feat: simplify custom health indicator creation

The abstract `HealthIndicator` class has been marked as deprecated as well as the `HealthCheckError` error.

Instead a `HealthIndicatorService` should be utilised
to indicate the state of a health indicator.

.github/workflows/build-samples.yml

@@ -39,5 +39,6 @@ jobs:
       # FIXME: Remove the `--legacy-peer-deps` flag once all dependencies are updated
     - run: npm ci --legacy-peer-deps
     - run: npm run build:all
+    - run: npm run test:samples
       env:
         CI: true

lib/errors/connection-not-found.error.ts

@@ -1,10 +1,16 @@
+/* eslint-disable deprecation/deprecation */
 import { CONNECTION_NOT_FOUND } from './messages.constant';
 import { HealthCheckError } from '../health-check/health-check.error';
 
 /**
  * Error which gets thrown when the connection
  * instance was not found in the application context
  * @publicApi
+ *
+ * @deprecated
+ * This class has been deprecated and will be removed in the next major release.
+ * Instead utilise the `HealthIndicatorService` to indicate the health of your health indicator.
+ *
  */
 export class ConnectionNotFoundError extends HealthCheckError {
   /**

lib/errors/storage-exceeded.error.ts

@@ -1,10 +1,15 @@
+/* eslint-disable deprecation/deprecation */
 import { STORAGE_EXCEEDED } from './messages.constant';
 import { HealthCheckError } from '../health-check/health-check.error';
 
 /**
  * Error which gets thrown when the given storage threshold
  * has exceeded.
  * @publicApi
+ *
+ * @deprecated
+ * This class has been deprecated and will be removed in the next major release.
+ * Instead utilise the `HealthIndicatorService` to indicate the health of your health indicator.
  */
 export class StorageExceededError extends HealthCheckError {
   /**

lib/errors/timeout-error.ts

@@ -1,9 +1,14 @@
+/* eslint-disable deprecation/deprecation */
 import { TIMEOUT_EXCEEDED } from './messages.constant';
 import { HealthCheckError } from '../health-check/health-check.error';
 
 /**
  * Gets thrown when the timeout of the health check exceeds
  * @publicApi
+ *
+ * @deprecated
+ * This class has been deprecated and will be removed in the next major release.
+ * Instead utilise the `HealthIndicatorService` to indicate the health of your health indicator.
  */
 export class TimeoutError extends HealthCheckError {
   /**

lib/errors/unhealthy-response-code.error.ts

@@ -1,10 +1,15 @@
+/* eslint-disable deprecation/deprecation */
 import { UNHEALTHY_RESPONSE_CODE } from './messages.constant';
 import { HealthCheckError } from '../health-check/health-check.error';
 
 /**
  * Error which gets thrown when the terminus client receives
  * an unhealthy response code from the server.
  * @publicApi
+ *
+ * @deprecated
+ * This class has been deprecated and will be removed in the next major release.
+ * Instead utilise the `HealthIndicatorService` to indicate the health of your health indicator.
  */
 export class UnhealthyResponseCodeError extends HealthCheckError {
   /**

lib/health-check/health-check-executor.service.spec.ts

@@ -1,47 +1,78 @@
 import { Test } from '@nestjs/testing';
 import { HealthCheckExecutor } from './health-check-executor.service';
-import { HealthIndicatorResult } from '../health-indicator';
+import {
+  HealthIndicatorResult,
+  HealthIndicatorService,
+} from '../health-indicator';
 import { HealthCheckResult } from './health-check-result.interface';
 import { HealthCheckError } from '../health-check/health-check.error';
 
-const healthyCheck = async (): Promise<HealthIndicatorResult> => {
+////////////////////////////////////////////////////////////////
+
+const healthIndicator = async (h: HealthIndicatorService) =>
+  h.check('healthy').up();
+
+const unhealthyHealthIndicator = async (h: HealthIndicatorService) =>
+  h.check('unhealthy').down();
+
+const unhealthyHealthIndicatorSync = (h: HealthIndicatorService) =>
+  h.check('unhealthy').down();
+
+// Legacy health indicator functions
+
+const legacyHealthyIndicator = async (): Promise<HealthIndicatorResult> => {
   return {
     healthy: {
       status: 'up',
     },
   };
 };
 
-const unhealthyCheck = async (): Promise<HealthIndicatorResult> => {
+const legacyUnhealthyIndicator = async (): Promise<HealthIndicatorResult> => {
   throw new HealthCheckError('error', {
     unhealthy: {
       status: 'down',
     },
   });
 };
 
-const unhealthyCheckSync = () => {
+const legacyUnhealthyIndicatorSync = () => {
   throw new HealthCheckError('error', {
     unhealthy: {
       status: 'down',
     },
   });
 };
 
