feat(biome_js_analyze): implement noMultiStr rule (#8218)

Hiroki Okada · web-flow · commit 91484d1d5309 · 2025-11-22T17:04:16.000Z
diff --git a/.changeset/happy-mirrors-grow.md b/.changeset/happy-mirrors-grow.md
@@ -0,0 +1,21 @@
+---
+"@biomejs/biome": patch
+---
+
+Added the [`noMultiStr`](https://biomejs.dev/linter/rules/no-multi-str) rule, which disallows creating multiline strings by escaping newlines.
+
+**Invalid:**
+
+```js
+const foo =
+	"Line 1\n\
+Line 2";
+```
+
+**Valid:**
+
+```js
+const foo = "Line 1\nLine 2";
+const bar = `Line 1
+Line 2`;
+```
diff --git a/crates/biome_cli/src/execute/migrate/eslint_any_rule_to_biome.rs b/crates/biome_cli/src/execute/migrate/eslint_any_rule_to_biome.rs
diff --git a/crates/biome_configuration/src/analyzer/linter/rules.rs b/crates/biome_configuration/src/analyzer/linter/rules.rs
diff --git a/crates/biome_diagnostics_categories/src/categories.rs b/crates/biome_diagnostics_categories/src/categories.rs
@@ -179,6 +179,7 @@ define_categories! {
     "lint/nursery/noLeakedRender": "https://biomejs.dev/linter/rules/no-leaked-render",
     "lint/nursery/noMissingGenericFamilyKeyword": "https://biomejs.dev/linter/rules/no-missing-generic-family-keyword",
     "lint/nursery/noMisusedPromises": "https://biomejs.dev/linter/rules/no-misused-promises",
+    "lint/nursery/noMultiStr": "https://biomejs.dev/linter/rules/no-multi-str",
     "lint/nursery/noNextAsyncClientComponent": "https://biomejs.dev/linter/rules/no-next-async-client-component",
     "lint/nursery/noParametersOnlyUsedInRecursion": "https://biomejs.dev/linter/rules/no-parameters-only-used-in-recursion",
     "lint/nursery/noReactForwardRef": "https://biomejs.dev/linter/rules/no-react-forward-ref",
diff --git a/crates/biome_js_analyze/src/lint/nursery.rs b/crates/biome_js_analyze/src/lint/nursery.rs
@@ -14,6 +14,7 @@ pub mod no_increment_decrement;
 pub mod no_jsx_literals;
 pub mod no_leaked_render;
 pub mod no_misused_promises;
+pub mod no_multi_str;
 pub mod no_next_async_client_component;
 pub mod no_parameters_only_used_in_recursion;
 pub mod no_react_forward_ref;
@@ -42,4 +43,4 @@ pub mod use_sorted_classes;
 pub mod use_spread;
 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_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_empty_source :: NoEmptySource , self :: no_equals_to_null :: NoEqualsToNull , 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_leaked_render :: NoLeakedRender , self :: no_misused_promises :: NoMisusedPromises , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_shadow :: NoShadow , self :: no_sync_scripts :: NoSyncScripts , self :: no_ternary :: NoTernary , 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_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_find :: UseFind , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , 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_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_empty_source :: NoEmptySource , self :: no_equals_to_null :: NoEqualsToNull , 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_leaked_render :: NoLeakedRender , self :: no_misused_promises :: NoMisusedPromises , self :: no_multi_str :: NoMultiStr , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_shadow :: NoShadow , self :: no_sync_scripts :: NoSyncScripts , self :: no_ternary :: NoTernary , 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_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_find :: UseFind , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , self :: use_vue_define_macros_order :: UseVueDefineMacrosOrder , self :: use_vue_multi_word_component_names :: UseVueMultiWordComponentNames ,] } }
diff --git a/crates/biome_js_analyze/src/lint/nursery/no_multi_str.rs b/crates/biome_js_analyze/src/lint/nursery/no_multi_str.rs
@@ -0,0 +1,74 @@
+use biome_analyze::{
+    Ast, Rule, RuleDiagnostic, RuleSource, context::RuleContext, declare_lint_rule,
+};
+use biome_console::markup;
+use biome_diagnostics::Severity;
+use biome_js_syntax::JsStringLiteralExpression;
+use biome_rowan::AstNode;
+use biome_rule_options::no_multi_str::NoMultiStrOptions;
+
+declare_lint_rule! {
+    /// Disallow creating multiline strings by escaping newlines.
