feat: introduce new command check-unnecessary-nullable (#874)

* feat: introduce new command check-unnecessary-nullable

* chore: update changelog

* fix: add support for property access

* fix: add support for index expressions

* fix: add support for all expressions as arguments

* fix: add null literal check

* fix: support dynamic type for arguments

* chore: downgrade react version

* chore: fix comments

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* feat: introduce new command [`check-unnecessary-nullable`](https://dartcodemetrics.dev/docs/cli/check-unnecessary-nullable).
 * feat: add [`avoid-banned-imports`](https://dartcodemetrics.dev/docs/rules/common/avoid-banned-imports) rule.
 * feat: add configuration to [`prefer-extracting-callbacks`](https://dartcodemetrics.dev/docs/rules/flutter/prefer-extracting-callbacks).
 * feat: improve [`checkstyle`](https://dartcodemetrics.dev/docs/cli/analyze#checkstyle) report, added metrics entries.

analysis_options.yaml

@@ -6,6 +6,7 @@ analyzer:
     - test/resources/unused_files_analyzer/**
     - test/resources/unused_l10n_analyzer/**
     - test/resources/unused_code_analyzer/generated/**
+    - test/resources/unnecessary_nullable_analyzer/generated/**
     - test/resources/file_path_folder/**
     - test/**/examples/**
   language:

lib/src/analyzers/unnecessary_nullable_analyzer/declarations_visitor.dart

@@ -0,0 +1,74 @@
+// ignore_for_file: public_member_api_docs
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/nullability_suffix.dart';
+
+import '../../utils/node_utils.dart';
+
+typedef DeclarationUsages = Map<Element, Iterable<FormalParameter>>;
+
+class DeclarationsVisitor extends RecursiveAstVisitor<void> {
+  final DeclarationUsages declarations = {};
+
+  @override
+  void visitMethodDeclaration(MethodDeclaration node) {
+    super.visitMethodDeclaration(node);
+
+    final parameters = node.parameters?.parameters;
+    if (parameters == null || !_hasNullableParameters(parameters)) {
+      return;
+    }
+
+    _getDeclarationElement(node, parameters);
+  }
+
+  @override
+  void visitFunctionDeclaration(FunctionDeclaration node) {
+    super.visitFunctionDeclaration(node);
+
+    final parameters = node.functionExpression.parameters?.parameters;
+    if (isEntrypoint(node.name.name, node.metadata) ||
+        (parameters == null || !_hasNullableParameters(parameters))) {
+      return;
+    }
+
+    _getDeclarationElement(node, parameters);
+  }
+
+  @override
+  void visitConstructorDeclaration(ConstructorDeclaration node) {
+    super.visitConstructorDeclaration(node);
+
+    final parameters = node.parameters.parameters;
+    if (!_hasNullableParameters(parameters)) {
+      return;
+    }
+
+    _getDeclarationElement(node, parameters);
+  }
+
+  bool _hasNullableParameters(Iterable<FormalParameter> parameters) =>
+      parameters.any((parameter) {
+        final type = parameter.declaredElement?.type;
+
+        return type != null &&
+                (type.nullabilitySuffix == NullabilitySuffix.question &&
+                    (!parameter.isOptional ||
+                        parameter.isOptional && parameter.isRequired)) ||
+            (parameter is DefaultFormalParameter &&
+                parameter.defaultValue == null);
+      });
+
+  void _getDeclarationElement(
+    Declaration node,
+    Iterable<FormalParameter> parameters,
+  ) {
+    final element = node.declaredElement;
+
+    if (element != null) {
+      declarations[element] = parameters;
+    }
+  }
+}

lib/src/analyzers/unnecessary_nullable_analyzer/invocations_visitor.dart

@@ -0,0 +1,56 @@
+// ignore_for_file: public_member_api_docs
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/element.dart';
+
+import 'models/invocations_usage.dart';
+
+class InvocationsVisitor extends RecursiveAstVisitor<void> {
+  final invocationsUsages = InvocationsUsage();
+
+  @override
+  void visitExportDirective(ExportDirective node) {
+    super.visitExportDirective(node);
+
+    final path = node.uriSource?.fullName;
+    if (path != null) {
+      invocationsUsages.exports.add(path);
+    }
+  }
+
+  @override
+  void visitMethodInvocation(MethodInvocation node) {
+    super.visitMethodInvocation(node);
+
+    _recordUsedElement(node.methodName.staticElement, node.argumentList);
+  }
+
+  @override
+  void visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {
+    super.visitFunctionExpressionInvocation(node);
+
+    _recordUsedElement(node.staticElement, node.argumentList);
+  }
+
+  @override
+  void visitInstanceCreationExpression(InstanceCreationExpression node) {
+    super.visitInstanceCreationExpression(node);
+
+    _recordUsedElement(node.constructorName.staticElement, node.argumentList);
+  }
+
+  /// Records use of a not prefixed [element].
+  void _recordUsedElement(Element? element, ArgumentList arguments) {
+    if (element == null) {
+      return;
+    }
+    // Ignore if an unknown library.
+    final containingLibrary = element.library;
+    if (containingLibrary == null) {
+      return;
+    }
+    // Remember the element.
+    invocationsUsages.addElementUsage(element, {arguments});
+  }
+}

