We don't emit by default ``no-member`` if we have opaque inference objects in the inference results

This is controlled through the new flag ``--ignore-on-opaque-inference``, which is by
default True. The inference can return  multiple potential results while
evaluating a Python object, but some branches might not be evaluated, which
results in partial inference. In that case, it might be useful to still emit
no-member and other checks for the rest of the inferred objects.

8 files changed, 54 insertions, 16 deletions

diff --git a/ChangeLog b/ChangeLog
index 81bdfb450..9896b7bdf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,10 +6,19 @@ What's New in Pylint 1.7?
 =========================
 
 Release date: tba
+
     * Don't emit missing-final-newline or trailing-whitespace for formfeeds (page breaks).
 
       Close #1218 and #1219
-      
+
+    * Don't emit by default no-member if we have opaque inference objects in the inference results
+
+      This is controlled through the new flag ignore-on-opaque-inference, which is by
+      default True. The inference can return  multiple potential results while
+      evaluating a Python object, but some branches might not be evaluated, which
+      results in partial inference. In that case, it might be useful to still emit
+      no-member and other checks for the rest of the inferred objects.
+
     * Added new message `assign-to-new-keyword` to warn about assigning to names which
       will become a keyword in future Python releases.
 
diff --git a/doc/whatsnew/1.7.rst b/doc/whatsnew/1.7.rst
index 219691760..662323536 100644
--- a/doc/whatsnew/1.7.rst
+++ b/doc/whatsnew/1.7.rst
@@ -596,6 +596,14 @@ New checkers
 Other Changes
 =============
 
+* We don't emit by default ``no-member`` if we have opaque inference objects in the inference results
+
+  This is controlled through the new flag ``--ignore-on-opaque-inference``, which is by
+  default True. The inference can return  multiple potential results while
+  evaluating a Python object, but some branches might not be evaluated, which
+  results in partial inference. In that case, it might be useful to still emit
+  no-member and other checks for the rest of the inferred objects.
+
 * Namespace packages are now supported by pylint. This includes both explicit namespace
   packages and implicit namespace packages, supported in Python 3 through PEP 420.
 
diff --git a/pylint/checkers/typecheck.py b/pylint/checkers/typecheck.py
index 89f5b34c4..a504c1c40 100644
--- a/pylint/checkers/typecheck.py
+++ b/pylint/checkers/typecheck.py
@@ -474,7 +474,17 @@ class TypeChecker(BaseChecker):
     msgs = MSGS
     priority = -1
     # configuration options
-    options = (('ignore-mixin-members',
+    options = (('ignore-on-opaque-inference',
+               {'default': True, 'type': 'yn', 'metavar': '<y_or_n>',
+                'help': 'This flag controls whether pylint should warn about '
+                        'no-member and similar checks whenever an opaque object '
+                        'is returned when inferring. The inference can return '
+                        'multiple potential results while evaluating a Python object, '
+                        'but some branches might not be evaluated, which results in '
+                        'partial inference. In that case, it might be useful to still emit '
+                        'no-member and other checks for the rest of the inferred objects.'}
+               ),
+              ('ignore-mixin-members',
                 {'default' : True, 'type' : 'yn', 'metavar': '<y_or_n>',
                  'help' : 'Tells whether missing members accessed in mixin \
 class should be ignored. A mixin class is detected if its name ends with \
@@ -610,22 +620,26 @@ accessed. Python regular expressions are accepted.'}
                 return
 
         try:
-            infered = list(node.expr.infer())
+            inferred = list(node.expr.infer())
         except exceptions.InferenceError:
             return
+
         # list of (node, nodename) which are missing the attribute
         missingattr = set()
-        inference_failure = False
-        for owner in infered:
-            # skip yes object
-            if owner is astroid.YES:
-                inference_failure = True
-                continue
 
