Refactor to use enhanced enums for Output and Show. (#1116)

Also some other minor clean-up while I was at it:

- Remove unneeded library tags.
- Fix some raw typed collections.
- Use list element where it makes sense.
- Remove unneeded .whereType<Rule>() calls. (They were to filter out
  null, but the rule field is non-nullable now.)

Author: munificent

benchmark/benchmark.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library dart_style.benchmark.benchmark;
-
 import 'dart:io';
 
 import 'package:dart_style/dart_style.dart';

lib/src/cli/format_command.dart

@@ -87,20 +87,16 @@ class FormatCommand extends Command<int> {
       usageException('Cannot print a summary with JSON output.');
     }
 
-    int pageWidth;
-    try {
-      pageWidth = int.parse(argResults['line-length']);
-    } on FormatException catch (_) {
-      usageException('--line-length must be an integer, was '
-          '"${argResults['line-length']}".');
-    }
+    var pageWidth = int.tryParse(argResults['line-length']) ??
+        usageException('--line-length must be an integer, was '
+            '"${argResults['line-length']}".');
 
-    int indent;
-    try {
-      indent = int.parse(argResults['indent']);
-      if (indent < 0 || indent.toInt() != indent) throw FormatException();
-    } on FormatException catch (_) {
-      usageException('--indent must be a non-negative integer, was '
+    var indent = int.tryParse(argResults['indent']) ??
+        usageException('--indent must be an integer, was '
+            '"${argResults['indent']}".');
+
+    if (indent < 0) {
+      usageException('--indent must be non-negative, was '
           '"${argResults['indent']}".');
     }
 

lib/src/cli/formatter_options.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library dart_style.src.formatter_options;
-
 import 'dart:io';
 
 import '../source_code.dart';

lib/src/cli/output.dart

@@ -7,36 +7,26 @@ import 'dart:io';
 import '../source_code.dart';
 
 /// Where formatted code results should go.
-class Output {
+enum Output {
   /// Overwrite files on disc.
-  static const Output write = _WriteOutput();
+  write,
 
   /// Print the code to the terminal as human-friendly text.
-  static const Output show = _ShowOutput();
+  show,
 
   /// Print the code to the terminal as JSON.
-  static const Output json = _JsonOutput();
+  json,
 
   /// Do nothing. (Used when the user just wants the list of files that would
   /// be changed.)
-  static const Output none = Output._();
-
-  const Output._();
+  none;
 
   /// Write the file to disc.
   ///
   /// If stdin is being formatted, then [file] is `null`.
-  bool writeFile(File? file, String displayPath, SourceCode result) => false;
-
-  /// Print the file to the terminal in some way.
-  void showFile(String path, SourceCode result) {}
-}
-
-class _WriteOutput extends Output {
-  const _WriteOutput() : super._();
-
-  @override
   bool writeFile(File? file, String displayPath, SourceCode result) {
+    if (this != Output.write) return false;
+
     try {
       file!.writeAsStringSync(result.text);
     } on FileSystemException catch (err) {
@@ -46,35 +36,35 @@ class _WriteOutput extends Output {
 
     return true;
   }
-}
-
-class _ShowOutput extends Output {
-  const _ShowOutput() : super._();
 
-  @override
+  /// Print the file to the terminal in some way.
   void showFile(String path, SourceCode result) {
-    // Don't add an extra newline.
-    stdout.write(result.text);
-  }
-}
+    switch (this) {
+      case Output.show:
+        // Don't add an extra newline.
+        stdout.write(result.text);
+        break;
 
-class _JsonOutput extends Output {
-  const _JsonOutput() : super._();
+      case Output.json:
+        // TODO(rnystrom): Put an empty selection in here to remain compatible with
+        // the old formatter. Since there's no way to pass a selection on the
+        // command line, this will never be used, which is why it's hard-coded to
+        // -1, -1. If we add support for passing in a selection, put the real
+        // result here.
+        print(jsonEncode({
+          'path': path,
+          'source': result.text,
+          'selection': {
+            'offset': result.selectionStart ?? -1,
+            'length': result.selectionLength ?? -1
+          }
+        }));
+        break;
 
-  @override
-  void showFile(String path, SourceCode result) {
-    // TODO(rnystrom): Put an empty selection in here to remain compatible with
-    // the old formatter. Since there's no way to pass a selection on the
-    // command line, this will never be used, which is why it's hard-coded to
-    // -1, -1. If we add support for passing in a selection, put the real
-    // result here.
-    print(jsonEncode({
-      'path': path,
-      'source': result.text,
-      'selection': {
-        'offset': result.selectionStart ?? -1,
-        'length': result.selectionLength ?? -1
-      }
-    }));
+      case Output.write:
+      case Output.none:
+        // Do nothing.
+        break;
+    }
   }
 }

lib/src/cli/show.dart

@@ -4,49 +4,90 @@
 import 'package:path/path.dart' as p;
 
 /// Which file paths should be printed.
-abstract class Show {
+enum Show {
   /// No files.
-  static const Show none = _NoneShow();
+  none,
 
   /// All traversed files.
-  static const Show all = _AllShow();
+  all,
 
   /// Only files whose formatting changed.
-  static const Show changed = _ChangedShow();
+  changed,
 
   /// The legacy dartfmt output style when not overwriting files.
-  static const Show legacy = _LegacyShow();
+  legacy,
 
   /// The legacy dartfmt output style when overwriting files.
-  static const Show overwrite = _OverwriteShow();
+  overwrite,
 
