Fix default argument check on py> operator

[chezou]

Fix #912

Checked with a.dig and a.py described in #912

Before

➜  test-py3 digdag run a.dig
2018-10-31 17:36:09 +0900: Digdag v0.9.30
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.inject.internal.cglib.core.$ReflectUtils$2 (file:/Users/ariga/bin/digdag) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of com.google.inject.internal.cglib.core.$ReflectUtils$2
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2018-10-31 17:36:10 +0900 [WARN] (main): Using a new session time 2018-10-31T00:00:00+00:00.
2018-10-31 17:36:10 +0900 [INFO] (main): Using session /Users/ariga/src/test-py3/.digdag/status/20181031T000000+0000.
2018-10-31 17:36:10 +0900 [INFO] (main): Starting a new session project id=1 workflow name=a session_time=2018-10-31T00:00:00+00:00
2018-10-31 17:36:17 +0900 [INFO] (0019@[0:default]+a+t1): py>: a.ok
(111, 2, 3)
2018-10-31 17:36:23 +0900 [INFO] (0019@[0:default]+a+t2): py>: a.ng
Traceback (most recent call last):
  File "<stdin>", line 147, in <module>
  File "<stdin>", line 129, in digdag_inspect_arguments
TypeError: Method 'ng' requires parameter 'arg3' but not set
2018-10-31 17:36:23 +0900 [ERROR] (0019@[0:default]+a+t2): Task failed with unexpected error: Python command failed with code 1
java.lang.RuntimeException: Python command failed with code 1
	at io.digdag.standards.operator.PyOperatorFactory$PyOperator.runCode(PyOperatorFactory.java:153)
	at io.digdag.standards.operator.PyOperatorFactory$PyOperator.runTask(PyOperatorFactory.java:91)
	at io.digdag.util.BaseOperator.run(BaseOperator.java:35)
	at io.digdag.core.agent.OperatorManager.callExecutor(OperatorManager.java:312)
	at io.digdag.cli.Run$OperatorManagerWithSkip.callExecutor(Run.java:694)
	at io.digdag.core.agent.OperatorManager.runWithWorkspace(OperatorManager.java:254)
	at io.digdag.core.agent.OperatorManager.lambda$runWithHeartbeat$2(OperatorManager.java:137)
	at io.digdag.core.agent.LocalWorkspaceManager.withExtractedArchive(LocalWorkspaceManager.java:25)
	at io.digdag.core.agent.OperatorManager.runWithHeartbeat(OperatorManager.java:135)
	at io.digdag.core.agent.OperatorManager.run(OperatorManager.java:119)
	at io.digdag.cli.Run$OperatorManagerWithSkip.run(Run.java:676)
	at io.digdag.core.agent.MultiThreadAgent.lambda$null$0(MultiThreadAgent.java:127)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:514)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:844)
2018-10-31 17:36:28 +0900 [INFO] (0019@[0:default]+a^failure-alert): type: notify
error:
  * +a+t2:
    Python command failed with code 1 (runtime)

Task state is saved at /Users/ariga/src/test-py3/.digdag/status/20181031T000000+0000 directory.
  * Use --session <daily | hourly | "yyyy-MM-dd[ HH:mm:ss]"> to not reuse the last session time.
  * Use --rerun, --start +NAME, or --goal +NAME argument to rerun skipped tasks.

After

➜  test-py3 ~/src/digdag/pkg/digdag-0.9.32-SNAPSHOT.jar run a.dig
2018-10-31 17:37:01 +0900: Digdag v0.9.31
2018-10-31 17:37:02 +0900 [WARN] (main): Using a new session time 2018-10-31T00:00:00+00:00.
2018-10-31 17:37:03 +0900 [INFO] (main): Using session /Users/ariga/src/test-py3/.digdag/status/20181031T000000+0000.
2018-10-31 17:37:03 +0900 [INFO] (main): Starting a new session project id=1 workflow name=a session_time=2018-10-31T00:00:00+00:00
2018-10-31 17:37:03 +0900 [INFO] (0017@[0:default]+a+t1): py>: a.ok
(111, 2, 3)
2018-10-31 17:37:04 +0900 [INFO] (0017@[0:default]+a+t2): py>: a.ng
(111, 222, 3)
Success. Task state is saved at /Users/ariga/src/test-py3/.digdag/status/20181031T000000+0000 directory.
  * Use --session <daily | hourly | "yyyy-MM-dd[ HH:mm:ss]"> to not reuse the last session time.
  * Use --rerun, --start +NAME, or --goal +NAME argument to rerun skipped tasks.

@muga Can you check this PR if you have a spare time?

[hiroyuki-sato]

@chezou Thank you for fixing #912.
The original Reporter said LGTM 👍
Twitter

I'm not familiar Python.

[chezou]

Just for note.
spec.args returns all arguments in a list, while spec.defaults returns a tuple of default values.

For example:

In [2]: def ng(arg1, arg2, arg3=3):
   ...:     print(arg1, arg2, arg3)

In [4]: spec = inspect.getargspec(ng)

In [5]: spec.args
Out[5]: ['arg1', 'arg2', 'arg3']

In [6]: spec.defaults
Out[6]: (3,)

In [7]: spec
Out[7]: ArgSpec(args=['arg1', 'arg2', 'arg3'], varargs=None, keywords=None, defaults=(3,))

Default arguments should be in the end of arguments, so we need to check front arguments.

[chezou]

@muga Just for reminder. Can you check it if you have a time?
It'd be nice if you could give some feedback; add test, something like that...

[muga]

Sorry to be late. Let me take a look and will check CI failure.

[muga]

Looks good. thank you for fixing. Let me merge after CI will be passed.