fix: add optional generics to metric groups (#2665)

To give a bit more type safety to metric groups, add optional
generics that allow you to specify which grouped metrics you can
update/increment.

Author: achingbrain

packages/interface/src/metrics/index.ts

@@ -76,23 +76,23 @@ export interface Metric {
  * A group of related metrics loosely based on the interfaces exposed by the
  * prom-client module
  */
-export interface MetricGroup {
+export interface MetricGroup<T extends string = any> {
   /**
    * Update the stored metric group to the passed value
    */
-  update(values: Record<string, number>): void
+  update(values: Partial<Record<T, number>>): void
 
   /**
    * Increment the metric group keys by the passed number or
-   * any non-numeric value to increment by 1
+   * `true` to increment by 1
    */
-  increment(values: Record<string, number | unknown>): void
+  increment(values: Partial<Record<T, number | true>>): void
 
   /**
    * Decrement the metric group keys by the passed number or
-   * any non-numeric value to decrement by 1
+   * `true` to decrement by 1
    */
-  decrement(values: Record<string, number | unknown>): void
+  decrement(values: Partial<Record<T, number | true>>): void
 
   /**
    * Reset the passed key in this metric group to its default value
@@ -128,12 +128,12 @@ export interface Counter {
  * exposed by the prom-client module - counters are metrics that only
  * go up
  */
-export interface CounterGroup {
+export interface CounterGroup<T extends string = any> {
   /**
    * Increment the metric group keys by the passed number or
    * any non-numeric value to increment by 1
    */
-  increment(values: Record<string, number | unknown>): void
+  increment(values: Partial<Record<T, number | true>>): void
 
   /**
    * Reset the passed key in this metric group to its default value

packages/metrics-prometheus/test/metric-groups.spec.ts

@@ -34,7 +34,7 @@ describe('metric groups', () => {
       label: metricLabel
     })
     metric.increment({
-      [metricKey]: false
+      [metricKey]: true
     })
 
     await expect(client.register.metrics()).to.eventually.include(`${metricName}{${metricLabel}="${metricKey}"} 1`, 'did not include updated metric')
@@ -69,7 +69,7 @@ describe('metric groups', () => {
       label: metricLabel
     })
     metric.decrement({
-      [metricKey]: false
+      [metricKey]: true
     })
 
     await expect(client.register.metrics()).to.eventually.include(`${metricName}{${metricLabel}="${metricKey}"} -1`, 'did not include updated metric')

packages/transport-tcp/src/index.ts

@@ -121,7 +121,7 @@ export interface TCPComponents {
 }
 
 export interface TCPMetrics {
-  dialerEvents: CounterGroup
+  dialerEvents: CounterGroup<'error' | 'timeout' | 'connect' | 'abort'>
 }
 
 export function tcp (init: TCPOptions = {}): (components: TCPComponents) => Transport {