Add flake8-pie PIE800: no-unnecessary-spread (#1881)

Checks for unnecessary spreads, like `{**foo, **{"bar": True}}`
rel: https://github.com/charliermarsh/ruff/issues/1879
rel: https://github.com/charliermarsh/ruff/issues/1543

README.md

@@ -1151,6 +1151,7 @@ For more, see [flake8-pie](https://pypi.org/project/flake8-pie/) on PyPI.
 | PIE790 | no-unnecessary-pass | Unnecessary `pass` statement | 🛠 |
 | PIE794 | dupe-class-field-definitions | Class field `{name}` is defined multiple times | 🛠 |
 | PIE796 | prefer-unique-enums | Enum contains duplicate value: `{value}` |  |
+| PIE800 | no-unnecessary-spread | Unnecessary spread `**` |  |
 | PIE804 | no-unnecessary-dict-kwargs | Unnecessary `dict` kwargs |  |
 | PIE807 | prefer-list-builtin | Prefer `list` over useless lambda | 🛠 |
 

resources/test/fixtures/flake8_pie/PIE800.py

@@ -0,0 +1,17 @@
+{"foo": 1, **{"bar": 1}}  # PIE800
+
+foo({**foo, **{"bar": True}})  # PIE800
+
+{**foo, **{"bar": 10}}  # PIE800
+
+{**foo, **buzz, **{bar: 10}}  # PIE800
+
+{**foo,    "bar": True  }  # OK
+
+{"foo": 1, "buzz": {"bar": 1}}  # OK
+
+{**foo,    "bar": True  }  # OK
+
+Table.objects.filter(inst=inst, **{f"foo__{bar}__exists": True})  # OK
+
+buzz = {**foo, "bar": { 1: 2 }}  # OK

ruff.schema.json

@@ -1553,6 +1553,7 @@
         "PIE796",
         "PIE8",
         "PIE80",
+        "PIE800",
         "PIE804",
         "PIE807",
         "PL",

src/checkers/ast.rs

@@ -2596,6 +2596,10 @@ where
                 {
                     pyflakes::rules::repeated_keys(self, keys, values);
                 }
+
+                if self.settings.rules.enabled(&Rule::NoUnnecessarySpread) {
+                    flake8_pie::rules::no_unnecessary_spread(self, keys, values);
+                }
             }
             ExprKind::Yield { .. } => {
                 if self.settings.rules.enabled(&Rule::YieldOutsideFunction) {

src/registry.rs

@@ -413,6 +413,7 @@ ruff_macros::define_rule_mapping!(
     PIE790 => violations::NoUnnecessaryPass,
     PIE794 => violations::DupeClassFieldDefinitions,
     PIE796 => violations::PreferUniqueEnums,
+    PIE800 => violations::NoUnnecessarySpread,
     PIE804 => violations::NoUnnecessaryDictKwargs,
     PIE807 => violations::PreferListBuiltin,
     // flake8-commas

src/rules/flake8_pie/mod.rs

@@ -12,11 +12,12 @@ mod tests {
     use crate::registry::Rule;
     use crate::settings;
 
-    #[test_case(Rule::NoUnnecessaryPass, Path::new("PIE790.py"); "PIE790")]
     #[test_case(Rule::DupeClassFieldDefinitions, Path::new("PIE794.py"); "PIE794")]
-    #[test_case(Rule::PreferUniqueEnums, Path::new("PIE796.py"); "PIE796")]
     #[test_case(Rule::NoUnnecessaryDictKwargs, Path::new("PIE804.py"); "PIE804")]
+    #[test_case(Rule::NoUnnecessaryPass, Path::new("PIE790.py"); "PIE790")]
+    #[test_case(Rule::NoUnnecessarySpread, Path::new("PIE800.py"); "PIE800")]
     #[test_case(Rule::PreferListBuiltin, Path::new("PIE807.py"); "PIE807")]
+    #[test_case(Rule::PreferUniqueEnums, Path::new("PIE796.py"); "PIE796")]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.code(), path.to_string_lossy());
         let diagnostics = test_path(

src/rules/flake8_pie/rules.rs

@@ -153,6 +153,21 @@ where
     }
 }
 
+/// PIE800
+pub fn no_unnecessary_spread(checker: &mut Checker, keys: &[Option<Expr>], values: &[Expr]) {
+    for item in keys.iter().zip(values.iter()) {
+        if let (None, value) = item {
+            // We only care about when the key is None which indicates a spread `**`
+            // inside a dict.
+            if let ExprKind::Dict { .. } = value.node {
+                let diagnostic =
+                    Diagnostic::new(violations::NoUnnecessarySpread, Range::from_located(value));
+                checker.diagnostics.push(diagnostic);
+            }
+        }
+    }
+}
+
 /// Return `true` if a key is a valid keyword argument name.
 fn is_valid_kwarg_name(key: &Expr) -> bool {
     if let ExprKind::Constant {

src/rules/flake8_pie/snapshots/ruff__rules__flake8_pie__tests__PIE800_PIE800.py.snap

@@ -0,0 +1,45 @@
+---
+source: src/rules/flake8_pie/mod.rs
+expression: diagnostics
+---
+- kind:
+    NoUnnecessarySpread: ~
+  location:
+    row: 1
+    column: 13
+  end_location:
+    row: 1
+    column: 23
+  fix: ~
+  parent: ~
+- kind:
+    NoUnnecessarySpread: ~
+  location:
+    row: 3
+    column: 14
+  end_location:
+    row: 3
+    column: 27
+  fix: ~
+  parent: ~
+- kind:
+    NoUnnecessarySpread: ~
+  location:
+    row: 5
+    column: 10
+  end_location:
+    row: 5
+    column: 21
+  fix: ~
+  parent: ~
+- kind:
+    NoUnnecessarySpread: ~
+  location:
+    row: 7
+    column: 18
+  end_location:
+    row: 7
+    column: 27
+  fix: ~
+  parent: ~
+

src/violations.rs

@@ -4984,6 +4984,16 @@ impl Violation for PreferUniqueEnums {
     }
 }
 
+define_violation!(
+    pub struct NoUnnecessarySpread;
+);
+impl Violation for NoUnnecessarySpread {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Unnecessary spread `**`")
+    }
+}
+
 define_violation!(
     pub struct NoUnnecessaryDictKwargs;
 );