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suaveplan/openspec/archive/2026-05-12-primitives-cron/proposal.md
2026-05-27 23:29:53 +01:00

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# OpenSpec Change: primitives-cron
- **Change ID**: primitives-cron
- **Package**: `@suaveplan/cron`
- **Category**: primitives (universal-tier)
- **Target path**: `packages/primitives/cron`
- **Status**: PROPOSED
- **Date**: 2026-05-11
- **Reference**: croner (https://github.com/hexagon/croner) — design inspiration, not a dep
- **Related**: amends `enterprise-server-job-scheduler` (cron-parser removed from that package; replaced by a dep on this one)
---
## Summary
Deliver `@suaveplan/cron` as a standalone universal-tier primitive: cron-expression parsing, next-fire calculation, timezone + DST handling, optional in-process scheduling. Split out of `enterprise-server-job-scheduler` so that cron-expression parsing is reusable outside the job runner — e.g. config-schema validation (`isValidCron`), UI "next run" badges, declarative schedule rendering in admin tooling — without pulling the scheduler's queue/retry/concurrency/event-bus machinery.
Modeled on croner's surface (5/6/7-field cron + macros + `nextRun(tz)`), but written natively (no external cron-parsing dep) following the genesis primitive conventions (Zod boundaries, `defineCodes` registry, OTel surface, injectable `Clock`).
---
## Why split
The bundled design in `enterprise-server-job-scheduler` couples cron parsing to a server-tier package with deps on `@suaveplan/retry`, `@suaveplan/events`, `@suaveplan/logger`. Consumers that only need expression parsing (browser tier, validation tier, config tier) cannot use it without that footprint. Splitting `cron` as a leaf primitive:
1. Lets `@suaveplan/validation` / `@suaveplan/api-schemas` / future browser-tier UIs validate + display cron expressions without depending on the scheduler.
2. Keeps `@suaveplan/job-scheduler` focused on the runtime concern (queue, retry, concurrency, lifecycle).
3. Matches the existing genesis pattern of one-primitive-per-package (cf. `crypto-hash` / `crypto-curve` / `crypto-cipher` split out of `crypto`).
---
## Current-state audit (genesis)
Does not exist on genesis. `packages/primitives/timing` covers async scheduling (stopwatch, throttle/debounce, interval timer, countdown, vector clock) but NOT cron expressions. `packages/primitives/datetime` covers RRule-subset recurrence (iCalendar-style daily/weekly/monthly/yearly) but NOT crontab syntax. No overlap.
---
## Available workspace deps on genesis
| Package | Role |
|---|---|
| `@suaveplan/error` (`workspace:^`) | Typed `CRON.*` error codes |
| `@suaveplan/types` (`workspace:^`) | `Clock` injection |
| `zod` (`catalog:forms`) | Options validation |
| `@opentelemetry/api` (`catalog:observability`) | Parse + nextRun histograms, outcome counters |
| `tslib` (`catalog:build`) | Runtime helpers |
Zero deps on other `@suaveplan/*` primitives. Universal-tier (no Node built-ins, no browser globals).
