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JS: 'variable' is declared but its value is never read. #51814

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pocesar opened this issue Jun 14, 2018 · 13 comments
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JS: 'variable' is declared but its value is never read. #51814

pocesar opened this issue Jun 14, 2018 · 13 comments
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@mjbvz
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info-needed Issue requires more information from poster *not-reproducible Issue cannot be reproduced by VS Code Team member as described

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@pocesar
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pocesar commented Jun 14, 2018 •
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Version: 1.25.0-insider
Commit: 583f1e4
Date: 2018-06-13T05:18:10.709Z
Electron: 2.0.2
Chrome: 61.0.3163.100
Node.js: 8.9.3
V8: 6.1.534.41
Architecture: x64

Seems like a regression, the editor can't decide if passing the variable to a function counts as "read" it seems

image

const glob = require('glob')
const expressWinston = require('express-winston')
const bodyParser = require('body-parser')
const logger = require('./logger')
const config = require('./config')
const helpers = require('./helpers')
const cookieParser = require('cookie-parser')
const jsonwebtoken = require('jsonwebtoken')
const serveStatic = require('serve-static')

image

image

Steps to Reproduce:

express middleware in this example

  1. Create a const something = (req, res, next) => { next() }
  2. Assign it to the express application using app.use(something)

Does this issue occur when all extensions are disabled?: Yes
@pocesar
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pocesar commented Jun 14, 2018

not sure if it's relevant, but Output for Typescript shows:

[Info  - 11:35:35 PM] Started TSServer
[Error  - 11:43:31 PM] 'getApplicableRefactors' request failed with error.
Error processing request. Debug Failure. False expression.
Error: Debug Failure. False expression.
    at getJSDocTags (C:\nodejs\node_modules\typescript\lib\tsserver.js:11705:22)
    at getFirstJSDocTag (C:\nodejs\node_modules\typescript\lib\tsserver.js:11712:24)
    at Object.getJSDocType (C:\nodejs\node_modules\typescript\lib\tsserver.js:11689:19)
    at getContextualSignature (C:\nodejs\node_modules\typescript\lib\tsserver.js:35577:32)
    at checkFunctionExpressionOrObjectLiteralMethod (C:\nodejs\node_modules\typescript\lib\tsserver.js:38366:43)
    at checkExpressionWorker (C:\nodejs\node_modules\typescript\lib\tsserver.js:39292:28)
    at checkExpression (C:\nodejs\node_modules\typescript\lib\tsserver.js:39225:42)
    at checkExpressionCached (C:\nodejs\node_modules\typescript\lib\tsserver.js:39111:38)
    at getWidenedTypeFromJSSpecialPropertyDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:26652:46)
    at getTypeOfVariableOrParameterOrProperty (C:\nodejs\node_modules\typescript\lib\tsserver.js:26887:28)
    at getTypeOfSymbol (C:\nodejs\node_modules\typescript\lib\tsserver.js:27103:24)
    at checkPropertyAccessExpressionOrQualifiedName (C:\nodejs\node_modules\typescript\lib\tsserver.js:36627:53)
    at checkPropertyAccessExpression (C:\nodejs\node_modules\typescript\lib\tsserver.js:36582:20)
    at getSymbolOfEntityNameOrPropertyAccessExpression (C:\nodejs\node_modules\typescript\lib\tsserver.js:43271:25)
    at getSymbolAtLocation (C:\nodejs\node_modules\typescript\lib\tsserver.js:43324:28)
    at Object.getSymbolAtLocation (C:\nodejs\node_modules\typescript\lib\tsserver.js:22968:31)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88756:35)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13347:24)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13248:21)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNodes (C:\nodejs\node_modules\typescript\lib\tsserver.js:13185:30)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13338:24)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNodes (C:\nodejs\node_modules\typescript\lib\tsserver.js:13185:30)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13349:21)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNodes (C:\nodejs\node_modules\typescript\lib\tsserver.js:13185:30)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13349:21)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13406:24)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNodes (C:\nodejs\node_modules\typescript\lib\tsserver.js:13185:30)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13395:24)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13290:21)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13377:21)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNode (C:\nodejs\node_modules\typescript\lib\tsserver.js:13176:24)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13406:24)
    at checkForUsedDeclarations (C:\nodejs\node_modules\typescript\lib\tsserver.js:88772:24)
    at visitNodes (C:\nodejs\node_modules\typescript\lib\tsserver.js:13185:30)
    at Object.forEachChild (C:\nodejs\node_modules\typescript\lib\tsserver.js:13397:24)
    at collectReadsAndWrites (C:\nodejs\node_modules\typescript\lib\tsserver.js:88585:24)
    at getPossibleExtractionsWorker (C:\nodejs\node_modules\typescript\lib\tsserver.js:88029:38)
    at getPossibleExtractions (C:\nodejs\node_modules\typescript\lib\tsserver.js:87986:26)
    at Object.getAvailableActions (C:\nodejs\node_modules\typescript\lib\tsserver.js:87582:35)
    at C:\nodejs\node_modules\typescript\lib\tsserver.js:84109:128
    at getIterator (C:\nodejs\node_modules\typescript\lib\tsserver.js:1856:23)
    at Object.next (C:\nodejs\node_modules\typescript\lib\tsserver.js:1851:35)
    at Object.arrayFrom (C:\nodejs\node_modules\typescript\lib\tsserver.js:2407:32)
    at Object.getApplicableRefactors (C:\nodejs\node_modules\typescript\lib\tsserver.js:84108:23)
    at Object.getApplicableRefactors (C:\nodejs\node_modules\typescript\lib\tsserver.js:91429:32)
    at IOSession.Session.getApplicableRefactors (C:\nodejs\node_modules\typescript\lib\tsserver.js:97919:53)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (C:\nodejs\node_modules\typescript\lib\tsserver.js:96811:61)
    at C:\nodejs\node_modules\typescript\lib\tsserver.js:98126:88
    at IOSession.Session.executeWithRequestId (C:\nodejs\node_modules\typescript\lib\tsserver.js:98117:28)
    at IOSession.Session.executeCommand (C:\nodejs\node_modules\typescript\lib\tsserver.js:98126:33)
    at IOSession.Session.onMessage (C:\nodejs\node_modules\typescript\lib\tsserver.js:98146:35)
    at Interface.<anonymous> (C:\nodejs\node_modules\typescript\lib\tsserver.js:99377:27)
    at emitOne (events.js:116:13)
    at Interface.emit (events.js:211:7)
    at Interface._onLine (readline.js:282:10)
    at Interface._normalWrite (readline.js:424:12)
    at Socket.ondata (readline.js:141:10)
    at emitOne (events.js:116:13)
    at Socket.emit (events.js:211:7)
    at addChunk (_stream_readable.js:263:12)
    at readableAddChunk (_stream_readable.js:250:11)
    at Socket.Readable.push (_stream_readable.js:208:10)
    at Pipe.onread (net.js:594:20)

@weinand weinand assigned mjbvz and unassigned weinand Jun 14, 2018
@mjbvz
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mjbvz commented Jun 14, 2018

Possible duplicate of microsoft/TypeScript#24963

Please test this in the latest VS Code insiders build to see if it was already fixed

@mjbvz mjbvz added the info-needed Issue requires more information from poster label Jun 14, 2018
@pocesar
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pocesar commented Jun 14, 2018

@mjbvz same issue (the OP, not the TSServer error)

@mjbvz
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mjbvz commented Jun 14, 2018

Thanks. Can you please try upgrading your workspace to use typescript@next by following these instructions: https://code.visualstudio.com/docs/languages/typescript#_using-newer-typescript-versions

@pocesar
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pocesar commented Jun 15, 2018

already using typescript@next, I always use it alongside with vscode insiders

@mjbvz
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mjbvz commented Jun 15, 2018

Can you please share a small, complete example project

@writesandy
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writesandy commented Jun 17, 2018 •
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I'm having the same problem - anyone find a solution? When I type in the code below cherrio, db, PORT, app all say , 'is declared, but value is never read'.

const express = require("express");
const bodyParser = require("body-parser");
const mongoose = require("mongoose");

//Our scraping tools
const cheerio = require("cheerio");

//Require all models
const db = require("./models");

const PORT = 3000;

// Initialize Express
const app = express();

// Configure middleware

// request for logging requests

@JessePreiner
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Not 100% sure it's related, if not i'll open up a new issue. There are a few cases of variables reported as not being used when they are, this is one example with code 1.24.1
image

@mjbvz
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mjbvz commented Jun 19, 2018

@writesandy Please share a complete example. Those variable really not not used anywhere in the current example

@ManyouRisms Do you access .apiUrl anywhere? If not, marked it as unused is correct and you should remove private

@JessePreiner
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After injecting it I assign it directly to a private _apiUrl which I then use throughout the code. That in itself I would assume would classify as 'being used', because if i was to remove the declaration of apiUrl all together, the build would break because it is indeed getting used in the constructor.

@mjbvz
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mjbvz commented Jun 20, 2018 •
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@ManyouRisms with private apiUrl you now have two properties: this.apiUrl and this._apiUrl. You should remove private from private apiUrl in the constructor if you are not using it as a property

@BridgeAR
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Here another example that fails:

screenshot from 2018-06-24 13-49-08

In this case the return statement is "somewhat valid" in Node.js since all functions are wrapped in a function implicitly and I believe that is the issue for TS in this context (it just did not expect a return without being wrapped in a function).

@mjbvz
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mjbvz commented Jun 25, 2018

Closing as we do not have enough information to investigate the original issue

Please open new issues for other problems around unused variables

@mjbvz mjbvz closed this as completed Jun 25, 2018
@mjbvz mjbvz added the *not-reproducible Issue cannot be reproduced by VS Code Team member as described label Jun 25, 2018
@fabio-s-franco fabio-s-franco mentioned this issue Jun 26, 2018
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@mjbvz mjbvz mentioned this issue Jun 26, 2018
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