Backport of PR#1855

6 files changed, 61 insertions, 20 deletions

diff --git a/ChangeLog b/ChangeLog
index 54df5a277..26145f81a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,11 @@ Release date: -
 
       Close #1794
 
+    * Fix false positive ``inconsistent-return-statements`` message by
+      avoiding useless exception inference if the exception is not handled.
+
+      Close #1794 (second part)
+
 What's New in Pylint 1.8.2?
 ==========================
 
diff --git a/doc/whatsnew/1.8.rst b/doc/whatsnew/1.8.rst
index a0cf7d3ac..422aa70f6 100644
--- a/doc/whatsnew/1.8.rst
+++ b/doc/whatsnew/1.8.rst
@@ -381,3 +381,7 @@ Other Changes
 
 * Fix false positive ``inconsistent-return-statements`` message when a function
   is defined under an if statement. (backport from 2.0)
+
+* Fix false positive ``inconsistent-return-statements`` message by
+  avoiding useless exception inference if the exception is not handled.
+  (backport from 2.0)
diff --git a/pylint/checkers/refactoring.py b/pylint/checkers/refactoring.py
index 1f437799d..75a36af06 100644
--- a/pylint/checkers/refactoring.py
+++ b/pylint/checkers/refactoring.py
@@ -568,6 +568,11 @@ class RefactoringChecker(checkers.BaseTokenChecker):
             if not node.exc:
                 # Ignore bare raises
                 return True
+            if not utils.is_node_inside_try_except(node):
+                # If the raise statement is not inside a try/except statement
+                # then the exception is raised and cannot be caught. No need
+                # to infer it.
+                return True
             exc = utils.safe_infer(node.exc)
             if exc is None or exc is astroid.Uninferable:
                 return False
diff --git a/pylint/checkers/utils.py b/pylint/checkers/utils.py
index 9d8a18ba5..5b9525dfe 100644
--- a/pylint/checkers/utils.py
+++ b/pylint/checkers/utils.py
@@ -596,6 +596,7 @@ def unimplemented_abstract_methods(node, is_abstract_cb=None):
 
 
 def _import_node_context(node):
+    """Return the ExceptHandler or the TryExcept node in which the node is."""
     current = node
     ignores = (astroid.ExceptHandler, astroid.TryExcept)
     while current and not isinstance(current.parent, ignores):
@@ -642,17 +643,27 @@ def get_exception_handlers(node, exception):
         generator: the collection of handlers that are handling the exception or None.
 
     """
-    current = node
-    ignores = (astroid.ExceptHandler, astroid.TryExcept)
-    while current and not isinstance(current.parent, ignores):
-        current = current.parent
-
-    if current and isinstance(current.parent, astroid.TryExcept):
-        return (_handler for _handler in current.parent.handlers
+    context = _import_node_context(node)
+    if isinstance(context, astroid.TryExcept):
+        return (_handler for _handler in context.handlers
                 if error_of_type(_handler, exception))
     return None
 
 
+def is_node_inside_try_except(node):
+    """Check if the node is directly under a Try/Except statement.
+    (but not under an ExceptHandler!)
+
+    Args:
+        node (astroid.Raise): the node raising the exception.
+
+    Returns:
+        bool: True if the node is inside a try/except statement, False otherwise.
+    """
+    context = _import_node_context(node)
+    return isinstance(context, astroid.TryExcept)
+
+
 def node_ignores_exception(node, exception):
     """Check if the node is in a TryExcept which handles the given exception."""
     managing_handlers = get_exception_handlers(node, exception)
diff --git a/pylint/test/functional/inconsistent_returns.py b/pylint/test/functional/inconsistent_returns.py
index a6ec2cd1f..0524cd575 100644
--- a/pylint/test/functional/inconsistent_returns.py
+++ b/pylint/test/functional/inconsistent_returns.py
@@ -130,6 +130,22 @@ def bug_1794_inner_func_in_if(var):
     else:
         return None
 
+try:
+    import ConfigParser as configparser
+except ImportError:
+    import configparser
+
+# Due to the try/except import above, astroid cannot safely
+# infer the exception type. It doesn't matter here, because
+# as the raise statement is not inside a try/except one, there
+# is no need to infer the exception type. It is just an exception
+# that is raised.
+def bug_1794(a):
+    for x in range(a):
+        if x == 100:
+            return a
+    raise configparser.NoSectionError('toto')
+
 # Next ones are not consistent
 def explicit_implicit_returns(var): # [inconsistent-return-statements]
     if var >= 0:
diff --git a/pylint/test/functional/inconsistent_returns.txt b/pylint/test/functional/inconsistent_returns.txt
index 08ce9d7d9..8bc9c5eda 100644
--- a/pylint/test/functional/inconsistent_returns.txt
+++ b/pylint/test/functional/inconsistent_returns.txt
@@ -1,13 +1,13 @@
-inconsistent-return-statements:134:explicit_implicit_returns:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:138:empty_explicit_returns:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:143:explicit_implicit_returns2:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:151:explicit_implicit_returns3:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:159:returns_missing_in_catched_exceptions:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:169:complex_func:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:177:inconsistent_returns_in_nested_function.not_consistent_returns_inner:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:198:bug_1772_counter_example:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:206:bug_1771_counter_example:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:212:bug_1794_inner_func_in_if_counter_example_1:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:221:bug_1794_inner_func_in_if_counter_example_2:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:230:bug_1794_inner_func_in_if_counter_example_3:Either all return statements in a function should return an expression, or none of them should.
-inconsistent-return-statements:237:bug_1794_inner_func_in_if_counter_example_3._inner2:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:150:explicit_implicit_returns:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:154:empty_explicit_returns:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:159:explicit_implicit_returns2:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:167:explicit_implicit_returns3:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:175:returns_missing_in_catched_exceptions:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:185:complex_func:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:193:inconsistent_returns_in_nested_function.not_consistent_returns_inner:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:214:bug_1772_counter_example:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:222:bug_1771_counter_example:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:228:bug_1794_inner_func_in_if_counter_example_1:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:237:bug_1794_inner_func_in_if_counter_example_2:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:246:bug_1794_inner_func_in_if_counter_example_3:Either all return statements in a function should return an expression, or none of them should.
+inconsistent-return-statements:253:bug_1794_inner_func_in_if_counter_example_3._inner2:Either all return statements in a function should return an expression, or none of them should.