Migrate to null safety (WIP)

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';
@@ -14,7 +15,6 @@ 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/visitor/serialize.dart';
 
@@ -48,11 +48,11 @@ 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
@@ -90,7 +90,7 @@ String compile(String path,
     Logger logger,
     Iterable<Importer> importers,
     Iterable<String> loadPaths,
-    SyncPackageResolver packageResolver,
+    PackageConfig packageConfig,
     Iterable<Callable> functions,
     OutputStyle style,
     void sourceMap(SingleMapping map),
@@ -99,9 +99,7 @@ String compile(String path,
   var result = c.compile(path,
       logger: logger,
       importCache: ImportCache(importers,
-          logger: logger,
-          loadPaths: loadPaths,
-          packageResolver: packageResolver),
+          logger: logger, loadPaths: loadPaths, packageConfig: packageConfig),
       functions: functions,
       style: style,
       sourceMap: sourceMap != null,
@@ -132,11 +130,11 @@ 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
@@ -178,7 +176,7 @@ String compileString(String source,
     bool color = false,
     Logger logger,
     Iterable<Importer> importers,
-    SyncPackageResolver packageResolver,
+    PackageConfig packageConfig,
     Iterable<String> loadPaths,
     Iterable<Callable> functions,
     OutputStyle style,
@@ -192,9 +190,7 @@ String compileString(String source,
       syntax: syntax ?? (indented ? Syntax.sass : Syntax.scss),
       logger: logger,
       importCache: ImportCache(importers,
-          logger: logger,
-          packageResolver: packageResolver,
-          loadPaths: loadPaths),
+          logger: logger, packageConfig: packageConfig, loadPaths: loadPaths),
       functions: functions,
       style: style,
       importer: importer,
@@ -214,7 +210,7 @@ Future<String> compileAsync(String path,
     {bool color = false,
     Logger logger,
     Iterable<AsyncImporter> importers,
-    SyncPackageResolver packageResolver,
+    PackageConfig packageConfig,
     Iterable<String> loadPaths,
     Iterable<AsyncCallable> functions,
     OutputStyle style,
@@ -223,9 +219,7 @@ Future<String> compileAsync(String path,
   var result = await c.compileAsync(path,
       logger: logger,
       importCache: AsyncImportCache(importers,
-          logger: logger,
-          loadPaths: loadPaths,
-          packageResolver: packageResolver),
+          logger: logger, loadPaths: loadPaths, packageConfig: packageConfig),
       functions: functions,
       style: style,
       sourceMap: sourceMap != null);
@@ -243,7 +237,7 @@ Future<String> compileStringAsync(String source,
     bool color = false,
     Logger logger,
     Iterable<AsyncImporter> importers,
-    SyncPackageResolver packageResolver,
+    PackageConfig packageConfig,
     Iterable<String> loadPaths,
     Iterable<AsyncCallable> functions,
     OutputStyle style,
@@ -257,9 +251,7 @@ Future<String> compileStringAsync(String source,
       syntax: syntax ?? (indented ? Syntax.sass : Syntax.scss),
       logger: logger,
       importCache: AsyncImportCache(importers,
-          logger: logger,
-          packageResolver: packageResolver,
-          loadPaths: loadPaths),
+          logger: logger, packageConfig: packageConfig, loadPaths: loadPaths),
       functions: functions,
       style: style,
       importer: importer,

lib/src/ast/sass/argument_declaration.dart

@@ -25,7 +25,7 @@ class ArgumentDeclaration implements SassNode {
 
   /// Returns [span] expanded to include an identifier immediately before the
   /// declaration, if possible.
-  FileSpan get spanWithName {
+  FileSpan/*!*/ get spanWithName {
     var text = span.file.getText(0);
 
     // Move backwards through and whitspace between the name and the arguments.

lib/src/ast/sass/argument_invocation.dart

@@ -27,7 +27,7 @@ class ArgumentInvocation implements SassNode {
   bool get isEmpty => positional.isEmpty && named.isEmpty && rest == null;
 
   ArgumentInvocation(
-      Iterable<Expression> positional, Map<String, Expression> named, this.span,
+      Iterable<Expression/*!*/> positional, Map<String, Expression/*!*/> named, this.span,
       {this.rest, this.keywordRest})
       : positional = List.unmodifiable(positional),
         named = Map.unmodifiable(named) {

lib/src/ast/sass/at_root_query.dart

@@ -54,7 +54,7 @@ class AtRootQuery {
       AtRootQueryParser(contents, url: url, logger: logger).parse();
 
