feat(logger): add context decorator functionality (aws-powertools#13)

* refactor(logger): Logger class

* test(logger): set coverage 100

* test(logger): disabled coverage check temporarily

* feat(logger): add context decorator functionality

* docs(logger): Lambda first letter uppercase

* fix(logger): remove duplicate import line

* chore(logger): Lambda first letter uppercase

* test(all): hide implementation detail of tests in package

Author: saragerion

package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "commit": "commit",
     "lerna-ci": "lerna exec -- npm ci",
-    "lerna-test": "lerna exec -- jest --coverage  --detectOpenHandles",
+    "lerna-test": "lerna exec -- npm run test",
     "lerna-build": "lerna exec -- tsc",
     "lerna-lint": "lerna exec -- eslint \"./{src,tests}/**/*.ts\"",
     "lerna-format": "lerna exec -- eslint --fix \"./{src,tests}/**/*.ts\"",

packages/logger/README.md

@@ -50,6 +50,8 @@ logger.error('This is an ERROR log');
 
 ### Capturing Lambda context info
 
+Without decorators:
+
 ```typescript
 // Environment variables set for the Lambda
 process.env.LOG_LEVEL = 'WARN';
@@ -108,6 +110,51 @@ const lambdaHandler: Handler = async (event, context) => {
 </details>
 
 
+With decorators:
+
+```typescript
+// Environment variables set for the Lambda
+process.env.LOG_LEVEL = 'INFO';
+process.env.POWERTOOLS_SERVICE_NAME = 'hello-world';
+
+const logger = new Logger();
+
+class Lambda implements LambdaInterface {
+
+  @logger.injectLambdaContext()
+  public handler<TEvent, TResult>(_event: TEvent, _context: Context, _callback: Callback<TResult>): void | Promise<TResult> {
+
+    logger.info('This is an INFO log with some context');
+
+  }
+
+}
+
+new Lambda().handler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));
+
+```
+
+<details>
+ <summary>Click to expand and see the logs outputs</summary>
+
+```bash
+
+{
+  aws_request_id: 'c6af9ac6-7b61-11e6-9a41-93e8deadbeef',
+  lambda_function_arn: 'arn:aws:lambda:eu-central-1:123456789012:function:Example',
+  lambda_function_memory_size: 128,
+  lambda_function_name: 'foo-bar-function',
+  level: 'INFO',
+  message: 'This is an INFO log with some context',
+  service: 'hello-world',
+  timestamp: '2021-03-17T08:25:41.198Z',
+  xray_trace_id: 'abcdef123456abcdef123456abcdef123456'
+}
+
+```
+</details>
+
+
 ### Appending additional keys
 
 ```typescript

packages/logger/examples/child-logger.ts

@@ -30,4 +30,4 @@ const lambdaHandler: Handler = async () => {
 
 };
 
-lambdaHandler(dummyEvent, dummyContext, () => {});
+lambdaHandler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));

packages/logger/examples/hello-world-with-context-decorators.ts

@@ -0,0 +1,28 @@
+import { populateEnvironmentVariables } from '../tests/helpers';
+
+// Populate runtime
+populateEnvironmentVariables();
+// Additional runtime variables
+process.env.LOG_LEVEL = 'INFO';
+process.env.POWERTOOLS_SERVICE_NAME = 'hello-world';
+
+import * as dummyEvent from '../../../tests/resources/events/custom/hello-world.json';
+import { context as dummyContext } from '../../../tests/resources/contexts/hello-world';
+import { LambdaInterface } from '../src/lambda/LambdaInterface';
+import { Logger } from '../src';
+import { Callback, Context } from 'aws-lambda/handler';
+
+const logger = new Logger();
+
+class Lambda implements LambdaInterface {
+
+  @logger.injectLambdaContext()
+  public handler<TEvent, TResult>(_event: TEvent, _context: Context, _callback: Callback<TResult>): void | Promise<TResult> {
+
+    logger.info('This is an INFO log with some context');
+
+  }
+
+}
+
+new Lambda().handler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));

packages/logger/examples/sample-rate.ts

@@ -27,4 +27,4 @@ const lambdaHandler: Handler = async () => {
 
 };
 
-lambdaHandler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));
+lambdaHandler(dummyEvent, dummyContext, () => console.log('lambda invoked!'));

packages/logger/jest.config.js

@@ -22,10 +22,10 @@ module.exports = {
   ],
   'coverageThreshold': {
     'global': {
-      'statements': 70,
-      'branches': 60,
-      'functions': 70,
-      'lines': 70,
+      'statements': 100,
+      'branches': 100,
+      'functions': 100,
+      'lines': 100,
     },
   },
   'coverageReporters': [

packages/logger/package.json

@@ -8,7 +8,7 @@
   },
   "scripts": {
     "commit": "commit",
-    "test": "jest --coverage  --detectOpenHandles",
+    "test": "jest  --detectOpenHandles",
     "watch": "jest --watch",
     "build": "tsc",
     "lint": "eslint \"./{src,tests}/**/*.ts\"",
@@ -20,6 +20,7 @@
     "postversion": "git push && git push --tags",
     "example:hello-world": "ts-node examples/hello-world.ts",
     "example:hello-world-with-context": "ts-node examples/hello-world-with-context.ts",
+    "example:hello-world-with-context-decorators": "ts-node examples/hello-world-with-context-decorators.ts",
     "example:custom-logger-options": "ts-node examples/custom-logger-options.ts",
     "example:child-logger": "ts-node examples/child-logger.ts",
     "example:additional-keys": "ts-node examples/additional-keys.ts",