Enable strict null checks

bin/sass.dart

@@ -24,7 +24,7 @@ Future<void> main(List<String> args) async {
   // has been printed to stderr.
   //
   // If [trace] is passed, its terse representation is printed after the error.
-  void printError(String error, StackTrace stackTrace) {
+  void printError(String error, StackTrace? stackTrace) {
     if (printedError) stderr.writeln();
     printedError = true;
     stderr.writeln(error);
@@ -35,7 +35,7 @@ Future<void> main(List<String> args) async {
     }
   }
 
-  ExecutableOptions options;
+  ExecutableOptions? options;
   try {
     options = ExecutableOptions.parse(args);
     term_glyph.ascii = !options.unicode;
@@ -52,7 +52,7 @@ Future<void> main(List<String> args) async {
     }
 
     var graph = StylesheetGraph(
-        ImportCache([], loadPaths: options.loadPaths, logger: options.logger));
+        ImportCache(loadPaths: options.loadPaths, logger: options.logger));
     if (options.watch) {
       await watch(options, graph);
       return;
@@ -68,7 +68,9 @@ Future<void> main(List<String> args) async {
         // dart-lang/sdk#33400.
         () {
           try {
-            if (destination != null && !options.emitErrorCss) {
+            if (destination != null &&
+                // dart-lang/sdk#45348
+                !options!.emitErrorCss) {
               deleteFile(destination);
             }
           } on FileSystemException {
@@ -86,7 +88,11 @@ Future<void> main(List<String> args) async {
         if (exitCode != 66) exitCode = 65;
         if (options.stopOnError) return;
       } on FileSystemException catch (error, stackTrace) {
-        printError("Error reading ${p.relative(error.path)}: ${error.message}.",
+        var path = error.path;
+        printError(
+            path == null
+                ? error.message
+                : "Error reading ${p.relative(path)}: ${error.message}.",
             options.trace ? stackTrace : null);
 
         // Error 66 indicates no input.
@@ -115,12 +121,14 @@ Future<void> main(List<String> args) async {
 
 /// Loads and returns the current version of Sass.
 Future<String> _loadVersion() async {
-  var version = const String.fromEnvironment('version');
-  if (const bool.fromEnvironment('node')) {
-    version += " compiled with dart2js "
-        "${const String.fromEnvironment('dart-version')}";
+  if (const bool.hasEnvironment('version')) {
+    var version = const String.fromEnvironment('version');
+    if (const bool.fromEnvironment('node')) {
+      version += " compiled with dart2js "
+          "${const String.fromEnvironment('dart-version')}";
+    }
+    return version;
   }
-  if (version != null) return version;
 
   var libDir =
       p.fromUri(await Isolate.resolvePackageUri(Uri.parse('package:sass/')));

lib/sass.dart

@@ -5,6 +5,7 @@
 /// We strongly recommend importing this library with the prefix `sass`.
 library sass;
 
+import 'package:package_config/package_config_types.dart';
 import 'package:source_maps/source_maps.dart';
 
 import 'src/async_import_cache.dart';
@@ -14,8 +15,8 @@ import 'src/exception.dart';
 import 'src/import_cache.dart';
 import 'src/importer.dart';
 import 'src/logger.dart';
-import 'src/sync_package_resolver.dart';
 import 'src/syntax.dart';
+import 'src/util/nullable.dart';
 import 'src/visitor/serialize.dart';
 
