feat(formatter): add delimiterSpacing option

.changeset/delimiter-spacing-option.md

@@ -0,0 +1,26 @@
+---
+"@biomejs/biome": minor
+---
+
+Added the `delimiterSpacing` formatter option. This option inserts spaces inside delimiters. Affects parentheses `()`, square brackets `[]`, TypeScript angle brackets `<>`, and JSX curly braces `{}`. It can be configured globally via `formatter.delimiterSpacing` or per-language via `javascript.formatter.delimiterSpacing`, `json.formatter.delimiterSpacing`, and `css.formatter.delimiterSpacing`. Defaults to false.
+
+**JavaScript:**
+
+```diff
+- if (condition) {}
++ if ( condition ) {}
+```
+
+**JSON:**
+
+```diff
+- [1, 2, 3]
++ [ 1, 2, 3 ]
+```
+
+**CSS:**
+
+```diff
+- rgba(0, 0, 0, 1)
++ rgba( 0, 0, 0, 1 )
+```

crates/biome_cli/src/execute/migrate/prettier.rs

@@ -235,6 +235,7 @@ impl TryFrom<PrettierConfiguration> for biome_configuration::Configuration {
             bracket_same_line: Some(value.bracket_line.into()),
             attribute_position: Some(AttributePosition::default()),
             bracket_spacing: Some(BracketSpacing::default()),
+            delimiter_spacing: None,
             expand: Some(value.object_wrap.into()),
             format_with_errors: Some(false.into()),
             includes: None,
@@ -276,6 +277,7 @@ impl TryFrom<PrettierConfiguration> for biome_configuration::Configuration {
             quote_style: Some(quote_style),
             quote_properties: Some(value.quote_props.into()),
             bracket_spacing: Some(value.bracket_spacing.into()),
+            delimiter_spacing: None,
             jsx_quote_style: Some(jsx_quote_style),
             attribute_position: Some(AttributePosition::default()),
             operator_linebreak: None,

crates/biome_cli/tests/commands/format.rs

@@ -112,6 +112,14 @@ const APPLY_BRACKET_SPACING_AFTER_GRAPHQL: &str = r#"{
 }
 "#;
 
+const APPLY_DELIMITER_SPACING_BEFORE: &str = r#"const arr = [1, 2, 3];
+function foo(a, b) {}
+"#;
+
+const APPLY_DELIMITER_SPACING_AFTER: &str = r#"const arr = [ 1, 2, 3 ];
+function foo( a, b ) {}
+"#;
+
 const APPLY_BRACKET_SAME_LINE_BEFORE: &str = r#"<Foo
 	className={style}
 	reallyLongAttributeName1={longComplexValue}
@@ -869,6 +877,87 @@ fn applies_custom_bracket_spacing() {
     ));
 }
 
+#[test]
+fn applies_global_delimiter_spacing() {
+    let fs = MemoryFileSystem::default();
+    let mut console = BufferConsole::default();
+
+    let file_path = Utf8Path::new("file.js");
+    fs.insert(file_path.into(), APPLY_DELIMITER_SPACING_BEFORE.as_bytes());
+
+    let (fs, result) = run_cli(
+        fs,
+        &mut console,
+        Args::from(
+            [
+                "format",
+                "--delimiter-spacing",
+                "true",
+                "--write",
+                file_path.as_str(),
+            ]
+            .as_slice(),
+        ),
+    );
+
+    assert!(result.is_ok(), "run_cli returned {result:?}");
+
+    assert_file_contents(&fs, file_path, APPLY_DELIMITER_SPACING_AFTER);
+
+    assert_cli_snapshot(SnapshotPayload::new(
+        module_path!(),
+        "applies_global_delimiter_spacing",
+        fs,
+        console,
+        result,
+    ));
+}
+
+#[test]
+fn language_overrides_global_delimiter_spacing() {
+    let fs = MemoryFileSystem::default();
+    let mut console = BufferConsole::default();
+
+    let config_path = Utf8Path::new("biome.json");
+    fs.insert(
+        config_path.into(),
+        r#"{
+  "formatter": {
+    "delimiterSpacing": true
+  },
+  "javascript": {
+    "formatter": {
+      "delimiterSpacing": false
+    }
+  }
+}
+"#
+        .as_bytes(),
+    );
+
+    let file_path = Utf8Path::new("file.js");
+    fs.insert(file_path.into(), APPLY_DELIMITER_SPACING_AFTER.as_bytes());
+
+    let (fs, result) = run_cli(
+        fs,
+        &mut console,
+        Args::from(["format", "--write", file_path.as_str()].as_slice()),
+    );
+
+    assert!(result.is_ok(), "run_cli returned {result:?}");
+
+    // JS overrides global, so no spaces should be present (delimiterSpacing: false)
+    assert_file_contents(&fs, file_path, APPLY_DELIMITER_SPACING_BEFORE);
+
+    assert_cli_snapshot(SnapshotPayload::new(
+        module_path!(),
+        "language_overrides_global_delimiter_spacing",
+        fs,
+        console,
+        result,
+    ));
+}
+
 #[test]
 fn applies_custom_bracket_same_line() {
     let fs = MemoryFileSystem::default();

