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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Xml;
using Microsoft.Build.Framework;
using Microsoft.Build.ObjectModelRemoting;
using Microsoft.Build.Shared;
using ProjectXmlUtilities = Microsoft.Build.Internal.ProjectXmlUtilities;
#nullable disable
namespace Microsoft.Build.Construction
{
/// <summary>
/// Abstract base class for MSBuild construction object model elements.
/// </summary>
public abstract class ProjectElement : IProjectElement, ILinkableObject
{
/// <summary>
/// Parent container object.
/// </summary>
private ProjectElementContainer _parent;
/// <summary>
/// Condition value cached for performance
/// </summary>
private string _condition;
private bool _expressedAsAttribute;
private ProjectElement _previousSibling;
private ProjectElement _nextSibling;
/// <summary>
/// Constructor called by ProjectRootElement only.
/// XmlElement is set directly after construction.
/// </summary>
/// <comment>
/// Should be protected+internal.
/// </comment>
internal ProjectElement()
{
}
/// <summary>
/// External projects support
/// </summary>
internal ProjectElement(ProjectElementLink link)
{
ErrorUtilities.VerifyThrowArgumentNull(link, nameof(link));
_xmlSource = link;
}
/// <summary>
/// Constructor called by derived classes, except from ProjectRootElement.
/// Parameters may not be null, except parent.
/// </summary>
internal ProjectElement(XmlElement xmlElement, ProjectElementContainer parent, ProjectRootElement containingProject)
{
ErrorUtilities.VerifyThrowArgumentNull(xmlElement, nameof(xmlElement));
ErrorUtilities.VerifyThrowArgumentNull(containingProject, nameof(containingProject));
_xmlSource = (XmlElementWithLocation)xmlElement;
_parent = parent;
ContainingProject = containingProject;
}
/// <summary>
/// Allows data (for example, item metadata) to be represented as an attribute on the parent element instead of as a child element.
/// </summary>
/// <remarks>
/// If this is true, then the <see cref="XmlElement"/> will still be used to hold the data for this (pseudo) ProjectElement, but
/// it will not be added to the Xml tree.
/// </remarks>
internal virtual bool ExpressedAsAttribute
{
get => Link != null ? Link.ExpressedAsAttribute : _expressedAsAttribute;
set
{
if (Link != null)
{
Link.ExpressedAsAttribute = value;
}
else if (value != _expressedAsAttribute)
{
Parent?.RemoveFromXml(this);
_expressedAsAttribute = value;
Parent?.AddToXml(this);
MarkDirty("Set express as attribute: {0}", value.ToString());
}
}
}
/// <summary>
/// Gets or sets the Condition value.
/// It will return empty string IFF a condition attribute is legal but it’s not present or has no value.
/// It will return null IFF a Condition attribute is illegal on that element.
/// Removes the attribute if the value to set is empty.
/// It is possible for derived classes to throw an <see cref="InvalidOperationException"/> if setting the condition is
/// not applicable for those elements.
/// </summary>
/// <example> For the "ProjectExtensions" element, the getter returns null and the setter
/// throws an exception for any value. </example>
public virtual string Condition
{
[DebuggerStepThrough]
get
{
return GetAttributeValue(XMakeAttributes.condition, ref _condition);
}
[DebuggerStepThrough]
set
{
SetOrRemoveAttribute(XMakeAttributes.condition, value, ref _condition, "Set condition {0}", value);
}
}
/// <summary>
/// Gets or sets the Label value.
/// Returns empty string if it is not present.
/// Removes the attribute if the value to set is empty.
/// </summary>
public string Label
{
[DebuggerStepThrough]
get
{
return GetAttributeValue(XMakeAttributes.label);
}
[DebuggerStepThrough]
set
{
SetOrRemoveAttribute(XMakeAttributes.label, value, "Set label {0}", value);
}
}
/// <summary>
/// Null if this is a ProjectRootElement.
/// Null if this has not been attached to a parent yet.
/// </summary>
/// <remarks>
/// Parent should only be set by ProjectElementContainer.
/// </remarks>
public ProjectElementContainer Parent
{
[DebuggerStepThrough]
get
{
if (this.Link != null) { return this.Link.Parent; }
if (_parent is WrapperForProjectRootElement)
{
// We hijacked the field to store the owning PRE. This element is actually unparented.
return null;
}
return _parent;
}
internal set
{
ErrorUtilities.VerifyThrow(Link == null, "External project");
if (value == null)
{
// We're about to lose the parent. Hijack the field to store the owning PRE.
_parent = new WrapperForProjectRootElement(ContainingProject);
}
else
{
_parent = value;
}
OnAfterParentChanged(value);
}
}
/// <inheritdoc/>
public string OuterElement => Link != null ? Link.OuterElement : XmlElement.OuterXml;
/// <summary>
/// All parent elements of this element, going up to the ProjectRootElement.
/// None if this itself is a ProjectRootElement.
/// None if this itself has not been attached to a parent yet.
