feat(js_analyze): implement noFloatingClasses

.changeset/wild-times-design.md

@@ -0,0 +1,11 @@
+---
+"@biomejs/biome": patch
+---
+
+Added the nursery rule [`noFloatingClasses`](https://biomejs.dev/linter/rules/no-floating-classes). Disallow `new` operators outside of assignments or comparisons.
+
+**Invalid:**
+
+```js
+new Date();
+```

crates/biome_js_analyze/src/lint/nursery.rs

@@ -13,6 +13,7 @@ pub mod no_duplicated_spread_props;
 pub mod no_empty_source;
 pub mod no_equals_to_null;
 pub mod no_excessive_lines_per_file;
+pub mod no_floating_classes;
 pub mod no_floating_promises;
 pub mod no_for_in;
 pub mod no_import_cycles;
@@ -63,4 +64,4 @@ pub mod use_spread;
 pub mod use_vue_consistent_define_props_declaration;
 pub mod use_vue_define_macros_order;
 pub mod use_vue_multi_word_component_names;
-declare_lint_group! { pub Nursery { name : "nursery" , rules : [self :: no_ambiguous_anchor_text :: NoAmbiguousAnchorText , self :: no_before_interactive_script_outside_document :: NoBeforeInteractiveScriptOutsideDocument , self :: no_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_div_regex :: NoDivRegex , self :: no_duplicate_enum_values :: NoDuplicateEnumValues , self :: no_duplicated_spread_props :: NoDuplicatedSpreadProps , self :: no_empty_source :: NoEmptySource , self :: no_equals_to_null :: NoEqualsToNull , self :: no_excessive_lines_per_file :: NoExcessiveLinesPerFile , self :: no_floating_promises :: NoFloatingPromises , self :: no_for_in :: NoForIn , self :: no_import_cycles :: NoImportCycles , self :: no_increment_decrement :: NoIncrementDecrement , self :: no_jsx_literals :: NoJsxLiterals , self :: no_jsx_props_bind :: NoJsxPropsBind , self :: no_leaked_render :: NoLeakedRender , self :: no_misused_promises :: NoMisusedPromises , self :: no_multi_assign :: NoMultiAssign , self :: no_multi_str :: NoMultiStr , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_proto :: NoProto , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_return_assign :: NoReturnAssign , self :: no_script_url :: NoScriptUrl , self :: no_shadow :: NoShadow , self :: no_sync_scripts :: NoSyncScripts , self :: no_ternary :: NoTernary , self :: no_undeclared_env_vars :: NoUndeclaredEnvVars , self :: no_unknown_attribute :: NoUnknownAttribute , self :: no_unnecessary_conditions :: NoUnnecessaryConditions , self :: no_unresolved_imports :: NoUnresolvedImports , self :: no_unused_expressions :: NoUnusedExpressions , self :: no_useless_catch_binding :: NoUselessCatchBinding , self :: no_useless_undefined :: NoUselessUndefined , self :: no_vue_data_object_declaration :: NoVueDataObjectDeclaration , self :: no_vue_duplicate_keys :: NoVueDuplicateKeys , self :: no_vue_options_api :: NoVueOptionsApi , self :: no_vue_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: no_vue_setup_props_reactivity_loss :: NoVueSetupPropsReactivityLoss , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_await_thenable :: UseAwaitThenable , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_destructuring :: UseDestructuring , self :: use_error_cause :: UseErrorCause , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_find :: UseFind , self :: use_inline_script_id :: UseInlineScriptId , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_regexp_exec :: UseRegexpExec , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , self :: use_vue_consistent_define_props_declaration :: UseVueConsistentDefinePropsDeclaration , self :: use_vue_define_macros_order :: UseVueDefineMacrosOrder , self :: use_vue_multi_word_component_names :: UseVueMultiWordComponentNames ,] } }
