Use strict types

.github/workflows/build.yml

@@ -63,6 +63,6 @@ jobs:
       env:
         NPM_AUTH_TOKEN: ${{ secrets.NPM_AUTH_TOKEN }}
     - name: Bump versions
-      run: node ./common/scripts/install-run-rush.js rush version --bump --target-branch main
+      run: node ./common/scripts/install-run-rush.js version --bump --target-branch main
     - name: publish
       run: node ./common/scripts/install-run-rush.js publish -a -b main -p --set-access-level public --include-all

.gitignore

@@ -61,3 +61,6 @@ jspm_packages/
 # Rush temporary files
 common/temp/
 **/.rush/temp/
+
+# JetBrains IDEs
+.idea

README.md

@@ -71,6 +71,24 @@ export const handler = compose(
 })
 ```
 
+There's a [known issue with TypeScript](https://github.com/microsoft/TypeScript/issues/29904) that pipe and compose functions cannot
+infer types correctly if the innermost function is generic (in this case the last argument to `compose`).
+If you use TypeScript in strict mode, you can instead use the `composeHandler` function exported from `@lambda-middleware/compose`:
+
+```typescript
+export const handler = composeHandler(
+  someMiddleware(),
+  someOtherMiddleware(),
+  aThirdMiddleware(),
+  () => {
+    return {
+      body: '',
+      statusCode: 200
+    }
+  }
+)
+```
+
 Composing middleware is equivalent to calling it nested:
 ```typescript
 export const handler =

common/changes/@lambda-middleware/class-validator/use_strict_types_2020-10-29-19-31.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@lambda-middleware/class-validator",
+      "comment": "Make compatible with TypeScript strict mode",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@lambda-middleware/class-validator",
+  "email": "[email protected]"
+}

common/changes/@lambda-middleware/compose/use_strict_types_2020-10-29-19-31.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@lambda-middleware/compose",
+      "comment": "Add composeHandler function",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@lambda-middleware/compose",
+  "email": "[email protected]"
+}

common/changes/@lambda-middleware/http-header-normalizer/use_strict_types_2020-10-29-19-31.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@lambda-middleware/http-header-normalizer",
+      "comment": "Make compatible with TypeScript strict mode",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@lambda-middleware/http-header-normalizer",
+  "email": "[email protected]"
+}

common/changes/@lambda-middleware/middy-adaptor/use_strict_types_2020-10-29-19-31.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@lambda-middleware/middy-adaptor",
+      "comment": "Make compatible with TypeScript strict mode",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@lambda-middleware/middy-adaptor",
+  "email": "[email protected]"
+}

common/changes/@lambda-middleware/utils/use_strict_types_2020-10-29-19-31.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@lambda-middleware/utils",
+      "comment": "Make compatible with TypeScript strict mode",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@lambda-middleware/utils",
+  "email": "[email protected]"
+}

internal/e2e-tests/examples/helloWorld.ts

@@ -1,7 +1,7 @@
 import "reflect-metadata";
 
 import { classValidator } from "@lambda-middleware/class-validator";
-import { compose } from "@lambda-middleware/compose";
+import { composeHandler } from "@lambda-middleware/compose";
 import { cors } from "@lambda-middleware/cors";
 import { errorHandler } from "@lambda-middleware/http-error-handler";
 import { jsonSerializer } from "@lambda-middleware/json-serializer";
@@ -11,6 +11,11 @@ import { IsString } from "class-validator";
 
 // Define a validator for the body via class-validator
 class NameBody {
+  constructor(firstName: string, lastName: string) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
   @IsString()
   public firstName: string;
 
@@ -19,14 +24,16 @@ class NameBody {
 }
 
 // This is your AWS handler
-async function helloWorld(event: { body: NameBody }) {
+async function helloWorld(event: {
+  body: NameBody;
+}): Promise<{ message: string }> {
   // Thanks to the validation middleware you can be sure body is typed correctly
   return {
     message: `Hello ${event.body.firstName} ${event.body.lastName}`,
   };
 }
 
-const wrapper = compose(
+export const handler = composeHandler(
   // add cors headers last so even error responses from the
   // errorHandler middleware have cors headers applied
   cors(),
@@ -48,7 +55,6 @@ const wrapper = compose(
   // and other middlewares might not be able to handle the modified event
   classValidator({
     bodyType: NameBody,
-  })
-)(helloWorld);
-
-export const handler = wrapper;
+  }),
+  helloWorld
+);

packages/class-validator/README.md

@@ -22,12 +22,17 @@ This middleware is part of the [lambda middleware series](https://dbartholomae.g
 import "reflect-metadata";
 
 import { classValidator } from '@lambda-middleware/class-validator'
-import { compose } from "@lambda-middleware/compose";
+import { composeHandler } from "@lambda-middleware/compose";
 import { errorHandler } from "@lambda-middleware/http-error-handler";
 import { IsString } from "class-validator";
 
 // Define a validator for the body via class-validator
 class NameBody {
+  constructor(firstName: string, lastName: string) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
   @IsString()
   public firstName: string;
 
@@ -48,7 +53,7 @@ async function helloWorld(event: { body: NameBody }) {
 }
 
 // Let's add middleware to our handler, then we will be able to attach middlewares to it
-export const handler = compose(
+export const handler = composeHandler(
   // The class validator throws validation errors from http-errors which are compatible with
   // the error handler middlewares for middy
   errorHandler(),
@@ -63,6 +68,7 @@ export const handler = compose(
     // to set it to true manually as the default for class-validator would be
     // false
     validator: {},
-  })
-)(helloWorld);
+  }),
+  helloWorld
+);
 ```

packages/class-validator/examples/helloWorld.ts

@@ -2,12 +2,18 @@
 import "reflect-metadata";
 
 import { classValidator } from "../";
-import { compose } from "@lambda-middleware/compose";
+import { composeHandler } from "@lambda-middleware/compose";
 import { errorHandler } from "@lambda-middleware/http-error-handler";
 import { IsString } from "class-validator";
+import { APIGatewayProxyResult } from "aws-lambda";
 
 // Define a validator for the body via class-validator
 class NameBody {
+  constructor(firstName: string, lastName: string) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
   @IsString()
   public firstName: string;
 
@@ -16,7 +22,9 @@ class NameBody {
 }
 
 // This is your AWS handler
-async function helloWorld(event: { body: NameBody }) {
+async function helloWorld(event: {
+  body: NameBody;
+}): Promise<APIGatewayProxyResult> {
   // Thanks to the validation middleware you can be sure body is typed correctly
   return {
     body: `Hello ${event.body.firstName} ${event.body.lastName}`,
@@ -28,7 +36,7 @@ async function helloWorld(event: { body: NameBody }) {
 }
 
 // Let's add middleware to our handler, then we will be able to attach middlewares to it
-export const handler = compose(
+export const handler = composeHandler(
   // The class validator throws validation errors from http-errors which are compatible with
   // the error handler middlewares for middy
   errorHandler(),
@@ -43,5 +51,6 @@ export const handler = compose(
     // to set it to true manually as the default for class-validator would be
     // false
     validator: {},
-  })
-)(helloWorld);
+  }),
+  helloWorld
+);

packages/class-validator/src/classValidator.test.ts

@@ -4,6 +4,11 @@ import { IsOptional, IsString } from "class-validator";
 import { createEvent } from "@lambda-middleware/utils";
 
 class NameBody {
+  constructor(firstName: string, lastName: string) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
   @IsString()
   public firstName: string;