crates/biome_cli/tests/snapshots/main_commands_check/check_help.snap

@@ -46,6 +46,9 @@ The configuration that is contained inside the file `biome.json`
                               apply to self closing elements).
         --bracket-spacing=<true|false>  Whether to insert spaces around brackets in object literals.
                               Defaults to true.
+        --delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.  Affects
+                              parentheses `()`, square brackets `[]`, TypeScript angle brackets
+                              `<>`, and JSX curly braces `{}`.  Defaults to false.
         --expand=<auto|always|never>  Whether to expand arrays and objects on multiple lines. When
                               set to `auto`, object literals are formatted on multiple lines if the
                               first property has a newline, and array literals are formatted on a
@@ -99,6 +102,9 @@ The configuration that is contained inside the file `biome.json`
                               JSX elements. Defaults to auto.
         --javascript-formatter-bracket-spacing=<true|false>  Whether to insert spaces around
                               brackets in object literals. Defaults to true.
+        --javascript-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside
+                              delimiters. Affects parentheses `()`, square brackets `[]`, TypeScript
+                              angle brackets `<>`, and JSX curly braces `{}`. Defaults to false.
         --javascript-formatter-expand=<auto|always|never>  Whether to expand arrays and objects on
                               multiple lines. When set to `auto`, object literals are formatted on
                               multiple lines if the first property has a newline, and array literals
@@ -152,6 +158,8 @@ The configuration that is contained inside the file `biome.json`
                               Defaults to "auto".
         --json-formatter-bracket-spacing=<true|false>  Whether to insert spaces around brackets in
                               object literals. Defaults to true.
+        --json-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside square
+                              brackets `[]`. Defaults to false.
         --json-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it
@@ -183,6 +191,8 @@ The configuration that is contained inside the file `biome.json`
                               super languages) files. Defaults to 80.
         --css-formatter-quote-style=<double|single>  The type of quotes used in CSS code. Defaults
                               to double.
+        --css-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.
+                              Affects parentheses `()` and square brackets `[]`. Defaults to false.
         --css-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it

crates/biome_cli/tests/snapshots/main_commands_ci/ci_help.snap

@@ -47,6 +47,9 @@ The configuration that is contained inside the file `biome.json`
                               apply to self closing elements).
         --bracket-spacing=<true|false>  Whether to insert spaces around brackets in object literals.
                               Defaults to true.
+        --delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.  Affects
+                              parentheses `()`, square brackets `[]`, TypeScript angle brackets
+                              `<>`, and JSX curly braces `{}`.  Defaults to false.
         --expand=<auto|always|never>  Whether to expand arrays and objects on multiple lines. When
                               set to `auto`, object literals are formatted on multiple lines if the
                               first property has a newline, and array literals are formatted on a
@@ -100,6 +103,9 @@ The configuration that is contained inside the file `biome.json`
                               JSX elements. Defaults to auto.
         --javascript-formatter-bracket-spacing=<true|false>  Whether to insert spaces around
                               brackets in object literals. Defaults to true.
+        --javascript-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside
+                              delimiters. Affects parentheses `()`, square brackets `[]`, TypeScript
+                              angle brackets `<>`, and JSX curly braces `{}`. Defaults to false.
         --javascript-formatter-expand=<auto|always|never>  Whether to expand arrays and objects on
                               multiple lines. When set to `auto`, object literals are formatted on
                               multiple lines if the first property has a newline, and array literals
@@ -153,6 +159,8 @@ The configuration that is contained inside the file `biome.json`
                               Defaults to "auto".
         --json-formatter-bracket-spacing=<true|false>  Whether to insert spaces around brackets in
                               object literals. Defaults to true.
+        --json-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside square
+                              brackets `[]`. Defaults to false.
         --json-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it
@@ -184,6 +192,8 @@ The configuration that is contained inside the file `biome.json`
                               super languages) files. Defaults to 80.
         --css-formatter-quote-style=<double|single>  The type of quotes used in CSS code. Defaults
                               to double.
+        --css-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.
+                              Affects parentheses `()` and square brackets `[]`. Defaults to false.
         --css-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it

