如何创建fabric2任务装饰器？

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英文:

How to create fabric2 tasks decorators?

问题

以下是您要翻译的代码部分：

  1. 让我们首先考虑一些使用fabric2的未重构的工作代码片段：
  3. import traceback import inspect
  5. from fabric2.tasks import task
  6. from fabric2 import Config, Connection
  8. def get_function_name():
  9.     return traceback.extract_stack(None, 2)[0][2]
  11. def get_function_parameters_and_values():
  12.     frame = inspect.currentframe().f_back
  13.     args, _, _, values = inspect.getargvalues(frame)
  14.     return ", ".join([str(i) for i in args])
  16. @task def foo1(c, arg1):
  17.     print(f'<{get_function_name()} {get_function_parameters_and_values()}>)
  19.         def _inner():
  20.             if int(arg1) < 5:
  21.                 print('arg1 is not big enough')
  22.                 return
  23.             print('doing foo1 stuff')
  24.         res = _inner()
  25.         print(f'</{get_function_name()}')
  26.         return res
  28. @task def foo2(c, arg1, arg2):
  29.     print(f'<{get_function_name()} {get_function_parameters_and_values()}>)
  31.         def _inner():
  32.             if int(arg1) < 5 and int(arg2) < 5:
  33.                 print('arg1 & arg2 are not big enough')
  34.                 return
  35.             print('doing foo2 stuff')
  36.         res = _inner()
  37.         print(f'</{get_function_name()}')
  38.         return res
  40. 现在，如您所见，上面存在一些代码重复，我想通过包装器/装饰器的方式将其提取出来…问题出在如果我尝试像这样做：
  42. def wrap(func):
  43.     def wrapped(*args, **kwargs):
  44.         print('begin')
  45.         res = func(*args, **kwargs)
  46.         print('end')
  47.     return wrapped
  49. @task
  50. @wrap
  51. def foo3(c, arg1):
  52.     if int(arg1) < 5:
  53.         print('arg1 is not big enough')
  54.         return
  55.     print('doing foo3 stuff')
  57. @wrap
  58. @task
  59. def foo4(c, arg1):
  60.     if int(arg1) < 5:
  61.         print('arg1 is not big enough')
  62.         return
  63.     print('doing foo4 stuff')
  65. 当我运行其中任何一个任务时，都会出现异常，例如：
  67. (py364_32) D:\sources\personal\python\bplfab\examples>fab2 foo3 --arg1=3
  68. Traceback (most recent call last):
  69.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 160, in argspec
  70.     context_arg = arg_names.pop(0)
  71. IndexError: pop from empty list
  73. 在处理上述异常时，又出现了另一个异常：
  75. Traceback (most recent call last):
  76.   File "d:\software\python364_32\Lib\runpy.py", line 193, in _run_module_as_main
  77.     "__main__", mod_spec)
  78.   File "d:\software\python364_32\Lib\runpy.py", line 85, in _run_code
  79.     exec(code, run_globals)
  80.   File "D:\virtual_envs\py364_32\Scripts\fab2.exe\__main__.py", line 7, in <module>
  81.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py", line 352, in run
  82.     self.parse_collection()
  83.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py", line 444, in parse_collection
  84.     self.load_collection()
  85.   File "d:\virtual_envs\py364_32\lib\site-packages\fabric2\main.py", line 87, in load_collection
  86.     super(Fab, self).load_collection()
  87.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py", line 661, in load_collection
  88.     module, parent = loader.load(coll_name)
  89.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\loader.py", line 76, in load
  90.     module = imp.load_module(name, fd, path, desc)
  91.   File "<frozen importlib._bootstrap>", line 235, in load_module
  92.   File "<frozen importlib._bootstrap>", line 172, in load_source
  93.   File "D:\sources\personal\python\bplfab\examples\fabfile.py", line 59, in <module>
  94.     @wrap
  95.   File "d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py", line 71, in task
  96.     return invoke.task(*args, **kwargs)
  97.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 313, in task
  98.     return klass(args[0], **kwargs)
  99.   File "d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py", line 21, in __init__
  100.     super(Task, self).__init__(*args, **kwargs)
  101.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 77, in __init__
  102.     self.positional = self.fill_implicit_positionals(positional)
