emit-io-codegen

CLI code generator for emit-io-core — define analytics events in YAML, get a typed TypeScript tracker, drift detection, and JSON Schema / Avro export.

Install

npm install --save-dev emit-io-codegen
# or run without installing:
npx emit-io-codegen --help

Quick Start

1. Define a schema

# analytics-schema.yaml
events:
  purchase:
    description: "User completes a purchase"
    orderId: string
    total: number
    currency?: string   # optional field

  page-view:
    path: string
    referrer?: string

  user-signed-up:
    method: string
    plan: string

Fields use the format fieldName: type for required fields, fieldName?: type for optional. Supported types: string, number, boolean.

2. Generate TypeScript types + tracker

npx emit-io-codegen generate analytics-schema.yaml --out src/analytics

Outputs:

• src/analytics/analytics-events.types.ts — EventRegistry augmentation + per-event interfaces
• src/analytics/analytics-tracker.ts — typed wrapper around EmitIoStrategy

3. Use the generated tracker

import { createAnalyticsTracker } from './analytics/analytics-tracker'
import { EmitIoStrategy } from 'emit-io-core'

const emit = new EmitIoStrategy({ /* ... */ })
const tracker = createAnalyticsTracker(logger)

tracker.purchase({ orderId: 'x', total: 99 })      // typed
tracker['page-view']({ path: '/home' })            // typed
tracker['user-signed-up']({ method: 'google', plan: 'pro' })

Commands

generate

npx emit-io-codegen generate <schema.yaml> [options]

Options:
  --out <dir>      Output directory (default: same directory as schema file)
  --detect-pii     Warn on suspected PII fields (writes to stderr)
  --strict-pii     Exit 1 if any PII fields are detected

check

Detects schema drift against a stored snapshot. Used in CI to catch accidental event or property removals.

npx emit-io-codegen check <schema.yaml> [options]

Options:
  --update         Accept breaking changes and update the snapshot
  --strict         Fail on any change, including additions
  --detect-pii     Warn on suspected PII fields
  --strict-pii     Exit 1 if any PII fields are detected

On first run, a snapshot file .analytics-schema.snapshot.json is created next to the schema file. Subsequent runs diff against it:

• Breaking changes (events or properties removed) — exits 1 unless --update is passed
• Additions — allowed by default; --strict exits 1 on any change

export

npx emit-io-codegen export <schema.yaml> --format <fmt> [options]

Options:
  --format json-schema | avro    Required
  --out <dir>                    Output directory (default: same as schema file)

Generates one file per event:

• json-schema → <event-name>.schema.json
• avro → <event-name>.avsc

PII Detection

npx emit-io-codegen generate schema.yaml --detect-pii

Field names matching common PII patterns (email, phone, ssn, credit_card, ip, etc.) emit a warning to stderr:

[PII WARN] event 'user-signed-up' property 'email' suspected PII (matched: email)

Use --strict-pii to fail the build when PII is detected.

CI Integration

# .github/workflows/analytics.yml
- name: Check analytics schema drift
  run: npx emit-io-codegen check analytics-schema.yaml --strict

Schema Format Reference

events:
  <event-name>:
    description: "Optional human-readable description"
    <fieldName>: string | number | boolean      # required field
    <fieldName?>: string | number | boolean     # optional field (note the ?)

License

MIT