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Feature: Type safe custom context properties in TypeScript #1157

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Feature: Type safe custom context properties in TypeScript #1157

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76f7d96
feat: custom ts context
szydlovski Oct 13, 2021
8d453b8
fix: lint errors
szydlovski Oct 13, 2021
7170889
fix: lint error
szydlovski Oct 13, 2021
a799388
refactor: add custom context at AllMiddlewareArgs instead of Middleware
szydlovski Oct 13, 2021
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48 changes: 26 additions & 22 deletions src/App.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,7 @@ import {
import { IncomingEventType, getTypeAndConversation, assertNever } from './helpers';
import { CodedError, asCodedError, AppInitializationError, MultipleListenerError, ErrorCode } from './errors';
import { AllMiddlewareArgs } from './types/middleware';
import { StringIndexed } from './types/helpers';
// eslint-disable-next-line import/order
import allSettled = require('promise.allsettled'); // eslint-disable-line @typescript-eslint/no-require-imports
// eslint-disable-next-line @typescript-eslint/no-require-imports, import/no-commonjs
Expand Down Expand Up @@ -174,7 +175,7 @@ class WebClientPool {
/**
* A Slack App
*/
export default class App {
export default class App<CustomContext extends StringIndexed = StringIndexed> {
/** Slack Web API client */
public client: WebClient;

Expand Down Expand Up @@ -442,8 +443,8 @@ export default class App {
*
* @param m global middleware function
*/
public use(m: Middleware<AnyMiddlewareArgs>): this {
this.middleware.push(m);
public use(m: Middleware<AnyMiddlewareArgs, CustomContext>): this {
this.middleware.push(m as Middleware<AnyMiddlewareArgs>);
return this;
}

Expand Down Expand Up @@ -479,15 +480,15 @@ export default class App {

public event<EventType extends string = string>(
eventName: EventType,
...listeners: Middleware<SlackEventMiddlewareArgs<EventType>>[]
...listeners: Middleware<SlackEventMiddlewareArgs<EventType>, CustomContext>[]
): void;
public event<EventType extends RegExp = RegExp>(
eventName: EventType,
...listeners: Middleware<SlackEventMiddlewareArgs<string>>[]
...listeners: Middleware<SlackEventMiddlewareArgs<string>, CustomContext>[]
): void;
public event<EventType extends EventTypePattern = EventTypePattern>(
eventNameOrPattern: EventType,
...listeners: Middleware<SlackEventMiddlewareArgs<string>>[]
...listeners: Middleware<SlackEventMiddlewareArgs<string>, CustomContext>[]
): void {
let invalidEventName = false;
if (typeof eventNameOrPattern === 'string') {
Expand All @@ -513,9 +514,9 @@ export default class App {

// TODO: just make a type alias for Middleware<SlackEventMiddlewareArgs<'message'>>
// TODO: maybe remove the first two overloads
public message(...listeners: Middleware<SlackEventMiddlewareArgs<'message'>>[]): void;
public message(pattern: string | RegExp, ...listeners: Middleware<SlackEventMiddlewareArgs<'message'>>[]): void;
public message(...patternsOrMiddleware: (string | RegExp | Middleware<SlackEventMiddlewareArgs<'message'>>)[]): void {
public message(...listeners: Middleware<SlackEventMiddlewareArgs<'message'>, CustomContext>[]): void;
public message(pattern: string | RegExp, ...listeners: Middleware<SlackEventMiddlewareArgs<'message'>, CustomContext>[]): void;
public message(...patternsOrMiddleware: (string | RegExp | Middleware<SlackEventMiddlewareArgs<'message'>, CustomContext>)[]): void {
const messageMiddleware = patternsOrMiddleware.map((patternOrMiddleware) => {
if (typeof patternOrMiddleware === 'string' || util.types.isRegExp(patternOrMiddleware)) {
return matchMessage(patternOrMiddleware);
Expand All @@ -532,21 +533,21 @@ export default class App {

