fix(js_formatter): ensure flat conditional content is always written …

…in `RemoveSoftLinesBuffer` (#1357)

Co-authored-by: Emanuele Stoppa <[email protected]>

CHANGELOG.md

@@ -91,6 +91,8 @@ Biome now scores 97% compatibility with Prettier and features more than 180 lint
 
 - Fix [#1220](https://github.com/biomejs/biome/issues/1220). Avoid duplicating comments in type unions for mapped, empty object, and empty tuple types. [#1240](https://github.com/biomejs/biome/pull/1240) Contributed by @faultyserver
 
+- Fix [#1356](https://github.com/biomejs/biome/issues/1356). Ensure `if_group_fits_on_line` content is always written in `RemoveSoftLinesBuffer`s. [#1357](https://github.com/biomejs/biome/pull/1357) Contributed by @faultyserver
+
 - Fix [#1171](https://github.com/biomejs/biome/issues/1171). Correctly format empty statement with comment inside arrow body when used as single argument in call expression. Contributed by @kalleep
 
 ### JavaScript APIs

crates/biome_formatter/src/buffer.rs

@@ -606,16 +606,30 @@ impl<Context> Buffer for RemoveSoftLinesBuffer<'_, Context> {
 
     fn write_element(&mut self, element: FormatElement) -> FormatResult<()> {
         let element = match element {
-            FormatElement::Tag(Tag::StartConditionalContent(condition))
-                if condition.mode == PrintMode::Expanded =>
-            {
-                self.is_in_expanded_conditional_content = true;
-                return Ok(());
+            FormatElement::Tag(Tag::StartConditionalContent(condition)) => {
+                match condition.mode {
+                    PrintMode::Expanded => {
+                        // Mark that we're within expanded content so that it
+                        // can be dropped in all future writes until the ending
+                        // tag.
+                        self.is_in_expanded_conditional_content = true;
+                        return Ok(());
+                    }
+                    PrintMode::Flat => {
+                        // Flat groups have the conditional tag dropped as
+                        // well, since the content within it will _always_ be
+                        // printed by this buffer.
+                        return Ok(());
+                    }
+                }
             }
-            FormatElement::Tag(Tag::EndConditionalContent)
-                if self.is_in_expanded_conditional_content =>
-            {
+            FormatElement::Tag(Tag::EndConditionalContent) => {
+                // NOTE: This assumes that conditional content cannot be nested.
+                // This is true for all practical cases, but it's _possible_ to
+                // write IR that breaks this.
                 self.is_in_expanded_conditional_content = false;
+                // No matter if this was flat or expanded content, the ending
+                // tag gets dropped, since the starting tag was also dropped.
                 return Ok(());
             }
             // All content within an expanded conditional gets dropped. If there's a

crates/biome_js_formatter/tests/specs/ts/parameters/issue-1356/options.json

@@ -0,0 +1,8 @@
+{
+    "cases": [
+        {
+            "semicolon": "AsNeeded",
+            "line_width": 40
+        }
+    ]
+}

crates/biome_js_formatter/tests/specs/ts/parameters/issue-1356/parameter_type_annotation_semicolon.ts

@@ -0,0 +1,10 @@
+// Ensure that the type annotation preserves the semicolon in the type
+// annotation, even though the parent group breaks. This was only an issue when
+// `semicolon: AsNeeded` was set, since the semicolon became conditional on
+// whether the group was printed inline.
+//
+// https://github.com/biomejs/biome/issues/1356.
+
+foo((args: {a: string; b: string}) => {
+    return a;
+  })

crates/biome_js_formatter/tests/specs/ts/parameters/issue-1356/parameter_type_annotation_semicolon.ts.snap

@@ -0,0 +1,96 @@
+---
+source: crates/biome_formatter_test/src/snapshot_builder.rs
+info: ts/parameters/issue-1356/parameter_type_annotation_semicolon.ts
+---
+
+# Input
+
+```ts
+// Ensure that the type annotation preserves the semicolon in the type
+// annotation, even though the parent group breaks. This was only an issue when
+// `semicolon: AsNeeded` was set, since the semicolon became conditional on
+// whether the group was printed inline.
+//
+// https://github.com/biomejs/biome/issues/1356.
+
+foo((args: {a: string; b: string}) => {
+    return a;
+  })
+```
+
+
+=============================
+
+# Outputs
+
+## Output 1
+
+-----
+Indent style: Tab
+Indent width: 2
+Line ending: LF
+Line width: 80
+Quote style: Double Quotes
+JSX quote style: Double Quotes
+Quote properties: As needed
+Trailing comma: All
+Semicolons: Always
+Arrow parentheses: Always
+Bracket spacing: true
+Bracket same line: false
+-----
+
+```ts
+// Ensure that the type annotation preserves the semicolon in the type
+// annotation, even though the parent group breaks. This was only an issue when
+// `semicolon: AsNeeded` was set, since the semicolon became conditional on
+// whether the group was printed inline.
+//
+// https://github.com/biomejs/biome/issues/1356.
+
+foo((args: { a: string; b: string }) => {
+	return a;
+});
+```
+
+## Output 2
+
+-----
+Indent style: Tab
+Indent width: 2
+Line ending: LF
+Line width: 40
+Quote style: Double Quotes
+JSX quote style: Double Quotes
+Quote properties: As needed
+Trailing comma: All
+Semicolons: Always
+Arrow parentheses: Always
+Bracket spacing: true
+Bracket same line: false
+-----
+
+```ts
+// Ensure that the type annotation preserves the semicolon in the type
+// annotation, even though the parent group breaks. This was only an issue when
+// `semicolon: AsNeeded` was set, since the semicolon became conditional on
+// whether the group was printed inline.
+//
+// https://github.com/biomejs/biome/issues/1356.
+
+foo(
+	(args: { a: string; b: string }) => {
+		return a;
+	},
+);
+```
+
+# Lines exceeding max width of 40 characters
+```
+    1: // Ensure that the type annotation preserves the semicolon in the type
+    2: // annotation, even though the parent group breaks. This was only an issue when
+    3: // `semicolon: AsNeeded` was set, since the semicolon became conditional on
+    6: // https://github.com/biomejs/biome/issues/1356.
+```
+
+

website/src/content/docs/internals/changelog.mdx

@@ -97,6 +97,8 @@ Biome now scores 97% compatibility with Prettier and features more than 180 lint
 
 - Fix [#1220](https://github.com/biomejs/biome/issues/1220). Avoid duplicating comments in type unions for mapped, empty object, and empty tuple types. [#1240](https://github.com/biomejs/biome/pull/1240) Contributed by @faultyserver
 
+- Fix [#1356](https://github.com/biomejs/biome/issues/1356). Ensure `if_group_fits_on_line` content is always written in `RemoveSoftLinesBuffer`s. [#1357](https://github.com/biomejs/biome/pull/1357) Contributed by @faultyserver
+
 - Fix [#1171](https://github.com/biomejs/biome/issues/1171). Correctly format empty statement with comment inside arrow body when used as single argument in call expression. Contributed by @kalleep
 
 ### JavaScript APIs