crates/biome_cli/tests/snapshots/main_commands_format/applies_global_delimiter_spacing.snap

@@ -0,0 +1,17 @@
+---
+source: crates/biome_cli/tests/snap_test.rs
+expression: redactor(content)
+---
+## `file.js`
+
+```js
+const arr = [ 1, 2, 3 ];
+function foo( a, b ) {}
+
+```
+
+# Emitted Messages
+
+```block
+Formatted 1 file in <TIME>. Fixed 1 file.
+```

crates/biome_cli/tests/snapshots/main_commands_format/format_help.snap

@@ -23,6 +23,9 @@ Generic options applied to all files
                               apply to self closing elements).
         --bracket-spacing=<true|false>  Whether to insert spaces around brackets in object literals.
                               Defaults to true.
+        --delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.  Affects
+                              parentheses `()`, square brackets `[]`, TypeScript angle brackets
+                              `<>`, and JSX curly braces `{}`.  Defaults to false.
         --expand=<auto|always|never>  Whether to expand arrays and objects on multiple lines. When
                               set to `auto`, object literals are formatted on multiple lines if the
                               first property has a newline, and array literals are formatted on a
@@ -75,6 +78,9 @@ Formatting options specific to the JavaScript files
                               JSX elements. Defaults to auto.
         --javascript-formatter-bracket-spacing=<true|false>  Whether to insert spaces around
                               brackets in object literals. Defaults to true.
+        --javascript-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside
+                              delimiters. Affects parentheses `()`, square brackets `[]`, TypeScript
+                              angle brackets `<>`, and JSX curly braces `{}`. Defaults to false.
         --javascript-formatter-expand=<auto|always|never>  Whether to expand arrays and objects on
                               multiple lines. When set to `auto`, object literals are formatted on
                               multiple lines if the first property has a newline, and array literals
@@ -147,6 +153,8 @@ Options that changes how the CSS formatter behaves
                               super languages) files. Defaults to 80.
         --css-formatter-quote-style=<double|single>  The type of quotes used in CSS code. Defaults
                               to double.
+        --css-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside delimiters.
+                              Affects parentheses `()` and square brackets `[]`. Defaults to false.
         --css-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it
@@ -293,6 +301,8 @@ Available options:
                               Defaults to "auto".
         --json-formatter-bracket-spacing=<true|false>  Whether to insert spaces around brackets in
                               object literals. Defaults to true.
+        --json-formatter-delimiter-spacing=<true|false>  Whether to insert spaces inside square
+                              brackets `[]`. Defaults to false.
         --json-formatter-trailing-newline=<true|false>  Whether to add a trailing newline at the end
                               of the file.
                               Setting this option to `false` is **highly discouraged** because it

crates/biome_cli/tests/snapshots/main_commands_format/language_overrides_global_delimiter_spacing.snap

@@ -0,0 +1,32 @@
+---
+source: crates/biome_cli/tests/snap_test.rs
+expression: redactor(content)
+---
+## `biome.json`
+
+```json
+{
+  "formatter": {
+    "delimiterSpacing": true
+  },
+  "javascript": {
+    "formatter": {
+      "delimiterSpacing": false
+    }
+  }
+}
+```
+
+## `file.js`
+
+```js
+const arr = [1, 2, 3];
+function foo(a, b) {}
+
+```
+
+# Emitted Messages
+
+```block
+Formatted 1 file in <TIME>. Fixed 1 file.
+```

crates/biome_configuration/src/css.rs

@@ -1,7 +1,7 @@
 use crate::bool::Bool;
 use biome_deserialize_macros::{Deserializable, Merge};
 use biome_formatter::{
-    IndentStyle, IndentWidth, LineEnding, LineWidth, QuoteStyle, TrailingNewline,
+    DelimiterSpacing, IndentStyle, IndentWidth, LineEnding, LineWidth, QuoteStyle, TrailingNewline,
 };
 use bpaf::Bpaf;
 use serde::{Deserialize, Serialize};
@@ -101,6 +101,11 @@ pub struct CssFormatterConfiguration {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub quote_style: Option<QuoteStyle>,
 
