Some improvements to the command-line analyzer's output.

pkg/analyzer_cli/lib/src/error_severity.dart

Index: pkg/analyzer_cli/lib/src/error_severity.dart
diff --git a/pkg/analyzer_cli/lib/src/error_severity.dart b/pkg/analyzer_cli/lib/src/error_severity.dart
new file mode 100644
index 0000000000000000000000000000000000000000..29566237c246b04b15c674734cc63b8f5cdbdc07
--- /dev/null
+++ b/pkg/analyzer_cli/lib/src/error_severity.dart
@@ -0,0 +1,72 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/source/error_processor.dart';
+import 'package:analyzer/src/error/codes.dart';
+import 'package:analyzer/src/generated/engine.dart' hide AnalysisResult;
+import 'package:analyzer_cli/src/error_formatter.dart';
+import 'package:analyzer_cli/src/options.dart';
+
+/// Check various configuration options to get a desired severity for this
+/// [error] (or `null` if it's to be suppressed).
+ProcessedSeverity processError(AnalysisError error,
+    CommandLineOptions commandLineOptions, AnalysisOptions analysisOptions) {
+  ErrorSeverity severity = computeSeverity(error, commandLineOptions,
+      analysisOptions: analysisOptions);
+  bool isOverridden = false;
+
+  // Skip TODOs categorically (unless escalated to ERROR or HINT.)
+  // https://github.com/dart-lang/sdk/issues/26215
+  if (error.errorCode.type == ErrorType.TODO &&
+      severity == ErrorSeverity.INFO) {
+    return null;
+  }
+
+  // First check for a filter.
+  if (severity == null) {
+    // Null severity means the error has been explicitly ignored.
+    return null;
+  } else {
+    isOverridden = true;
+  }
+
+  // If not overridden, some "natural" severities get globally filtered.
+  if (!isOverridden) {
+    // Check for global hint filtering.
+    if (severity == ErrorSeverity.INFO && commandLineOptions.disableHints) {
+      return null;
+    }
+  }
+
+  return new ProcessedSeverity(severity, isOverridden);
+}
+
+/// Compute the severity of the error; however:
+/// - if [options.enableTypeChecks] is false, then de-escalate checked-mode
+///   compile time errors to a severity of [ErrorSeverity.INFO].
+/// - if [options.hintsAreFatal] is true, escalate hints to errors.
+/// - if [options.lintsAreFatal] is true, escalate lints to errors.
+ErrorSeverity computeSeverity(
+    AnalysisError error, CommandLineOptions commandLineOptions,
+    {AnalysisOptions analysisOptions}) {
+  if (analysisOptions != null) {
+    ErrorProcessor processor =
+        ErrorProcessor.getProcessor(analysisOptions, error);
+    // If there is a processor for this error, defer to it.
+    if (processor != null) {
+      return processor.severity;
+    }
+  }
+
+  if (!commandLineOptions.enableTypeChecks &&
+      error.errorCode.type == ErrorType.CHECKED_MODE_COMPILE_TIME_ERROR) {
+    return ErrorSeverity.INFO;
+  } else if (commandLineOptions.hintsAreFatal && error.errorCode is HintCode) {
+    return ErrorSeverity.ERROR;
+  } else if (commandLineOptions.lintsAreFatal && error.errorCode is LintCode) {
+    return ErrorSeverity.ERROR;
+  }
+  return error.errorCode.errorSeverity;
+}