public shortcut<Shortcut extends SlackShortcut = SlackShortcut>(
callbackId: string | RegExp,
...listeners: Middleware<SlackShortcutMiddlewareArgs<Shortcut>>[]
...listeners: Middleware<SlackShortcutMiddlewareArgs<Shortcut>, CustomContext>[]
): void;
public shortcut<
Shortcut extends SlackShortcut = SlackShortcut,
Constraints extends ShortcutConstraints<Shortcut> = ShortcutConstraints<Shortcut>,
>(
constraints: Constraints,
...listeners: Middleware<SlackShortcutMiddlewareArgs<Extract<Shortcut, { type: Constraints['type'] }>>>[]
...listeners: Middleware<SlackShortcutMiddlewareArgs<Extract<Shortcut, { type: Constraints['type'] }>>, CustomContext>[]
): void;
public shortcut<
Shortcut extends SlackShortcut = SlackShortcut,
Constraints extends ShortcutConstraints<Shortcut> = ShortcutConstraints<Shortcut>,
>(
callbackIdOrConstraints: string | RegExp | Constraints,
...listeners: Middleware<SlackShortcutMiddlewareArgs<Extract<Shortcut, { type: Constraints['type'] }>>>[]
...listeners: Middleware<SlackShortcutMiddlewareArgs<Extract<Shortcut, { type: Constraints['type'] }>>, CustomContext>[]
): void {
const constraints: ShortcutConstraints = typeof callbackIdOrConstraints === 'string' || util.types.isRegExp(callbackIdOrConstraints) ?
{ callback_id: callbackIdOrConstraints } :
Expand All @@ -572,22 +573,22 @@ export default class App {
// https://basarat.gitbooks.io/typescript/docs/types/generics.html#design-pattern-convenience-generic
public action<Action extends SlackAction = SlackAction>(
actionId: string | RegExp,
...listeners: Middleware<SlackActionMiddlewareArgs<Action>>[]
...listeners: Middleware<SlackActionMiddlewareArgs<Action>, CustomContext>[]
): 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'] }>>>[]
...listeners: Middleware<SlackActionMiddlewareArgs<Extract<Action, { type: Constraints['type'] }>>, CustomContext>[]
): 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'] }>>>[]
...listeners: Middleware<SlackActionMiddlewareArgs<Extract<Action, { type: Constraints['type'] }>>, CustomContext>[]
): void {
// Normalize Constraints
const constraints: ActionConstraints = typeof actionIdOrConstraints === 'string' || util.types.isRegExp(actionIdOrConstraints) ?
Expand All @@ -608,23 +609,26 @@ export default class App {
this.listeners.push([onlyActions, matchConstraints(constraints), ...listeners] as Middleware<AnyMiddlewareArgs>[]);
}

public command(commandName: string | RegExp, ...listeners: Middleware<SlackCommandMiddlewareArgs>[]): void {
public command(
commandName: string | RegExp,
...listeners: Middleware<SlackCommandMiddlewareArgs, CustomContext>[]
): void {
this.listeners.push([onlyCommands, matchCommandName(commandName), ...listeners] as Middleware<AnyMiddlewareArgs>[]);
}

public options<Source extends OptionsSource = 'block_suggestion'>(
actionId: string | RegExp,
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>>[]
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>, CustomContext>[]
): void;
// TODO: reflect the type in constraits to Source
public options<Source extends OptionsSource = OptionsSource>(
constraints: ActionConstraints,
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>>[]
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>, CustomContext>[]
): void;
// TODO: reflect the type in constraits to Source
public options<Source extends OptionsSource = OptionsSource>(
actionIdOrConstraints: string | RegExp | ActionConstraints,
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>>[]
...listeners: Middleware<SlackOptionsMiddlewareArgs<Source>, CustomContext>[]
): void {
const constraints: ActionConstraints = typeof actionIdOrConstraints === 'string' || util.types.isRegExp(actionIdOrConstraints) ?
{ action_id: actionIdOrConstraints } :
Expand All @@ -635,15 +639,15 @@ export default class App {

public view<ViewActionType extends SlackViewAction = SlackViewAction>(
callbackId: string | RegExp,
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>>[]
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>, CustomContext>[]
): void;
public view<ViewActionType extends SlackViewAction = SlackViewAction>(
constraints: ViewConstraints,
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>>[]
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>, CustomContext>[]
): void;
public view<ViewActionType extends SlackViewAction = SlackViewAction>(
callbackIdOrConstraints: string | RegExp | ViewConstraints,
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>>[]
...listeners: Middleware<SlackViewMiddlewareArgs<ViewActionType>, CustomContext>[]
): void {
const constraints: ViewConstraints = typeof callbackIdOrConstraints === 'string' || util.types.isRegExp(callbackIdOrConstraints) ?
{ callback_id: callbackIdOrConstraints, type: 'view_submission' } :
Expand Down
8 changes: 4 additions & 4 deletions src/types/middleware.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17,17 +17,17 @@ export type AnyMiddlewareArgs =
| SlackViewMiddlewareArgs
| SlackShortcutMiddlewareArgs;

export interface AllMiddlewareArgs {
context: Context;
export interface AllMiddlewareArgs<CustomContext = StringIndexed> {
context: Context & CustomContext;
logger: Logger;
client: WebClient;
next: NextFn;
}

// NOTE: Args should extend AnyMiddlewareArgs, but because of contravariance for function types, including that as a
// constraint would mess up the interface of App#event(), App#message(), etc.
export interface Middleware<Args> {
(args: Args & AllMiddlewareArgs): Promise<void>;
export interface Middleware<Args, CustomContext = StringIndexed> {
(args: Args & AllMiddlewareArgs<CustomContext>): Promise<void>;
}

/**
Expand Down