improved type resolution for action method

integration-tests/.gitignore

@@ -0,0 +1,3 @@
+# node / npm stuff
+/node_modules
+/package-lock.json

integration-tests/.vscode/launch.json

@@ -0,0 +1,53 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Integration Type Checker",
+            "program": "${workspaceFolder}/node_modules/dtslint/bin/index.js",
+            "args": [
+                "types"
+            ],
+            "internalConsoleOptions": "openOnSessionStart",
+            "skipFiles": [
+                "<node_internals>/**"
+            ],
+            "cwd": "${workspaceFolder}"
+        },
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "npm test",
+            "cwd": "${workspaceFolder}",
+            "runtimeExecutable": "npm",
+            "runtimeArgs": [
+                "run-script", "test"
+            ],
+            "port": 9229
+
+        },
+    ]
+}
+
+/*
+[
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Integration Type Checker",
+            "program": "${workspaceFolder}/node_modules/dtslint/bin/index.js",
+            "args": [
+                "types"
+            ],
+            "internalConsoleOptions": "openOnSessionStart",
+            "skipFiles": [
+                "<node_internals>/**"
+            ],
+            "cwd": "${workspaceFolder}"
+        },
+    ]
+*/

integration-tests/README.md

@@ -0,0 +1,22 @@
+## Integration tests
+
+This directory contains a minimal project used as an environment in which to run integration tests.
+
+It's important to isolate this test project from the overall project where the package is built in order to eliminate
+assumptions. Specifically, the `package.json` and other configuration files in this directory are meant to include
+the minimum requirements and nothing more. Here are a few ways this is set up:
+
+* The `@types/node` dependency is set to a version that corresponds to the lowest supported node version. This enforces
+  that the distribution should work in projects who have chosen that particular version, since its the most likely to
+  not have types that we accidentally depend on but shouldn't.
+
+* The `typescript` development dependency is set to the most modern version of typescript. It's not important to use the
+  oldest supported version because the `dtslint` tool will run the typechecker result integration tests on each
+  supported version of TypeScript. It reads the oldest supported version from `types/index.d.ts`.
+
+* The `tsconfig.json` file is specifically set to the most strict settings as well as the most minimal requirements.
+  This is specifically chosen to verify that the requirements expressed in the documentation are sufficient and
+  represent the least amount of configuration needed to get the package working.
+
+* In `package.json`, the `"private"` key must remain set to `true`. This enforces that this project doesn't get
+  accidentally published.

integration-tests/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "@slack/bolt-integration-tests",
+  "private": true,
+  "description": "Integration tests for Bolt",
+  "author": "Slack Technologies, Inc.",
+  "license": "MIT",
+  "scripts": {
+    "test": "npm run test:typechecker",
+    "test:typechecker": "dtslint types"
+  },
+  "dependencies": {
+    "@slack/bolt": "file:..",
+    "@types/node": "^10.0.0"
+  },
+  "devDependencies": {
+    "dtslint": "^0.5.4",
+    "typescript": "^3.7.3"
+  }
+}

integration-tests/types/action.ts

@@ -0,0 +1,64 @@
+// import App, { ActionConstraints } from '../../src/App';
+import { App, MessageAction } from '@slack/bolt';
+
+const app = new App({ token: 'TOKEN', signingSecret: 'Signing Secret' });
+
+// calling action method with incorrect an type constraint value should not work
+// $ExpectError
+app.action({ type: 'Something wrong' }, ({ action }) => {
+  return action;
+});
+
+/* Not working
+// Should error because message_action doesn't have type action_id
+// $ Expect Error
+app.action({ type: 'message_action', action_id: 'dafasf' }, ({ action }) => {
+    return action;
+});
+*/
+
+// Action in listner should be - MessageAction
+// $ExpectType void
+app.action({ type: 'message_action' }, ({
+  action, // $ExpectType MessageAction
+ }) => {
+  return action;
+});
+
+// $ExpectType void
+app.action({ type: 'block_actions' }, ({
+  action, // $ExpectType BlockElementAction
+ }) => {
+  return action;
+});
+
+// $ExpectType void
+app.action({ type: 'interactive_message' }, ({
+  action, // $ExpectType InteractiveAction
+ }) => {
+  return action;
+});
+
+// $ExpectType void
+app.action({ type: 'dialog_submission' }, ({
+  action, // $ExpectType DialogSubmitAction
+ }) => {
+  return action;
+});
+
+// If action is parameterized with MessageAction, action argument in callback should be type MessageAction
+// $ExpectType void
+app.action<MessageAction>({}, ({
+  action // $ExpectType MessageAction
+ }) => {
+  return action;
+});
+
+/* Not working
+// Should error because MessageAction doesn't have an action_id
+// $ Expect Error
+app.actiong<MessageAction>({ action_id: 'dafasf' }, ({ action }) => {
+    // NOT WORKING
+    return action;
+});
+*/

