fix: preserve comments between node and comma in separated lists (#684)

[todor-a]

Fixes #684.

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Transparency note: This PR was prepared with AI assistance (Claude).

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Problem

const clientCardTitle = useMemo(() =>
  <>{cardTitle ?? title}</>
  // eslint-disable-next-line react-hooks/exhaustive-deps
  , [myInfo]);

formats to (comment gone):

const clientCardTitle = useMemo(() =>
  <>{cardTitle ?? title}</>, [myInfo]);

Root cause

gen_node_with_separator (src/generation/generate.rs:8040) wraps each list element with its separator (comma) via an inner_gen closure. gen_node_with_inner_gen then runs the regular trailing-comments path:

items.extend(gen_comments_as_trailing(&node_range, trailing_comments, context));

gen_comments_as_trailing calls get_trailing_comments_same_line, which filters to comments whose start line is <= node_end_line. Anything beyond that — i.e. comments that live between the node and the upcoming comma on subsequent lines — is silently dropped. The next sibling's leading_comments_with_previous doesn't reach back across the comma, so those comments never reappear.

Fix

Before gen_node_with_inner_gen runs, collect the comma token's leading comments (the ones that sit after the node end and after node_end_line), mark them handled via gen_comment_collection, and emit them after the separator inside the same inner_gen invocation:

let between_node_and_comma = if let Some(comma_token) = comma_token {
  gen_comments_between_node_and_comma(value, comma_token, context)
} else {
  PrintItems::new()
};
…
items.push_optional_path(generated_separator);
items.push_optional_path(between_node_and_comma);

Output for issue case:

const clientCardTitle = useMemo(
  () => <>{cardTitle ?? title}</>,
  // eslint-disable-next-line react-hooks/exhaustive-deps
  [myInfo],
);

The fix lives in the shared gen_node_with_separator so it also covers comments before commas in:

• call arguments
• array literals
• object literals
• function parameters
• any other site routed through this helper

Tests

tests/specs/issues/issue0684.txt covers the issue regression plus mixed line/block comments, array/object/parameter cases. Verified against prettier's comment fixtures (before-comma.js, in-list/dangling-comment-in-list.js, first-argument/first-argument.js).

cargo test --release passes.