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fix(formatter): only expand mapped types when newline immediately follows opening brace #18087

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Merged
graphite-app merged 1 commit into from
Jan 20, 2026
Merged

fix(formatter): only expand mapped types when newline immediately follows opening brace #18087

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25 changes: 12 additions & 13 deletions crates/oxc_formatter/src/print/mapped_type.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ impl<'a> FormatWrite<'a> for AstNode<'a, TSMappedType<'a>> {
let key = self.key();
let constraint = self.constraint();
let name_type = self.name_type();
let should_expand = has_line_break_before_property_name(self, f.source_text());
let should_expand = has_line_break_after_opening_brace(self, f.source_text());

let format_inner = format_with(|f| {
if should_expand {
Expand Down Expand Up @@ -84,16 +84,15 @@ impl<'a> FormatWrite<'a> for AstNode<'a, TSMappedType<'a>> {
}
}

/// Check if the user introduced a new line inside the node, but only if
/// that new line occurs at or before the property name. For example,
/// this would break:
/// { [
/// A in B]: T}
/// Because the line break occurs before `A`, the property name. But this
/// would _not_ break:
/// { [A
/// in B]: T}
/// Because the break is _after_ the `A`.
fn has_line_break_before_property_name(node: &TSMappedType, f: SourceText) -> bool {
f.contains_newline_between(node.span.start, node.key.span.start)
/// Check if the user introduced a new line immediately after the opening brace.
/// For example, this would break:
/// {
/// readonly [A in B]: T}
/// Because the line break occurs right after `{`. But this would _not_ break:
/// { readonly
/// [A in B]: T}
/// Because the break is not immediately after `{`.
fn has_line_break_after_opening_brace(node: &TSMappedType, f: SourceText) -> bool {
// Check if there's a newline immediately after `{` (before any non-whitespace)
f.has_newline_after(node.span.start + 1)
}
3 changes: 1 addition & 2 deletions tasks/prettier_conformance/snapshots/prettier.ts.snap.md
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
ts compatibility: 584/605 (96.53%)
ts compatibility: 585/605 (96.69%)

# Failed

Expand All @@ -17,7 +17,6 @@ ts compatibility: 584/605 (96.53%)
| typescript/interface2/comments-ts-only/18278.ts | 💥 | 95.65% |
| typescript/last-argument-expansion/decorated-function.tsx | 💥 | 29.06% |
| typescript/mapped-type/issue-11098.ts | 💥 | 97.03% |
| typescript/mapped-type/break-mode/break-mode.ts | 💥 | 68.75% |
| typescript/property-signature/consistent-with-flow/comments.ts | 💥 | 80.00% |
| typescript/top-level-await/test.ts | 💥 | 0.00% |
| typescript/top-level-await/test.tsx | 💥 | 0.00% |
Expand Down
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