refactor: maintability index (#452)

* refactor: remove unused code

* feat: provide otherMetricsValues in computeImplementation

* refactor: implement Maintainability Index metric

* chore: setup mi metric

Author: dkrutskikh

README.md

@@ -157,6 +157,7 @@ Usage: metrics [arguments...] <directories>
     --number-of-parameters=<4>                    Number of Parameters threshold.
     --source-lines-of-code=<50>                   Source lines of Code threshold.
     --weight-of-class=<0.33>                      Weight Of a Class threshold.
+    --maintainability-index=<50>                  Maintainability Index threshold.
 
 
     --root-folder=<./>                            Root folder.

analysis_options.yaml

@@ -17,6 +17,7 @@ dart_code_metrics:
     - long-parameter-list
   metrics:
     cyclomatic-complexity: 20
+    maintainability-index: 50
     maximum-nesting: 5
     number-of-parameters: 5
   metrics-exclude:

lib/src/analyzers/lint_analyzer/lint_analyzer.dart

@@ -1,9 +1,7 @@
 import 'dart:io';
-import 'dart:math';
 
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:collection/collection.dart';
 import 'package:path/path.dart';
 
 import '../../config_builder/config_builder.dart';
@@ -15,14 +13,8 @@ import '../../utils/file_utils.dart';
 import '../../utils/node_utils.dart';
 import 'lint_analysis_config.dart';
 import 'lint_config.dart';
-import 'metrics/metrics_list/cyclomatic_complexity/cyclomatic_complexity_metric.dart';
-import 'metrics/metrics_list/halstead_volume/halstead_volume_metric.dart';
-import 'metrics/metrics_list/source_lines_of_code/source_lines_of_code_metric.dart';
-import 'metrics/models/metric_documentation.dart';
 import 'metrics/models/metric_value.dart';
-import 'metrics/models/metric_value_level.dart';
 import 'metrics/scope_visitor.dart';
-import 'models/entity_type.dart';
 import 'models/internal_resolved_unit_result.dart';
 import 'models/issue.dart';
 import 'models/lint_file_report.dart';
@@ -322,50 +314,6 @@ class LintAnalyzer {
         }
       }
 
-      final cyclomatic = metrics.firstWhereOrNull(
-        (value) => value.metricsId == CyclomaticComplexityMetric.metricId,
-      );
-
-      final halsteadVolume = metrics.firstWhereOrNull(
-        (value) => value.metricsId == HalsteadVolumeMetric.metricId,
-      );
-
-      final sourceLinesOfCode = metrics.firstWhereOrNull(
-        (value) => value.metricsId == SourceLinesOfCodeMetric.metricId,
-      );
-
-      if (cyclomatic != null &&
-          halsteadVolume != null &&
-          sourceLinesOfCode != null) {
-        final maintainabilityIndex = max(
-          0,
-          (171 -
-                  5.2 * log(max(1, halsteadVolume.value)) -
-                  cyclomatic.value * 0.23 -
-                  16.2 * log(max(1, sourceLinesOfCode.value))) *
-              100 /
-              171,
-        ).toDouble();
-
-        metrics.add(
-          MetricValue<double>(
-            metricsId: 'maintainability-index',
-            documentation: const MetricDocumentation(
-              name: 'Maintainability index',
-              shortName: '',
-              brief: '',
-              measuredType: EntityType.classEntity,
-              recomendedThreshold: 0,
-            ),
-            value: maintainabilityIndex,
-            level: _maintainabilityIndexViolationLevel(
-              maintainabilityIndex,
-            ),
-            comment: '',
-          ),
-        );
-      }
-
       functionRecords[function] = Report(
         location: nodeLocation(node: function.declaration, source: source),
         declaration: function.declaration,
@@ -376,18 +324,6 @@ class LintAnalyzer {
     return functionRecords;
   }
 