/// </summary>
public IEnumerable<ProjectElementContainer> AllParents
{
get
{
ProjectElementContainer currentParent = Parent;
while (currentParent != null)
{
yield return currentParent;
currentParent = currentParent.Parent;
}
}
}
/// <summary>
/// Previous sibling element.
/// May be null.
/// </summary>
/// <remarks>
/// Setter should ideally be "protected AND internal"
/// </remarks>
public ProjectElement PreviousSibling
{
[DebuggerStepThrough]
get => Link != null ? Link.PreviousSibling : _previousSibling;
[DebuggerStepThrough]
internal set => _previousSibling = value;
}
/// <summary>
/// Next sibling element.
/// May be null.
/// </summary>
/// <remarks>
/// Setter should ideally be "protected AND internal"
/// </remarks>
public ProjectElement NextSibling
{
[DebuggerStepThrough]
get => Link != null ? Link.NextSibling : _nextSibling;
[DebuggerStepThrough]
internal set => _nextSibling = value;
}
/// <summary>
/// ProjectRootElement (possibly imported) that contains this Xml.
/// Cannot be null.
/// </summary>
/// <remarks>
/// Setter ideally would be "protected and internal"
/// There are some tricks here in order to save the space of a field: there are a lot of these objects.
/// </remarks>
public ProjectRootElement ContainingProject
{
get
{
if (Link != null)
{
return Link.ContainingProject;
}
// If this element is unparented, we have hijacked the 'parent' field and stored the owning PRE in a special wrapper; get it from that.
if (_parent is WrapperForProjectRootElement wrapper)
{
return wrapper.ContainingProject;
}
// If this element is parented, the parent field is the true parent, and we ask that for the PRE.
// It will call into this same getter on itself and figure it out.
return Parent.ContainingProject;
}
// ContainingProject is set ONLY when an element is first constructed.
internal set
{
ErrorUtilities.VerifyThrow(Link == null, "External project");
ErrorUtilities.VerifyThrowArgumentNull(value, "ContainingProject");
if (_parent == null)
{
// Not parented yet, hijack the field to store the ContainingProject
_parent = new WrapperForProjectRootElement(value);
}
}
}
/// <summary>
/// Location of the "Condition" attribute on this element, if any.
/// If there is no such attribute, returns null.
/// </summary>
public virtual ElementLocation ConditionLocation => GetAttributeLocation(XMakeAttributes.condition);
/// <summary>
/// Location of the "Label" attribute on this element, if any.
/// If there is no such attribute, returns null;
/// </summary>
public ElementLocation LabelLocation => GetAttributeLocation(XMakeAttributes.label);
/// <summary>
/// Location of the corresponding Xml element.
/// May not be correct if file is not saved, or
/// file has been edited since it was last saved.
/// In the case of an unsaved edit, the location only
/// contains the path to the file that the element originates from.
/// </summary>
public ElementLocation Location => Link != null ? Link.Location : XmlElement.Location;
/// <inheritdoc/>
public string ElementName => Link != null ? Link.ElementName : XmlElement.Name;
// Using ILinkedXml to share single field for either Linked (external) and local (XML backed) nodes.
private ILinkedXml _xmlSource;
internal ProjectElementLink Link => _xmlSource?.Link;
/// <summary>
/// <see cref="ILinkableObject.Link"/>
/// </summary>
object ILinkableObject.Link => Link;
/// <summary>
/// Gets the XmlElement associated with this project element.
/// The setter is used when adding new elements.
/// Never null except during load or creation.
/// </summary>
/// <remarks>
/// This should be protected, but "protected internal" means "OR" not "AND",
/// so this is not possible.
/// </remarks>
internal XmlElementWithLocation XmlElement => _xmlSource?.Xml;
/// <summary>
/// Gets the XmlDocument associated with this project element.
/// </summary>
/// <remarks>
/// Never null except during load or creation.
/// This should be protected, but "protected internal" means "OR" not "AND",
/// so this is not possible.
/// </remarks>
internal XmlDocumentWithLocation XmlDocument
{
[DebuggerStepThrough]
get
{
return (XmlDocumentWithLocation)XmlElement?.OwnerDocument;
}
}
/// <summary>
/// Returns a shallow clone of this project element.
/// </summary>
/// <returns>The cloned element.</returns>
public ProjectElement Clone()
{
return Clone(ContainingProject);
}
/// <summary>
/// Applies properties from the specified type to this instance.
/// </summary>
/// <param name="element">The element to act as a template to copy from.</param>
public virtual void CopyFrom(ProjectElement element)
{
ErrorUtilities.VerifyThrowArgumentNull(element, nameof(element));
ErrorUtilities.VerifyThrowArgument(GetType().IsEquivalentTo(element.GetType()), "CannotCopyFromElementOfThatType");
if (this == element)
{
return;
}
if (Link != null)
{
Link.CopyFrom(element);
return;
}
// Remove all the current attributes and textual content.