  103.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 168, in fill_implicit_positionals
  104.     args, spec_dict = self.argspec(self.body)
  105.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 163, in argspec
  106.     raise TypeError("Tasks must have an initial Context argument!")
  107. TypeError: Tasks must have an initial Context argument!
  109. (py364_32) D:\sources\personal\python\bplfab\examples>fab2 foo4 --arg1=3
  110. Traceback (most recent call last):
  111.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py", line 160, in argspec
  112.     context_arg = arg_names.pop(0)
  113. IndexError: pop from empty list
  115. 在处理上述异常时，又出现了另一个异常：
  117. Traceback (most recent call last):
  118.   File "d:\software\python364_32\Lib\runpy.py", line 193, in _run_module_as_main
  119.     "__main__", mod_spec)
  120.   File "d:\software\python364_32\Lib\runpy.py", line 85, in _run_code
  121.     exec(code, run_globals)
  122.   File "D:\virtual_envs\py364_32\Scripts\fab2.exe\__main__.py", line 7, in <module>
  123.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py", line 352, in run
  124.     self.parse_collection()
  125.   File "d:\virtual_envs\py364_32\lib\site-packages\invoke\program
  127. <details>
  128. <summary>英文:</summary>
  130. Let&#39;s start by considering some unrefactored working piece of code that uses fabric2:
  132.     import traceback import inspect
  133.     
  134.     
  135.     from fabric2.tasks import task 
  136.     from fabric2 import Config, Connection
  137.     
  138.     
  139.     def get_function_name():
  140.         return traceback.extract_stack(None, 2)[0][2]
  141.     
  142.     
  143.     def get_function_parameters_and_values():
  144.         frame = inspect.currentframe().f_back
  145.         args, _, _, values = inspect.getargvalues(frame)
  146.         return &quot;, &quot;.join([str(i) for i in args])
  147.     
  148.     
  149.     @task def foo1(c, arg1):
  150.         print(f&#39;&lt;{get_function_name()} {get_function_parameters_and_values()}&gt;&#39;)
  151.     
  152.         def _inner():
  153.             if int(arg1) &lt; 5:
  154.                 print(&#39;arg1 is not big enough&#39;)
  155.                 return
  156.             print(&#39;doing foo1 stuff&#39;)
  157.         res = _inner()
  158.         print(f&#39;&lt;/{get_function_name}&#39;)
  159.         return res
  160.     
  161.     
  162.     @task def foo2(c, arg1, arg2):
  163.         print(f&#39;&lt;{get_function_name()} {get_function_parameters_and_values()}&gt;&#39;)
  164.     
  165.         def _inner():
  166.             if int(arg1) &lt; 5 and int(arg2) &lt; 5:
  167.                 print(&#39;arg1 &amp; arg2 are not big enough&#39;)
  168.                 return
  169.             print(&#39;doing foo2 stuff&#39;)
  170.         res = _inner()
  171.         print(f&#39;&lt;/{get_function_name}&#39;)
  172.         return res
  173.     
  174. Now, as you can see above, there is some code duplication I&#39;d like to factor out in the way of a wrapper/decorator... Problem comes if I try something like this:
  176.     def wrap(func):
  177.         def wrapped(*args, **kwargs):
  178.             print(&#39;begin&#39;)
  179.             res = func(*args, **kwargs)
  180.             print(&#39;end&#39;)
  181.         return wrapped
  182.     
  183.     
  184.     @task
  185.     @wrap
  186.     def foo3(c, arg1):
  187.         if int(arg1) &lt; 5:
  188.             print(&#39;arg1 is not big enough&#39;)
  189.             return
  190.         print(&#39;doing foo3 stuff&#39;)
  191.     
  192.     
  193.     @wrap
  194.     @task
  195.     def foo4(c, arg1):
  196.         if int(arg1) &lt; 5:
  197.             print(&#39;arg1 is not big enough&#39;)
  198.             return
  199.         print(&#39;doing foo4 stuff&#39;)
  201. And I run either of these tasks I&#39;ll get exceptions with both such as:
  203.     (py364_32) D:\sources\personal\python\bplfab\examples&gt;fab2 foo3 --arg1=3
  204.     Traceback (most recent call last):
