inconsistent results with inspect.getsource / .getsourcelines

[isedev]

BPO	22355
Nosy	@1st1, @tirkarthi

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2014-09-07.14:45:41.213>
labels = ['type-bug', 'library']
title = 'inconsistent results with inspect.getsource / .getsourcelines'
updated_at = <Date 2018-11-07.06:22:23.846>
user = 'https://bugs.python.org/isedev'

bugs.python.org fields:

activity = <Date 2018-11-07.06:22:23.846>
actor = 'xtreak'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2014-09-07.14:45:41.213>
creator = 'isedev'
dependencies = []
files = []
hgrepos = []
issue_num = 22355
keywords = []
message_count = 3.0
messages = ['226537', '226538', '329406']
nosy_count = 3.0
nosy_names = ['isedev', 'yselivanov', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22355'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[isedev]

The functions inspect.getsource() and inspect.getsourcelines() return inconsistent results for frames corresponding to class definitions within a function.

Test code:

import sys
import inspect

def case1():
    class C:
        def __init__(self):
            pass
    c = C()

def case2():
    a = 1
    class C:
        def __init__(self):
            pass
    c = C()

def case3():
    def fn():
        pass
    class C:
        def __init__(self):
            pass
    c = C()

def trace(frame,event,arg):
    code = frame.f_code
    print('name:',code.co_name)
    print('source:\n',inspect.getsource(code),'\n')

for case in ('case1','case2','case3'):
    print('#####',case)
    call = getattr(sys.modules[__name__],case)
    sys.settrace(trace)
    try:
        call()
    finally:
        sys.settrace(None)

Result:

##### case1
name: case1
source:
def case1():
class C:
def __init__(self):
pass
c = C()

name: C
source:
def case1():
class C:
def __init__(self):
pass
c = C()

name: __init__
source:
def __init__(self):
pass

##### case2
name: case2
source:
def case2():
a = 1
class C:
def __init__(self):
pass
c = C()

name: C
source:
def case2():
a = 1
class C:
def __init__(self):
pass
c = C()

name: __init__
source:
def __init__(self):
pass

##### case3
name: case3
source:
def case3():
def fn():
pass
class C:
def __init__(self):
pass
c = C()

name: C
source:
def fn():
pass

name: __init__
source:
def __init__(self):
pass

The source listed for frames named 'C' (the class creation code) is not consistent across all three cases. It could be considered incorrect in all cases as it does not correspond only to the class definition source lines.

[isedev]

Possible fix:

--- /usr/lib64/python3.3/inspect.py     2014-06-30 19:21:52.000000000 +0200
+++ inspect.py  2014-09-07 17:41:29.463936079 +0200
@@ -600,7 +600,8 @@
         if not hasattr(object, 'co_firstlineno'):
             raise IOError('could not find function definition')
         lnum = object.co_firstlineno - 1
-        pat = re.compile(r'^(\s*def\s)|(.*(?<!\w)lambda(:|\s))|^(\s*@)')
+        pat = re.compile(
+            r'^(\s*(?:def|class)\s)|(.*(?<!\w)lambda(:|\s))|^(\s*@)')
         while lnum > 0:
             if pat.match(lines[lnum]): break
             lnum = lnum - 1

[tirkarthi]

I think this issue is covered with bpo-35101. It has an open PR as per the proposed fix with tests : https://github.com/python/cpython/pull/10209/files