 export 'src/callable.dart' show Callable, AsyncCallable;
@@ -48,11 +49,11 @@ export 'src/warn.dart' show warn;
 /// * Each load path specified in the `SASS_PATH` environment variable, which
 ///   should be semicolon-separated on Windows and colon-separated elsewhere.
 ///
-/// * `package:` resolution using [packageResolver], which is a
-///   [`SyncPackageResolver`][] from the `package_resolver` package. Note that
+/// * `package:` resolution using [packageConfig], which is a
+///   [`PackageConfig`][] from the `package_resolver` package. Note that
 ///   this is a shorthand for adding a [PackageImporter] to [importers].
 ///
-/// [`SyncPackageResolver`]: https://www.dartdocs.org/documentation/package_resolver/latest/package_resolver/SyncPackageResolver-class.html
+/// [`PackageConfig`]: https://pub.dev/documentation/package_config/latest/package_config.package_config/PackageConfig-class.html
 ///
 /// Dart functions that can be called from Sass may be passed using [functions].
 /// Each [Callable] defines a top-level function that will be invoked when the
@@ -87,26 +88,27 @@ export 'src/warn.dart' show warn;
 /// Throws a [SassException] if conversion fails.
 String compile(String path,
     {bool color = false,
-    Logger logger,
-    Iterable<Importer> importers,
-    Iterable<String> loadPaths,
-    SyncPackageResolver packageResolver,
-    Iterable<Callable> functions,
-    OutputStyle style,
-    void sourceMap(SingleMapping map),
+    Logger? logger,
+    Iterable<Importer>? importers,
+    Iterable<String>? loadPaths,
+    PackageConfig? packageConfig,
+    Iterable<Callable>? functions,
+    OutputStyle? style,
+    void sourceMap(SingleMapping map)?,
     bool charset = true}) {
   logger ??= Logger.stderr(color: color);
   var result = c.compile(path,
       logger: logger,
-      importCache: ImportCache(importers,
+      importCache: ImportCache(
+          importers: importers,
           logger: logger,
           loadPaths: loadPaths,
-          packageResolver: packageResolver),
+          packageConfig: packageConfig),
       functions: functions,
       style: style,
       sourceMap: sourceMap != null,
       charset: charset);
-  if (sourceMap != null) sourceMap(result.sourceMap);
+  result.sourceMap.andThen(sourceMap);
   return result.css;
 }
 
@@ -132,11 +134,11 @@ String compile(String path,
 /// * Each load path specified in the `SASS_PATH` environment variable, which
 ///   should be semicolon-separated on Windows and colon-separated elsewhere.
 ///
-/// * `package:` resolution using [packageResolver], which is a
-///   [`SyncPackageResolver`][] from the `package_resolver` package. Note that
+/// * `package:` resolution using [packageConfig], which is a
+///   [`PackageConfig`][] from the `package_resolver` package. Note that
 ///   this is a shorthand for adding a [PackageImporter] to [importers].
 ///
-/// [`SyncPackageResolver`]: https://www.dartdocs.org/documentation/package_resolver/latest/package_resolver/SyncPackageResolver-class.html
+/// [`PackageConfig`]: https://pub.dev/documentation/package_config/latest/package_config.package_config/PackageConfig-class.html
 ///
 /// Dart functions that can be called from Sass may be passed using [functions].
 /// Each [Callable] defines a top-level function that will be invoked when the
@@ -174,34 +176,35 @@ String compile(String path,
 ///
 /// Throws a [SassException] if conversion fails.
 String compileString(String source,
-    {Syntax syntax,
+    {Syntax? syntax,
     bool color = false,
-    Logger logger,
-    Iterable<Importer> importers,
-    SyncPackageResolver packageResolver,
-    Iterable<String> loadPaths,
-    Iterable<Callable> functions,
-    OutputStyle style,
-    Importer importer,
-    Object url,
-    void sourceMap(SingleMapping map),
+    Logger? logger,
+    Iterable<Importer>? importers,
+    PackageConfig? packageConfig,
+    Iterable<String>? loadPaths,
+    Iterable<Callable>? functions,
+    OutputStyle? style,
+    Importer? importer,
+    Object? url,
+    void sourceMap(SingleMapping map)?,
     bool charset = true,
     @Deprecated("Use syntax instead.") bool indented = false}) {
   logger ??= Logger.stderr(color: color);
   var result = c.compileString(source,
       syntax: syntax ?? (indented ? Syntax.sass : Syntax.scss),
       logger: logger,
-      importCache: ImportCache(importers,
+      importCache: ImportCache(
+          importers: importers,
           logger: logger,
-          packageResolver: packageResolver,
+          packageConfig: packageConfig,
           loadPaths: loadPaths),
       functions: functions,
       style: style,
       importer: importer,
       url: url,
       sourceMap: sourceMap != null,
       charset: charset);
-  if (sourceMap != null) sourceMap(result.sourceMap);
+  result.sourceMap.andThen(sourceMap);
   return result.css;
 }
 
