Refine detection for NNBD cases and tag generated pages with "Null safety" (#2221)

* Beginnings

* wow, this mostly works

* Very simple SDK NNBD detection

* Basic templates and tagging for nnbd interfaces

* dartfmt, update tests

* Fix duplicitous comment

* Update with review comments

Author: jcollins-g

Diff for: lib/resources/styles.css

@@ -460,6 +460,22 @@ h1 .category {
   vertical-align: middle;
 }
 
+.feature {
+  display: inline-block;
+  background: white;
+  border: 1px solid #0175c2;
+  border-radius: 20px;
+  color: #0175c2;
+
+  font-size: 12px;
+  padding: 1px 6px;
+  margin: 0 8px 0 0;
+}
+
+h1 .feature {
+  vertical-align: middle;
+}
+
 .source-link {
   padding: 18px 4px;
   vertical-align: middle;

Diff for: lib/src/element_type.dart

@@ -74,8 +74,23 @@ abstract class ElementType extends Privacy {
 
   String get name;
 
+  /// Name with generics and nullability indication.
   String get nameWithGenerics;
 
+  /// Return a dartdoc nullability suffix for this type.
+  String get nullabilitySuffix {
+    if (library.isNNBD && !type.isVoid && !type.isBottom) {
+      /// If a legacy type appears inside the public interface of a
+      /// NNBD library, we pretend it is nullable for the purpose of
+      /// documentation (since star-types are not supposed to be public).
+      if (type.nullabilitySuffix == NullabilitySuffix.question ||
+          type.nullabilitySuffix == NullabilitySuffix.star) {
+        return '?';
+      }
+    }
+    return '';
+  }
+
   List<Parameter> get parameters => [];
 
   DartType get instantiatedType;
@@ -120,7 +135,7 @@ class UndefinedElementType extends ElementType {
   }
 
   @override
-  String get nameWithGenerics => name;
+  String get nameWithGenerics => '$name${nullabilitySuffix}';
 
   /// Assume that undefined elements don't have useful bounds.
   @override

Diff for: lib/src/generator/templates.dart

@@ -22,6 +22,7 @@ const _partials_html = <String>[
   'class',
   'constant',
   'extension',
+  'feature_set',
   'footer',
   'head',
   'library',
@@ -55,6 +56,8 @@ const _partials_md = <String>[
   'documentation',
   'extension',
   'features',
+  'feature_set',
+  'footer',
   'footer',
   'head',
   'library',

Diff for: lib/src/model/feature_set.dart

@@ -0,0 +1,30 @@
+// Copyright (c) 2020, 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:dartdoc/src/model/language_feature.dart';
+import 'package:dartdoc/src/model/model.dart';
+
+/// [ModelElement]s can have different language features that can alter
+/// the user interpretation of the interface.
+mixin FeatureSet {
+  PackageGraph get packageGraph;
+  Library get library;
+
+  /// A list of language features that both apply to this [ModelElement] and
+  /// make sense to display in context.
+  Iterable<LanguageFeature> get displayedLanguageFeatures sync* {
+    // TODO(jcollins-g): Implement mixed-mode handling and the tagging of
+    // legacy interfaces.
+    if (isNNBD) {
+      yield LanguageFeature(
+          'Null safety', packageGraph.rendererFactory.featureRenderer);
+    }
+  }
+
+  bool get hasFeatureSet => displayedLanguageFeatures.isNotEmpty;
+
+  // TODO(jcollins-g): This is an approximation and not strictly true for
+  // inheritance/reexports.
+  bool get isNNBD => library.isNNBD;
+}

Diff for: lib/src/model/language_feature.dart

@@ -0,0 +1,24 @@
+// Copyright (c) 2020, 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:dartdoc/src/render/feature_renderer.dart';
+
+const Map<String, String> _featureDescriptions = {
+  'Null safety': 'Supports the null safety language feature.',
+};
+
+/// An abstraction for a language feature; used to render tags to notify
+/// the user that the documentation should be specially interpreted.
+class LanguageFeature {
+  String get featureDescription => _featureDescriptions[name];
+  String get featureLabel => _featureRenderer.renderFeatureLabel(this);
+
+  final String name;
+
+  final FeatureRenderer _featureRenderer;
+
+  LanguageFeature(this.name, this._featureRenderer) {
+    assert(_featureDescriptions.containsKey(name));
+  }
+}

Diff for: lib/src/model/library.dart

@@ -107,6 +107,19 @@ class Library extends ModelElement with Categorization, TopLevelContainer {
 
