Add metric type tests

packages/utils/package.json

@@ -27,7 +27,7 @@
     "build:watch": "yarn run build --watch",
     "build:release": "yarn clean && yarn build",
     "check-build": "node -e \"(async function() { await import('./lib/index.js') })()\"",
-    "check-types": "tsc",
+    "check-types": "tsc && vitest --run --typecheck --dir test/types/",
     "lint": "eslint --color --ext .ts src/ test/",
     "lint:fix": "yarn run lint --fix",
     "pretest": "yarn run check-types",
@@ -50,6 +50,7 @@
   "devDependencies": {
     "@types/js-yaml": "^4.0.5",
     "@types/triple-beam": "^1.3.2",
+    "prom-client": "^15.1.0",
     "triple-beam": "^1.3.0"
   },
   "keywords": [

packages/utils/test/types/metrics.test-d.ts

@@ -0,0 +1,114 @@
+import {describe, it, expectTypeOf} from "vitest";
+import {Counter as PromCounter, Gauge as PromGauge, Histogram as PromHistogram} from "prom-client";
+import {Counter, Gauge, Histogram, MetricsRegister} from "../../src/metrics.js";
+
+describe("Metric types", () => {
+  type Labels = {label: string};
+  type MultipleLabels = {label1: string; label2: string};
+
+  describe("MetricsRegister", () => {
+    const register = {} as MetricsRegister;
+
+    it("should require name and help to be defined on each metric", () => {
+      expectTypeOf(register.gauge).parameter(0).toHaveProperty("name").toBeString();
+      expectTypeOf(register.gauge).parameter(0).toHaveProperty("help").toBeString();
+    });
+
+    it("should require to set labelNames if metric has defined labels", () => {
+      expectTypeOf(register.gauge<Labels>)
+        .parameter(0)
+        .toHaveProperty("labelNames")
+        .toMatchTypeOf<"label"[]>();
+
+      expectTypeOf(register.gauge<MultipleLabels>)
+        .parameter(0)
+        .toHaveProperty("labelNames")
+        .toMatchTypeOf<("label1" | "label2")[]>();
+    });
+
+    it("should not require to set labelNames if metric has no labels", () => {
+      expectTypeOf(register.gauge).parameter(0).toHaveProperty("labelNames").toEqualTypeOf<undefined>();
+    });
+  });
+
+  describe("Gauge", () => {
+    it("should be compatible with prom-client type", () => {
+      expectTypeOf<PromGauge>().toMatchTypeOf<Gauge>();
+    });
+
+    it("should require to set labels if metric has defined labels", () => {
+      const gauge = {} as Gauge<Labels>;
+
+      expectTypeOf(gauge.inc).toEqualTypeOf<(labels: Labels, value?: number | undefined) => void>();
+      expectTypeOf(gauge.dec).toEqualTypeOf<(labels: Labels, value?: number | undefined) => void>();
+      expectTypeOf(gauge.set).toEqualTypeOf<(labels: Labels, value: number) => void>();
+    });
+
+    it("should not require to set labels if metric has no labels", () => {
+      const gauge = {} as Gauge;
+
+      expectTypeOf(gauge.inc).toEqualTypeOf<(value?: number | undefined) => void>();
+      expectTypeOf(gauge.dec).toEqualTypeOf<(value?: number | undefined) => void>();
+      expectTypeOf(gauge.set).toEqualTypeOf<(value: number) => void>();
+    });
+  });
+
+  describe("Histogram", () => {
+    it("should be compatible with prom-client type", () => {
+      expectTypeOf<PromHistogram>().toMatchTypeOf<Histogram>();
+    });
+
+    it("should require to set labels if metric has defined labels", () => {
+      const histogram = {} as Histogram<Labels>;
+
+      expectTypeOf(histogram.startTimer).toMatchTypeOf<(labels: Labels) => () => number>();
+      expectTypeOf(histogram.observe).toEqualTypeOf<(labels: Labels, value: number) => void>();
+    });
+
+    it("should require to set labels in timer if not set in startTimer", () => {
+      const histogram = {} as Histogram<MultipleLabels>;
+
+      const timer = histogram.startTimer();
+      expectTypeOf(timer).toEqualTypeOf<(labels: MultipleLabels) => number>();
+    });
+
+    it("should not require to set labels in timer if already set in startTimer", () => {
+      const histogram = {} as Histogram<MultipleLabels>;
+
+      const timer = histogram.startTimer({label1: "value1", label2: "label2"});
+      expectTypeOf(timer).toEqualTypeOf<() => number>();
+    });
+
+    it("should allow to set labels in either startTimer or timer", () => {
+      const histogram = {} as Histogram<MultipleLabels>;
+
+      const timer = histogram.startTimer({label1: "value1"});
+      expectTypeOf(timer).toEqualTypeOf<(labels: {label2: string}) => number>();
+    });
+
+    it("should not require to set labels if metric has no labels", () => {
+      const histogram = {} as Histogram;
+
+      expectTypeOf(histogram.startTimer).toMatchTypeOf<() => () => number>();
+      expectTypeOf(histogram.observe).toEqualTypeOf<(value: number) => void>();
+    });
+  });
+
+  describe("Counter", () => {
+    it("should be compatible with prom-client type", () => {
+      expectTypeOf<PromCounter>().toMatchTypeOf<Counter>();
+    });
+
+    it("should require to set labels if metric has defined labels", () => {
+      const counter = {} as Counter<Labels>;
+
+      expectTypeOf(counter.inc).toEqualTypeOf<(labels: Labels, value?: number | undefined) => void>();
+    });
+
+    it("should not require to set labels if metric has no labels", () => {
+      const counter = {} as Counter;
+
+      expectTypeOf(counter.inc).toEqualTypeOf<(value?: number | undefined) => void>();
+    });
+  });
+});