  205.       File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 160, in argspec
  206.         context_arg = arg_names.pop(0)
  207.     IndexError: pop from empty list
  209.     During handling of the above exception, another exception occurred:
  211.         Traceback (most recent call last):
  212.           File &quot;d:\software\python364_32\Lib\runpy.py&quot;, line 193, in _run_module_as_main
  213.             &quot;__main__&quot;, mod_spec)
  214.           File &quot;d:\software\python364_32\Lib\runpy.py&quot;, line 85, in _run_code
  215.             exec(code, run_globals)
  216.           File &quot;D:\virtual_envs\py364_32\Scripts\fab2.exe\__main__.py&quot;, line 7, in &lt;module&gt;
  217.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 352, in run
  218.             self.parse_collection()
  219.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 444, in parse_collection
  220.             self.load_collection()
  221.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\main.py&quot;, line 87, in load_collection
  222.             super(Fab, self).load_collection()
  223.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 661, in load_collection
  224.             module, parent = loader.load(coll_name)
  225.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\loader.py&quot;, line 76, in load
  226.             module = imp.load_module(name, fd, path, desc)
  227.           File &quot;d:\virtual_envs\py364_32\lib\imp.py&quot;, line 235, in load_module
  228.             return load_source(name, filename, file)
  229.           File &quot;d:\virtual_envs\py364_32\lib\imp.py&quot;, line 172, in load_source
  230.             module = _load(spec)
  231.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 684, in _load
  232.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 665, in _load_unlocked
  233.           File &quot;&lt;frozen importlib._bootstrap_external&gt;&quot;, line 678, in exec_module
  234.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 219, in _call_with_frames_removed
  235.           File &quot;D:\sources\personal\python\bplfab\examples\fabfile.py&quot;, line 59, in &lt;module&gt;
  236.             @wrap
  237.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py&quot;, line 71, in task
  238.             return invoke.task(*args, **kwargs)
  239.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 313, in task
  240.             return klass(args[0], **kwargs)
  241.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py&quot;, line 21, in __init__
  242.             super(Task, self).__init__(*args, **kwargs)
  243.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 77, in __init__
  244.             self.positional = self.fill_implicit_positionals(positional)
  245.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 168, in fill_implicit_positionals
  246.             args, spec_dict = self.argspec(self.body)
  247.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 163, in argspec
  248.             raise TypeError(&quot;Tasks must have an initial Context argument!&quot;)
  249.         TypeError: Tasks must have an initial Context argument!
  250.         
  251.         (py364_32) D:\sources\personal\python\bplfab\examples&gt;fab2 foo4 --arg1=3
  252.         Traceback (most recent call last):
  253.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 160, in argspec
  254.             context_arg = arg_names.pop(0)
  255.         IndexError: pop from empty list
  256.         
  257.         During handling of the above exception, another exception occurred:
  258.         
  259.         Traceback (most recent call last):
  260.           File &quot;d:\software\python364_32\Lib\runpy.py&quot;, line 193, in _run_module_as_main
  261.             &quot;__main__&quot;, mod_spec)
  262.           File &quot;d:\software\python364_32\Lib\runpy.py&quot;, line 85, in _run_code
  263.             exec(code, run_globals)
  264.           File &quot;D:\virtual_envs\py364_32\Scripts\fab2.exe\__main__.py&quot;, line 7, in &lt;module&gt;
  265.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 352, in run
  266.             self.parse_collection()