   List<String> _allOriginalModelElementNames;
 
+  /// Return true if this library is in a package configured to be treated as
+  /// as non-nullable by default and is itself NNBD.
+  // TODO(jcollins-g): packageMeta.allowsNNBD may be redundant after package
+  // allow list support is published in analyzer
+  bool get _allowsNNBD =>
+      element.isNonNullableByDefault && packageMeta.allowsNNBD;
+
+  /// Return true if this library should be documented as non-nullable.
+  /// A library may be NNBD but not documented that way.
+  @override
+  bool get isNNBD =>
+      config.enableExperiment.contains('non-nullable') && _allowsNNBD;
+
   bool get isInSdk => element.isInSdk;
 
   final Package _package;

Diff for: lib/src/model/model_element.dart

@@ -21,6 +21,7 @@ import 'package:crypto/crypto.dart';
 import 'package:dartdoc/src/dartdoc_options.dart';
 import 'package:dartdoc/src/element_type.dart';
 import 'package:dartdoc/src/logging.dart';
+import 'package:dartdoc/src/model/feature_set.dart';
 import 'package:dartdoc/src/model/model.dart';
 import 'package:dartdoc/src/model_utils.dart' as utils;
 import 'package:dartdoc/src/render/model_element_renderer.dart';
@@ -148,7 +149,14 @@ ModelElement resolveMultiplyInheritedElement(
 /// ModelElement will reference itself as part of the "wrong" [Library]
 /// from the public interface perspective.
 abstract class ModelElement extends Canonicalization
-    with Privacy, Warnable, Locatable, Nameable, SourceCodeMixin, Indexable
+    with
+        Privacy,
+        Warnable,
+        Locatable,
+        Nameable,
+        SourceCodeMixin,
+        Indexable,
+        FeatureSet
     implements Comparable, Documentable {
   final Element _element;
 

Diff for: lib/src/package_meta.dart

@@ -10,6 +10,7 @@ import 'dart:io';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:dartdoc/dartdoc.dart';
 import 'package:path/path.dart' as path;
+import 'package:pub_semver/pub_semver.dart';
 import 'package:yaml/yaml.dart';
 
 import 'logging.dart';
@@ -106,6 +107,14 @@ abstract class PackageMeta {
 
   String get homepage;
 
+  /// If true, libraries in this package can be be read as non-nullable by
+  /// default.  Whether they will be will be documented that way will depend
+  /// on the experiment flag.
+  ///
+  /// A package property, as this depends in part on the pubspec version
+  /// constraint and/or the package allow list.
+  bool get allowsNNBD;
+
   FileContents getReadmeContents();
 
   FileContents getLicenseContents();
@@ -272,6 +281,7 @@ class _FilePackageMeta extends PubPackageMeta {
   FileContents _license;
   FileContents _changelog;
   Map _pubspec;
+  Map _analysisOptions;
 
   _FilePackageMeta(Directory dir) : super(dir) {
     var f = File(path.join(dir.path, 'pubspec.yaml'));
@@ -280,6 +290,12 @@ class _FilePackageMeta extends PubPackageMeta {
     } else {
       _pubspec = {};
     }
+    f = File(path.join(dir.path, 'analysis_options.yaml'));
+    if (f.existsSync()) {
+      _analysisOptions = loadYaml(f.readAsStringSync());
+    } else {
+      _analysisOptions = {};
+    }
   }
 
   bool _setHostedAt = false;
@@ -360,6 +376,29 @@ class _FilePackageMeta extends PubPackageMeta {
   @override
   String get homepage => _pubspec['homepage'];
 
+  /// This is a magic range that triggers detection of [allowsNNBD].
+  static final _nullableRange =
+      VersionConstraint.parse('>=2.9.0-dev.0 <2.10.0') as VersionRange;
+
+  @override
+  bool get allowsNNBD {
+    // TODO(jcollins-g): override/add to with allow list once that exists
+    var sdkConstraint;
+    if (_pubspec?.containsKey('sdk') ?? false) {
+      // TODO(jcollins-g): VersionConstraint.parse returns [VersionRange]s right
+      // now, but the interface doesn't guarantee that.
+      sdkConstraint = VersionConstraint.parse(_pubspec['sdk']) as VersionRange;
+    }
+    if (sdkConstraint == _nullableRange &&
+        (_analysisOptions['analyzer']?.containsKey('enable-experiment') ??
+            false) &&
+        _analysisOptions['analyzer']['enable-experiment']
+            .contains('non-nullable')) {
+      return true;
+    }
+    return false;
+  }
+
   @override
   bool get requiresFlutter =>
       _pubspec['environment']?.containsKey('flutter') == true ||
@@ -423,6 +462,14 @@ class _SdkMeta extends PubPackageMeta {
     sdkReadmePath = path.join(dir.path, 'lib', 'api_readme.md');
   }
 