+const legacyUnhealthyIndicatorWithoutError =
+  async (): Promise<HealthIndicatorResult> => {
+    return {
+      unhealthy: {
+        status: 'down',
+      },
+    };
+  };
+
+////////////////////////////////////////////////////////////////
+
 describe('HealthCheckExecutorService', () => {
   let healthCheckExecutor: HealthCheckExecutor;
+  let h: HealthIndicatorService;
 
   beforeEach(async () => {
     const module = Test.createTestingModule({
-      providers: [HealthCheckExecutor],
+      providers: [HealthCheckExecutor, HealthIndicatorService],
     });
     const context = await module.compile();
     healthCheckExecutor = context.get(HealthCheckExecutor);
+    h = context.get(HealthIndicatorService);
   });
 
   describe('execute', () => {
     it('should return a result object without errors', async () => {
-      const result = await healthCheckExecutor.execute([() => healthyCheck()]);
+      const result = await healthCheckExecutor.execute([
+        () => healthIndicator(h),
+      ]);
       expect(result).toEqual<HealthCheckResult>({
         status: 'ok',
         info: {
@@ -60,7 +91,7 @@ describe('HealthCheckExecutorService', () => {
 
     it('should return a result object with errors', async () => {
       const result = await healthCheckExecutor.execute([
-        () => unhealthyCheck(),
+        () => unhealthyHealthIndicator(h),
       ]);
       expect(result).toEqual<HealthCheckResult>({
         status: 'error',
@@ -80,7 +111,7 @@ describe('HealthCheckExecutorService', () => {
 
     it('should return a result object with errors with sync indicator function', async () => {
       const result = await healthCheckExecutor.execute([
-        () => unhealthyCheckSync(),
+        () => unhealthyHealthIndicatorSync(h),
       ]);
       expect(result).toEqual<HealthCheckResult>({
         status: 'error',
@@ -100,8 +131,8 @@ describe('HealthCheckExecutorService', () => {
 
     it('should return a result object without errors and with errors', async () => {
       const result = await healthCheckExecutor.execute([
-        () => unhealthyCheck(),
-        () => healthyCheck(),
+        () => unhealthyHealthIndicator(h),
+        () => healthIndicator(h),
       ]);
       expect(result).toEqual<HealthCheckResult>({
         status: 'error',
@@ -125,5 +156,115 @@ describe('HealthCheckExecutorService', () => {
         },
       });
     });
+
+    describe('backwards compatibility', () => {
+      it('should return a result object without errors', async () => {
+        const result = await healthCheckExecutor.execute([
+          () => legacyHealthyIndicator(),
+        ]);
+        expect(result).toEqual<HealthCheckResult>({
+          status: 'ok',
+          info: {
+            healthy: {
+              status: 'up',
+            },
+          },
+          error: {},
+          details: {
+            healthy: {
+              status: 'up',
+            },
+          },
+        });
+      });
+
+      it('should return a result object with errors', async () => {
+        const result = await healthCheckExecutor.execute([
+          () => legacyUnhealthyIndicator(),
+        ]);
+        expect(result).toEqual<HealthCheckResult>({
+          status: 'error',
+          info: {},
+          error: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+          details: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+        });
+      });
+
+      it('should return a result object with errors with sync indicator function', async () => {
+        const result = await healthCheckExecutor.execute([
+          () => legacyUnhealthyIndicatorSync(),
+        ]);
+        expect(result).toEqual<HealthCheckResult>({
+          status: 'error',
+          info: {},
+          error: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+          details: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+        });
+      });
+
+      it('should return a result object without errors and with errors', async () => {
+        const result = await healthCheckExecutor.execute([
+          () => legacyUnhealthyIndicator(),
+          () => legacyHealthyIndicator(),
+        ]);
+        expect(result).toEqual<HealthCheckResult>({
+          status: 'error',
+          info: {
+            healthy: {
+              status: 'up',
+            },
+          },
+          error: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+          details: {
+            healthy: {
+              status: 'up',
+            },
+            unhealthy: {
+              status: 'down',
+            },
+          },
+        });
+      });
+
+      it('should return a result object with errors when error is not an instance of HealthCheckError', async () => {
+        const result = await healthCheckExecutor.execute([
+          () => legacyUnhealthyIndicatorWithoutError(),
+        ]);
+        expect(result).toEqual<HealthCheckResult>({
+          status: 'error',
+          info: {},
+          error: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+          details: {
+            unhealthy: {
+              status: 'down',
+            },
+          },
+        });
+      });
+    });
   });
 });

lib/health-check/health-check-executor.service.ts

@@ -65,14 +65,21 @@ export class HealthCheckExecutor implements BeforeApplicationShutdown {
 
     result.forEach((res) => {
       if (res.status === 'fulfilled') {
-        results.push(res.value);
+        Object.entries(res.value).forEach(([key, value]) => {
+          if (value.status === 'up') {
+            results.push({ [key]: value });
+          } else if (value.status === 'down') {
+            errors.push({ [key]: value });
+          }
+        });
       } else {
         const error = res.reason;
         // Is not an expected error. Throw further!
         if (!isHealthCheckError(error)) {
           throw error;
         }
-        // Is a expected health check error
+
+        // eslint-disable-next-line deprecation/deprecation
         errors.push((error as HealthCheckError).causes);
       }
     });

lib/health-check/health-check.error.ts

@@ -1,3 +1,8 @@
+/**
+ * @deprecated
+ * This class has been deprecated and will be removed in the next major release.
+ * Instead utilise the `HealthIndicatorService` to indicate the health of your health indicator.
+ */
 export class HealthCheckError extends Error {
   causes: any;
   isHealthCheckError = true;