+    ///
+    /// Escaping newlines to create multiline strings is discouraged because it
+    /// can lead to subtle errors caused by unexpected whitespace after the
+    /// backslash.
+    ///
+    /// ## Examples
+    ///
+    /// ### Invalid
+    ///
+    /// ```js,expect_diagnostic
+    /// const foo =
+    ///     "Line 1\n\
+    /// Line 2";
+    /// ```
+    ///
+    /// ### Valid
+    ///
+    /// ```js
+    /// const foo = "Line 1\nLine 2";
+    /// ```
+    ///
+    /// ```js
+    /// const bar = `Line 1
+    /// Line 2`;
+    /// ```
+    pub NoMultiStr {
+        version: "next",
+        name: "noMultiStr",
+        language: "js",
+        recommended: false,
+        sources: &[RuleSource::Eslint("no-multi-str").same()],
+        severity: Severity::Error,
+    }
+}
+
+impl Rule for NoMultiStr {
+    type Query = Ast<JsStringLiteralExpression>;
+    type State = ();
+    type Signals = Option<Self::State>;
+    type Options = NoMultiStrOptions;
+
+    fn run(ctx: &RuleContext<Self>) -> Self::Signals {
+        let node = ctx.query();
+        let text = node.value_token().ok()?.token_text_trimmed();
+
+        if text.contains("\\\n") || text.contains("\\\r\n") {
+            return Some(());
+        }
+
+        None
+    }
+
+    fn diagnostic(ctx: &RuleContext<Self>, _state: &Self::State) -> Option<RuleDiagnostic> {
+        let node = ctx.query();
+        Some(RuleDiagnostic::new(
+            rule_category!(),
+            node.range(),
+            markup! {
+                "Escaping newlines to create multiline strings is disallowed."
+            },
+        ))
+    }
+}
diff --git a/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/invalid.js b/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/invalid.js
@@ -0,0 +1,4 @@
+/* should generate diagnostics */
+const foo =
+	"Line 1\n\
+Line 2";
diff --git a/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/invalid.js.snap b/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/invalid.js.snap
@@ -0,0 +1,29 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: invalid.js
+---
+# Input
+```js
+/* should generate diagnostics */
+const foo =
+	"Line 1\n\
+Line 2";
+
+```
+
+# Diagnostics
+```
+invalid.js:3:2 lint/nursery/noMultiStr ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  × Escaping newlines to create multiline strings is disallowed.
+  
+    1 │ /* should generate diagnostics */
+    2 │ const foo =
+  > 3 │ 	"Line 1\n\
+      │ 	^^^^^^^^^^
+  > 4 │ Line 2";
+      │ ^^^^^^^
+    5 │ 
+  
+
+```
diff --git a/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/valid.js b/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/valid.js
@@ -0,0 +1,4 @@
+/* should not generate diagnostics */
+const foo = "Line 1\nLine 2";
+const bar = `Line 1
+Line 2`;
diff --git a/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/valid.js.snap b/crates/biome_js_analyze/tests/specs/nursery/noMultiStr/valid.js.snap
@@ -0,0 +1,12 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: valid.js
+---
+# Input
+```js
+/* should not generate diagnostics */
+const foo = "Line 1\nLine 2";
+const bar = `Line 1
+Line 2`;
+
+```
diff --git a/crates/biome_rule_options/src/lib.rs b/crates/biome_rule_options/src/lib.rs
@@ -129,6 +129,7 @@ pub mod no_misplaced_assertion;
 pub mod no_misrefactored_shorthand_assign;
 pub mod no_missing_var_function;
 pub mod no_misused_promises;
+pub mod no_multi_str;
 pub mod no_namespace;
 pub mod no_namespace_import;
 pub mod no_negation_else;
diff --git a/crates/biome_rule_options/src/no_multi_str.rs b/crates/biome_rule_options/src/no_multi_str.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 NoMultiStrOptions {}
diff --git a/packages/@biomejs/backend-jsonrpc/src/workspace.ts b/packages/@biomejs/backend-jsonrpc/src/workspace.ts
diff --git a/packages/@biomejs/biome/configuration_schema.json b/packages/@biomejs/biome/configuration_schema.json
