Add Logger.defaultLogger to automatically choose whether to use colors

CHANGELOG.md

@@ -1,4 +1,10 @@
-## 1.97.4-dev
+## 1.98.0-dev
+
+### Dart API
+
+* Add a `const Logger.defaultLogger` field. This provides a logger that emits to
+  standard error or the browser console, but automatically chooses whether to
+  use terminal colors.
 
 ### JavaScript API
 
@@ -8,6 +14,9 @@
 * Properly emit deprecation warnings as text rather than `StringBuffer` objects
   when running in a browser.
 
+* Emit colored warnings and other messages on the console when running in a
+  browser.
+
 ## 1.97.3
 
 * Fix a bug where nesting an at-rule within multiple style rules in plain CSS

lib/src/async_compile.dart

@@ -49,7 +49,7 @@ Future<CompileResult> compileAsync(
 }) async {
   DeprecationProcessingLogger deprecationLogger =
       logger = DeprecationProcessingLogger(
-    logger ?? Logger.stderr(),
+    logger ?? Logger.defaultLogger,
     silenceDeprecations: {...?silenceDeprecations},
     fatalDeprecations: {...?fatalDeprecations},
     futureDeprecations: {...?futureDeprecations},
@@ -124,7 +124,7 @@ Future<CompileResult> compileStringAsync(
 }) async {
   DeprecationProcessingLogger deprecationLogger =
       logger = DeprecationProcessingLogger(
-    logger ?? Logger.stderr(),
+    logger ?? Logger.defaultLogger,
     silenceDeprecations: {...?silenceDeprecations},
     fatalDeprecations: {...?fatalDeprecations},
     futureDeprecations: {...?futureDeprecations},

lib/src/compile.dart

@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_compile.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: d305a0f75e329a29f5aff734ac31ce145fd3b8d5
+// Checksum: aa378886d9a3d697d466ac916f7902cbc1b282ee
 //
 // ignore_for_file: unused_import
 
@@ -58,7 +58,7 @@ CompileResult compile(
 }) {
   DeprecationProcessingLogger deprecationLogger =
       logger = DeprecationProcessingLogger(
-    logger ?? Logger.stderr(),
+    logger ?? Logger.defaultLogger,
     silenceDeprecations: {...?silenceDeprecations},
     fatalDeprecations: {...?fatalDeprecations},
     futureDeprecations: {...?futureDeprecations},
@@ -133,7 +133,7 @@ CompileResult compileString(
 }) {
   DeprecationProcessingLogger deprecationLogger =
       logger = DeprecationProcessingLogger(
-    logger ?? Logger.stderr(),
+    logger ?? Logger.defaultLogger,
     silenceDeprecations: {...?silenceDeprecations},
     fatalDeprecations: {...?fatalDeprecations},
     futureDeprecations: {...?futureDeprecations},

lib/src/evaluation_context.dart

@@ -69,18 +69,18 @@ void warn(String message, {bool deprecation = false}) =>
           message,
           deprecation ? Deprecation.userAuthored : null,
         ),
-      _ when deprecation => (const Logger.stderr()).warnForDeprecation(
+      _ when deprecation => Logger.defaultLogger.warnForDeprecation(
           Deprecation.userAuthored,
           message,
         ),
-      _ => (const Logger.stderr()).warn(message),
+      _ => Logger.defaultLogger.warn(message),
     };
 
 /// Prints a deprecation warning with [message] of type [deprecation].
 void warnForDeprecation(String message, Deprecation deprecation) =>
     switch (EvaluationContext.currentOrNull) {
       var context? => context.warn(message, deprecation),
-      _ => (const Logger.stderr()).warnForDeprecation(deprecation, message),
+      _ => Logger.defaultLogger.warnForDeprecation(deprecation, message),
     };
 