   /// Returns whether [this] excludes [node].
-  bool excludes(CssParentNode node) {
+  bool excludes(CssParentNode/*!*/ node) {
     if (_all) return !include;
     if (node is CssStyleRule) return excludesStyleRules;
     if (node is CssMediaRule) return excludesName("media");

lib/src/ast/sass/configured_variable.dart

@@ -13,7 +13,7 @@ class ConfiguredVariable implements SassNode {
   final String name;
 
   /// The variable's value.
-  final Expression expression;
+  final Expression/*!*/ expression;
 
   /// Whether the variable can be further configured by outer modules.
   ///

lib/src/ast/sass/expression/binary_operation.dart

@@ -15,10 +15,10 @@ class BinaryOperationExpression implements Expression {
   final BinaryOperator operator;
 
   /// The left-hand operand.
-  final Expression left;
+  final Expression /*!*/ left;
 
   /// The right-hand operand.
-  final Expression right;
+  final Expression /*!*/ right;
 
   /// Whether this is a [BinaryOperator.dividedBy] operation that may be
   /// interpreted as slash-separated numbers.

lib/src/ast/sass/expression/color.dart

@@ -11,7 +11,7 @@ import '../expression.dart';
 /// A color literal.
 class ColorExpression implements Expression {
   /// The value of this color.
-  final SassColor value;
+  final SassColor/*!*/ value;
 
   FileSpan get span => value.originalSpan;
 

lib/src/ast/sass/expression/list.dart

@@ -24,7 +24,7 @@ class ListExpression implements Expression {
 
   final FileSpan span;
 
-  ListExpression(Iterable<Expression> contents, ListSeparator separator,
+  ListExpression(Iterable<Expression/*!*/> contents, ListSeparator separator,
       {bool brackets = false, FileSpan span})
       : this._(List.unmodifiable(contents), separator, brackets, span);
 

lib/src/ast/sass/expression/map.dart

@@ -18,7 +18,7 @@ class MapExpression implements Expression {
 
   final FileSpan span;
 
-  MapExpression(Iterable<Tuple2<Expression, Expression>> pairs, this.span)
+  MapExpression(Iterable<Tuple2<Expression/*!*/, Expression/*!*/>> pairs, this.span)
       : pairs = List.unmodifiable(pairs);
 
   T accept<T>(ExpressionVisitor<T> visitor) => visitor.visitMapExpression(this);

lib/src/ast/sass/expression/parenthesized.dart

@@ -10,7 +10,7 @@ import '../expression.dart';
 /// An expression wrapped in parentheses.
 class ParenthesizedExpression implements Expression {
   /// The internal expression.
-  final Expression expression;
+  final Expression/*!*/ expression;
 
   final FileSpan span;
 

lib/src/ast/sass/expression/string.dart

@@ -26,7 +26,7 @@ class StringExpression implements Expression {
 
   /// Returns Sass source for a quoted string that, when evaluated, will have
   /// [text] as its contents.
-  static String quoteText(String text) =>
+  static String/*!*/ quoteText(String text) =>
       StringExpression.plain(text, null, quotes: true)
           .asInterpolation(static: true)
           .asPlain;
@@ -51,9 +51,9 @@ class StringExpression implements Expression {
   Interpolation asInterpolation({bool static = false, int quote}) {
     if (!hasQuotes) return text;
 
-    quote ??= hasQuotes ? _bestQuote() : null;
+    quote ??= _bestQuote();
     var buffer = InterpolationBuffer();
-    if (quote != null) buffer.writeCharCode(quote);
+    buffer.writeCharCode(quote);
     for (var value in text.contents) {
       assert(value is Expression || value is String);
       if (value is Expression) {
@@ -85,7 +85,7 @@ class StringExpression implements Expression {
         }
       }
     }
-    if (quote != null) buffer.writeCharCode(quote);
+    buffer.writeCharCode(quote);
 
     return buffer.interpolation(text.span);
   }

lib/src/ast/sass/expression/unary_operation.dart

@@ -11,10 +11,10 @@ import '../expression.dart';
 /// A unary operator, as in `+$var` or `not fn()`.
 class UnaryOperationExpression implements Expression {
   /// The operator being invoked.
-  final UnaryOperator operator;
+  final UnaryOperator/*!*/ operator;
 
   /// The operand.
-  final Expression operand;
+  final Expression/*!*/ operand;
 
   final FileSpan span;
 

lib/src/ast/sass/expression/value.dart

@@ -14,7 +14,7 @@ import '../expression.dart';
 /// constructed dynamically, as for the `call()` function.
 class ValueExpression implements Expression {
   /// The embedded value.
-  final Value value;
+  final Value/*!*/ value;
 
   final FileSpan span;
 

lib/src/ast/sass/interpolation.dart

@@ -33,7 +33,7 @@ class Interpolation implements SassNode {
     return first is String ? first : '';
   }
 
