Currently, if we have multiple placeholders of the same modules (eg: json.output) in a step, the results are positional as a list in the step result (eg: json.output_all https://code.google.com/p/chromium/codesearch#chromium/infra/recipes-py/recipe_modules/json/example.py&l=42).

My proposal is to have them indexed by names. This will be more explicit/convenient and less error-prone. For example:

  result = api.python.inline(                                                    
      'foo',                                                                     
      """                                                                        
      import json                                                                
      import sys                                                                 
      with open(sys.argv[1], 'w') as f:                                          
        f.write(json.dumps([1, 2, 3]))                                           
      with open(sys.argv[2], 'w') as f:                                          
        f.write(json.dumps(['x', 'y', %s]))                                      
      """ % repr(FULLWIDTH_Z),                                                   
      args=[api.json.output(identifier='name1'), api.json.output(identifier='name2')],   
  )
  assert result.json.outputs['name1'] == [1, 2, 3]                                   
  assert result.json.outputs['name2'] == ['x', 'y', FULLWIDTH_Z] 


Sine a couple of recipes/recipe_modules already use json.output_all, my plan is to do it in three steps:
1. In recipe framework, add support for index, eg: json.outputs[name].
2. Update recipes/recipe_modules to use name index instead of positional, eg: use json.outputs instead json.output_all
3. In recipe framework, do the clean-up, eg: remove json.output_all.