[Lldb-commits] [PATCH] D131085: [lldb/crashlog] Refactor the CrashLogParser logic

[Med Ismail Bennani via Phabricator via lldb-commits]

mib marked 2 inline comments as done.
mib added inline comments.


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Comment at: lldb/examples/python/crashlog.py:434
         except CrashLogFormatException:
-            return TextCrashLogParser(debugger, path, verbose).parse()
+            return  object().__new__(TextCrashLogParser)
 
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JDevlieghere wrote:
> kastiglione wrote:
> > mib wrote:
> > > JDevlieghere wrote:
> > > > mib wrote:
> > > > > kastiglione wrote:
> > > > > > I have not seen the `object().__new__(SomeClass)` syntax. Why is it being used for `TextCrashLogParser` but not `JSONCrashLogParser`? Also, `__new__` is a static method, could it be `object.__new__(...)`? Or is there a subtly that requires an `object` instance? Somewhat related, would it be better to say `super().__new__(...)`?
> > > > > > 
> > > > > > Also: one class construction explicitly forwards the arguments, the other does not. Is there a reason both aren't implicit (or both explicit)?
> > > > > As you know, python class are implicitly derived from the `object` type, making `object.__new__` and `super().__new__` pretty much the same thing.
> > > > > 
> > > > > In this specific case, both the `TextCrashLogParser` and `JSONCrashLogParser` inherits from the `CrashLogParser` class, so `JSONCrashLogParser` will just inherits `CrashLogParser.__new__` implementation if we don't override it, which creates a recursive loop.
> > > > > That's why I'm calling the `__new__` method specifying the class.
> > > > What's the advantage of this over this compared to a factory method? Seems like this could be:
> > > > 
> > > > ```
> > > > def create(debugger, path, verbose)
> > > >     try:
> > > >             return JSONCrashLogParser(debugger, path, verbose)
> > > >         except CrashLogFormatException:
> > > >             return  TextCrashLogParser(debugger, path, verbose)
> > > > ```
> > > If we make a factory, then users could still call `__init__` on `CrashLogParser` and create a bogus object. With this approach, they're forced to instantiate a CrashLogParser like any another object.
> > `CrashLogParser.__init__` could raise an exception. With intricacy of this approach, maybe it's better to use a factor method combined with an exception if the base class `__init__` is called.
> +1, or maybe `abc` provide a capability to achieve the same?
IMHO, having to call an arbitrary-called method (`create/make/...`) to instantiate an object and having the `__init__` raise an exception introduces more intricacies in the usage of this class, compared to what I'm doing. 

I prefer to keep it this way since it's more natural / safe to use. If the implementation exercises some python internal  features, that's fine because that shouldn't matter to the user.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D131085/new/

https://reviews.llvm.org/D131085