  267.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 444, in parse_collection
  268.             self.load_collection()
  269.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\main.py&quot;, line 87, in load_collection
  270.             super(Fab, self).load_collection()
  271.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\program.py&quot;, line 661, in load_collection
  272.             module, parent = loader.load(coll_name)
  273.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\loader.py&quot;, line 76, in load
  274.             module = imp.load_module(name, fd, path, desc)
  275.           File &quot;d:\virtual_envs\py364_32\lib\imp.py&quot;, line 235, in load_module
  276.             return load_source(name, filename, file)
  277.           File &quot;d:\virtual_envs\py364_32\lib\imp.py&quot;, line 172, in load_source
  278.             module = _load(spec)
  279.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 684, in _load
  280.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 665, in _load_unlocked
  281.           File &quot;&lt;frozen importlib._bootstrap_external&gt;&quot;, line 678, in exec_module
  282.           File &quot;&lt;frozen importlib._bootstrap&gt;&quot;, line 219, in _call_with_frames_removed
  283.           File &quot;D:\sources\personal\python\bplfab\examples\fabfile.py&quot;, line 59, in &lt;module&gt;
  284.             @wrap
  285.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py&quot;, line 71, in task
  286.             return invoke.task(*args, **kwargs)
  287.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 313, in task
  288.             return klass(args[0], **kwargs)
  289.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\fabric2\tasks.py&quot;, line 21, in __init__
  290.             super(Task, self).__init__(*args, **kwargs)
  291.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 77, in __init__
  292.             self.positional = self.fill_implicit_positionals(positional)
  293.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 168, in fill_implicit_positionals
  294.             args, spec_dict = self.argspec(self.body)
  295.           File &quot;d:\virtual_envs\py364_32\lib\site-packages\invoke\tasks.py&quot;, line 163, in argspec
  296.             raise TypeError(&quot;Tasks must have an initial Context argument!&quot;)
  297.         TypeError: Tasks must have an initial Context argument!
  299. It seems there is already an opened issue related somehow to this https://github.com/pyinvoke/invoke/issues/555 but so far I haven&#39;t been able to find a workaround for this.
  301. Could you explain me what I&#39;m doing wrong here? But the most important, could you provide a way to workaround this fabric2 &quot;limitation&quot; and being able to create a decorator that allows me to use inspect to capture the task&#39;s name as well as the arguments passed in the command line?
  303. Thanks in advance.
  305. </details>
  308. # 答案1
  309. **得分**: 1
  311. Custom decorators必须具有一个固定的初始上下文参数，就像异常所说的那样，所以`func(c, *args, **kwargs)`有效，而`func(*args, **kwargs)`无效：
  313. ```py
  314. def trace(func):
  315.     @functools.wraps(func)
  316.     def wrapper(c, *args, **kwargs):
  317.         print(f'开始 {func.__name__}')
  318.         func(c, *args, **kwargs)
  319.         print(f'结束 {func.__name__}')
  320.     return wrapper
  322. @task
  323. @trace
  324. def uname(c):
  325.     c.run('uname -a')
英文:

Custom decorators must have a fixed initial context argument as the exception says, so func(c, *args, **kwargs) works while func(*args, **kwargs) doesn't:

  1. def trace(func):
  2.     @functools.wraps(func)
  3.     def wrapper(c, *args, **kwargs):
  4.         print(f&#39;Begin {func.__name__}&#39;)
  5.         func(c, *args, **kwargs)
  6.         print(f&#39;End {func.__name__}&#39;)
  7.     return wrapper
  9. @task
  10. @trace
  11. def uname(c):
  12.     c.run(&#39;uname -a&#39;)

huangapple
  • 本文由 发表于 2020年1月3日 23:00:19
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  • fabric
  • python
  • python-fabric-2
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