Vue.js variable __VUE_SSR_CONTEXT__ is undeclared

Got a error. After add jscomp_off: “checkVars” option, vuejs died with erorr: TypeError: a is undefined.

ERROR in app.js from Closure Compiler
The compiler is waiting for input via stdin.
stdin:127: ERROR - variable __VUE_SSR_CONTEXT__ is undeclared
      if (!context && typeof __VUE_SSR_CONTEXT__ !== 'undefined') {
                             ^^^^^^^^^^^^^^^^^^^

stdin:1044: ERROR - variable WXEnvironment is undeclared
var inWeex = typeof WXEnvironment !== 'undefined' && !!WXEnvironment.platform;
                    ^^^^^^^^^^^^^

stdin:2428: ERROR - variable Proxy is undeclared
    typeof Proxy !== 'undefined' &&
           ^^^^^

[MatrixFrog]

See https://developers.google.com/closure/compiler/docs/api-tutorial3#externs

It doesn’t need to be defined – it just needs to be declared in an externs file which tells the compiler that it might exist (and what type it will have in the event that it does exist). In this case all you need (at least to get rid of the errors reported here) is a file custom-externs.js:

/**
 * @fileoverview
 * @externs
 */

var __VUE_SSR_CONTEXT__;
var WXEnvironment;

and then pass --externs=custom-externs.js on the compiler command line. Hopefully that makes sense? If not let us know.

[ChadKillingsworth]

Make sure you are using webpack 3.x