SIM901: Add rule for unnecessary bool function calls (#90)

Closes #88

README.md

@@ -66,6 +66,7 @@ Simplifying Comparations:
 * [`SIM221`](https://github.com/MartinThoma/flake8-simplify/issues/6): Use 'True' instead of 'a or not a' ([example](#SIM221))
 * [`SIM222`](https://github.com/MartinThoma/flake8-simplify/issues/6): Use 'True' instead of '... or True' ([example](#SIM222))
 * [`SIM223`](https://github.com/MartinThoma/flake8-simplify/issues/6): Use 'False' instead of '... and False' ([example](#SIM223))
+* [`SIM224`](https://github.com/MartinThoma/flake8-simplify/issues/88): Reserved for SIM901 once it's stable
 * [`SIM300`](https://github.com/MartinThoma/flake8-simplify/issues/16): Use 'age == 42' instead of '42 == age' ([example](#SIM300))
 
 Simplifying usage of dictionaries:
@@ -80,11 +81,24 @@ General Code Style:
 * [`SIM106`](https://github.com/MartinThoma/flake8-simplify/issues/8): Handle error-cases first ([example](#SIM106))
 * [`SIM112`](https://github.com/MartinThoma/flake8-simplify/issues/19): Use CAPITAL environment variables ([example](#SIM112))
 
+**Experimental rules:**
+
+Getting rules right for every possible case is hard. I don't want to disturb
+peoples workflows. For this reason, flake8-simplify introduces new rules with
+the `SIM9` prefix. Every new rule will start with SIM9 and stay there for at
+least 6 months. In this time people can give feedback. Once the rule is stable,
+the code will change to another number.
+
+Current experimental rules:
+
+* `SIM901`: Use comparisons directly instead of wrapping them in a `bool(...)` call ([example](#SIM901))
+
+
 You might have good reasons to ignore some rules. To do that, use the standard Flake8 configuration. For example, within the `setup.cfg` file:
 
 ```python
 [flake8]
-ignore = SIM106, SIM113, SIM119
+ignore = SIM106, SIM113, SIM119, SIM9
 ```
 
 
@@ -494,3 +508,18 @@ else:
 # Good
 thing = a_dict.get(key, "default_value")
 ```
+
+### SIM901
+
+This rule will be renamed to `SIM224` after its 6-month trial period is over.
+Please report any issues you encounter with this rule!
+
+The trial period starts on 23rd of January and will end on 23rd of August 2022.
+
+```python
+# Bad
+bool(a == b)
+
+# Good
+a == b
+```

flake8_simplify.py

@@ -107,6 +107,7 @@ def __init__(self, orig: ast.Call) -> None:
     "SIM401 Use '{value} = {dict}.get({key}, {default_value})' "
     "instead of an if-block"
 )
+SIM901 = "SIM901 Use '{better}' instead of '{current}'"
 
 # ast.Constant in Python 3.8, ast.NameConstant in Python 3.6 and 3.7
 BOOL_CONST_TYPES = (ast.Constant, ast.NameConstant)
@@ -1775,12 +1776,51 @@ def _get_sim401(node: ast.If) -> List[Tuple[int, int, str]]:
     return errors
 
 
+def _get_sim901(node: ast.Call) -> List[Tuple[int, int, str]]:
+    """
+    Get a list of all calls of the type "bool(comparison)".
+
+    Call(
+        func=Name(id='bool', ctx=Load()),
+        args=[
+            Compare(
+                left=Name(id='a', ctx=Load()),
+                ops=[Eq()],
+                comparators=[Name(id='b', ctx=Load())],
+            ),
+        ],
+        keywords=[],
+    )
+    """
+    errors: List[Tuple[int, int, str]] = []
+    if not (
+        isinstance(node.func, ast.Name)
+        and node.func.id == "bool"
+        and len(node.args) == 1
+        and isinstance(node.args[0], ast.Compare)
+    ):
+        return errors
+
+    current = to_source(node)
+    better = to_source(node.args[0])
+
+    errors.append(
+        (
+            node.lineno,
+            node.col_offset,
+            SIM901.format(current=current, better=better),
+        )
+    )
+    return errors
+
+
 class Visitor(ast.NodeVisitor):
     def __init__(self) -> None:
         self.errors: List[Tuple[int, int, str]] = []
 
     def visit_Call(self, node: ast.Call) -> Any:
         self.errors += _get_sim115(Call(node))
+        self.errors += _get_sim901(node)
         self.generic_visit(node)
 
     def visit_With(self, node: ast.With) -> Any:

tests/test_simplify.py

@@ -878,3 +878,8 @@ def test_sim401_positive_msg_check_issue89():
             has_sim401 = True
             assert msg == expected_proposal
     assert has_sim401
+
+
+def test_sim901():
+    results = _results("bool(a == b)")
+    assert results == {"1:0 SIM901 Use 'a == b' instead of 'bool(a == b)'"}