-  MetricValueLevel _maintainabilityIndexViolationLevel(double index) {
-    if (index < 10) {
-      return MetricValueLevel.alarm;
-    } else if (index < 20) {
-      return MetricValueLevel.warning;
-    } else if (index < 40) {
-      return MetricValueLevel.noted;
-    }
-
-    return MetricValueLevel.none;
-  }
-
   bool _isSupported(AnalysisResult result) =>
       result.path.endsWith('.dart') && !result.path.endsWith('.g.dart');
 }

lib/src/analyzers/lint_analyzer/metrics/metrics_factory.dart

@@ -2,6 +2,7 @@ import '../models/entity_type.dart';
 import 'metrics_list/cyclomatic_complexity/cyclomatic_complexity_metric.dart';
 import 'metrics_list/halstead_volume/halstead_volume_metric.dart';
 import 'metrics_list/lines_of_code_metric.dart';
+import 'metrics_list/maintainability_index_metric.dart';
 import 'metrics_list/maximum_nesting_level/maximum_nesting_level_metric.dart';
 import 'metrics_list/number_of_methods_metric.dart';
 import 'metrics_list/number_of_parameters_metric.dart';
@@ -24,6 +25,10 @@ final _implementedMetrics = <String, Metric Function(Map<String, Object>)>{
   SourceLinesOfCodeMetric.metricId: (config) =>
       SourceLinesOfCodeMetric(config: config),
   WeightOfClassMetric.metricId: (config) => WeightOfClassMetric(config: config),
+  // Complex metrics:
+  // Depend on CyclomaticComplexityMetric, HalsteadVolumeMetric and SourceLinesOfCodeMetric metrics
+  MaintainabilityIndexMetric.metricId: (config) =>
+      MaintainabilityIndexMetric(config: config),
 };
 
 Iterable<Metric> getMetrics({

lib/src/analyzers/lint_analyzer/metrics/metrics_list/cyclomatic_complexity/cyclomatic_complexity_metric.dart

@@ -13,6 +13,7 @@ import '../../metric_utils.dart';
 import '../../models/function_metric.dart';
 import '../../models/metric_computation_result.dart';
 import '../../models/metric_documentation.dart';
+import '../../models/metric_value.dart';
 import 'cyclomatic_complexity_flow_visitor.dart';
 
 const _documentation = MetricDocumentation(
@@ -45,6 +46,7 @@ class CyclomaticComplexityMetric extends FunctionMetric<int> {
     Iterable<ScopedClassDeclaration> classDeclarations,
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
   ) {
     final visitor = CyclomaticComplexityFlowVisitor();
     node.visitChildren(visitor);

lib/src/analyzers/lint_analyzer/metrics/metrics_list/halstead_volume/halstead_volume_metric.dart

@@ -10,6 +10,7 @@ import '../../metric_utils.dart';
 import '../../models/function_metric.dart';
 import '../../models/metric_computation_result.dart';
 import '../../models/metric_documentation.dart';
+import '../../models/metric_value.dart';
 import 'halstead_volume_ast_visitor.dart';
 
 const _documentation = MetricDocumentation(
@@ -46,6 +47,7 @@ class HalsteadVolumeMetric extends FunctionMetric<double> {
     Iterable<ScopedClassDeclaration> classDeclarations,
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
   ) {
     final visitor = HalsteadVolumeAstVisitor();
     node.visitChildren(visitor);

lib/src/analyzers/lint_analyzer/metrics/metrics_list/lines_of_code_metric.dart

@@ -8,6 +8,7 @@ import '../metric_utils.dart';
 import '../models/function_metric.dart';
 import '../models/metric_computation_result.dart';
 import '../models/metric_documentation.dart';
+import '../models/metric_value.dart';
 
 const _documentation = MetricDocumentation(
   name: 'Lines of Code',
@@ -40,6 +41,7 @@ class LinesOfCodeMetric extends FunctionMetric<int> {
     Iterable<ScopedClassDeclaration> classDeclarations,
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
   ) =>
       MetricComputationResult(
         value: 1 +

lib/src/analyzers/lint_analyzer/metrics/metrics_list/maintainability_index_metric.dart

