fix(json_formatter): handle comments in empty arrays/objects (#1323)

crates/biome_json_formatter/src/comments.rs

@@ -1,11 +1,12 @@
 use crate::prelude::*;
 use biome_diagnostics::category;
 use biome_formatter::comments::{
-    is_alignable_comment, CommentKind, CommentStyle, Comments, SourceComment,
+    is_alignable_comment, CommentKind, CommentPlacement, CommentStyle, Comments, DecoratedComment,
+    SourceComment,
 };
 use biome_formatter::formatter::Formatter;
 use biome_formatter::{write, FormatResult, FormatRule};
-use biome_json_syntax::{JsonLanguage, TextLen};
+use biome_json_syntax::{JsonArrayValue, JsonLanguage, JsonObjectValue, JsonSyntaxKind, TextLen};
 use biome_rowan::SyntaxTriviaPieceComments;
 use biome_suppression::parse_suppression_comment;
 
@@ -82,4 +83,35 @@ impl CommentStyle for JsonCommentStyle {
             CommentKind::Line
         }
     }
+
+    fn place_comment(
+        &self,
+        comment: biome_formatter::comments::DecoratedComment<Self::Language>,
+    ) -> biome_formatter::comments::CommentPlacement<Self::Language> {
+        handle_empty_list_comment(comment)
+    }
+}
+
+fn handle_empty_list_comment(
+    comment: DecoratedComment<JsonLanguage>,
+) -> CommentPlacement<JsonLanguage> {
+    if !matches!(
+        comment.enclosing_node().kind(),
+        JsonSyntaxKind::JSON_ARRAY_VALUE | JsonSyntaxKind::JSON_OBJECT_VALUE,
+    ) {
+        return CommentPlacement::Default(comment);
+    }
+
+    if let Some(array) = JsonArrayValue::cast_ref(comment.enclosing_node()) {
+        if array.elements().is_empty() {
+            return CommentPlacement::dangling(comment.enclosing_node().clone(), comment);
+        }
+    }
+    if let Some(object) = JsonObjectValue::cast_ref(comment.enclosing_node()) {
+        if object.json_member_list().is_empty() {
+            return CommentPlacement::dangling(comment.enclosing_node().clone(), comment);
+        }
+    }
+
+    CommentPlacement::Default(comment)
 }

crates/biome_json_formatter/src/json/value/array_value.rs

@@ -1,7 +1,6 @@
 use crate::prelude::*;
-use biome_formatter::write;
-use biome_json_syntax::JsonArrayValue;
-use biome_json_syntax::JsonArrayValueFields;
+use biome_formatter::{format_args, write};
+use biome_json_syntax::{JsonArrayValue, JsonArrayValueFields};
 
 #[derive(Debug, Clone, Default)]
 pub(crate) struct FormatJsonArrayValue;
@@ -13,13 +12,25 @@ impl FormatNodeRule<JsonArrayValue> for FormatJsonArrayValue {
             r_brack_token,
         } = node.as_fields();
 
+        let should_expand = f.comments().has_dangling_comments(node.syntax());
+
         write!(
             f,
             [
                 l_brack_token.format(),
-                group(&soft_block_indent(&elements.format())),
+                group(&soft_block_indent(&format_args![
+                    elements.format(),
+                    format_dangling_comments(node.syntax())
+                ]))
+                .should_expand(should_expand),
+                line_suffix_boundary(),
                 r_brack_token.format()
             ]
         )
     }
+
+    fn fmt_dangling_comments(&self, _: &JsonArrayValue, _: &mut JsonFormatter) -> FormatResult<()> {
+        // Handled as part of `fmt_fields`
+        Ok(())
+    }
 }

crates/biome_json_formatter/src/json/value/object_value.rs

@@ -8,17 +8,20 @@ pub(crate) struct FormatJsonObjectValue;
 
 impl FormatNodeRule<JsonObjectValue> for FormatJsonObjectValue {
     fn fmt_fields(&self, node: &JsonObjectValue, f: &mut JsonFormatter) -> FormatResult<()> {
-        let should_expand = node.json_member_list().syntax().has_leading_newline();
+        let should_expand = node.json_member_list().syntax().has_leading_newline()
+            || f.comments().has_dangling_comments(node.syntax());
 
         let list = format_with(|f| {
             write!(
                 f,
-                [group(&soft_space_or_block_indent(
-                    &node.json_member_list().format()
-                ))
+                [group(&soft_space_or_block_indent(&format_args![
+                    &node.json_member_list().format(),
+                    format_dangling_comments(node.syntax()),
+                ]))
                 .should_expand(should_expand)]
             )
         });
+
         if f.comments().has_leading_comments(node.syntax()) {
             write!(
                 f,
@@ -47,4 +50,13 @@ impl FormatNodeRule<JsonObjectValue> for FormatJsonObjectValue {
         // Formatted as part of `fmt_fields`
         Ok(())
     }
+
+    fn fmt_dangling_comments(
+        &self,
+        _: &JsonObjectValue,
+        _: &mut JsonFormatter,
+    ) -> FormatResult<()> {
+        // Formatted as part of `fmt_fields`
+        Ok(())
+    }
 }

crates/biome_json_formatter/tests/specs/json/comments/empty_with_comments.json

@@ -0,0 +1,16 @@
+{
+    "object-block": { /* here's a block comment */},
+    "object-line": { // here's a line comment
+    },
+    "object-ownline": {
+        /* here's a block comment */
+        // and a line comment
+    },
+    "array-block": [ /* here's a block comment */],
+    "array-line": [ // here's a line comment
+    ],
+    "array-ownline": [
+        /* here's a block comment */
+        // and a line comment
+    ]
+}

crates/biome_json_formatter/tests/specs/json/comments/empty_with_comments.json.snap

@@ -0,0 +1,66 @@
+---
+source: crates/biome_formatter_test/src/snapshot_builder.rs
+info: json/comments/empty_with_comments.json
+---
+
+# Input
+
+```json
+{
+    "object-block": { /* here's a block comment */},
+    "object-line": { // here's a line comment
+    },
+    "object-ownline": {
+        /* here's a block comment */
+        // and a line comment
+    },
+    "array-block": [ /* here's a block comment */],
+    "array-line": [ // here's a line comment
+    ],
+    "array-ownline": [
+        /* here's a block comment */
+        // and a line comment
+    ]
+}
+```
+
+
+=============================
+
+# Outputs
+
+## Output 1
+
+-----
+Indent style: Tab
+Indent width: 2
+Line ending: LF
+Line width: 80
+-----
+
+```json
+{
+	"object-block": {
+		/* here's a block comment */
+	},
+	"object-line": {
+		// here's a line comment
+	},
+	"object-ownline": {
+		/* here's a block comment */
+		// and a line comment
+	},
+	"array-block": [
+		/* here's a block comment */
+	],
+	"array-line": [
+		// here's a line comment
+	],
+	"array-ownline": [
+		/* here's a block comment */
+		// and a line comment
+	]
+}
+```
+
+