feat(fmt): support CSS, SCSS, Sass and Less (#24870)

This PR integrates [Malva](https://github.com/g-plane/malva) into `deno
fmt`, which introduces the ability to format CSS, SCSS, Sass and Less
files.

On Linux x64 6.10, this PR increases about 800KiB:

```                                                                                                                                                                      
❯ wc -c target/release/deno
125168728 target/release/deno

❯ wc -c target/release/deno
124349456 target/release/deno
```

5 files changed, 129 insertions, 3 deletions

diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index 0ea7d95ee..df7323e71 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -123,6 +123,7 @@ libc.workspace = true
 libz-sys.workspace = true
 log = { workspace = true, features = ["serde"] }
 lsp-types.workspace = true
+malva = "=0.8.0"
 memmem.workspace = true
 monch.workspace = true
 notify.workspace = true
diff --git a/cli/args/flags.rs b/cli/args/flags.rs
index e28ce549b..acdcaf8a7 100644
--- a/cli/args/flags.rs
+++ b/cli/args/flags.rs
@@ -200,6 +200,7 @@ pub struct FmtFlags {
   pub prose_wrap: Option<String>,
   pub no_semicolons: Option<bool>,
   pub watch: Option<WatchFlags>,
+  pub unstable_css: bool,
   pub unstable_yaml: bool,
 }
 
@@ -2018,8 +2019,8 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
             // prefer using ts for formatting instead of js because ts works in more scenarios
             .default_value("ts")
             .value_parser([
-              "ts", "tsx", "js", "jsx", "md", "json", "jsonc", "yml", "yaml",
-              "ipynb",
+              "ts", "tsx", "js", "jsx", "md", "json", "jsonc", "css", "scss",
+              "sass", "less", "yml", "yaml", "ipynb",
             ]),
         )
         .arg(
@@ -2097,6 +2098,13 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
             ),
         )
         .arg(
+          Arg::new("unstable-css")
+            .long("unstable-css")
+            .help("Enable formatting CSS, SCSS, Sass and Less files.")
+            .value_parser(FalseyValueParser::new())
+            .action(ArgAction::SetTrue),
+        )
+        .arg(
           Arg::new("unstable-yaml")
             .long("unstable-yaml")
             .help("Enable formatting YAML files.")
@@ -4163,6 +4171,7 @@ fn fmt_parse(flags: &mut Flags, matches: &mut ArgMatches) {
   let single_quote = matches.remove_one::<bool>("single-quote");
   let prose_wrap = matches.remove_one::<String>("prose-wrap");
   let no_semicolons = matches.remove_one::<bool>("no-semicolons");
+  let unstable_css = matches.get_flag("unstable-css");
   let unstable_yaml = matches.get_flag("unstable-yaml");
 
   flags.subcommand = DenoSubcommand::Fmt(FmtFlags {
@@ -4175,6 +4184,7 @@ fn fmt_parse(flags: &mut Flags, matches: &mut ArgMatches) {
     prose_wrap,
     no_semicolons,
     watch: watch_arg_parse(matches),
+    unstable_css,
     unstable_yaml,
   });
 }
@@ -5881,6 +5891,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5905,6 +5916,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5929,6 +5941,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5953,6 +5966,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -5966,6 +5980,7 @@ mod tests {
       "fmt",
       "--watch",
       "--no-clear-screen",
+      "--unstable-css",
       "--unstable-yaml"
     ]);
     assert_eq!(
@@ -5983,6 +5998,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: true,
           unstable_yaml: true,
           watch: Some(WatchFlags {
             hmr: false,
@@ -6018,6 +6034,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -6042,6 +6059,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -6074,6 +6092,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -6111,6 +6130,7 @@ mod tests {
           single_quote: Some(true),
           prose_wrap: Some("never".to_string()),
           no_semicolons: Some(true),
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -6142,6 +6162,7 @@ mod tests {
           single_quote: Some(false),
           prose_wrap: None,
           no_semicolons: Some(false),
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index bd49c0c15..afad0528c 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -281,6 +281,7 @@ impl BenchOptions {
 