@@ -0,0 +1,105 @@
+import 'dart:math';
+
+import 'package:analyzer/dart/ast/ast.dart';
+
+import '../../models/entity_type.dart';
+import '../../models/internal_resolved_unit_result.dart';
+import '../../models/scoped_class_declaration.dart';
+import '../../models/scoped_function_declaration.dart';
+import '../metric_utils.dart';
+import '../models/function_metric.dart';
+import '../models/metric_computation_result.dart';
+import '../models/metric_documentation.dart';
+import '../models/metric_value.dart';
+import 'cyclomatic_complexity/cyclomatic_complexity_metric.dart';
+import 'halstead_volume/halstead_volume_metric.dart';
+import 'source_lines_of_code/source_lines_of_code_metric.dart';
+
+const _documentation = MetricDocumentation(
+  name: 'Maintainability Index',
+  shortName: 'MI',
+  brief:
+      'Maintainability Index is a software metric which measures how maintainable (easy to support and change) the source code is.',
+  measuredType: EntityType.methodEntity,
+  recomendedThreshold: 50,
+);
+
+/// Maintainability Index (MI)
+///
+/// Maintainability Index is a software metric which measures how maintainable
+/// (easy to support and change) the source code is.
+class MaintainabilityIndexMetric extends FunctionMetric<int> {
+  static const String metricId = 'maintainability-index';
+
+  MaintainabilityIndexMetric({Map<String, Object> config = const {}})
+      : super(
+          id: metricId,
+          documentation: _documentation,
+          threshold: readNullableThreshold<int>(config, metricId),
+          levelComputer: invertValueLevel,
+        );
+
+  @override
+  bool supports(
+    Declaration node,
+    Iterable<ScopedClassDeclaration> classDeclarations,
+    Iterable<ScopedFunctionDeclaration> functionDeclarations,
+    InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
+  ) =>
+      super.supports(
+        node,
+        classDeclarations,
+        functionDeclarations,
+        source,
+        otherMetricsValues,
+      ) &&
+      [
+        CyclomaticComplexityMetric.metricId,
+        HalsteadVolumeMetric.metricId,
+        SourceLinesOfCodeMetric.metricId,
+      ].every((metricId) =>
+          otherMetricsValues.any((value) => value.metricsId == metricId));
+
+  @override
+  MetricComputationResult<int> computeImplementation(
+    Declaration node,
+    Iterable<ScopedClassDeclaration> classDeclarations,
+    Iterable<ScopedFunctionDeclaration> functionDeclarations,
+    InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
+  ) {
+    final halVol = otherMetricsValues.firstWhere(
+      (value) => value.metricsId == HalsteadVolumeMetric.metricId,
+    );
+
+    final cyclomatic = otherMetricsValues.firstWhere(
+      (value) => value.metricsId == CyclomaticComplexityMetric.metricId,
+    );
+
+    final sloc = otherMetricsValues.firstWhere(
+      (value) => value.metricsId == SourceLinesOfCodeMetric.metricId,
+    );
+
+    final halVolScale = log(max(1, halVol.value));
+    final cycloScale = cyclomatic.value;
+    final slocScale = log(max(1, sloc.value));
+
+    final maintainabilityIndex =
+        (171 - halVolScale * 5.2 - cycloScale * 0.23 - slocScale * 16.2) / 171;
+
+    return MetricComputationResult(
+      value: (maintainabilityIndex * 100).clamp(0, 100).ceil(),
+    );
+  }
+
+  @override
+  String commentMessage(String nodeType, int value, int? threshold) {
+    final exceeds = threshold != null && value > threshold
+        ? ', exceeds the minimum of $threshold allowed'
+        : '';
+    final index = '$value maintability index';
+
+    return 'This $nodeType has $index$exceeds.';
+  }
+}

lib/src/analyzers/lint_analyzer/metrics/metrics_list/maximum_nesting_level/maximum_nesting_level_metric.dart

@@ -11,6 +11,7 @@ import '../../metric_utils.dart';
 import '../../models/function_metric.dart';
 import '../../models/metric_computation_result.dart';
 import '../../models/metric_documentation.dart';
+import '../../models/metric_value.dart';
 import 'nesting_level_visitor.dart';
 
 const _documentation = MetricDocumentation(
@@ -44,6 +45,7 @@ class MaximumNestingLevelMetric extends FunctionMetric<int> {
     Iterable<ScopedClassDeclaration> classDeclarations,
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
   ) {
     final visitor = NestingLevelVisitor(node);
     node.visitChildren(visitor);

lib/src/analyzers/lint_analyzer/metrics/metrics_list/number_of_methods_metric.dart

@@ -10,6 +10,7 @@ import '../metric_utils.dart';
 import '../models/class_metric.dart';
 import '../models/metric_computation_result.dart';
 import '../models/metric_documentation.dart';
+import '../models/metric_value.dart';
 import '../scope_utils.dart';
 
 const _documentation = MetricDocumentation(
@@ -41,6 +42,7 @@ class NumberOfMethodsMetric extends ClassMetric<int> {
     Iterable<ScopedClassDeclaration> classDeclarations,
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
+    Iterable<MetricValue<num>> otherMetricsValues,
   ) {
     final methods = classMethods(node, functionDeclarations);