Fix null safety code generation and migrate to null safety

analysis_options.yaml

@@ -2,6 +2,8 @@ analyzer:
   exclude:
     - lib/**/*.g.dart
     - test/**/*.g.dart
+  errors:
+    uri_has_not_been_generated: ignore
 
 linter:
   rules:

lib/src/generators/class_checks_collector.dart

@@ -1,5 +1,3 @@
-// @dart = 2.9
-
 // Copyright 2017 Google Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -22,7 +20,7 @@ import 'methods/core.dart' as core;
 String _generateCheck(Annotation annotation) {
   if (annotation.arguments == null) throw 'bad';
   return '${annotation.name.toString()}'
-      '(${annotation.arguments.arguments.join(', ')})';
+      '(${annotation.arguments?.arguments.join(', ')})';
 }
 
 /// Generates a comma separated list of class check declarations for the given

lib/src/generators/collector_visitor.dart

@@ -1,5 +1,3 @@
-// @dart = 2.9
-
 // Copyright 2017 Google Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -17,7 +15,7 @@ import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
-import 'package:pageloader/src/api/page_object_annotation.dart';
+import '../api/page_object_annotation.dart';
 
 import 'methods/core.dart';
 import 'methods/core_method_information.dart';
@@ -305,12 +303,12 @@ class CollectorVisitor extends GeneralizingAstVisitor<void> {
               : parameter;
           final type =
               (declaration is SimpleFormalParameter && declaration.type != null)
-                  ? declaration.type.toSource()
+                  ? declaration.type?.toSource()
                   : 'var';
 
           var defaultValue = (parameter is DefaultFormalParameter &&
                   parameter.defaultValue != null)
-              ? parameter.defaultValue.toSource()
+              ? parameter.defaultValue?.toSource()
               : null;
 
           if (defaultValue == 'null') {
@@ -323,20 +321,20 @@ class CollectorVisitor extends GeneralizingAstVisitor<void> {
 
           if (parameter.isRequired) {
             buffer.writeln('''{
-                'name': '${parameter.declaredElement.name}',
+                'name': '${parameter.declaredElement?.name}',
                 'kind': 'required',
                 'type': '$type'
                },''');
           } else if (parameter.isNamed) {
             buffer.writeln('''{
-                'name': '${parameter.declaredElement.name}',
+                'name': '${parameter.declaredElement?.name}',
                 'kind': 'named',
                 'type': '$type',
                 'default': $defaultValue
                },''');
           } else if (parameter.isOptionalPositional) {
             buffer.writeln('''{
-                'name': '${parameter.declaredElement.name}',
+                'name': '${parameter.declaredElement?.name}',
                 'kind': 'positional',
                 'type': '$type',
                 'default': $defaultValue

lib/src/generators/methods/annotation_evaluators.dart

@@ -1,5 +1,3 @@
-// @dart = 2.9
-
 // Copyright 2017 Google Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -29,7 +27,8 @@ final String pageLoaderAnnotationInterface =
 
 /// Returns set of AnnotationKinds that match '@root', '@Mouse', '@nullElement'
 /// and '@Pointer'.
-Set<AnnotationKind> evaluateAsAtomicAnnotation(Element element) {
+/// TODO(null-safety): argument null-optional might be unnecessary
+Set<AnnotationKind> evaluateAsAtomicAnnotation(Element? element) {
   final returnSet = <AnnotationKind>{};
   if (element is PropertyAccessorElement &&
       element.library.name == pageLoaderAnnotations) {
@@ -43,18 +42,18 @@ Set<AnnotationKind> evaluateAsAtomicAnnotation(Element element) {
 
 /// Returns set of AnnotationKinds if the annotation is a subclass of
 /// Finder, Checker, and/or Filter.
-Set<AnnotationKind> evaluateAsInterfaceAnnotation(Element element) {
-  final returnSet = <AnnotationKind>{};
+Set<AnnotationKind?> evaluateAsInterfaceAnnotation(Element element) {
+  final returnSet = <AnnotationKind?>{};
 
-  DartType type;
+  DartType? type;
   if (element is PropertyAccessorElement && element.isGetter) {
     type = element.returnType;
   } else if (element is ConstructorElement) {
     type = element.returnType;
   }
 
   if (type is InterfaceType) {
-    final seenValidAnnotations = <AnnotationKind>{};
+    final seenValidAnnotations = <AnnotationKind?>{};
     final interfaces = [type, ...type.allSupertypes];
     for (var interface in interfaces) {
       final interfaceElement = interface.element;
@@ -84,7 +83,7 @@ enum AnnotationKind {
 }
 
