Cannot redeclare block-scoped variable 'React'

I receive this and several other similar messages for other libraries whenever I compile my code with ts-node. I don’t receive similar errors when running the same code through tsc.

I have tried to change the target and the lib and several other settings but nothing seems to help.

I’m running the following versions: ts-node v3.3.0 node v8.5.0 typescript v2.5.2

Here’s my config:

{
  "compilerOptions": {
    /* Basic Options */
    "target": "esnext",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    // "lib": ["es2015", "dom"],                             /* Specify library files to be included in the compilation:  */
    "allowJs": true,                       /* Allow javascript files to be compiled. */
    "checkJs": false,                       /* Report errors in .js files. */
    "jsx": "react",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
    "outDir": "build",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "removeComments": true,                /* Do not emit comments to output. */
    // "noEmit": true,                        /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */
    "strict": true,                            /* Enable all strict type-checking options. */
    "noImplicitAny": false,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Additional Checks */
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */
    "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    "baseUrl": "./src",                       /* Base directory to resolve non-absolute module names. */
    "paths": {
      "~/*" : ["*"]   // resolve any `~/foo/bar` to `<baseUrl>/foo/bar`
    }                          /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    //"types": ["./vendor.d.ts"]                           /* Type declaration files to be included in compilation. */
    // "allowSyntheticDefaultImports": true  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */

    /* Source Map Options */
    // "sourceRoot": "./",                    /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "./",                       /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
  },
  "include": [
    "vendor.d.ts",
    "src/**/*.ts",
    "src/**/*.tsx",
    "src/**/*.js",
    //"install/**/*.ts",
    "config/**/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

[blakeembrey]

From the looks of things like styled_components_1, it’s going through transpilation multiple times. Have you registered ts-node twice, or another transpiler before ts-node?

[mcavaliere]

For anyone interested, I’ve run into this as well. The resolution was removing a require call to ts-node or @babel/register from the codebase.