General cleanup (#1516)

* Use one StringBuffer, make it private and final
* Move PackageWarningCounter into its own file
* dartfmt
* Make packageWarningText const
* Remove unnecessary indirection of sets
* _writeWarning cleanup
* Update dependencies - including latest markdown, etc
* Put braces on conditional
* Cleanup nameAndLocation Tuple

Author: kevmoo

analysis_options.yaml

@@ -15,4 +15,5 @@ linter:
     - no_adjacent_strings_in_list
     - package_api_docs
     - slash_for_doc_comments
+    - prefer_final_fields
 #    - unnecessary_brace_in_string_interps

lib/dartdoc.dart

@@ -36,6 +36,7 @@ import 'src/io_utils.dart';
 import 'src/model.dart';
 import 'src/model_utils.dart';
 import 'src/package_meta.dart';
+import 'src/warnings.dart';
 
 export 'src/config.dart';
 export 'src/element_type.dart';
@@ -107,15 +108,14 @@ class DartDoc {
   final Set<String> writtenFiles = new Set();
 
   // Fires when the self checks make progress.
-  StreamController<String> _onCheckProgress;
+  final StreamController<String> _onCheckProgress =
+      new StreamController(sync: true);
 
   Stopwatch _stopwatch;
 
   DartDoc(this.rootDir, this.excludes, this.sdkDir, this.generators,
       this.outputDir, this.packageMeta, this.includes,
-      {this.includeExternals: const []}) {
-    _onCheckProgress = new StreamController(sync: true);
-  }
+      {this.includeExternals: const []});
 
   Stream<String> get onCheckProgress => _onCheckProgress.stream;
 

lib/src/config.dart

@@ -4,7 +4,6 @@
 
 library dartdoc.config;
 
-import 'dart:collection' show UnmodifiableListView;
 import 'dart:io';
 
 class Config {
@@ -46,10 +45,8 @@ void setConfig(
     bool autoIncludeDependencies: false,
     List<String> categoryOrder,
     double reexportMinConfidence: 0.1,
-    verboseWarnings: true,
+    bool verboseWarnings: true,
     List<String> dropTextFrom}) {
-  categoryOrder ??= new UnmodifiableListView<String>([]);
-  dropTextFrom ??= new UnmodifiableListView<String>([]);
   _config = new Config._(
       inputDir,
       showWarnings,
@@ -58,8 +55,8 @@ void setConfig(
       includeSource,
       sdkVersion,
       autoIncludeDependencies,
-      categoryOrder,
+      categoryOrder ?? const <String>[],
       reexportMinConfidence,
       verboseWarnings,
-      dropTextFrom);
+      dropTextFrom ?? const <String>[]);
 }

lib/src/html/html_generator_instance.dart

@@ -11,6 +11,7 @@ import 'package:collection/collection.dart' show compareNatural;
 import 'package:path/path.dart' as path;
 
 import '../model.dart';
+import '../warnings.dart';
 import 'html_generator.dart' show HtmlGeneratorOptions;
 import 'resource_loader.dart' as loader;
 import 'resources.g.dart' as resources;

lib/src/markdown_processor.dart

@@ -16,6 +16,7 @@ import 'package:markdown/markdown.dart' as md;
 import 'package:tuple/tuple.dart';
 
 import 'model.dart';
+import 'warnings.dart';
 
 const validHtmlTags = const [
   "a",