Migrate package:analyzer_utilities to null safety.

Note that it uses package:analyzer that is not migrated yet, but is
being migrated. But it also uses package:html that we did not have
plans to migrate yet. Anyway, this CL will move us forward.

Change-Id: I6210c6baef8c20c0803a304d7bd99acc1f8ccd37
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/177200
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

.dart_tool/package_config.json

@@ -95,7 +95,7 @@
       "name": "analyzer_utilities",
       "rootUri": "../pkg/analyzer_utilities",
       "packageUri": "lib/",
-      "languageVersion": "2.1"
+      "languageVersion": "2.12"
     },
     {
       "name": "args",

pkg/analyzer_utilities/lib/html.dart

@@ -76,7 +76,7 @@ dom.Element makeElement(
  * Mixin class for generating HTML.
  */
 mixin HtmlGenerator {
-  List<dom.Node> _html;
+  List<dom.Node> _html = [];
 
   /**
    * Add the given [node] to the HTML output.
@@ -99,7 +99,7 @@ mixin HtmlGenerator {
    * [writeln], [add], [addAll] or [element], and return the result as a list
    * of HTML nodes.
    */
-  List<dom.Node> collectHtml(void callback()) {
+  List<dom.Node> collectHtml(void Function()? callback) {
     List<dom.Node> oldHtml = _html;
     try {
       _html = <dom.Node>[];
@@ -117,7 +117,7 @@ mixin HtmlGenerator {
    * [name] and [attributes].
    */
   void element(String name, Map<dynamic, String> attributes,
-      [void callback()]) {
+      [void Function()? callback]) {
     add(makeElement(name, attributes, collectHtml(callback)));
   }
 

pkg/analyzer_utilities/lib/tools.dart

@@ -56,7 +56,7 @@ typedef Future<String> FileContentsComputer(String pkgPath);
  * Mixin class for generating code.
  */
 class CodeGenerator {
-  _CodeGeneratorState _state;
+  _CodeGeneratorState _state = _CodeGeneratorState();
 
   /**
    * Settings that specialize code generation behavior for a given
@@ -98,16 +98,23 @@ class CodeGenerator {
    */
   void docComment(List<dom.Node> docs, {bool removeTrailingNewLine: false}) {
     if (containsOnlyWhitespace(docs)) return;
-    if (codeGeneratorSettings.docCommentStartMarker != null)
-      writeln(codeGeneratorSettings.docCommentStartMarker);
+
+    var startMarker = codeGeneratorSettings.docCommentStartMarker;
+    if (startMarker != null) {
+      writeln(startMarker);
+    }
+
     int width = codeGeneratorSettings.commentLineLength;
     bool javadocStyle = codeGeneratorSettings.languageName == 'java';
     indentBy(codeGeneratorSettings.docCommentLineLeader, () {
       write(nodesToText(docs, width - _state.indent.length, javadocStyle,
           removeTrailingNewLine: removeTrailingNewLine));
     });
-    if (codeGeneratorSettings.docCommentEndMarker != null)
-      writeln(codeGeneratorSettings.docCommentEndMarker);
+
+    var endMarker = codeGeneratorSettings.docCommentEndMarker;
+    if (endMarker != null) {
+      writeln(endMarker);
+    }
   }
 
   /**
@@ -154,7 +161,7 @@ class CodeGenerator {
     });
   }
 
-  void outputHeader({bool javaStyle: false, String year = null}) {
+  void outputHeader({bool javaStyle: false, String? year = null}) {
     String header;
     if (codeGeneratorSettings.languageName == 'java') {
       header = '''
@@ -224,7 +231,7 @@ class CodeGeneratorSettings {
   /**
    * Start marker for doc comments.
    */
-  String docCommentStartMarker;
+  String? docCommentStartMarker;
 
   /**
    * Line leader for body lines in doc comments.
@@ -234,7 +241,7 @@ class CodeGeneratorSettings {
   /**
    * End marker for doc comments.
    */
-  String docCommentEndMarker;
+  String? docCommentEndMarker;
 
