no output for --py3k checker with python3 env

[rednaks]

Hello,

I'm testing pylint --py3k with a python 3 env (Python 3.5.2) with a basic file but the command is not returning any output:

PS. Python 3.5.2 is the default version on ubuntu xenial.

print "hello"


try:
    pass
except Exception, e:
    pass


a = xrange(10**8)

Version

pylint --version
pylint 2.3.1
astroid 2.2.5
Python 3.5.2 (default, Nov 12 2018, 13:43:14) 
[GCC 5.4.0 20160609]

with a python 2 (and pylint 1.9.4, astroid 1.6.6) it's working well, except for the exception syntax. (which is already mentioned in #2582)

I understand that two different pylint version for two different python versions, but are they maintained separately ? if yes, why ?

Thanks !

[justinfx]

We just discovered this as well, and I am wondering why the syntax errors aren't reported during --py3k. This happens as far back as pylint 1.6.4 on python2.7 and on pylint 2.3.1 with python3. I would think part of a py3k check would be to catch syntax errors. But there doesn't seem to be a way to even force it to catch them: pylint --py3k -e E0001

[PCManticore]

This happens mainly because we use the Python 3's parser module for parsing this Python 2 file. Given you have Python 2 specific syntax, the parser fails to parse the file, resulting in syntax-error not being emitted when you have the --py3k mode enabled.

Ideally we should use a Python 2 specific parser, which we can actually expose via the typed_ast module that we use internally: https://github.com/PyCQA/astroid/blob/master/astroid/_ast.py#L26

Regarding your question on two versions of pylint, the issue is that Pylint 2.X is incompatible in terms of code changes with Pylint 1.9.X. The former works only for Python <3.7 and Python 2.7, and will be unsupported starting from 2020.

[rednaks]

Alright, that makes sense now, thank you for your answer, I'll try to work on it, and I'll PR when I have a patch :)

[huguesb]

At the very least, pylint should report parse errors properly in py3k mode, which is easily done with this patch:

diff --git a/pylint/lint.py b/pylint/lint.py
index bbb01d35..dd651b5d 100644
--- a/pylint/lint.py
+++ b/pylint/lint.py
@@ -804,6 +804,11 @@ class PyLinter(
     def python3_porting_mode(self):
         """Disable all other checkers and enable Python 3 warnings."""
         self.disable("all")
+        # re-enable some errors, or 'print', 'raise', 'async', 'await' will mistakenly lint fine
+        self.enable("F0001")
+        self.enable("F0002")
+        self.enable("F0010")
+        self.enable("E0001")
         self.enable("python3")
         if self._error_mode:
             # The error mode was activated, using the -E flag.