code: @GwtIncompatible("Unnecessary")
    private List<SourceFile> createSourceInputs(
        List<JsModuleSpec> jsModuleSpecs,
        List<FlagEntry<JsSourceType>> files,
        List<JsonFileSpec> jsonFiles,
        List<String> moduleRoots)
        throws IOException {
      if (isInTestMode()) {
        return inputsSupplierForTesting != null ? inputsSupplierForTesting.get()
            : null;
      }
      if (files.isEmpty() && jsonFiles == null) {
        // Request to read from stdin.
        files = ImmutableList.of(new FlagEntry<JsSourceType>(JsSourceType.JS, "-"));
      }
  
      for (JSError error : deduplicateIjsFiles(files, moduleRoots, !jsModuleSpecs.isEmpty())) {
        compiler.report(error);
      }
  
      try {
        if (jsonFiles != null) {
          return createInputs(files, jsonFiles, jsModuleSpecs);
        } else {
          return createInputs(files, true, jsModuleSpecs);
        }
      } catch (FlagUsageException e) {
        throw new FlagUsageException("Bad --js flag. " + e.getMessage());
      }
    }
docs: Creates JS source code inputs from a list of files.