lib/src/analyzers/unnecessary_nullable_analyzer/models/invocations_usage.dart

@@ -0,0 +1,24 @@
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+
+/// A container with information about used imports prefixes and used imported
+/// elements.
+class InvocationsUsage {
+  /// The set of referenced top-level elements.
+  final Map<Element, Set<ArgumentList>> elements = {};
+
+  final Set<String> exports = {};
+
+  void addElementUsage(Element element, Set<ArgumentList> expressions) {
+    elements.update(
+      element,
+      (value) => value..addAll(expressions),
+      ifAbsent: () => expressions,
+    );
+  }
+
+  void merge(InvocationsUsage other) {
+    other.elements.forEach(addElementUsage);
+    exports.addAll(other.exports);
+  }
+}

lib/src/analyzers/unnecessary_nullable_analyzer/models/unnecessary_nullable_file_report.dart

@@ -0,0 +1,22 @@
+import '../../../reporters/models/file_report.dart';
+import 'unnecessary_nullable_issue.dart';
+
+/// Represents unused code report collected for a file.
+class UnnecessaryNullableFileReport implements FileReport {
+  /// The path to the target file.
+  @override
+  final String path;
+
+  /// The path to the target file relative to the package root.
+  @override
+  final String relativePath;
+
+  /// The issues detected in the target file.
+  final Iterable<UnnecessaryNullableIssue> issues;
+
+  const UnnecessaryNullableFileReport({
+    required this.path,
+    required this.relativePath,
+    required this.issues,
+  });
+}

lib/src/analyzers/unnecessary_nullable_analyzer/models/unnecessary_nullable_issue.dart

@@ -0,0 +1,26 @@
+import 'package:source_span/source_span.dart';
+
+/// Represents an issue detected by the unused code check.
+class UnnecessaryNullableIssue {
+  /// The name of the unused declaration.
+  final String declarationName;
+
+  /// The type of the unused declaration.
+  final String declarationType;
+
+  final Iterable<String> parameters;
+
+  /// The source location associated with this issue.
+  final SourceLocation location;
+
+  /// Initialize a newly created [UnnecessaryNullableIssue].
+  ///
+  /// The issue is associated with the given [location]. Used for
+  /// creating an unused code report.
+  const UnnecessaryNullableIssue({
+    required this.declarationName,
+    required this.declarationType,
+    required this.parameters,
+    required this.location,
+  });
+}

lib/src/analyzers/unnecessary_nullable_analyzer/reporters/reporter_factory.dart

@@ -0,0 +1,30 @@
+import 'dart:io';
+
+import '../../../reporters/models/console_reporter.dart';
+import '../../../reporters/models/json_reporter.dart';
+import '../../../reporters/models/reporter.dart';
+import '../models/unnecessary_nullable_file_report.dart';
+import 'reporters_list/console/unnecessary_nullable_console_reporter.dart';
+import 'reporters_list/json/unnecessary_nullable_json_reporter.dart';
+import 'unnecessary_nullable_report_params.dart';
+
+final _implementedReports = <
+    String,
+    Reporter<UnnecessaryNullableFileReport, void,
+            UnnecessaryNullableReportParams>
+        Function(
+  IOSink output,
+)>{
+  ConsoleReporter.id: (output) => UnnecessaryNullableConsoleReporter(output),
+  JsonReporter.id: (output) => UnnecessaryNullableJsonReporter(output),
+};
+
+Reporter<UnnecessaryNullableFileReport, void, UnnecessaryNullableReportParams>?
+    reporter({
+  required String name,
+  required IOSink output,
+}) {
+  final constructor = _implementedReports[name];
+
+  return constructor != null ? constructor(output) : null;
+}

lib/src/analyzers/unnecessary_nullable_analyzer/reporters/reporters_list/console/unnecessary_nullable_console_reporter.dart

