fix(rome_js_formatter): 🐛 preserve new-lines after directives (#2500)

crates/rome_formatter/src/format_element.rs

@@ -819,30 +819,30 @@ where
     join_elements_with(elements, hard_line_break)
 }
 
+/// Get the number of line breaks between two consecutive SyntaxNodes in the tree
+pub fn get_lines_before<L: Language>(next_node: &SyntaxNode<L>) -> usize {
+    // Count the newlines in the leading trivia of the next node
+    if let Some(leading_trivia) = next_node.first_leading_trivia() {
+        leading_trivia
+            .pieces()
+            .take_while(|piece| {
+                // Stop at the first comment piece, the comment printer
+                // will handle newlines between the comment and the node
+                !piece.is_comments()
+            })
+            .filter(|piece| piece.is_newline())
+            .count()
+    } else {
+        0
+    }
+}
+
 #[inline]
 pub fn join_elements_with<I, L>(elements: I, separator: fn() -> FormatElement) -> FormatElement
 where
     I: IntoIterator<Item = (SyntaxNode<L>, FormatElement)>,
     L: Language,
 {
-    /// Get the number of line breaks between two consecutive SyntaxNodes in the tree
-    fn get_lines_before<L: Language>(next_node: &SyntaxNode<L>) -> usize {
-        // Count the newlines in the leading trivia of the next node
-        if let Some(leading_trivia) = next_node.first_leading_trivia() {
-            leading_trivia
-                .pieces()
-                .take_while(|piece| {
-                    // Stop at the first comment piece, the comment printer
-                    // will handle newlines between the comment and the node
-                    !piece.is_comments()
-                })
-                .filter(|piece| piece.is_newline())
-                .count()
-        } else {
-            0
-        }
-    }
-
     concat_elements(IntersperseFn::new(
         elements.into_iter(),
         |_, next_node, next_elem| {

crates/rome_js_formatter/src/js/lists/directive_list.rs

@@ -1,14 +1,36 @@
 use crate::{empty_element, format_elements, hard_line_break, Format, FormatElement, Formatter};
-use rome_formatter::FormatResult;
+use rome_formatter::{empty_line, format_element::get_lines_before, FormatResult};
 use rome_js_syntax::JsDirectiveList;
-use rome_rowan::AstNodeList;
+use rome_rowan::{AstNode, AstNodeList};
 
 impl Format for JsDirectiveList {
     fn format(&self, formatter: &Formatter) -> FormatResult<FormatElement> {
         if !self.is_empty() {
+            let syntax_node = self.syntax();
+            let next_sibling = syntax_node.next_sibling();
+            // if next_sibling's first leading_trivia has more than one new_line, we should add an extra empty line at the end of
+            // JsDirectiveList, for example:
+            //```js
+            // "use strict"; <- first leading new_line
+            //  			 <- second leading new_line
+            // function foo() {
+
+            // }
+            //```
+            // so we should keep an extra empty line after JsDirectiveList
+            let need_extra_empty_line = if let Some(next_sibling) = next_sibling {
+                get_lines_before(&next_sibling) > 1
+            } else {
+                false
+            };
             Ok(format_elements![
                 formatter.format_list(self.clone()),
-                hard_line_break()
+                hard_line_break(),
+                if need_extra_empty_line {
+                    empty_line()
+                } else {
+                    empty_element()
+                }
             ])
         } else {
             Ok(empty_element())

crates/rome_js_formatter/tests/specs/js/module/newlines.js.snap

@@ -1,6 +1,8 @@
 ---
 source: crates/rome_js_formatter/tests/spec_test.rs
+assertion_line: 242
 expression: newlines.js
+
 ---
 # Input
 "directive";
@@ -97,6 +99,7 @@ Quote style: Double Quotes
 "directive";
 
 "directive";
+
 statement();
 // comment
 statement();

crates/rome_js_formatter/tests/specs/prettier/js/directives/newline.js.snap

@@ -1,6 +1,6 @@
 ---
 source: crates/rome_js_formatter/tests/prettier_tests.rs
-assertion_line: 144
+assertion_line: 175
 expression: newline.js
 
 ---
@@ -21,6 +21,7 @@ a();
 /* @flow */
 
 "use strict";
+
 import a from "a";
 
 a();

crates/rome_js_formatter/tests/specs/prettier/js/directives/test.js.snap

@@ -1,6 +1,8 @@
 ---
 source: crates/rome_js_formatter/tests/prettier_tests.rs
+assertion_line: 175
 expression: test.js
+
 ---
 # Input
 ```js
@@ -35,6 +37,7 @@ function f4() {
 # Output
 ```js
 "use strict";
+
 function f1() {
   "use strict";
 }
@@ -46,11 +49,13 @@ function f2() {
 
 function f3() {
   "ngInject";
+
   Object.assign(this, { $log, $uibModal });
 }
 
 function f4() {
   "ngInject";
+
   Object.assign(this, { $log, $uibModal });
 }