   /**
    * Line length for doc comment lines.
@@ -273,16 +280,20 @@ class DartFormat {
 
   static void formatFile(File file) {
     ProcessResult result = Process.runSync(_dartfmtPath, ['-w', file.path]);
-    if (result.exitCode != 0) throw result.stderr;
+    _throwIfExitCode(result);
   }
 
   static String formatText(String text) {
     File file = new File(join(Directory.systemTemp.path, 'gen.dart'));
     file.writeAsStringSync(text);
     ProcessResult result = Process.runSync(_dartfmtPath, ['-w', file.path]);
-    if (result.exitCode != 0) throw result.stderr;
+    _throwIfExitCode(result);
     return file.readAsStringSync();
   }
+
+  static void _throwIfExitCode(ProcessResult result) {
+    if (result.exitCode != 0) throw result.stderr as Object;
+  }
 }
 
 /**
@@ -383,8 +394,9 @@ class GeneratedDirectory extends GeneratedContent {
     Directory outputDirectory = output(pkgPath);
     Map<String, FileContentsComputer> map = directoryContentsComputer(pkgPath);
     try {
-      for (String file in map.keys) {
-        FileContentsComputer fileContentsComputer = map[file];
+      for (var entry in map.entries) {
+        String file = entry.key;
+        FileContentsComputer fileContentsComputer = entry.value;
         String expectedContents = await fileContentsComputer(pkgPath);
         File outputFile = new File(posix.join(outputDirectory.path, file));
         String actualContents = outputFile.readAsStringSync();
@@ -433,8 +445,9 @@ class GeneratedDirectory extends GeneratedContent {
 
     // generate all of the files in the directory
     Map<String, FileContentsComputer> map = directoryContentsComputer(pkgPath);
-    for (String file in map.keys) {
-      FileContentsComputer fileContentsComputer = map[file];
+    for (var entry in map.entries) {
+      String file = entry.key;
+      FileContentsComputer fileContentsComputer = entry.value;
       File outputFile = new File(posix.join(outputDirectory.path, file));
       print('  ${outputFile.path}');
       String contents = await fileContentsComputer(pkgPath);
@@ -510,7 +523,7 @@ class GeneratedFile extends GeneratedContent {
  * for enclosing inside a <pre> element.
  */
 abstract class HtmlCodeGenerator {
-  _HtmlCodeGeneratorState _state;
+  _HtmlCodeGeneratorState _state = _HtmlCodeGeneratorState();
 
   /**
    * Add the given [node] to the HTML output.
@@ -533,7 +546,7 @@ abstract class HtmlCodeGenerator {
    * [writeln], [add], or [addAll], and return the result as a list of DOM
    * nodes.
    */
-  List<dom.Node> collectHtml(void callback()) {
+  List<dom.Node> collectHtml(void Function()? callback) {
     _HtmlCodeGeneratorState oldState = _state;
     try {
       _state = new _HtmlCodeGeneratorState();
@@ -551,7 +564,7 @@ abstract class HtmlCodeGenerator {
    * [name] and [attributes].
    */
   void element(String name, Map<dynamic, String> attributes,
-      [void callback()]) {
+      [void Function()? callback]) {
     add(makeElement(name, attributes, collectHtml(callback)));
   }
 

pkg/analyzer_utilities/lib/verify_tests.dart

@@ -18,7 +18,7 @@ class VerifyTests {
   final String testDirPath;
 
   /// Paths to exclude from analysis completely.
-  final List<String> excludedPaths;
+  final List<String>? excludedPaths;
 
   VerifyTests(this.testDirPath, {this.excludedPaths});
 
@@ -66,7 +66,7 @@ class VerifyTests {
   void _buildTestsIn(
       AnalysisSession session, String testDirPath, Folder directory) {
     var testFileNames = <String>[];
-    File testAllFile;
+    File? testAllFile;
     var children = directory.getChildren();
     children
         .sort((first, second) => first.shortName.compareTo(second.shortName));