registered exception filters to policy-engine

apps/policy-engine/src/app/app.controller.ts

@@ -1,7 +1,6 @@
 import { EvaluationRequest } from '@narval/policy-engine-shared'
 import { Body, Controller, Get, Logger, Post } from '@nestjs/common'
 import { generateInboundRequest } from '../app/persistence/repository/mock_data'
-import { ApplicationException } from '../shared/exception/application.exception'
 import { AppService } from './app.service'
 import { EvaluationRequestDto } from './evaluation-request.dto'
 
@@ -21,15 +20,6 @@ export class AppController {
     this.logger.log({
       message: 'Received ping'
     })
-
-    throw new ApplicationException({
-      message: 'Test error message',
-      context: {
-        foo: 'bar'
-      },
-      suggestedHttpStatusCode: 400
-    })
-    // throw new HttpException('THIS SHOULD SHOW SOMEHWERE', 500)
     return 'pong'
   }
 

apps/policy-engine/src/main.ts

@@ -4,6 +4,9 @@ import { NestFactory } from '@nestjs/core'
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger'
 import { lastValueFrom, map, of, switchMap } from 'rxjs'
 import { AppModule } from './app/app.module'
+import { Config } from './policy-engine.config'
+import { ApplicationExceptionFilter } from './shared/filter/application-exception.filter'
+import { HttpExceptionFilter } from './shared/filter/http-exception.filter'
 
 /**
  * Adds Swagger documentation to the application.
@@ -37,6 +40,21 @@ const withGlobalPipes = (app: INestApplication): INestApplication => {
   return app
 }
 
+/**
+ * Adds a global exception filter to the application.
+ *
+ * @param app - The Nest application instance.
+ * @param configService - The configuration service instance.
+ * @returns The modified Nest application instance.
+ */
+const withGlobalFilters =
+  (configService: ConfigService<Config, true>) =>
+  (app: INestApplication): INestApplication => {
+    app.useGlobalFilters(new HttpExceptionFilter(configService), new ApplicationExceptionFilter(configService))
+
+    return app
+  }
+
 async function bootstrap() {
   const logger = new Logger('AuthorizationNodeBootstrap')
   const application = await NestFactory.create(AppModule, { bodyParser: true })
@@ -51,6 +69,7 @@ async function bootstrap() {
     of(application).pipe(
       map(withSwagger),
       map(withGlobalPipes),
+      map(withGlobalFilters(configService)),
       switchMap((app) => app.listen(port))
     )
   )

apps/policy-engine/src/shared/filter/application-exception.filter.ts

@@ -0,0 +1,52 @@
+import { ArgumentsHost, Catch, ExceptionFilter, LogLevel, Logger } from '@nestjs/common'
+import { ConfigService } from '@nestjs/config'
+import { Response } from 'express'
+import { Config, Env } from '../../policy-engine.config'
+import { ApplicationException } from '../../shared/exception/application.exception'
+
+@Catch(ApplicationException)
+export class ApplicationExceptionFilter implements ExceptionFilter {
+  private logger = new Logger(ApplicationExceptionFilter.name)
+
+  constructor(private configService: ConfigService<Config, true>) {}
+
+  catch(exception: ApplicationException, host: ArgumentsHost) {
+    const ctx = host.switchToHttp()
+    const response = ctx.getResponse<Response>()
+    const status = exception.getStatus()
+    const isProduction = this.configService.get('env') === Env.PRODUCTION
+
+    this.log(exception)
+
+    response.status(status).json(
+      isProduction
+        ? {
+            statusCode: status,
+            message: exception.message,
+            context: exception.context
+          }
+        : {
+            statusCode: status,
+            message: exception.message,
+            context: exception.context,
+            stack: exception.stack,
+            ...(exception.origin && { origin: exception.origin })
+          }
+    )
+  }
+
+  // TODO (@wcalderipe, 16/01/24): Unit test the logging logic. For that, we
+  // must inject the logger in the constructor via dependency injection.
+  private log(exception: ApplicationException) {
+    const level: LogLevel = exception.getStatus() >= 500 ? 'error' : 'warn'
+
+    if (this.logger[level]) {
+      this.logger[level](exception.message, {
+        status: exception.getStatus(),
+        context: exception.context,
+        stacktrace: exception.stack,
+        origin: exception.origin
+      })
+    }
+  }
+}

apps/policy-engine/src/shared/filter/http-exception.filter.ts

@@ -0,0 +1,41 @@
+import { ArgumentsHost, Catch, ExceptionFilter, HttpException, Logger } from '@nestjs/common'
+import { ConfigService } from '@nestjs/config'
+import { Response } from 'express'
+import { Config, Env } from '../../policy-engine.config'
+
+@Catch(HttpException)
+export class HttpExceptionFilter implements ExceptionFilter {
+  private logger = new Logger(HttpExceptionFilter.name)
+
+  constructor(private configService: ConfigService<Config, true>) {}
+
+  catch(exception: HttpException, host: ArgumentsHost) {
+    const ctx = host.switchToHttp()
+    const response = ctx.getResponse<Response>()
+    const status = exception.getStatus()
+
+    const isProduction = this.configService.get('env') === Env.PRODUCTION
+
+    this.logger.error({
+      message: exception.message,
+      stack: exception.stack,
+      response: exception.getResponse(),
+      statusCode: status
+    })
+
+    response.status(status).json(
+      isProduction
+        ? {
+            statusCode: status,
+            message: exception.message,
+            response: exception.getResponse()
+          }
+        : {
+            statusCode: status,
+            message: exception.message,
+            response: exception.getResponse(),
+            stack: exception.stack
+          }
+    )
+  }
+}