-  Interpolation(Iterable<Object /* String | Expression */ > contents, this.span)
+  Interpolation(Iterable<Object/*!*/ /* String | Expression */ > contents, this.span)
       : contents = List.unmodifiable(contents) {
     for (var i = 0; i < this.contents.length; i++) {
       if (this.contents[i] is! String && this.contents[i] is! Expression) {

lib/src/ast/sass/statement/at_root_rule.dart

@@ -19,7 +19,7 @@ class AtRootRule extends ParentStatement {
 
   final FileSpan span;
 
-  AtRootRule(Iterable<Statement> children, this.span, {this.query})
+  AtRootRule(Iterable<Statement/*!*/> children, this.span, {this.query})
       : super(List.unmodifiable(children));
 
   T accept<T>(StatementVisitor<T> visitor) => visitor.visitAtRootRule(this);

lib/src/ast/sass/statement/at_rule.dart

@@ -19,7 +19,7 @@ class AtRule extends ParentStatement {
 
   final FileSpan span;
 
-  AtRule(this.name, this.span, {this.value, Iterable<Statement> children})
+  AtRule(this.name, this.span, {this.value, Iterable<Statement/*!*/> children})
       : super(children == null ? null : List.unmodifiable(children));
 
   T accept<T>(StatementVisitor<T> visitor) => visitor.visitAtRule(this);

lib/src/ast/sass/statement/callable_declaration.dart

@@ -26,7 +26,7 @@ abstract class CallableDeclaration extends ParentStatement {
   final FileSpan span;
 
   CallableDeclaration(
-      this.name, this.arguments, Iterable<Statement> children, this.span,
+      this.name, this.arguments, Iterable<Statement/*!*//*!*/> children, this.span,
       {SilentComment comment})
       : comment = comment,
         super(List.unmodifiable(children));

lib/src/ast/sass/statement/content_block.dart

@@ -11,7 +11,7 @@ import 'callable_declaration.dart';
 
 /// An anonymous block of code that's invoked for a [ContentRule].
 class ContentBlock extends CallableDeclaration {
-  ContentBlock(ArgumentDeclaration arguments, Iterable<Statement> children,
+  ContentBlock(ArgumentDeclaration arguments, Iterable<Statement/*!*/> children,
       FileSpan span)
       : super(null /* name */, arguments, children, span);
 

lib/src/ast/sass/statement/use_rule.dart

@@ -31,7 +31,7 @@ class UseRule implements Statement {
       {Iterable<ConfiguredVariable> configuration})
       : configuration = configuration == null
             ? const []
-            : List.unmodifiable(configuration) {
+            : List<ConfiguredVariable>.unmodifiable(configuration) {
     for (var variable in this.configuration) {
       if (variable.isGuarded) {
         throw ArgumentError.value(variable, "configured variable",

lib/src/ast/sass/statement/while_rule.dart

@@ -20,7 +20,7 @@ class WhileRule extends ParentStatement {
   final FileSpan span;
 
   WhileRule(this.condition, Iterable<Statement> children, this.span)
-      : super(List.unmodifiable(children));
+      : super(List<Statement>.unmodifiable(children));
 
   T accept<T>(StatementVisitor<T> visitor) => visitor.visitWhileRule(this);
 

lib/src/ast/sass/supports_condition/declaration.dart

@@ -11,10 +11,10 @@ import '../supports_condition.dart';
 /// supported.
 class SupportsDeclaration implements SupportsCondition {
   /// The name of the declaration being tested.
-  final Expression name;
+  final Expression/*!*/ name;
 
   /// The value of the declaration being tested.
-  final Expression value;
+  final Expression/*!*/ value;
 
   final FileSpan span;
 

lib/src/async_compile.dart

@@ -15,7 +15,6 @@ import 'importer.dart';
 import 'importer/node.dart';
 import 'io.dart';
 import 'logger.dart';
-import 'sync_package_resolver.dart';
 import 'syntax.dart';
 import 'utils.dart';
 import 'visitor/async_evaluate.dart';
@@ -77,7 +76,6 @@ Future<CompileResult> compileStringAsync(String source,
     NodeImporter nodeImporter,
     Iterable<AsyncImporter> importers,
     Iterable<String> loadPaths,
-    SyncPackageResolver packageResolver,
     AsyncImporter importer,
     Iterable<AsyncCallable> functions,
     OutputStyle style,