-            if isinstance(owner, astroid.nodes.Unknown):
-                inference_failure = True
-                continue
+        non_opaque_inference_results = [
+            owner for owner in inferred
+            if owner is not astroid.Uninferable
+            and not isinstance(owner, astroid.nodes.Unknown)
+        ]
+        if (len(non_opaque_inference_results) != len(inferred)
+                and self.config.ignore_on_opaque_inference):
+            # There is an ambiguity in the inference. Since we can't
+            # make sure that we won't emit a false positive, we just stop
+            # whenever the inference returns an opaque inference object.
+            return
 
+        for owner in non_opaque_inference_results:
             name = getattr(owner, 'name', None)
             if _is_owner_ignored(owner, name, self.config.ignored_classes,
                                  self.config.ignored_modules):
@@ -666,7 +680,6 @@ accessed. Python regular expressions are accepted.'}
                 if actual in done:
                     continue
                 done.add(actual)
-                confidence = INFERENCE if not inference_failure else INFERENCE_FAILURE
 
                 if self.config.missing_member_hint:
                     hint = _missing_member_hint(owner, node.attrname,
@@ -678,7 +691,7 @@ accessed. Python regular expressions are accepted.'}
                 self.add_message('no-member', node=node,
                                  args=(owner.display_type(), name,
                                        node.attrname, hint),
-                                 confidence=confidence)
+                                 confidence=INFERENCE)
 
     @check_messages('assignment-from-no-return', 'assignment-from-none')
     def visit_assign(self, node):
diff --git a/pylint/test/functional/member_checks.py b/pylint/test/functional/member_checks.py
index 86dcc0d0a..cb5f2313c 100644
--- a/pylint/test/functional/member_checks.py
+++ b/pylint/test/functional/member_checks.py
@@ -83,7 +83,7 @@ class Getattribute(object):
 
 print(object.__init__)
 print(property.__init__)
-print(Client().set_later.lower())  # [no-member]
+print(Client().set_later.lower())
 print(Mixin().nanana())
 print(Getattr().nananan())
 print(Getattribute().batman())
diff --git a/pylint/test/functional/member_checks.txt b/pylint/test/functional/member_checks.txt
index f599da943..bf5f2c2c8 100644
--- a/pylint/test/functional/member_checks.txt
+++ b/pylint/test/functional/member_checks.txt
@@ -7,7 +7,6 @@ no-member:55:Client.test_bt_types:Instance of 'tuple' has no 'append' member:INF
 no-member:57:Client.test_bt_types:Instance of 'str' has no 'loower' member; maybe 'lower'?:INFERENCE
 no-member:59:Client.test_bt_types:Instance of 'int' has no 'whatever' member:INFERENCE
 no-member:65:Client.test_no_false_positives:Super of 'Client' has no 'misssing' member:INFERENCE
-no-member:86::Instance of 'int' has no 'lower' member:INFERENCE_FAILURE
 no-member:97::Instance of 'Client' has no 'indeed' member:INFERENCE
 no-member:104::Class 'Client' has no 'missing' member:INFERENCE
 no-member:110::Class 'Client' has no 'missing' member:INFERENCE
diff --git a/pylint/test/functional/member_checks_opaque.py b/pylint/test/functional/member_checks_opaque.py
new file mode 100644
index 000000000..d5e71a775
--- /dev/null
+++ b/pylint/test/functional/member_checks_opaque.py
@@ -0,0 +1,6 @@
+# pylint: disable=missing-docstring
+
+import json
+
+
+json.loads('bar').get('baz') # [no-member]
diff --git a/pylint/test/functional/member_checks_opaque.rc b/pylint/test/functional/member_checks_opaque.rc
new file mode 100644
index 000000000..025cd2a0f
--- /dev/null
+++ b/pylint/test/functional/member_checks_opaque.rc
@@ -0,0 +1,2 @@
+[TYPECHECK]
+ignore-on-opaque-inference=n
diff --git a/pylint/test/functional/member_checks_opaque.txt b/pylint/test/functional/member_checks_opaque.txt
new file mode 100644
index 000000000..68af2e6b9
--- /dev/null
+++ b/pylint/test/functional/member_checks_opaque.txt
@@ -0,0 +1 @@
+no-member:6::Instance of 'bool' has no 'get' member:INFERENCE