 /// Prints a deprecation warning with [message] of type [deprecation],
@@ -89,7 +89,7 @@ void warnForDeprecationFromApi(String message, Deprecation deprecation) {
   if (EvaluationContext._currentOrNull case var context?) {
     context.warn(message, deprecation);
   } else {
-    Logger.stderr().warnForDeprecation(deprecation, message);
+    Logger.defaultLogger.warnForDeprecation(deprecation, message);
   }
 }
 

lib/src/io/js.dart

@@ -278,8 +278,9 @@ bool get isWindows => _process?.platform == 'win32';
 
 bool get isMacOS => _process?.platform == 'darwin';
 
-// Node seems to support ANSI escapes on all terminals.
-bool get supportsAnsiEscapes => hasTerminal;
+// Node seems to support ANSI escapes on all terminals, and browser consoles
+// support them as well..
+bool get supportsAnsiEscapes => hasTerminal || isBrowser;
 
 int get exitCode => _process?.exitCode ?? 0;
 

lib/src/js/compile.dart

@@ -34,7 +34,7 @@ NodeCompileResult compile(String path, [CompileOptions? options]) {
   if (!isNodeJs) {
     jsThrow(JsError("The compile() method is only available in Node.js."));
   }
-  var color = options?.alertColor ?? hasTerminal;
+  var color = options?.alertColor ?? supportsAnsiEscapes;
   var ascii = options?.alertAscii ?? glyph.ascii;
   var logger = JSToDartLogger(
     options?.logger,
@@ -82,7 +82,7 @@ NodeCompileResult compile(String path, [CompileOptions? options]) {
 /// See https://github.com/sass/sass/spec/tree/main/js-api/compile.d.ts for
 /// details.
 NodeCompileResult compileString(String text, [CompileStringOptions? options]) {
-  var color = options?.alertColor ?? hasTerminal;
+  var color = options?.alertColor ?? supportsAnsiEscapes;
   var ascii = options?.alertAscii ?? glyph.ascii;
   var logger = JSToDartLogger(
     options?.logger,
@@ -137,7 +137,7 @@ Promise compileAsync(String path, [CompileOptions? options]) {
   if (!isNodeJs) {
     jsThrow(JsError("The compileAsync() method is only available in Node.js."));
   }
-  var color = options?.alertColor ?? hasTerminal;
+  var color = options?.alertColor ?? supportsAnsiEscapes;
   var ascii = options?.alertAscii ?? glyph.ascii;
   var logger = JSToDartLogger(
     options?.logger,
@@ -189,7 +189,7 @@ Promise compileAsync(String path, [CompileOptions? options]) {
 /// See https://github.com/sass/sass/spec/tree/main/js-api/compile.d.ts for
 /// details.
 Promise compileStringAsync(String text, [CompileStringOptions? options]) {
-  var color = options?.alertColor ?? hasTerminal;
+  var color = options?.alertColor ?? supportsAnsiEscapes;
   var ascii = options?.alertAscii ?? glyph.ascii;
   var logger = JSToDartLogger(
     options?.logger,

lib/src/js/legacy.dart

@@ -90,7 +90,7 @@ Future<RenderResult> _renderAsync(RenderOptions options) async {
   var file = options.file.andThen(p.absolute);
   var logger = JSToDartLogger(
     options.logger,
-    Logger.stderr(color: hasTerminal),
+    Logger.defaultLogger,
   );
   if (options.data case var data?) {
     result = await compileStringAsync(
@@ -171,7 +171,7 @@ RenderResult renderSync(RenderOptions options) {
     var file = options.file.andThen(p.absolute);
     var logger = JSToDartLogger(
       options.logger,
-      Logger.stderr(color: hasTerminal),
+      Logger.defaultLogger,
     );
     if (options.data case var data?) {
       result = compileString(

lib/src/logger.dart

@@ -9,6 +9,7 @@ import 'package:stack_trace/stack_trace.dart';
 import 'deprecation.dart';
 import 'logger/deprecation_processing.dart';
 import 'logger/stderr.dart';
+import 'logger/default.dart';
 
 /// An interface for loggers that print messages produced by Sass stylesheets.
 ///
@@ -23,6 +24,11 @@ abstract class Logger {
   /// colors if [color] is `true` (default `false`).
   const factory Logger.stderr({bool color}) = StderrLogger;
 
