TypeScript "redefinition" errors in 4.1.0

[guyellis]

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• Summary

Just trying out connect-mongo@4.1.0. Thank you for converting this to TypeScript!

I'm getting a number of TypeScript transpiler errors from the definitions.

For example, in lib/MongoStore.d.ts the MongoStore extends session.Store and redefines get as:

get(sid: string, callback: (err: ErrorOrNull, session?: session.SessionData | null) => void): void;

MongoStore itself is extending (from express-session) session.Store. There get is defined as:

get: (sid: string, callback: (err: any, session?: Express.SessionData | null) => void) => void;

From that we get this TypeScript error:

"Class 'Store' defines instance member property 'get', but extended class 'MongoStore' defines it as instance member function.ts(2425)"

[mingchuno]

@guyellis It is actually a bit tricky here. The TS definition of the store state that it is err: any but it is too general. In reality, it will only be Error | null. But since major store impl are not written in TS, so it does not matter before. May be I can change it back to any 🤔 Any way to bypass the error?

[guyellis]

When you extend that class is it possible to use some sort of Omit<> trick that removes that definition completely and then allows you to redefine it?

Omit Utility Type: https://www.typescriptlang.org/docs/handbook/utility-types.html#omittype-keys

[guyellis]

I just skimmed through this article that might have some clues on how to do this: https://medium.com/dailyjs/typescript-create-a-condition-based-subset-types-9d902cea5b8c

[mingchuno]

@guyellis Try to align with the original typedef but it just doesn't work.
https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/express-session/index.d.ts#L342
https://github.com/expressjs/session#storetouchsid-session-callback
You can see the typedef of touch is:

callback?: () => void

But the doc said the implementation should call callback(error)

[mingchuno]

released in 4.2.0 please check

[Koslun]

@mingchuno
Still getting this error in version 4.4.1. So don't think this fixed it.

Some other dependencies in-use:

    "express": "4.17.1",
    "express-session": "1.17.1",
    "mongoose": "5.12.6",
    
     "@types/express": "4.17.1",
    "@types/express-session": "1.17.0",
    "typescript": "4.1.5"

Excerpt of usage in code:

import MongoStore from 'connect-mongo';
import mongoose = require('mongoose');

  app.use(
    session({
      secret: config.secrets.session,
      saveUninitialized: true,
      resave: false,
      store: MongoStore.create({
        client: mongoose.connection.getClient(),
      }),
    }),
  );

Error log:

> tsc

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:56:5 - error TS2425: Class 'Store' defines instance member property 'get', but extended class 'MongoStore' defines it as instance member function.

56     get(sid: string, callback: (err: any, session?: session.SessionData | null) => void): void;
       ~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:56:61 - error TS2694: Namespace 'session' has no exported member 'SessionData'.

56     get(sid: string, callback: (err: any, session?: session.SessionData | null) => void): void;
                                                               ~~~~~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:62:5 - error TS2425: Class 'Store' defines instance member property 'set', but extended class 'MongoStore' defines it as instance member function.

62     set(sid: string, session: session.SessionData, callback?: (err: any) => void): void;
       ~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:62:39 - error TS2694: Namespace 'session' has no exported member 'SessionData'.

62     set(sid: string, session: session.SessionData, callback?: (err: any) => void): void;
                                         ~~~~~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:63:5 - error TS2425: Class 'Store' defines instance member property 'touch', but extended class 'MongoStore' defines it as instance member function.

63     touch(sid: string, session: session.SessionData & {
       ~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:63:41 - error TS2694: Namespace 'session' has no exported member 'SessionData'.

63     touch(sid: string, session: session.SessionData & {
                                           ~~~~~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:69:5 - error TS2416: Property 'all' in type 'MongoStore' is not assignable to the same property in base type 'Store'.
  Type '(callback: (err: any, obj?: any[] | { [sid: string]: any; }) => void) => void' is not assignable to type '(callback: (err: any, obj?: { [sid: string]: SessionData; }) => void) => void'.
    Types of parameters 'callback' and 'callback' are incompatible.
      Types of parameters 'obj' and 'obj' are incompatible.
        Type 'any[] | { [sid: string]: any; }' is not assignable to type '{ [sid: string]: SessionData; }'.
          Type 'any[]' is not assignable to type '{ [sid: string]: SessionData; }'.
            Index signature is missing in type 'any[]'.

69     all(callback: (err: any, obj?: session.SessionData[] | {
       ~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:69:5 - error TS2425: Class 'Store' defines instance member property 'all', but extended class 'MongoStore' defines it as instance member function.

69     all(callback: (err: any, obj?: session.SessionData[] | {
       ~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:69:44 - error TS2694: Namespace 'session' has no exported member 'SessionData'.

69     all(callback: (err: any, obj?: session.SessionData[] | {
                                              ~~~~~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:70:32 - error TS2694: Namespace 'session' has no exported member 'SessionData'.

70         [sid: string]: session.SessionData;
                                  ~~~~~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:76:5 - error TS2425: Class 'Store' defines instance member property 'destroy', but extended class 'MongoStore' defines it as instance member function.

76     destroy(sid: string, callback?: (err: any) => void): void;
       ~~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:80:5 - error TS2425: Class 'Store' defines instance member property 'length', but extended class 'MongoStore' defines it as instance member function.

80     length(callback: (err: any, length: number) => void): void;
       ~~~~~~

node_modules/connect-mongo/build/main/lib/MongoStore.d.ts:84:5 - error TS2425: Class 'Store' defines instance member property 'clear', but extended class 'MongoStore' defines it as instance member function.

84     clear(callback?: (err: any) => void): void;
       ~~~~~

Found 13 errors.

[mingchuno]

@Koslun Try to upgrade the @types/express-session to 1.17.3?

[Koslun]

@mingchuno

It did work now, might've been @types/express-session to 1.17.3 like you said but related changes I also made:

"dependencies": {
    // ...other deps
    "express": "4.17.1",
    "express-form-data": "2.0.17",
    "express-jwt": "6.0.0",
    "express-session": "1.17.2",
    "mongoose": "5.12.7",
    // ...other deps
  },
  "devDependencies": {
    // ...other deps
    "@types/express": "4.17.12",
    "@types/express-session": "1.17.3",
    "@types/node": "^12.0.7",
    "typescript": "4.3.4"
    // ...other deps
  },
  "resolutions": {
    "@types/serve-static": "1.13.9"
  },

The last resolution is for another issue: DefinitelyTyped/DefinitelyTyped#49595 (comment)