code: Map<String, String> processJsonInputs(Iterable<CompilerInput> inputsToProcess) {
      RewriteJsonToModule rewriteJson = new RewriteJsonToModule(this);
      for (CompilerInput input : inputsToProcess) {
        if (!input.getSourceFile().getOriginalPath().endsWith(".json")) {
          continue;
        }
  
        input.setCompiler(this);
        try {
          // JSON objects need wrapped in parens to parse properly
          input.getSourceFile().setCode("(" + input.getSourceFile().getCode() + ")");
        } catch (IOException e) {
          continue;
        }
  
        Node root = checkNotNull(input.getAstRoot(this));
        input.setJsModuleType(CompilerInput.ModuleType.JSON);
        rewriteJson.process(null, root);
      }
      return rewriteJson.getPackageJsonMainEntries();
    }
docs: Transforms JSON files to a module export that closure compiler can process and keeps track of
  any "main" entries in package.json files.