+  /// 2.9.0-9.0.dev is the first unforked SDK, and therefore the first version
+  /// of the SDK it makes sense to allow NNBD documentation for.
+  static final _sdkNullableRange = VersionConstraint.parse('>=2.9.0-9.0.dev');
+
+  @override
+  // TODO(jcollins-g): There should be a better way to determine this.
+  bool get allowsNNBD => _sdkNullableRange.allows(Version.parse(version));
+
   @override
   String get hostedAt => null;
 

Diff for: lib/src/render/element_type_renderer.dart

@@ -9,6 +9,13 @@ abstract class ElementTypeRenderer<T extends ElementType> {
   String renderLinkedName(T elementType);
 
   String renderNameWithGenerics(T elementType) => '';
+
+  String wrapNullabilityParens(T elementType, String inner) =>
+      elementType.nullabilitySuffix.isEmpty
+          ? inner
+          : '($inner${elementType.nullabilitySuffix})';
+  String wrapNullability(T elementType, String inner) =>
+      '$inner${elementType.nullabilitySuffix}';
 }
 
 // Html implementations
@@ -24,7 +31,7 @@ class FunctionTypeElementTypeRendererHtml
     buf.write(
         ParameterRendererHtml().renderLinkedParams(elementType.parameters));
     buf.write(')</span>');
-    return buf.toString();
+    return wrapNullabilityParens(elementType, buf.toString());
   }
 
   @override
@@ -39,7 +46,7 @@ class FunctionTypeElementTypeRendererHtml
         buf.write('</span>&gt;');
       }
     }
-    return buf.toString();
+    return wrapNullability(elementType, buf.toString());
   }
 }
 
@@ -58,7 +65,7 @@ class ParameterizedElementTypeRendererHtml
       buf.write('</span>&gt;');
       buf.write('</span>');
     }
-    return buf.toString();
+    return wrapNullability(elementType, buf.toString());
   }
 
   @override
@@ -72,7 +79,8 @@ class ParameterizedElementTypeRendererHtml
           '</span>, <span class="type-parameter">');
       buf.write('</span>&gt;');
     }
-    return buf.toString();
+    buf.write(elementType.nullabilitySuffix);
+    return wrapNullability(elementType, buf.toString());
   }
 }
 
@@ -92,7 +100,7 @@ class CallableElementTypeRendererHtml
         .trim());
     buf.write(') → ');
     buf.write(elementType.returnType.linkedName);
-    return buf.toString();
+    return wrapNullabilityParens(elementType, buf.toString());
   }
 }
 
@@ -108,7 +116,7 @@ class FunctionTypeElementTypeRendererMd
     buf.write('(');
     buf.write(ParameterRendererMd().renderLinkedParams(elementType.parameters));
     buf.write(')');
-    return buf.toString();
+    return wrapNullabilityParens(elementType, buf.toString());
   }
 
   @override
@@ -122,7 +130,7 @@ class FunctionTypeElementTypeRendererMd
         buf.write('>');
       }
     }
-    return buf.toString();
+    return wrapNullabilityParens(elementType, buf.toString());
   }
 }
 
@@ -138,7 +146,7 @@ class ParameterizedElementTypeRendererMd
       buf.writeAll(elementType.typeArguments.map((t) => t.linkedName), ', ');
       buf.write('>');
     }
-    return buf.toString();
+    return wrapNullability(elementType, buf.toString());
   }
 
   @override
@@ -152,7 +160,8 @@ class ParameterizedElementTypeRendererMd
           elementType.typeArguments.map((t) => t.nameWithGenerics), ', ');
       buf.write('>');
     }
-    return buf.toString();
+    buf.write(elementType.nullabilitySuffix);
+    return wrapNullability(elementType, buf.toString());
   }
 }
 
@@ -172,6 +181,6 @@ class CallableElementTypeRendererMd
         .trim());
     buf.write(') → ');
     buf.write(elementType.returnType.linkedName);
-    return buf.toString();
+    return wrapNullabilityParens(elementType, buf.toString());
   }
 }