@@ -0,0 +1,62 @@
+import 'dart:io';
+
+import '../../../../../reporters/models/console_reporter.dart';
+import '../../../models/unnecessary_nullable_file_report.dart';
+import '../../unnecessary_nullable_report_params.dart';
+
+/// Unnecessary nullable console reporter.
+///
+/// Use it to create reports in console format.
+class UnnecessaryNullableConsoleReporter extends ConsoleReporter<
+    UnnecessaryNullableFileReport, void, UnnecessaryNullableReportParams> {
+  UnnecessaryNullableConsoleReporter(IOSink output) : super(output);
+
+  @override
+  Future<void> report(
+    Iterable<UnnecessaryNullableFileReport> records, {
+    Iterable<void> summary = const [],
+    UnnecessaryNullableReportParams? additionalParams,
+  }) async {
+    if (records.isEmpty) {
+      if (additionalParams?.congratulate ?? true) {
+        output
+            .writeln('${okPen('✔')} no unnecessary nullable parameters found!');
+      }
+
+      return;
+    }
+
+    final sortedRecords = records.toList()
+      ..sort((a, b) => a.relativePath.compareTo(b.relativePath));
+
+    var warnings = 0;
+
+    for (final analysisRecord in sortedRecords) {
+      output.writeln('${analysisRecord.relativePath}:');
+
+      for (final issue in analysisRecord.issues) {
+        final line = issue.location.line;
+        final column = issue.location.column;
+        final path = analysisRecord.relativePath;
+
+        final offset = ''.padRight(3);
+        final pathOffset = offset.padRight(5);
+
+        output
+          ..writeln(
+            '$offset ${warningPen('⚠')} ${issue.declarationType} ${issue.declarationName} has unnecessary nullable parameters',
+          )
+          ..writeln('$pathOffset ${issue.parameters}')
+          ..writeln('$pathOffset at $path:$line:$column');
+      }
+
+      warnings += analysisRecord.issues.length;
+
+      output.writeln('');
+    }
+
+    output.writeln(
+      '${alarmPen('✖')} total declarations (functions, methods and constructors) with unnecessary nullable parameters - ${alarmPen(warnings)}',
+    );
+  }
+}

lib/src/analyzers/unnecessary_nullable_analyzer/reporters/reporters_list/json/unnecessary_nullable_json_reporter.dart

@@ -0,0 +1,52 @@
+import 'dart:convert';
+import 'dart:io';
+
+import '../../../../../reporters/models/json_reporter.dart';
+import '../../../models/unnecessary_nullable_file_report.dart';
+import '../../../models/unnecessary_nullable_issue.dart';
+import '../../unnecessary_nullable_report_params.dart';
+
+/// Unnecessary nullable JSON reporter.
+///
+/// Use it to create reports in JSON format.
+class UnnecessaryNullableJsonReporter extends JsonReporter<
+    UnnecessaryNullableFileReport, void, UnnecessaryNullableReportParams> {
+  const UnnecessaryNullableJsonReporter(IOSink output) : super(output, 2);
+
+  @override
+  Future<void> report(
+    Iterable<UnnecessaryNullableFileReport> records, {
+    Iterable<void> summary = const [],
+    UnnecessaryNullableReportParams? additionalParams,
+  }) async {
+    if (records.isEmpty) {
+      return;
+    }
+
+    final encodedReport = json.encode({
+      'formatVersion': formatVersion,
+      'timestamp': getTimestamp(),
+      'unnecessaryNullable':
+          records.map(_unnecessaryNullableFileReportToJson).toList(),
+    });
+
+    output.write(encodedReport);
+  }
+
+  Map<String, Object> _unnecessaryNullableFileReportToJson(
+    UnnecessaryNullableFileReport report,
+  ) =>
+      {
+        'path': report.relativePath,
+        'issues': report.issues.map(_issueToJson).toList(),
+      };
+
+  Map<String, Object> _issueToJson(UnnecessaryNullableIssue issue) => {
+        'declarationType': issue.declarationType,
+        'declarationName': issue.declarationName,
+        'parameters': issue.parameters,
+        'column': issue.location.column,
+        'line': issue.location.line,
+        'offset': issue.location.offset,
+      };
+}

lib/src/analyzers/unnecessary_nullable_analyzer/reporters/unnecessary_nullable_report_params.dart

@@ -0,0 +1,6 @@
+/// Represents additional unnecessary nullable reporter params.
+class UnnecessaryNullableReportParams {
+  final bool congratulate;
+
+  const UnnecessaryNullableReportParams({required this.congratulate});
+}

lib/src/analyzers/unnecessary_nullable_analyzer/unnecessary_nullable_analysis_config.dart

@@ -0,0 +1,12 @@
+import 'package:glob/glob.dart';
+
+/// Represents converted unused code config which contains parsed entities.
+class UnnecessaryNullableAnalysisConfig {
+  final Iterable<Glob> globalExcludes;
+  final Iterable<Glob> analyzerExcludedPatterns;
+
+  const UnnecessaryNullableAnalysisConfig(
+    this.globalExcludes,
+    this.analyzerExcludedPatterns,
+  );
+}