 #[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
 pub struct UnstableFmtOptions {
+  pub css: bool,
   pub yaml: bool,
 }
 
@@ -314,6 +315,7 @@ impl FmtOptions {
     Self {
       options: resolve_fmt_options(fmt_flags, fmt_config.options),
       unstable: UnstableFmtOptions {
+        css: unstable.css || fmt_flags.unstable_css,
         yaml: unstable.yaml || fmt_flags.unstable_yaml,
       },
       files: fmt_config.files,
@@ -1330,8 +1332,10 @@ impl CliOptions {
   }
 
   pub fn resolve_config_unstable_fmt_options(&self) -> UnstableFmtOptions {
+    let workspace = self.workspace();
     UnstableFmtOptions {
-      yaml: self.workspace().has_unstable("fmt-yaml"),
+      css: workspace.has_unstable("fmt-css"),
+      yaml: workspace.has_unstable("fmt-yaml"),
     }
   }
 
@@ -1664,6 +1668,7 @@ impl CliOptions {
         "sloppy-imports",
         "byonm",
         "bare-node-builtins",
+        "fmt-css",
         "fmt-yaml",
       ]);
       // add more unstable flags to the same vector holding granular flags
diff --git a/cli/lsp/language_server.rs b/cli/lsp/language_server.rs
index 314c9ec14..186c94198 100644
--- a/cli/lsp/language_server.rs
+++ b/cli/lsp/language_server.rs
@@ -1368,6 +1368,9 @@ impl Inner {
         .data_for_specifier(&specifier)
         .map(|d| &d.member_dir.workspace);
       let unstable_options = UnstableFmtOptions {
+        css: maybe_workspace
+          .map(|w| w.has_unstable("fmt-css"))
+          .unwrap_or(false),
         yaml: maybe_workspace
           .map(|w| w.has_unstable("fmt-yaml"))
           .unwrap_or(false),
diff --git a/cli/tools/fmt.rs b/cli/tools/fmt.rs
index c4eebddf7..348e2d862 100644
--- a/cli/tools/fmt.rs
+++ b/cli/tools/fmt.rs
@@ -244,6 +244,10 @@ fn format_markdown(
           | "typescript"
           | "json"
           | "jsonc"
+          | "css"
+          | "scss"
+          | "sass"
+          | "less"
           | "yml"
           | "yaml"
       ) {
@@ -263,6 +267,13 @@ fn format_markdown(
             json_config.line_width = line_width;
             dprint_plugin_json::format_text(&fake_filename, text, &json_config)
           }
+          "css" | "scss" | "sass" | "less" => {
+            if unstable_options.css {
+              format_css(&fake_filename, text, fmt_options)
+            } else {
+              Ok(None)
+            }
+          }
           "yml" | "yaml" => {
             if unstable_options.yaml {
               pretty_yaml::format_text(
@@ -305,6 +316,20 @@ pub fn format_json(
   dprint_plugin_json::format_text(file_path, file_text, &config)
 }
 
+pub fn format_css(
+  file_path: &Path,
+  file_text: &str,
+  fmt_options: &FmtOptionsConfig,
+) -> Result<Option<String>, AnyError> {
+  malva::format_text(
+    file_text,
+    malva::detect_syntax(file_path).unwrap_or(malva::Syntax::Css),
+    &get_resolved_malva_config(fmt_options),
+  )
+  .map(Some)
+  .map_err(AnyError::from)
+}
+
 /// Formats a single TS, TSX, JS, JSX, JSONC, JSON, MD, or IPYNB file.
 pub fn format_file(
   file_path: &Path,
@@ -319,6 +344,13 @@ pub fn format_file(
       format_markdown(file_text, fmt_options, unstable_options)
     }
     "json" | "jsonc" => format_json(file_path, file_text, fmt_options),
+    "css" | "scss" | "sass" | "less" => {
+      if unstable_options.css {
+        format_css(file_path, file_text, fmt_options)
+      } else {
+        Ok(None)
+      }
+    }
     "yml" | "yaml" => {
       if unstable_options.yaml {
         pretty_yaml::format_text(
@@ -737,6 +769,58 @@ fn get_resolved_json_config(
   builder.build()
 }
 
