens are allowed. Adding a new category is a
deliberate decision recorded in this document, not an ad-hoc choice
inside a module.

| Category | Use |
|---|---|
| `MODULE` | The module's canonical 4-letter alias as a string constant. **Single source of truth** for the module's identity. Used wherever the module's identifier is needed: logger category, error message prefix, event scope, etc. Every module declares exactly one `<MOD>_MODULE = '<alias>'`. |
| `ERR` | Error codes (`ErrCode` values from `$libs/errs`) |
| `EVENT` | Bus or lifecycle event names (string discriminators) |
| `DIAGNOSTIC_EVENTS` | Event values published through `Logger` (catalog object) |
| `METHOD` | Method labels for error messages (`ensureLive(METHOD)`) |
| `STATE` | Tagged-union state discriminators |
| `STATUS` | Tagged-union status discriminators |
| `KIND` | Tagged-union kind discriminators |
| `REASON` | Tagged-union reason discriminators |
| `TYPE` | Tagged-union type discriminators (when none of the above fits) |
| `MODE` | Mode discriminators (e.g. listener error mode) |
| `DEFAULT` | Default values for options |
| `LIMIT` | Maximum / minimum values |
| `ID_PREFIX` | Prefix used by ID factories |
| `LOG_MSG` | Log message strings |
| `ERROR_MSG` | Error message strings (technical, dev-facing). Must use a template referencing `<MOD>_MODULE` for the prefix, never a hardcoded literal: `` `[${MOD_MODULE}] ...` ``. |
| `ERROR_NAME` | Legacy `Error.name` strings (being replaced by `ERR` codes) |
| `CONTEXT_KEY` | Svelte context keys |

Categories that are **not** in this list (e.g. `AUTO_REAUTH`,
`AUTO_INVALIDATE`, `BACKOFF`, `BUFFER_POLICY`, `CHANNEL_STATE`) must
fold into one of the above. Examples:

- `CONNECTION_AUTO_REAUTH_*` → `CONN_REASON_AUTO_REAUTH_*` if the value
  drives a "why this happened" branch, or `CONN_MODE_AUTO_REAUTH_*` if
  it configures behavior.
- `CACHE_AUTO_INVALIDATE_*` → `CACH_MODE_AUTO_INVALIDATE_*`.
- `CONN_BUFFER_POLICY_*` → `CONN_MODE_BUFFER_*`.

When in doubt, propose the addition here before introducing it.

---

## 4. Error codes (`ErrCode`) — special case under rule 2

Error codes from `$libs/errs` follow rule 2 with category `ERR`. Each
module declares one `<MOD>_ERR` seed and builds the individual codes
from it via `errCode(parent, segment)` so the module string never
appears as a literal in error declarations:

```ts
import { errCode, moduleSeed, type ErrCode, type ModuleSeed } from '$libs/errs';

export const BUSS_ERR: ModuleSeed = moduleSeed('buss');                       // 'buss::'
export const BUSS_ERR_DISPOSED: ErrCode = errCode(BUSS_ERR, 'disposed');      // 'buss::disposed'
export const BUSS_ERR_INVALID_PAYLOAD: ErrCode = errCode(BUSS_ERR, 'invalid_payload');
export const BUSS_ERR_LISTENER: ErrCode = errCode(BUSS_ERR, 'listener');      // 'buss::listener'
export const BUSS_ERR_LISTENER_FAILED: ErrCode = errCode(BUSS_ERR_LISTENER, 'failed'); // 'buss::listener.failed'
```

The constant's `<NAME>` part mirrors the path segments inside the
runtime value: `BUSS_ERR_LISTENER_FAILED` ↔ `'buss::listener.failed'`.
The module name lives in exactly one place: `moduleSeed('buss')`.

The `::` separator distinguishes module from hierarchy. `errCode`
picks the right separator automatically — `::` after a seed, `.`
between segments. A helper `codeToLangPath(c)` converts
`'buss::listener.failed'` → `'buss.listener.failed'` for the i18n
path.

### Family matching

A single predicate `matches(err, family)` from `$libs/errs` covers
both common cases. `family` can be:

- A **module seed** (`BUSS_ERR`) — matches any error from that
  module regardless of hierarchy.
- An **`ErrCode`** — matches the code itself or any hierarchical
  descendant within the same module.

```ts
matches(err, BUSS_ERR_DISPOSED)   // exact code
matches(err, BUSS_ERR_LISTENER)   // any descendant of buss::listener
matches(err, BUSS_ERR)            // any error declared by buss
```

---

## 5. String values inside diagnostic / event constants

Already enforced after audit section 2:

```ts
// good — value carries the module scope
export const CONN_DIAGNOSTIC_EVENTS = {
  AUTH_FAILED: 'conn.auth_failed',
  RECONNECT_EXHAUSTED: 'conn.reconnect_exhausted'
} as const;

// bad — bare value collides across modules
export const CONN_DIAGNOSTIC_EVENTS = {
  AUTH_FAILED: 'auth_failed',          // collides with auth.* events
  LISTENER_THREW: 'listener_threw'     // collides with sess and timr
} as const;
```

Rule: every string value emitted as an event identifier must start
with the module's 4-letter alias (rule 1) followed by `.` and the
value-specific path.

---

## 6. File and folder structure

| Layer | Rule |
|---|---|
| `libs/<mod>/` | Pure contracts: types, constants, error classes, helpers. No Svelte runes, no engine state. |
| `arts/<mod>/` | Runtime engine + `*.svelte.ts` active wrappers. May import from `$libs/<mod>` and from its own files. |
| `arts/<mod>/index.ts` | Public barrel. Re-exports the artifact's surface. |
| `arts/<mod>/test/` | Tests for engine and active wrappers. |
| `svrs/<mod>/` | Server-side counterparts (cookies, db adapters, route handlers). |
| `arts/aapp/` | Composition root. Allowed to import any `$<mod>`. |

**Cross-artifact imports are forbidden** (`arts/X` cannot import
`$Y`). Sole exception: `arts/aapp/`.

---

## 7. When this document is updated

- A new category in section 3 requires a record-of-decision: who, when,
  why.
- Module aliases are frozen: a new artifact picks a 4-letter alias
  not yet taken; renaming an existing alias is a breaking change.
- Drift found in the codebase that violates these rules is filed as an
  audit finding and resolved in a dedicated commit.

Last updated: `2026-05-02` — initial version after audit-1-5.md
sections 1–2 closed.