   /// The legacy dartfmt output style in "--dry-run".
-  static const Show dryRun = _DryRunShow();
-
-  const Show._();
+  dryRun;
 
   /// The display path to show for [file] which is in [directory].
   ///
   /// In the old CLI, this does not include [directory], since the directory
   /// name is printed separately. The new CLI only prints file paths, so this
   /// includes the root directory to disambiguate which directory the file is
   /// in.
-  String displayPath(String directory, String file) => p.normalize(file);
+  String displayPath(String directory, String file) {
+    switch (this) {
+      case Show.legacy:
+      case Show.overwrite:
+      case Show.dryRun:
+        return p.relative(file, from: directory);
+
+      default:
+        return p.normalize(file);
+    }
+  }
 
   /// Describes a file that was processed.
   ///
   /// Returns whether or not this file should be displayed.
-  bool file(String path, {required bool changed, required bool overwritten}) =>
-      true;
+  bool file(String path, {required bool changed, required bool overwritten}) {
+    switch (this) {
+      case Show.all:
+      case Show.overwrite:
+        if (changed) {
+          _showFileChange(path, overwritten: overwritten);
+        } else {
+          print('Unchanged $path');
+        }
+        return true;
+
+      case Show.changed:
+        if (changed) _showFileChange(path, overwritten: overwritten);
+        return changed;
+
+      case Show.dryRun:
+        if (changed) print(path);
+        return true;
+
+      default:
+        return true;
+    }
+  }
 
   /// Describes the directory whose contents are about to be processed.
-  void directory(String path) {}
+  void directory(String path) {
+    if (this == Show.legacy || this == Show.overwrite) {
+      print('Formatting directory $directory:');
+    }
+  }
 
   /// Describes the symlink at [path] that wasn't followed.
-  void skippedLink(String path) {}
+  void skippedLink(String path) {
+    if (this == Show.legacy || this == Show.overwrite) {
+      print('Skipping link $path');
+    }
+  }
 
   /// Describes the hidden [path] that wasn't processed.
-  void hiddenPath(String path) {}
+  void hiddenPath(String path) {
+    if (this == Show.legacy || this == Show.overwrite) {
+      print('Skipping hidden path $path');
+    }
+  }
 
   void _showFileChange(String path, {required bool overwritten}) {
     if (overwritten) {
@@ -56,77 +97,3 @@ abstract class Show {
     }
   }
 }
-
-mixin _ShowFileMixin on Show {
-  @override
-  bool file(String path, {required bool changed, required bool overwritten}) {
-    if (changed) {
-      _showFileChange(path, overwritten: overwritten);
-    } else {
-      print('Unchanged $path');
-    }
-
-    return true;
-  }
-}
-
-mixin _LegacyMixin on Show {
-  @override
-  String displayPath(String directory, String file) =>
-      p.relative(file, from: directory);
-
-  @override
-  void directory(String directory) {
-    print('Formatting directory $directory:');
-  }
-
-  @override
-  void skippedLink(String path) {
-    print('Skipping link $path');
-  }
-
-  @override
-  void hiddenPath(String path) {
-    print('Skipping hidden path $path');
-  }
-}
-
-class _NoneShow extends Show {
-  const _NoneShow() : super._();
-}
-
-class _AllShow extends Show with _ShowFileMixin {
-  const _AllShow() : super._();
-}
-
-class _ChangedShow extends Show {
-  const _ChangedShow() : super._();
-
-  @override
-  bool file(String path, {required bool changed, required bool overwritten}) {
-    if (changed) _showFileChange(path, overwritten: overwritten);
-    return changed;
-  }
-}
-
-class _LegacyShow extends Show with _LegacyMixin {
-  const _LegacyShow() : super._();
-}
-
-class _OverwriteShow extends Show with _ShowFileMixin, _LegacyMixin {
-  const _OverwriteShow() : super._();
-}
-
-class _DryRunShow extends Show {
-  const _DryRunShow() : super._();
-
-  @override
-  String displayPath(String directory, String file) =>
-      p.relative(file, from: directory);
-
-  @override
-  bool file(String path, {required bool changed, required bool overwritten}) {
-    if (changed) print(path);
-    return true;
-  }
-}

lib/src/debug.dart

@@ -7,7 +7,6 @@ import 'dart:math' as math;
 
 import 'chunk.dart';
 import 'line_splitting/rule_set.dart';
-import 'rule/rule.dart';
 
 /// Set this to `true` to turn on diagnostic output while building chunks.
 bool traceChunkBuilder = false;
@@ -189,12 +188,12 @@ void dumpChunks(int start, List<Chunk> chunks) {
 
 /// Shows all of the constraints between the rules used by [chunks].
 void dumpConstraints(List<Chunk> chunks) {
-  var rules = chunks.map((chunk) => chunk.rule).whereType<Rule>().toSet();
+  var rules = chunks.map((chunk) => chunk.rule).toSet();
 
   for (var rule in rules) {
-    var constrainedValues = [];
+    var constrainedValues = <String>[];
     for (var value = 0; value < rule.numValues; value++) {
-      var constraints = [];
+      var constraints = <String>[];
       for (var other in rules) {
         if (rule == other) continue;
 

lib/src/exceptions.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library dart_style.src.formatter_exception;
-
 import 'package:analyzer/error/error.dart';
 import 'package:source_span/source_span.dart';
 

lib/src/fast_hash.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library dart_style.src.fast_hash;
-
 /// A mixin for classes with identity equality that need to be frequently
 /// hashed.
 abstract class FastHash {