 /// Maps library and className to proper AnnotationKind.
-AnnotationKind classNameToAnnotationKind(String className, {bool isAtomic}) {
+AnnotationKind? classNameToAnnotationKind(String className, {required bool isAtomic}) {
   if (isAtomic) {
     switch (className) {
       case 'LegacyPageObject':

lib/src/generators/methods/core.dart

@@ -1,5 +1,3 @@
-// @dart = 2.9
-
 // Copyright 2017 Google Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -40,12 +38,14 @@ final String pageObjectList = 'PageObjectList';
 
 /// Returns a declaration of a annotation.
 String generateAnnotationDeclaration(Annotation annotation) =>
-    '${annotation.name}(${annotation.arguments.arguments.join(", ")})';
+    '${annotation.name}(${annotation.arguments?.arguments.join(", ")})';
 
 /// Returns a 'ByTagName' declaration from the 'ByCheckTag' annotation.
 String generateByTagNameFromByCheckTag(
-    InterfaceType node, String methodSource) {
-  final defaultTagName = _extractTagName(node.element);
+    DartType? node, String methodSource) {
+	// Original(null-safety): node is InterfaceType and no "?"
+	// Also no cast below.
+  final defaultTagName = _extractTagName(node?.element as ClassElement);
   if (defaultTagName.isEmpty) {
     throw "'@ByCheckTag' can only be used on getters that return a "
         "PageObject type with the'@CheckTag' annotation.\n\nCheck the type on "
@@ -58,15 +58,15 @@ String generateByTagNameFromByCheckTag(
 /// If there is no tag name associated with the Page Object,
 /// returns and empty string.
 String _extractTagName(ClassElement poTypeElement) {
-  var expectedTag = '';
+  late String expectedTag;
   for (final annotation in poTypeElement.metadata) {
     final annotationElement = annotation.element;
     if (annotationElement is ConstructorElement) {
       final annotationName = annotationElement.enclosingElement.displayName;
       final annotationValue = annotation.computeConstantValue();
       if (annotationName == 'CheckTag') {
-        final inner = annotationValue.getField('_expectedTagName');
-        expectedTag = inner.toStringValue();
+        final inner = annotationValue?.getField('_expectedTagName');
+        expectedTag = inner?.toStringValue() ?? '';
       }
     }
   }
@@ -100,8 +100,8 @@ bool isPageloaderAnnotation(Annotation annotation) =>
     getAnnotationKind(annotation).isNotEmpty;
 
 /// Returns set of all Pageloader annotation the current annotation satisfies.
-Set<AnnotationKind> getAnnotationKind(Annotation annotation) {
-  final returnSet = <AnnotationKind>{};
+Set<AnnotationKind?> getAnnotationKind(Annotation annotation) {
+  final returnSet = <AnnotationKind?>{};
   final element = annotation.element;
   if (element != null) {
     returnSet
@@ -164,20 +164,21 @@ List<String> getReturnTypeArguments(String returnStr) {
 /// matching name [matchingType].
 ///
 /// Assumes that the inner-type has a single type (ex: not Foo<A, B>).
-DartType getInnerType(DartType topType, String matchingType) {
+DartType getInnerType(DartType? topType, String matchingType) {
   // Filter out type name incase prefixes exist on the type.
   matchingType =
       matchingType.contains('.') ? matchingType.split('.')[1] : matchingType;
   final typeArgs = (topType as ParameterizedType).typeArguments;
   final first = typeArgs.first;
-  if (first.name == matchingType) {
+	// TODO(null-safety): nullability: true or false?
+  if (first.getDisplayString(withNullability: true) == matchingType) {
     return first;
   }
   return getInnerType(first, matchingType);
 }
 
 /// Return the Dart code that corresponds to the [type].
-String typeToCode(DartType type) {
+String? typeToCode(DartType? type) {
   // TODO: This should be replaced with actual code generation.
-  return type?.getDisplayString(withNullability: false);
+  return type?.getDisplayString(withNullability: true);
 }

lib/src/generators/methods/core_method_information.dart

@@ -1,5 +1,3 @@
-// @dart = 2.9
-
 // Copyright 2017 Google Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -73,7 +71,11 @@ TypeInformation extractPageObjectInfo(
 
 CoreMethodInformation collectCoreMethodInformation(MethodDeclaration node) {
   // Extract type info.
-  final typeInfo = getTypeInformation(node.returnType.toSource());
+	// TODO(null-safety): verify logic.
+  // Before: final typeInfo = getTypeInformation((node.returnType).toSource());
+  // The reason is because for Dart, if a method doesn't declare a return type,
+  // it's automatically `dynamic`.
+  final typeInfo = getTypeInformation(node.returnType?.toSource() ?? 'dynamic');
 
   final isFuture = typeInfo.type == 'Future';
   final isList = typeInfo.type == 'List' ||