integration-tests/types/index.d.ts

@@ -0,0 +1,2 @@
+// tslint:disable:no-useless-files
+// TypeScript Version: 3.3

integration-tests/types/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "commonjs",
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "lib": ["es5"]
+  }
+}

package.json

@@ -30,7 +30,8 @@
     "build:clean": "shx rm -rf ./dist ./coverage ./.nyc_output",
     "lint": "tslint --project .",
     "mocha": "nyc mocha --config .mocharc.json \"src/**/*.spec.ts\"",
-    "test": "npm run lint && npm run mocha",
+    "test": "npm run lint && npm run mocha && npm run test:integration",
+    "test:integration": "cd integration-tests && npm install && npm test",
     "coverage": "codecov"
   },
   "repository": "slackapi/bolt",

src/App.ts

@@ -86,11 +86,11 @@ export interface AuthorizeResult {
   [key: string]: any;
 }
 
-export interface ActionConstraints {
-  type?: string;
-  block_id?: string | RegExp;
-  action_id?: string | RegExp;
-  callback_id?: string | RegExp;
+export interface ActionConstraints<A extends SlackAction = SlackAction> {
+  type?: A['type'];
+  block_id?: A extends BlockAction ? (string | RegExp) : never;
+  action_id?: A extends BlockAction ? (string | RegExp) : never;
+  callback_id?: Extract<A, { callback_id?: string }> extends any ? (string | RegExp) : never;
 }
 
 export interface ViewConstraints {
@@ -265,19 +265,23 @@ export default class App {
 
   // NOTE: this is what's called a convenience generic, so that types flow more easily without casting.
   // https://basarat.gitbooks.io/typescript/docs/types/generics.html#design-pattern-convenience-generic
-  public action<ActionType extends SlackAction = SlackAction>(
-    actionId: string | RegExp,
-    ...listeners: Middleware<SlackActionMiddlewareArgs<ActionType>>[]
-  ): void;
-  public action<ActionType extends SlackAction = SlackAction>(
-    constraints: ActionConstraints,
-    ...listeners: Middleware<SlackActionMiddlewareArgs<ActionType>>[]
-  ): void;
-  public action<ActionType extends SlackAction = SlackAction>(
-    actionIdOrConstraints: string | RegExp | ActionConstraints,
-    ...listeners: Middleware<SlackActionMiddlewareArgs<ActionType>>[]
-  ): void {
-    const constraints: ActionConstraints =
+  public action<Action extends SlackAction = SlackAction>(
+      actionId: string | RegExp,
+      ...listeners: Middleware<SlackActionMiddlewareArgs<Action>>[]
+    ): void;
+  public action<Action extends SlackAction = SlackAction,
+    Constraints extends ActionConstraints<Action> = ActionConstraints<Action>>(
+      constraints: Constraints,
+      // NOTE: Extract<> is able to return the whole union when type: undefined. Why?
+      ...listeners: Middleware<SlackActionMiddlewareArgs<Extract<Action, { type: Constraints['type'] }>>>[]
+    ): void;
+  public action<Action extends SlackAction = SlackAction,
+    Constraints extends ActionConstraints<Action> = ActionConstraints<Action>>(
+      actionIdOrConstraints: string | RegExp | Constraints,
+      ...listeners: Middleware<SlackActionMiddlewareArgs<Extract<Action, { type: Constraints['type'] }>>>[]
+    ): void {
+    // Normalize Constraints
+    const constraints: ActionConstraints  =
       (typeof actionIdOrConstraints === 'string' || util.types.isRegExp(actionIdOrConstraints)) ?
         { action_id: actionIdOrConstraints } : actionIdOrConstraints;