Implemented new check unnecessary-dict-index-lookup (#4485)

2 files changed, 86 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..901e176b3
--- /dev/null
+++ b/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.py
@@ -0,0 +1,63 @@
+# pylint: disable=missing-docstring, too-few-public-methods, expression-not-assigned, line-too-long
+
+a_dict = dict()
+b_dict = 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])  # [unnecessary-dict-index-lookup]
+    k = "another key"
+    print(a_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]
+    Foo.c_dict[k] += 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
diff --git a/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.txt b/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.txt
new file mode 100644
index 000000000..dedf9e7cc
--- /dev/null
+++ b/tests/functional/u/unnecessary/unnecessary_dict_index_lookup.txt
@@ -0,0 +1,23 @@
+unnecessary-dict-index-lookup:7:10::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:11:10::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:17:36::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:19:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:20:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:20:44::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:22:33::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:24:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:25:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:25:41::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:34:10::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:35:21::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:39:40::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:41:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:42:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:42:52::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:44:37::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:46:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:47:1::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:47:49::Unnecessary dictionary index lookup, use 'v' instead
+unnecessary-dict-index-lookup:53:10::Unnecessary dictionary index lookup, use 'item[1]' instead
+unnecessary-dict-index-lookup:56:1::Unnecessary dictionary index lookup, use 'item[1]' instead
+unnecessary-dict-index-lookup:61:10::Unnecessary dictionary index lookup, use 'item[1]' instead