+  /// The logger that's used when no others are selected. This is always
+  /// [Logger.stderr], but with the value for `color` chosen based on whether
+  /// the current system supports terminal colors.
+  static const Logger defaultLogger = DefaultLogger();
+
   /// Emits a warning with the given [message].
   ///
   /// If [span] is passed, it's the location in the Sass source that generated

lib/src/logger/default.dart

@@ -0,0 +1,39 @@
+// Copyright 2026 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:source_span/source_span.dart';
+import 'package:stack_trace/stack_trace.dart';
+
+import '../deprecation.dart';
+import '../io.dart';
+import '../logger.dart';
+import 'stderr.dart';
+
+/// The logger "wrapped" by [DefaultLogger].
+///
+/// This must be global because it's assigned based on non-const function
+/// results.
+StderrLogger? _default;
+
+/// A logger that wraps [StderrLogger] and chooses whether to activate colors
+/// based on whether the current system supports it.
+final class DefaultLogger extends LoggerWithDeprecationType {
+  const DefaultLogger();
+
+  /// Ensures [_defaultStderr] is initialized and returns it.
+  StderrLogger get _inner {
+    return _default ??= StderrLogger(color: supportsAnsiEscapes);
+  }
+
+  void internalWarn(
+    String message, {
+    FileSpan? span,
+    Trace? trace,
+    Deprecation? deprecation,
+  }) =>
+      _inner.internalWarn(message,
+          span: span, trace: trace, deprecation: deprecation);
+
+  void debug(String message, SourceSpan span) => _inner.debug(message, span);
+}

lib/src/visitor/async_evaluate.dart

@@ -369,7 +369,7 @@ final class _EvaluateVisitor
   })  : _importCache = importCache ??
             (nodeImporter == null ? AsyncImportCache.none() : null),
         _nodeImporter = nodeImporter,
-        _logger = logger ?? const Logger.stderr(),
+        _logger = logger ?? Logger.defaultLogger,
         _quietDeps = quietDeps,
         _sourceMap = sourceMap,
         // The default environment is overridden in [_execute] for full

lib/src/visitor/evaluate.dart

@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_evaluate.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: 57da0468055183da41deb31e5675447fe569975f
+// Checksum: 4f4c80ef555355f888e134d764121a1117d4020c
 //
 // ignore_for_file: unused_import
 
@@ -377,7 +377,7 @@ final class _EvaluateVisitor
   })  : _importCache =
             importCache ?? (nodeImporter == null ? ImportCache.none() : null),
         _nodeImporter = nodeImporter,
-        _logger = logger ?? const Logger.stderr(),
+        _logger = logger ?? Logger.defaultLogger,
         _quietDeps = quietDeps,
         _sourceMap = sourceMap,
         // The default environment is overridden in [_execute] for full

lib/src/visitor/serialize.dart

@@ -166,7 +166,7 @@ final class _SerializeVisitor
         _indentCharacter = useSpaces ? $space : $tab,
         _indentWidth = indentWidth ?? 2,
         _lineFeed = lineFeed ?? LineFeed.lf,
-        _logger = logger ?? const Logger.stderr() {
+        _logger = logger ?? Logger.defaultLogger {
     RangeError.checkValueInInterval(_indentWidth, 0, 10, "indentWidth");
   }
 

pkg/sass_api/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 17.3.4-dev
+## 17.4.0-dev
 
 * No user-visible changes.
 

pkg/sass_api/pubspec.yaml

@@ -2,15 +2,15 @@ name: sass_api
 # Note: Every time we add a new Sass AST node, we need to bump the *major*
 # version because it's a breaking change for anyone who's implementing the
 # visitor interface(s).
-version: 17.3.4-dev
+version: 17.4.0-dev
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: ">=3.6.0 <4.0.0"
 
 dependencies:
-  sass: 1.97.4
+  sass: 1.98.0
 
 dev_dependencies:
   dartdoc: ">=8.0.14 <10.0.0"

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.97.4-dev
+version: 1.98.0-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass