lib/src/model/inheritable.dart

// Copyright (c) 2019, 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/dart/element/element.dart';
import 'package:collection/collection.dart' show IterableExtension;
import 'package:dartdoc/src/model/feature.dart';
import 'package:dartdoc/src/model/model.dart';
import 'package:dartdoc/src/special_elements.dart';

/// Mixin for subclasses of ModelElement representing Elements that can be
/// inherited from one class to another.
///
/// We can search the inheritance chain between this instance and
/// [definingEnclosingContainer] in [Inheritable.canonicalEnclosingContainer],
/// for the canonical [Class] closest to where this member was defined.  We
/// can then know that when we find [Inheritable.modelElement] inside that [Class]'s
/// namespace, that's the one we should treat as canonical and implementors
/// of this class can use that knowledge to determine canonicalization.
///
/// We pick the class closest to the [definingEnclosingContainer] so that all
/// children of that class inheriting the same member will point to the same
/// place in the documentation, and we pick a canonical class because that's
/// the one in the public namespace that will be documented.
mixin Inheritable on ContainerMember {
  /// True if this [Inheritable] is inherited from a different class.
  bool get isInherited;

  /// True if this [Inheritable] has a parameter whose type is overridden
  /// by a subtype.
  bool get isCovariant;

  @override
  Set<Feature> get features => {
        ...super.features,
        if (isOverride) Feature.overrideFeature,
        if (isInherited) Feature.inherited,
        if (isCovariant) Feature.covariant,
      };

  @override
  Library? get canonicalLibrary =>
      canonicalEnclosingContainer?.canonicalLibrary;

  @override
  late final ModelElement? canonicalModelElement = () {
    final canonicalEnclosingContainer = this.canonicalEnclosingContainer;
    if (canonicalEnclosingContainer == null) {
      return null;
    }
    return canonicalEnclosingContainer.allCanonicalModelElements
        .firstWhereOrNull((m) =>
            m.name == name &&
            m is PropertyAccessorElement == this is PropertyAccessorElement);
  }();

  @override
  Container? computeCanonicalEnclosingContainer() {
    if (isInherited) {
      var searchElement = element.declaration;
      // TODO(jcollins-g): generate warning if an inherited element's definition
      // is in an intermediate non-canonical class in the inheritance chain?
      Container? previous;
      Container? previousNonSkippable;
      Container? found;
      for (var c in inheritance.reversed) {
        // Filter out mixins.
        if (c.containsElement(searchElement)) {
          if ((packageGraph.inheritThrough.contains(previous) &&
                  c != definingEnclosingContainer) ||
              (packageGraph.inheritThrough.contains(c) &&
                  c == definingEnclosingContainer)) {
            return previousNonSkippable!
                .memberByExample(this)
                .canonicalEnclosingContainer;
          }
          var canonicalContainer = packageGraph
              .findCanonicalModelElementFor(c.element) as Container?;
          // TODO(jcollins-g): invert this lookup so traversal is recursive
          // starting from the ModelElement.
          if (canonicalContainer != null) {
            assert(canonicalContainer.isCanonical);
            assert(canonicalContainer.containsElement(searchElement));
            found = canonicalContainer;
            break;
          }
        }
        previous = c;
        if (!packageGraph.inheritThrough.contains(c)) {
          previousNonSkippable = c;
        }
      }
      // This is still OK because we're never supposed to cloak public
      // classes.
      if (definingEnclosingContainer.isCanonical &&
          definingEnclosingContainer.isPublic) {
        assert(definingEnclosingContainer == found);
      }
      if (found != null) {
        return found;
      }
    } else if (definingEnclosingContainer is! Extension) {
      // TODO(jcollins-g): factor out extension logic into [Extendable].
      return packageGraph.findCanonicalModelElementFor(element.enclosingElement)
          as Container?;
    }
    return super.computeCanonicalEnclosingContainer();
  }

  List<InheritingContainer> get inheritance {
    var inheritance = [
      ...(enclosingElement as InheritingContainer).inheritanceChain,
    ];
    var object = packageGraph.specialClasses[SpecialClass.object];
    assert(definingEnclosingContainer == object ||
        inheritance.contains(definingEnclosingContainer));

    // Unless the code explicitly extends dart-core's Object, we won't get
    // an entry here.  So add it.
    if (inheritance.last != object && object != null) {
      inheritance.add(object);
    }
    assert(inheritance.where((e) => e == object).length == 1);
    return inheritance;
  }

  Inheritable? get overriddenElement;

  /// True if this [Inheritable] is overriding a superclass.
  late final bool isOverride = () {
    // The canonical version of the enclosing element -- not
    // [canonicalEnclosingElement], as that is the element enclosing the
    // canonical version of this element; two different things.  Defaults to the
    // enclosing element.
    //
    // We use canonical elements here where possible to deal with reexports
    // as seen in Flutter.
    if (enclosingElement is Extension) {
      return false;
    }

    final overriddenElement = this.overriddenElement;
    if (overriddenElement == null) {
      // We have to have an overridden element for it to be possible for this
      // element to be an override.
      return false;
    }

    final enclosingCanonical =
        enclosingElement.canonicalModelElement as InheritingContainer?;
    // The container in which this element was defined, canonical if available.
    final definingCanonical =
        definingEnclosingContainer.canonicalModelElement as Container? ??
            definingEnclosingContainer;
    if (enclosingCanonical != definingCanonical) {
      // The defining class and the enclosing class for this element must be the
      // same (element is defined here).
      assert(isInherited);
      return false;
    }

    // The canonical version of the element we're overriding, if available.
    final overriddenCanonical =
        overriddenElement.canonicalModelElement ?? overriddenElement;

    // If the overridden element isn't public, we shouldn't be an override in
    // most cases.  Approximation until #1623 is fixed.
    final isOverride = overriddenCanonical.isPublic;
    assert(!isOverride || !isInherited);
    return isOverride;
  }();

  @override
  late final int overriddenDepth = () {
    var depth = 0;
    var e = this;
    while (e.overriddenElement != null) {
      depth += 1;
      e = e.overriddenElement!;
    }
    return depth;
  }();
}