@@ -212,24 +215,25 @@ String compileString(String source,
 /// slower, so [compile] should be preferred if possible.
 Future<String> compileAsync(String path,
     {bool color = false,
-    Logger logger,
-    Iterable<AsyncImporter> importers,
-    SyncPackageResolver packageResolver,
-    Iterable<String> loadPaths,
-    Iterable<AsyncCallable> functions,
-    OutputStyle style,
-    void sourceMap(SingleMapping map)}) async {
+    Logger? logger,
+    Iterable<AsyncImporter>? importers,
+    PackageConfig? packageConfig,
+    Iterable<String>? loadPaths,
+    Iterable<AsyncCallable>? functions,
+    OutputStyle? style,
+    void sourceMap(SingleMapping map)?}) async {
   logger ??= Logger.stderr(color: color);
   var result = await c.compileAsync(path,
       logger: logger,
-      importCache: AsyncImportCache(importers,
+      importCache: AsyncImportCache(
+          importers: importers,
           logger: logger,
           loadPaths: loadPaths,
-          packageResolver: packageResolver),
+          packageConfig: packageConfig),
       functions: functions,
       style: style,
       sourceMap: sourceMap != null);
-  if (sourceMap != null) sourceMap(result.sourceMap);
+  result.sourceMap.andThen(sourceMap);
   return result.css;
 }
 
@@ -239,33 +243,34 @@ Future<String> compileAsync(String path,
 /// synchronous [Importer]s. However, running asynchronously is also somewhat
 /// slower, so [compileString] should be preferred if possible.
 Future<String> compileStringAsync(String source,
-    {Syntax syntax,
+    {Syntax? syntax,
     bool color = false,
-    Logger logger,
-    Iterable<AsyncImporter> importers,
-    SyncPackageResolver packageResolver,
-    Iterable<String> loadPaths,
-    Iterable<AsyncCallable> functions,
-    OutputStyle style,
-    AsyncImporter importer,
-    Object url,
-    void sourceMap(SingleMapping map),
+    Logger? logger,
+    Iterable<AsyncImporter>? importers,
+    PackageConfig? packageConfig,
+    Iterable<String>? loadPaths,
+    Iterable<AsyncCallable>? functions,
+    OutputStyle? style,
+    AsyncImporter? importer,
+    Object? url,
+    void sourceMap(SingleMapping map)?,
     bool charset = true,
     @Deprecated("Use syntax instead.") bool indented = false}) async {
   logger ??= Logger.stderr(color: color);
   var result = await c.compileStringAsync(source,
       syntax: syntax ?? (indented ? Syntax.sass : Syntax.scss),
       logger: logger,
-      importCache: AsyncImportCache(importers,
+      importCache: AsyncImportCache(
+          importers: importers,
           logger: logger,
-          packageResolver: packageResolver,
+          packageConfig: packageConfig,
           loadPaths: loadPaths),
       functions: functions,
       style: style,
       importer: importer,
       url: url,
       sourceMap: sourceMap != null,
       charset: charset);
-  if (sourceMap != null) sourceMap(result.sourceMap);
+  result.sourceMap.andThen(sourceMap);
   return result.css;
 }

lib/src/ast/css/at_rule.dart

@@ -12,7 +12,7 @@ abstract class CssAtRule extends CssParentNode {
   CssValue<String> get name;
 
   /// The value of this rule.
-  CssValue<String> get value;
+  CssValue<String>? get value;
 
   /// Whether the rule has no children.
   ///

lib/src/ast/css/import.dart

@@ -15,10 +15,10 @@ abstract class CssImport extends CssNode {
   CssValue<String> get url;
 