+declare_lint_group! { pub Nursery { name : "nursery" , rules : [self :: no_ambiguous_anchor_text :: NoAmbiguousAnchorText , self :: no_before_interactive_script_outside_document :: NoBeforeInteractiveScriptOutsideDocument , self :: no_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_div_regex :: NoDivRegex , self :: no_duplicate_enum_values :: NoDuplicateEnumValues , self :: no_duplicated_spread_props :: NoDuplicatedSpreadProps , self :: no_empty_source :: NoEmptySource , self :: no_equals_to_null :: NoEqualsToNull , self :: no_excessive_lines_per_file :: NoExcessiveLinesPerFile , self :: no_floating_classes :: NoFloatingClasses , self :: no_floating_promises :: NoFloatingPromises , self :: no_for_in :: NoForIn , self :: no_import_cycles :: NoImportCycles , self :: no_increment_decrement :: NoIncrementDecrement , self :: no_jsx_literals :: NoJsxLiterals , self :: no_jsx_props_bind :: NoJsxPropsBind , self :: no_leaked_render :: NoLeakedRender , self :: no_misused_promises :: NoMisusedPromises , self :: no_multi_assign :: NoMultiAssign , self :: no_multi_str :: NoMultiStr , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_proto :: NoProto , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_return_assign :: NoReturnAssign , self :: no_script_url :: NoScriptUrl , self :: no_shadow :: NoShadow , self :: no_sync_scripts :: NoSyncScripts , self :: no_ternary :: NoTernary , self :: no_undeclared_env_vars :: NoUndeclaredEnvVars , self :: no_unknown_attribute :: NoUnknownAttribute , self :: no_unnecessary_conditions :: NoUnnecessaryConditions , self :: no_unresolved_imports :: NoUnresolvedImports , self :: no_unused_expressions :: NoUnusedExpressions , self :: no_useless_catch_binding :: NoUselessCatchBinding , self :: no_useless_undefined :: NoUselessUndefined , self :: no_vue_data_object_declaration :: NoVueDataObjectDeclaration , self :: no_vue_duplicate_keys :: NoVueDuplicateKeys , self :: no_vue_options_api :: NoVueOptionsApi , self :: no_vue_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: no_vue_setup_props_reactivity_loss :: NoVueSetupPropsReactivityLoss , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_await_thenable :: UseAwaitThenable , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_destructuring :: UseDestructuring , self :: use_error_cause :: UseErrorCause , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_find :: UseFind , self :: use_inline_script_id :: UseInlineScriptId , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_regexp_exec :: UseRegexpExec , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , self :: use_vue_consistent_define_props_declaration :: UseVueConsistentDefinePropsDeclaration , self :: use_vue_define_macros_order :: UseVueDefineMacrosOrder , self :: use_vue_multi_word_component_names :: UseVueMultiWordComponentNames ,] } }

