Confusing “duplicate identifier” Typescript error message

Question

Why am I getting this and many more errors of this kind? I am adding a link to the repo as well as key code snippets below. I think I have a basic misunderstanding of how the dependency and "include" chaining works.

csvproc(master)> tsc
node_modules/typescript/bin/lib.core.d.ts(83,5): error TS2300: Duplicate identifier 'configurable'.
node_modules/typescript/bin/lib.core.d.ts(84,5): error TS2300: Duplicate identifier 'enumerable'.
node_modules/typescript/bin/lib.core.d.ts(85,5): error TS2300: Duplicate identifier 'value'.
node_modules/typescript/bin/lib.core.d.ts(86,5): error TS2300: Duplicate identifier 'writable'.

All code can be found here.

My tsconfig.json:

{
    "compilerOptions": {
        "module": "commonjs",
        "noImplicitAny": false,
        "outDir": "built/",
        "sourceMap": true,
        "target": "es5"
    }
}

My tsd.json:

{
  "version": "v4",
  "repo": "borisyankov/DefinitelyTyped",
  "ref": "master",
  "path": "typings",
  "bundle": "typings/tsd.d.ts",
  "installed": {
    "node/node-0.10.d.ts": {
      "commit": "6387999eb899d0ba02d37dd8697647718caca230"
    },
    "should/should.d.ts": {
      "commit": "e1182d56ccb192379eade6055d9ba3fb6a0bacc4"
    }
  }
}

My tsd.d.ts:

{
  "version": "v4",
  "repo": "borisyankov/DefinitelyTyped",
  "ref": "master",
  "path": "typings",
  "bundle": "typings/tsd.d.ts",
  "installed": {
    "node/node-0.10.d.ts": {
      "commit": "6387999eb899d0ba02d37dd8697647718caca230"
    },
    "should/should.d.ts": {
      "commit": "e1182d56ccb192379eade6055d9ba3fb6a0bacc4"
    }
  }
}

Answer 1

This is because of the combination of two things:

• tsconfig not having any files section. From http://www.typescriptlang.org/docs/handbook/tsconfig-json.html

  If no "files" property is present in a tsconfig.json, the compiler defaults to including all files in the containing directory and subdirectories. When a "files" property is specified, only those files are included.

• Including typescript as an npm dependency : node_modules/typescript/ This means that all of typescript gets included .... there is an implicitly included lib.d.ts in your project anyways (http://basarat.gitbook.io/typescript/content/docs/types/lib.d.ts.html) and its conflicting with the one that ships with the NPM version of typescript.

Fix

Either list files or include explicitly https://basarat.gitbook.io/typescript/docs/project/files.html 🌹

Answer 2

Update: Version 1.0 of Typings changed the output structure and the below answer relates to pre 1.0 version.

If you are using Typings and exclude in your tsconfig.json, you may run into the issue of duplicate types and need something like the following:

{
  "exclude": [
    "typings/browser.d.ts",
    "typings/browser",
    "node_modules"
  ]
}

To simplify integration with TypeScript, two files - typings/main.d.ts and typings/browser.d.ts - are generated which reference all the typings installed in the project only one of which can be used at a time.

So depending on which version you need, you should exclude (or include) the "browser" or the "main" type files, but not both, as this is where the duplicates come from.

This Typings issue discusses it more.

Answer 3

If you have installed typings separately under typings folder

{
  "exclude": [
    "node_modules",
    "typings"
  ]
}

Answer 4

Problem was solved by simply:

1. Deleting the node_modules folder
2. Running npm install to get all packages with correct versions

In my case, the problem occurred after changing Git branches, where a new branch was using a different set of node modules. The old branch was using TypeScript v1.8, the new one v2.0

Answer 5

You could also use the exclude option in tsconfig.json file like so:

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "declaration": false,
    "noImplicitAny": false,
    "removeComments": true,
    "noLib": false,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true
  },
  "exclude": [
    "node_modules"
  ]
}

Answer 6

I just ran into this problem. When I ran npm start, I got a bunch of duplicate identifier errors.

SOLUTION:

From the project root folder run:

rm -r typings
typings install
npm start

and everything works fine.

Answer 7

In my case I got the error as

node_modules/@types/es6-promise/index.d.ts(11,15): error TS2300: Duplicate identifier 'Promise'.

And I had @types/es6-promise on my package.json but my tsconfig was already with target: "es6". So I guess there was a conflict with Promise when compiling.

Removing @types/es6-promise from my package.json file solved the issue.

Answer 8

Using webpack I came across same error, just in case excluding the .d.ts file in your tsconfig.json and node_modules solved my issue:

"exclude": [
    "node_modules",
    "typings/main",
    "typings/main.d.ts",
    "typings/index.d.ts"
] 

Answer 9

I had this issue caused by having an unexpected folder on disk (jspm_packages, no longer being used) which was not tracked by source control (and hidden from my IDE). This had a duplicate install of TypeScript in it, which caused the issues.

Bit of an edge case but leaving an answer here just in case someone else is hunting for this solution.

Answer 10

run the following command will fix this issue.

npm install @types/node --save-dev

Answer 11

I had this problem and it turns out I had a a second node_modules folder in my project that wasn't supposed to be there :-(

Answer 12

I had this error, along with others, after I changed my tsconfig.json to target:"es2015", and module:"es2015".

The base (AngularJS2 quickstart) used /// <reference path="../../typings/index.d.ts" /> in the main.ts file. To solve this, I had to remove that line.

Answer 13

we removed a lib folder from the website folder. this was created by a previous installation of typings. this became duplicate. When this was removed it worked!

Answer 14

It can be because of having both typing and dependency in your node folder. so first check what you have in your @types folder and if you have them in dependencies, remove the duplicate. for me it was core.js

Answer 15

remove this @types/express-validator from package.json file, then run npm install

Read More

Author message: This package has been deprecated This is a stub types definition for express-validator (https://github.com/ctavan/express-validator). express-validator provides its own type definitions, so you don't need @types/express-validator installed!

Answer 16

Closing the solution completely and rerunning the project solved my issue.

Answer 17

Adding "typeRoots": ["node_modules/@types"], to "compilerOptions" in tsconfig.json file worked for me.

Answer 18

I ran into a similar problem. Simply moving my tsconfig.json from the root of my project up to a different scope helped. In my project, I moved tsconfig.json from the root up to wwwroot.