fix: remove unexpected new line when adding a readonly class property

.changeset/fuzzy-dragons-invent.md

@@ -0,0 +1,5 @@
+---
+"@biomejs/biome": patch
+---
+
+Fixed [#7948](https://github.com/biomejs/biome/issues/7948): The `useReadonlyClassProperties` code fix when `checkAllProperties` is enabled will no longer insert a newline after `readonly` and the class property.

crates/biome_js_analyze/src/lint/style/use_readonly_class_properties.rs

@@ -219,7 +219,7 @@ impl Rule for UseReadonlyClassProperties {
                 );
 
                 if let Some(modified_member) =
-                    extract_property_member_name_trimmed_whitespace(member_name.clone())
+                    extract_class_member_name_trimmed_whitespace(member_name.clone())
                 {
                     let mut builder =
                         make::js_property_class_member(replace_modifiers, modified_member);
@@ -353,10 +353,10 @@ fn collect_non_readonly_constructor_parameters(
         .collect()
 }
 
-/// Removes leading whitespace from `#privateProperty` names. Without this, the name might include
-/// unwanted whitespace (e.g., "\n #privateProperty"). This ensures that when adding modifiers like
-/// `readonly`, they are appended correctly without being affected by the whitespace.
-fn extract_property_member_name_trimmed_whitespace(
+/// Removes leading trivia from class member names. Without this, the name might include
+/// unwanted trivia (e.g., "\n #privateProperty"). This ensures that when adding modifiers like
+/// `readonly`, they are appended correctly without being affected by the trivia.
+fn extract_class_member_name_trimmed_whitespace(
     member_name: AnyJsClassMemberName,
 ) -> Option<AnyJsClassMemberName> {
     match member_name {
@@ -367,6 +367,13 @@ fn extract_property_member_name_trimmed_whitespace(
 
             Some(AnyJsClassMemberName::JsPrivateClassMemberName(trimmed))
         }
+        AnyJsClassMemberName::JsLiteralMemberName(name) => {
+            let value = name.value().ok()?;
+            let new_value = value.with_leading_trivia([]);
+            let trimmed = name.replace_token_discard_trivia(value, new_value)?;
+
+            Some(AnyJsClassMemberName::JsLiteralMemberName(trimmed))
+        }
         _ => Some(member_name),
     }
 }

crates/biome_js_analyze/tests/specs/style/useReadonlyClassProperties/invalid_checkAllPropertiesTrue.ts

@@ -3,6 +3,7 @@ class Example1 {
 	private prop1: number = 42;
 	protected prop2: string;
 	public prop3: string;
+	prop4: string;
 }
 
 class Example2 {