Use compilerInput before sending to worker.

src/app/compiler/compiler-input.js

 'use strict'
 
-/*
-  opts:
-   - optimize
-   - { file_name: { library_name: address } }
-*/
 module.exports = (sources, opts) => {
+  var target = opts.target ? opts.target : '*'
   return JSON.stringify({
-    target: opts.target,
     language: 'Solidity',
     sources: sources,
     settings: {
@@ -18,7 +13,7 @@ module.exports = (sources, opts) => {
     },
     libraries: opts.libraries,
     outputSelection: {
-      '*': {
+      [target]: {
         '*': [ 'metadata', 'evm.bytecode', 'evm.deployedBytecode', 'abi', 'legacyAST', 'metadata', 'evm.assembly', 'evm.methodIdentifiers', 'evm.gasEstimates' ]
       }
     }

src/app/compiler/compiler-worker.js

 'use strict'
 
 var solc = require('solc/wrapper')
-var compilerInput = require('./compiler-input')
 
 var compileJSON = function () { return '' }
 var missingInputs = []
@@ -21,11 +20,9 @@ module.exports = function (self) {
 
         var compiler = solc(self.Module)
 
-        compileJSON = function (input, optimize) {
+        compileJSON = function (input) {
           try {
-            input = JSON.parse(input)
-            var inputStandard = compilerInput(input.sources, {optimize: optimize, target: input.target})
-            return compiler.compileStandardWrapper(inputStandard, function (path) {
+            return compiler.compileStandardWrapper(input, function (path) {
               missingInputs.push(path)
               return { 'error': 'Deferred import' }
             })
@@ -42,7 +39,7 @@ module.exports = function (self) {
         break
       case 'compile':
         missingInputs.length = 0
-        self.postMessage({cmd: 'compiled', job: data.job, data: compileJSON(data.source, data.optimize), missingInputs: missingInputs})
+        self.postMessage({cmd: 'compiled', job: data.job, data: compileJSON(data.input), missingInputs: missingInputs})
         break
     }
   }, false)

src/app/compiler/compiler.js

@@ -288,7 +288,7 @@ function Compiler (handleImportCall) {
     })
     compileJSON = function (source, optimize) {
       jobs.push({sources: source})
-      worker.postMessage({cmd: 'compile', job: jobs.length - 1, source: JSON.stringify(source), optimize: optimize})
+      worker.postMessage({cmd: 'compile', job: jobs.length - 1, input: compilerInput(source.sources, {optimize: optimize, target: source.target})})
     }
     worker.postMessage({cmd: 'loadVersion', data: url})
   }