+    /// Whether to insert spaces inside delimiters. Affects parentheses `()` and square brackets `[]`. Defaults to false.
+    #[bpaf(long("css-formatter-delimiter-spacing"), argument("true|false"))]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub delimiter_spacing: Option<DelimiterSpacing>,
+
     /// Whether to add a trailing newline at the end of the file.
     ///
     /// Setting this option to `false` is **highly discouraged** because it could cause many problems with other tools:

crates/biome_configuration/src/formatter.rs

@@ -1,8 +1,8 @@
 use crate::bool::Bool;
 use biome_deserialize_macros::{Deserializable, Merge};
 use biome_formatter::{
-    AttributePosition, BracketSameLine, BracketSpacing, Expand, IndentStyle, IndentWidth,
-    LineEnding, LineWidth, TrailingNewline,
+    AttributePosition, BracketSameLine, BracketSpacing, DelimiterSpacing, Expand, IndentStyle,
+    IndentWidth, LineEnding, LineWidth, TrailingNewline,
 };
 use bpaf::Bpaf;
 use serde::{Deserialize, Serialize};
@@ -64,6 +64,13 @@ pub struct FormatterConfiguration {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub bracket_spacing: Option<BracketSpacing>,
 
+    /// Whether to insert spaces inside delimiters.  Affects parentheses `()`,
+    /// square brackets `[]`, TypeScript angle brackets `<>`, and JSX curly
+    /// braces `{}`.  Defaults to false.
+    #[bpaf(long("delimiter-spacing"), argument("true|false"))]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub delimiter_spacing: Option<DelimiterSpacing>,
+
     /// Whether to expand arrays and objects on multiple lines.
     /// When set to `auto`, object literals are formatted on multiple lines if the first property has a newline,
     /// and array literals are formatted on a single line if it fits in the line.
@@ -136,6 +143,10 @@ impl FormatterConfiguration {
         self.bracket_spacing.unwrap_or_default()
     }
 
+    pub fn delimiter_spacing_resolved(&self) -> DelimiterSpacing {
+        self.delimiter_spacing.unwrap_or_default()
+    }
+
     pub fn expand_resolved(&self) -> Expand {
         self.expand.unwrap_or_default()
     }

crates/biome_configuration/src/javascript/formatter.rs

@@ -1,8 +1,8 @@
 use crate::bool::Bool;
 use biome_deserialize_macros::{Deserializable, Merge};
 use biome_formatter::{
-    AttributePosition, BracketSameLine, BracketSpacing, Expand, IndentStyle, IndentWidth,
-    LineEnding, LineWidth, QuoteStyle, TrailingNewline,
+    AttributePosition, BracketSameLine, BracketSpacing, DelimiterSpacing, Expand, IndentStyle,
+    IndentWidth, LineEnding, LineWidth, QuoteStyle, TrailingNewline,
 };
 use biome_js_formatter::context::{
     ArrowParentheses, OperatorLinebreak, QuoteProperties, Semicolons,
@@ -108,6 +108,12 @@ pub struct JsFormatterConfiguration {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub bracket_spacing: Option<BracketSpacing>,
 
+    // it's also a top-level configurable property.
+    /// Whether to insert spaces inside delimiters. Affects parentheses `()`, square brackets `[]`, TypeScript angle brackets `<>`, and JSX curly braces `{}`. Defaults to false.
+    #[bpaf(long("javascript-formatter-delimiter-spacing"), argument("true|false"))]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub delimiter_spacing: Option<DelimiterSpacing>,
+
     /// Whether to expand arrays and objects on multiple lines.
     /// When set to `auto`, object literals are formatted on multiple lines if the first property has a newline,
     /// and array literals are formatted on a single line if it fits in the line.