+fn get_resolved_malva_config(
+  options: &FmtOptionsConfig,
+) -> malva::config::FormatOptions {
+  use malva::config::*;
+
+  let layout_options = LayoutOptions {
+    print_width: options.line_width.unwrap_or(80) as usize,
+    use_tabs: options.use_tabs.unwrap_or_default(),
+    indent_width: options.indent_width.unwrap_or(2) as usize,
+    line_break: LineBreak::Lf,
+  };
+
+  let language_options = LanguageOptions {
+    hex_case: HexCase::Lower,
+    hex_color_length: None,
+    quotes: if let Some(true) = options.single_quote {
+      Quotes::PreferSingle
+    } else {
+      Quotes::PreferDouble
+    },
+    operator_linebreak: OperatorLineBreak::Before,
+    block_selector_linebreak: BlockSelectorLineBreak::Consistent,
+    omit_number_leading_zero: false,
+    trailing_comma: true,
+    format_comments: false,
+    linebreak_in_pseudo_parens: true,
+    declaration_order: None,
+    single_line_block_threshold: None,
+    keyframe_selector_notation: None,
+    attr_value_quotes: AttrValueQuotes::Always,
+    prefer_single_line: false,
+    selectors_prefer_single_line: None,
+    function_args_prefer_single_line: None,
+    sass_content_at_rule_prefer_single_line: None,
+    sass_include_at_rule_prefer_single_line: None,
+    sass_map_prefer_single_line: None,
+    sass_module_config_prefer_single_line: None,
+    sass_params_prefer_single_line: None,
+    less_import_options_prefer_single_line: None,
+    less_mixin_args_prefer_single_line: None,
+    less_mixin_params_prefer_single_line: None,
+    top_level_declarations_prefer_single_line: None,
+    selector_override_comment_directive: "deno-fmt-selector-override".into(),
+    ignore_comment_directive: "deno-fmt-ignore".into(),
+  };
+
+  FormatOptions {
+    layout: layout_options,
+    language: language_options,
+  }
+}
+
 fn get_resolved_yaml_config(
   options: &FmtOptionsConfig,
 ) -> pretty_yaml::config::FormatOptions {
@@ -864,6 +948,10 @@ fn is_supported_ext_fmt(path: &Path) -> bool {
         | "mts"
         | "json"
         | "jsonc"
+        | "css"
+        | "scss"
+        | "sass"
+        | "less"
         | "md"
         | "mkd"
         | "mkdn"
@@ -906,6 +994,14 @@ mod test {
     assert!(is_supported_ext_fmt(Path::new("foo.JSONC")));
     assert!(is_supported_ext_fmt(Path::new("foo.json")));
     assert!(is_supported_ext_fmt(Path::new("foo.JsON")));
+    assert!(is_supported_ext_fmt(Path::new("foo.css")));
+    assert!(is_supported_ext_fmt(Path::new("foo.Css")));
+    assert!(is_supported_ext_fmt(Path::new("foo.scss")));
+    assert!(is_supported_ext_fmt(Path::new("foo.SCSS")));
+    assert!(is_supported_ext_fmt(Path::new("foo.sass")));
+    assert!(is_supported_ext_fmt(Path::new("foo.Sass")));
+    assert!(is_supported_ext_fmt(Path::new("foo.less")));
+    assert!(is_supported_ext_fmt(Path::new("foo.LeSS")));
     assert!(is_supported_ext_fmt(Path::new("foo.yml")));
     assert!(is_supported_ext_fmt(Path::new("foo.Yml")));
     assert!(is_supported_ext_fmt(Path::new("foo.yaml")));