1 files changed, 84 insertions, 0 deletions
diff --git a/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.py b/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.py
new file mode 100644
index 000000000..55dd5688c
--- /dev/null
+++ b/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.py
@@ -0,0 +1,84 @@
+# pylint: disable=missing-docstring, too-few-public-methods, expression-not-assigned, line-too-long
+
+a_dict = {}
+b_dict = {}
+
+for k, v in a_dict.items():
+    print(a_dict[k])  # [unnecessary-dict-index-lookup]
+    print(b_dict[k])  # Should not emit warning, accessing other dictionary
+    a_dict[k] = 123  # Should not emit warning, key access necessary
+    a_dict[k] += 123  # Should not emit warning, key access necessary
+    print(a_dict[k])  # Should not emit warning, v != a_dict[k]
+
+for k, v in b_dict.items():
+    k = "another key"
+    print(b_dict[k])  # This is fine, key reassigned
+
+
+# Tests on comprehensions
+{v: 1 for k, v in a_dict.items() if a_dict[k]}  # [unnecessary-dict-index-lookup]
+{v: 1 for k, v in a_dict.items() if k}  # This is fine, no indexing
+{a_dict[k]: 1 for k, v in a_dict.items() if k}  # [unnecessary-dict-index-lookup]
+{a_dict[k]: 1 for k, v in a_dict.items() if a_dict[k]}  # [unnecessary-dict-index-lookup, unnecessary-dict-index-lookup]
+
+[v for k, v in a_dict.items() if a_dict[k]]  # [unnecessary-dict-index-lookup]
+[v for k, v in a_dict.items() if k]  # This is fine, no indexing
+[a_dict[k] for k, v in a_dict.items() if k]  # [unnecessary-dict-index-lookup]
+[a_dict[k] for k, v in a_dict.items() if a_dict[k]]  # [unnecessary-dict-index-lookup, unnecessary-dict-index-lookup]
+
+
+# Tests on dict attribute of a class
+class Foo:
+    c_dict = {}
+
+
+for k, v in Foo.c_dict.items():
+    print(b_dict[k])  # Should not emit warning, accessing other dictionary
+    print(Foo.c_dict[k])  # [unnecessary-dict-index-lookup]
+    unnecessary = 0 # pylint: disable=invalid-name
+    unnecessary += Foo.c_dict[k]  # [unnecessary-dict-index-lookup]
+    Foo.c_dict[k] += v  # key access necessary
+
+# Tests on comprehensions
+{v: 1 for k, v in Foo.c_dict.items() if Foo.c_dict[k]}  # [unnecessary-dict-index-lookup]
+{v: 1 for k, v in Foo.c_dict.items() if k}  # This is fine, no indexing
+{Foo.c_dict[k]: 1 for k, v in Foo.c_dict.items() if k}  # [unnecessary-dict-index-lookup]
+{Foo.c_dict[k]: 1 for k, v in Foo.c_dict.items() if Foo.c_dict[k]}  # [unnecessary-dict-index-lookup, unnecessary-dict-index-lookup]
+
+[v for k, v in Foo.c_dict.items() if Foo.c_dict[k]]  # [unnecessary-dict-index-lookup]
+[v for k, v in Foo.c_dict.items() if k]  # This is fine, no indexing
+[Foo.c_dict[k] for k, v in Foo.c_dict.items() if k]  # [unnecessary-dict-index-lookup]
+[Foo.c_dict[k] for k, v in Foo.c_dict.items() if Foo.c_dict[k]]  # [unnecessary-dict-index-lookup, unnecessary-dict-index-lookup]
+
+# Test assigning d.items() to a single variable
+d = {1: "a", 2: "b"}
+for item in d.items():
+    print(item[0])
+    print(d[item[0]])  # [unnecessary-dict-index-lookup]
+
+[item[0] for item in d.items()]
+[d[item[0]] for item in d.items()]  # [unnecessary-dict-index-lookup]
+
+# Reassigning single var
+for item in d.items():
+    print(item[0])
+    print(d[item[0]])  # [unnecessary-dict-index-lookup]
+    item = (2, "b")
+    print(d[item[0]])  # This is fine, no warning thrown as key has been reassigned
+
+
+# Test false positive described in #4630
+# (https://github.com/PyCQA/pylint/issues/4630)
+
+d = {'key': 'value'}
+
+for k, _ in d.items():
+    d[k] += 'VALUE'
+    if 'V' in d[k]:  # This is fine, if d[k] is replaced with _, the semantics change
+        print('found V')
+
+
+for k, _ in d.items():
+    if 'V' in d[k]:  # [unnecessary-dict-index-lookup]
+        d[k] = "value"
+        print(d[k])  # This is fine