   /// The supports condition attached to this import.
-  CssValue<String> get supports;
+  CssValue<String>? get supports;
 
   /// The media query attached to this import.
-  List<CssMediaQuery> get media;
+  List<CssMediaQuery>? get media;
 
   T accept<T>(CssVisitor<T> visitor) => visitor.visitCssImport(this);
 }

lib/src/ast/css/media_query.dart

@@ -11,12 +11,12 @@ class CssMediaQuery {
   /// The modifier, probably either "not" or "only".
   ///
   /// This may be `null` if no modifier is in use.
-  final String modifier;
+  final String? modifier;
 
   /// The media type, for example "screen" or "print".
   ///
   /// This may be `null`. If so, [features] will not be empty.
-  final String type;
+  final String? type;
 
   /// Feature queries, including parentheses.
   final List<String> features;
@@ -33,11 +33,11 @@ class CssMediaQuery {
   ///
   /// Throws a [SassFormatException] if parsing fails.
   static List<CssMediaQuery> parseList(String contents,
-          {Object url, Logger logger}) =>
+          {Object? url, Logger? logger}) =>
       MediaQueryParser(contents, url: url, logger: logger).parse();
 
   /// Creates a media query specifies a type and, optionally, features.
-  CssMediaQuery(this.type, {this.modifier, Iterable<String> features})
+  CssMediaQuery(this.type, {this.modifier, Iterable<String>? features})
       : features = features == null ? const [] : List.unmodifiable(features);
 
   /// Creates a media query that only specifies features.
@@ -59,8 +59,8 @@ class CssMediaQuery {
           CssMediaQuery.condition([...this.features, ...other.features]));
     }
 
-    String modifier;
-    String type;
+    String? modifier;
+    String? type;
     List<String> features;
     if ((ourModifier == 'not') != (theirModifier == 'not')) {
       if (ourType == theirType) {

lib/src/ast/css/modifiable/at_rule.dart

@@ -12,7 +12,7 @@ import 'node.dart';
 /// A modifiable version of [CssAtRule] for use in the evaluation step.
 class ModifiableCssAtRule extends ModifiableCssParentNode implements CssAtRule {
   final CssValue<String> name;
-  final CssValue<String> value;
+  final CssValue<String>? value;
   final bool isChildless;
   final FileSpan span;
 

lib/src/ast/css/modifiable/declaration.dart

@@ -2,7 +2,6 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import 'package:meta/meta.dart';
 import 'package:source_span/source_span.dart';
 
 import '../../../value.dart';
@@ -24,9 +23,9 @@ class ModifiableCssDeclaration extends ModifiableCssNode
 
   /// Returns a new CSS declaration with the given properties.
   ModifiableCssDeclaration(this.name, this.value, this.span,
-      {@required bool parsedAsCustomProperty, FileSpan valueSpanForMap})
+      {required bool parsedAsCustomProperty, FileSpan? valueSpanForMap})
       : parsedAsCustomProperty = parsedAsCustomProperty,
-        valueSpanForMap = valueSpanForMap ?? span {
+        valueSpanForMap = valueSpanForMap ?? value.span {
     if (parsedAsCustomProperty) {
       if (!isCustomProperty) {
         throw ArgumentError(

lib/src/ast/css/modifiable/import.dart

@@ -18,15 +18,15 @@ class ModifiableCssImport extends ModifiableCssNode implements CssImport {
   final CssValue<String> url;
 
   /// The supports condition attached to this import.
-  final CssValue<String> supports;
+  final CssValue<String>? supports;
 
   /// The media query attached to this import.
-  final List<CssMediaQuery> media;
+  final List<CssMediaQuery>? media;
 
   final FileSpan span;
 
   ModifiableCssImport(this.url, this.span,
-      {this.supports, Iterable<CssMediaQuery> media})
+      {this.supports, Iterable<CssMediaQuery>? media})
       : media = media == null ? null : List.unmodifiable(media);
 
   T accept<T>(ModifiableCssVisitor<T> visitor) => visitor.visitCssImport(this);