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  gt  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

User · Answer

If you have installed typings separately under typings folder       exclude          node modules        typings

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

I had this error  along with others  after I changed my tsconfig json to target  es2015   and module  es2015    The base  AngularJS2 quickstart  used      lt reference path        typings index d ts    gt  in the main ts file   To solve this  I had to remove that line

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

Closing the solution completely and rerunning the project solved my issue

User · Answer

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  -

User · Answer

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

User · Answer

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

User · Answer

Problem was solved by simply    Deleting the node modules folder  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

User · Answer

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

User · Answer

run the following command will fix this issue    npm install  types node --save-dev

User · Answer

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

User · Answer

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

[typescript] Confusing "duplicate identifier" Typescript error message

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