crates/biome_js_analyze/src/lint/nursery/no_floating_classes.rs

@@ -0,0 +1,80 @@
+use biome_analyze::{
+    Ast, Rule, RuleDiagnostic, RuleSource, context::RuleContext, declare_lint_rule,
+};
+use biome_console::markup;
+use biome_js_syntax::{JsNewExpression, JsSyntaxKind};
+use biome_rowan::{AstNode, SyntaxNodeOptionExt};
+use biome_rule_options::no_floating_classes::NoFloatingClassesOptions;
+
+declare_lint_rule! {
+    /// Disallow `new` operators outside of assignments or comparisons.
+    ///
+    /// The goal of using `new` with a constructor is typically to create an object of a particular type and store that object in a variable, such as:
+    ///
+    /// ```js
+    /// const person = new Person();
+    /// ```
+    ///
+    /// It's less common to use `new` and not store the result, such as:
+    ///
+    /// ```js,ignore
+    /// new Person();
+    /// ```
+    ///
+    /// In this case, the created object is thrown away because its reference isn't stored anywhere, and in many cases, this means that the constructor should be replaced with a function that doesn't require `new` to be used.
+    ///
+    /// ## Examples
+    ///
+    /// ### Invalid
+    ///
+    /// ```js,expect_diagnostic
+    /// new Thing();
+    /// ```
+    ///
+    /// ### Valid
+    ///
+    /// ```js
+    /// const thing = new Thing();
+    /// ```
+    ///
+    pub NoFloatingClasses {
+        version: "next",
+        name: "noFloatingClasses",
+        language: "js",
+        recommended: false,
+        sources: &[RuleSource::Eslint("no-new").same()],
+    }
+}
+
+impl Rule for NoFloatingClasses {
+    type Query = Ast<JsNewExpression>;
+    type State = ();
+    type Signals = Option<Self::State>;
+    type Options = NoFloatingClassesOptions;
+
+    fn run(ctx: &RuleContext<Self>) -> Self::Signals {
+        let node = ctx.query();
+
+        node.syntax()
+            .parent()
+            .kind()
+            .is_some_and(|kind| kind == JsSyntaxKind::JS_EXPRESSION_STATEMENT)
+            .then_some(())
+    }
+
+    fn diagnostic(ctx: &RuleContext<Self>, _state: &Self::State) -> Option<RuleDiagnostic> {
+        let node = ctx.query();
+        Some(
+            RuleDiagnostic::new(
+                rule_category!(),
+                node.range(),
+                markup! {
+                    "Using the `new` operator outside of assignments or comparisons is not allowed."
+                },
+            )
+            .note(markup! {
+                "The created object is thrown away because its reference isn't stored anywhere. Assign the object to a variable or replace with a function that doesn't require `new` to be used."
+            }),
+        )
+    }
+}

crates/biome_js_analyze/tests/specs/nursery/noFloatingClasses/invalid.js

@@ -0,0 +1,2 @@
+/* should generate diagnostics */
+new Date()

crates/biome_js_analyze/tests/specs/nursery/noFloatingClasses/invalid.js.snap

@@ -0,0 +1,28 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: invalid.js
+---
+# Input
+```js
+/* should generate diagnostics */
+new Date()
+
+```
+
+# Diagnostics
+```
+invalid.js:2:1 lint/nursery/noFloatingClasses ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Using the `new` operator outside of assignments or comparisons is not allowed.
+
+    1 │ /* should generate diagnostics */
+  > 2 │ new Date()
+      │ ^^^^^^^^^^
+    3 │ 
+
+  i The created object is thrown away because its reference isn't stored anywhere. Assign the object to a variable or replace with a function that doesn't require `new` to be used.
+
+  i This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
+
+
+```

crates/biome_js_analyze/tests/specs/nursery/noFloatingClasses/valid.js

@@ -0,0 +1,7 @@
+/* should not generate diagnostics */
+var a = new Date()
+
+var a;
+if (a === new Date()) {
+	a = false;
+}

crates/biome_js_analyze/tests/specs/nursery/noFloatingClasses/valid.js.snap

@@ -0,0 +1,15 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: valid.js
+---
+# Input
+```js
+/* should not generate diagnostics */
+var a = new Date()
+
+var a;
+if (a === new Date()) {
+	a = false;
+}
+
+```

crates/biome_rule_options/src/lib.rs

@@ -98,6 +98,7 @@ pub mod no_extra_boolean_cast;
 pub mod no_extra_non_null_assertion;
 pub mod no_fallthrough_switch_clause;
 pub mod no_flat_map_identity;
+pub mod no_floating_classes;
 pub mod no_floating_promises;
 pub mod no_focused_tests;
 pub mod no_for_each;

crates/biome_rule_options/src/no_floating_classes.rs

@@ -0,0 +1,6 @@
+use biome_deserialize_macros::{Deserializable, Merge};
+use serde::{Deserialize, Serialize};
+#[derive(Default, Clone, Debug, Deserialize, Deserializable, Merge, Eq, PartialEq, Serialize)]
+#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
+#[serde(rename_all = "camelCase", deny_unknown_fields, default)]
+pub struct NoFloatingClassesOptions {}