fix(rome_js_analyze): only emit control flow side-effects for variable declarators with an initializer

crates/rome_js_analyze/src/control_flow/nodes.rs

@@ -11,6 +11,7 @@ mod statement;
 mod switch_stmt;
 mod throw_stmt;
 mod try_catch;
+mod variable;
 mod while_stmt;
 
 pub(super) use block::*;
@@ -26,4 +27,5 @@ pub(super) use statement::*;
 pub(super) use switch_stmt::*;
 pub(super) use throw_stmt::*;
 pub(super) use try_catch::*;
+pub(super) use variable::*;
 pub(super) use while_stmt::*;

crates/rome_js_analyze/src/control_flow/nodes/statement.rs

@@ -1,6 +1,4 @@
-use rome_js_syntax::{
-    JsDebuggerStatement, JsEmptyStatement, JsExpressionStatement, JsVariableStatement,
-};
+use rome_js_syntax::{JsDebuggerStatement, JsEmptyStatement, JsExpressionStatement};
 use rome_rowan::{declare_node_union, AstNode, SyntaxResult};
 
 use crate::control_flow::{
@@ -9,7 +7,7 @@ use crate::control_flow::{
 };
 
 declare_node_union! {
-    pub(in crate::control_flow) JsSimpleStatement = JsDebuggerStatement | JsEmptyStatement | JsExpressionStatement | JsVariableStatement
+    pub(in crate::control_flow) JsSimpleStatement = JsDebuggerStatement | JsEmptyStatement | JsExpressionStatement
 }
 
 pub(in crate::control_flow) struct StatementVisitor;

crates/rome_js_analyze/src/control_flow/nodes/variable.rs

@@ -0,0 +1,29 @@
+use rome_js_syntax::JsVariableStatement;
+use rome_rowan::{AstNode, SyntaxResult};
+
+use crate::control_flow::{
+    visitor::{NodeVisitor, StatementStack},
+    FunctionBuilder,
+};
+
+pub(in crate::control_flow) struct VariableVisitor;
+
+impl<B> NodeVisitor<B> for VariableVisitor {
+    type Node = JsVariableStatement;
+
+    fn enter(
+        node: Self::Node,
+        builder: &mut FunctionBuilder,
+        _: StatementStack,
+    ) -> SyntaxResult<Self> {
+        let declaration = node.declaration()?;
+        for declarator in declaration.declarators() {
+            if let Some(initializer) = declarator?.initializer() {
+                let expr = initializer.expression()?;
+                builder.append_statement().with_node(expr.into_syntax());
+            }
+        }
+
+        Ok(Self)
+    }
+}

crates/rome_js_analyze/src/control_flow/visitor.rs

@@ -102,6 +102,7 @@ declare_visitor! {
         continue_stmt: ContinueVisitor,
         return_stmt: ReturnVisitor,
         throw: ThrowVisitor,
+        variable: VariableVisitor,
     }
 }
 

crates/rome_js_analyze/tests/specs/noDeadCode/JsVariableStatement.js

@@ -0,0 +1,30 @@
+function JsVariableStatement1() {
+    return;
+    var variable;
+}
+
+function JsVariableStatement2() {
+    return;
+    var variable = initializer();
+}
+
+function JsVariableStatement3() {
+    return;
+    let variable;
+}
+
+function JsVariableStatement4() {
+    return;
+    let variable = initializer();
+}
+
+function JsVariableStatement5() {
+    return;
+    const variable = initializer();
+}
+
+function JsVariableStatement6() {
+    return;
+    var variable1 = initializer(),
+        variable2 = initializer();
+}

crates/rome_js_analyze/tests/specs/noDeadCode/JsVariableStatement.js.snap

@@ -0,0 +1,103 @@
+---
+source: crates/rome_js_analyze/tests/spec_tests.rs
+assertion_line: 98
+expression: JsVariableStatement.js
+---
+# Input
+```js
+function JsVariableStatement1() {
+    return;
+    var variable;
+}
+
+function JsVariableStatement2() {
+    return;
+    var variable = initializer();
+}
+
+function JsVariableStatement3() {
+    return;
+    let variable;
+}
+
+function JsVariableStatement4() {
+    return;
+    let variable = initializer();
+}
+
+function JsVariableStatement5() {
+    return;
+    const variable = initializer();
+}
+
+function JsVariableStatement6() {
+    return;
+    var variable1 = initializer(),
+        variable2 = initializer();
+}
+
+```
+
+# Diagnostics
+```
+warning[noDeadCode]: This code is unreachable
+  ┌─ JsVariableStatement.js:8:20
+  │
+7 │     return;
+  │     ------- This statement will return from the function ...
+8 │     var variable = initializer();
+  │                    ------------- ... before it can reach this code
+
+
+```
+
+```
+warning[noDeadCode]: This code is unreachable
+   ┌─ JsVariableStatement.js:18:20
+   │
+17 │     return;
+   │     ------- This statement will return from the function ...
+18 │     let variable = initializer();
+   │                    ------------- ... before it can reach this code
+
+
+```
+
+```
+warning[noDeadCode]: This code is unreachable
+   ┌─ JsVariableStatement.js:23:22
+   │
+22 │     return;
+   │     ------- This statement will return from the function ...
+23 │     const variable = initializer();
+   │                      ------------- ... before it can reach this code
+
+
+```
+
+```
+warning[noDeadCode]: This code is unreachable
+   ┌─ JsVariableStatement.js:28:21
+   │
+27 │     return;
+   │     ------- This statement will return from the function ...
+28 │     var variable1 = initializer(),
+   │                     ------------- ... before it can reach this code
+
+
+```
+
+```
+warning[noDeadCode]: This code is unreachable
+   ┌─ JsVariableStatement.js:29:21
+   │
+27 │     return;
+   │     ------- This statement will return from the function ...
+28 │     var variable1 = initializer(),
+29 │         variable2 = initializer();
+   │                     ------------- ... before it can reach this code
+
+
+```
+
+