---
## Public API surface
```ts
// Parsing
function parseCron(expr: string, options?: ParseOptions): CronExpression
function isValidCron(expr: string, options?: ParseOptions): boolean
// Next-fire calculation
interface CronExpression {
readonly expr: string
readonly fields: CronFields
nextRun(after?: number | Date, tz?: string): number | null
nextRuns(count: number, after?: number | Date, tz?: string): number[]
previousRun(before?: number | Date, tz?: string): number | null
matches(when: number | Date, tz?: string): boolean
}
interface CronFields {
seconds?: number[] // 0-59 (only when 6/7-field)
minutes: number[] // 0-59
hours: number[] // 0-23
daysOfMonth: number[] // 1-31
months: number[] // 1-12
daysOfWeek: number[] // 0-6 (Sun=0; both 0 and 7 accepted on parse)
years?: number[] // when 7-field (Quartz-style)
}
interface ParseOptions {
/** Accept 6-field (seconds + 5 std) or 7-field (Quartz). Default: 5 only. */
seconds?: boolean
/** Accept Quartz year field. Default: false. */
years?: boolean
/** Reject day-of-month + day-of-week both specified (Vixie semantics). Default: false (OR them). */
strictDoW?: boolean
}
// Macros: @yearly @annually @monthly @weekly @daily @midnight @hourly
// Step values: * /5, 10-20/2
// Ranges: 1-5
// Lists: 1,3,5
// Aliases: JAN-DEC, SUN-SAT (case-insensitive)
// Optional in-process scheduler (thin wrapper; full job runner lives in @suaveplan/job-scheduler)
class CronScheduler {
constructor(options?: CronSchedulerOptions)
add(expr: string, handler: () => void | Promise<void>, options?: { tz?: string; id?: string }): string
remove(id: string): boolean
list(): Array<{ id: string; expr: string; nextRun: number | null }>
start(): void
stop(): Promise<void>
}
interface CronSchedulerOptions {
clock?: Clock
/** Errors thrown by handlers are swallowed by default; pass a sink to observe. */
onError?: (err: unknown, id: string) => void
}
type CronErrorCode =
| 'CRON.INVALID_EXPRESSION'
| 'CRON.FIELD_OUT_OF_RANGE'
| 'CRON.UNSUPPORTED_SYNTAX'
| 'CRON.TIMEZONE_INVALID'
| 'CRON.NEXT_RUN_NOT_FOUND' // search horizon exhausted
function registerCronErrorCodes(): void
```
---
## Timezone + DST semantics
- Timezone defaults to UTC. Pass IANA name (e.g. `"America/New_York"`) per-call to `nextRun` / `nextRuns` / `previousRun` / `matches`.
- Use the platform `Intl.DateTimeFormat` (`timeZone`, `hourCycle: 'h23'`) to compute wall-clock components — no external timezone DB dep.
- DST spring-forward: schedules during the skipped hour fire at the next existing wall-clock minute (e.g. `0 2 * * *` on a US spring-forward day fires at 03:00 local).
- DST fall-back: schedules during the doubled hour fire **once** (first occurrence wins).
- `CRON.TIMEZONE_INVALID` thrown when `Intl.DateTimeFormat` rejects the IANA name.
---
## File layout
```text
packages/primitives/cron/
package.json # 0.0.0; "sideEffects": false; subpaths "./parse", "./scheduler"
tsconfig.json # extends library.json (universal)
vitest.config.ts # createTestConfig()
README.md
src/
index.ts # explicit named re-exports (rule 10)
error-codes.ts # defineCodes("CRON", [...])
constants/index.ts
types/
cron.types.ts
cron.types.md
parse/
cron-expression/
cron-expression.ts
cron-expression.md
cron-expression.test.ts
index.ts
cron-fields/
cron-fields.ts
cron-fields.md
cron-fields.test.ts
index.ts
macros/
macros.ts
macros.md
macros.test.ts
index.ts
next-run/
next-run/
next-run.ts
next-run.md
next-run.test.ts
index.ts
timezone/
timezone.ts
timezone.md
timezone.test.ts
index.ts
scheduler/
cron-scheduler/
cron-scheduler.ts
cron-scheduler.md
cron-scheduler.test.ts
index.ts
otel/
cron-otel.ts
cron-otel.md
tests/
integration.test.ts
property.test.ts
vectors.test.ts # known cron expression → expected fire times
```
---
## Impact
- **Downstream now**: `@suaveplan/job-scheduler` (amended proposal) depends on this for cron parsing + next-run; the scheduler keeps queue/retry/concurrency/lifecycle.
- **Downstream future**: `@suaveplan/validation` / `@suaveplan/api-schemas` for `cronExpression()` schema; browser-tier admin UIs for "next run" displays.
- **No genesis package currently depends on it** — greenfield primitive.
**Prerequisites on Verdaccio**: `@suaveplan/error`, `@suaveplan/types`.