XmlElement.RemoveAllAttributes();
if (XmlElement.ChildNodes.Count == 1 && XmlElement.FirstChild.NodeType == XmlNodeType.Text)
{
XmlElement.RemoveChild(XmlElement.FirstChild);
}
// Ensure the element name itself matches.
ReplaceElement(XmlUtilities.RenameXmlElement(XmlElement, element.ElementName, XmlElement.NamespaceURI));
// hard case when argument is a linked object (slight duplication).
if (element.Link != null)
{
foreach (var remoteAttribute in element.Link.Attributes)
{
if (ShouldCloneXmlAttribute(remoteAttribute))
{
XmlElement.SetAttribute(remoteAttribute.LocalName, remoteAttribute.NamespaceURI, remoteAttribute.Value);
}
}
var pureText = element.Link.PureText;
if (pureText != null)
{
XmlElement.AppendChild(XmlElement.OwnerDocument.CreateTextNode(pureText));
}
_expressedAsAttribute = element.ExpressedAsAttribute;
}
else
{
// Copy over the attributes from the template element.
foreach (XmlAttribute attribute in element.XmlElement.Attributes)
{
if (ShouldCloneXmlAttribute(attribute))
{
XmlElement.SetAttribute(attribute.LocalName, attribute.NamespaceURI, attribute.Value);
}
}
// If this element has pure text content, copy that over.
if (element.XmlElement.ChildNodes.Count == 1 && element.XmlElement.FirstChild.NodeType == XmlNodeType.Text)
{
XmlElement.AppendChild(XmlElement.OwnerDocument.CreateTextNode(element.XmlElement.FirstChild.Value));
}
_expressedAsAttribute = element._expressedAsAttribute;
}
MarkDirty("CopyFrom", null);
ClearAttributeCache();
}
/// <summary>
/// Hook for subclasses to specify whether the given <paramref name="attribute"></paramref> should be cloned or not
/// </summary>
protected virtual bool ShouldCloneXmlAttribute(XmlAttribute attribute) => true;
internal virtual bool ShouldCloneXmlAttribute(XmlAttributeLink attributeLink) => true;
/// <summary>
/// Called only by the parser to tell the ProjectRootElement its backing XmlElement and its own parent project (itself)
/// This can't be done during construction, as it hasn't loaded the document at that point and it doesn't have a 'this' pointer either.
/// </summary>
internal void SetProjectRootElementFromParser(XmlElementWithLocation xmlElement, ProjectRootElement projectRootElement)
{
_xmlSource = xmlElement;
ContainingProject = projectRootElement;
}
/// <summary>
/// Called by ProjectElementContainer to clear the parent when
/// removing an element from its parent.
/// </summary>
internal void ClearParent()
{
Parent = null;
}
/// <summary>
/// Called by a DERIVED CLASS to indicate its XmlElement has changed.
/// This normally shouldn't happen, so it's broken out into an explicit method.
/// An example of when it has to happen is when an item's type is changed.
/// We trust the caller to have fixed up the XmlDocument properly.
/// We ASSUME that attributes were copied verbatim. If this is not the case,
/// any cached attribute values would have to be cleared.
/// If the new element is actually the existing element, does nothing, and does
/// not mark the project dirty.
/// </summary>
/// <remarks>
/// This should be protected, but "protected internal" means "OR" not "AND",
/// so this is not possible.
/// </remarks>
internal void ReplaceElement(XmlElementWithLocation newElement)
{
if (ReferenceEquals(newElement, XmlElement))
{
return;
}
_xmlSource = newElement;
MarkDirty("Replace element {0}", newElement.Name);
}
/// <summary>
/// Overridden to verify that the potential parent and siblings
/// are acceptable. Throws InvalidOperationException if they are not.
/// </summary>
internal abstract void VerifyThrowInvalidOperationAcceptableLocation(ProjectElementContainer proposedParent, ProjectElement previousSibling, ProjectElement nextSibling);
/// <summary>
/// Marks this element as dirty.
/// The default implementation simply marks the parent as dirty.
/// If there is no parent, because the element has not been parented, do nothing. The parent
/// will be dirtied when the element is added.
/// Accepts a reason for debugging purposes only, and optional reason parameter.
/// </summary>
/// <comment>
/// Should ideally be protected+internal.
/// </comment>
internal virtual void MarkDirty(string reason, string param)
{
Parent?.MarkDirty(reason, param);
}
/// <summary>
/// Called after a new parent is set. Parent may be null.
/// By default does nothing.
/// </summary>
internal virtual void OnAfterParentChanged(ProjectElementContainer newParent)
{
}
/// <summary>
/// Returns a shallow clone of this project element.
/// </summary>
/// <param name="factory">The factory to use for creating the new instance.</param>
/// <returns>The cloned element.</returns>
protected internal virtual ProjectElement Clone(ProjectRootElement factory)
{
var clone = CreateNewInstance(factory);
if (!clone.GetType().IsEquivalentTo(GetType()))
{
ErrorUtilities.ThrowInternalError("{0}.Clone() returned an instance of type {1}.", GetType().Name, clone.GetType().Name);
}
clone.CopyFrom(this);
return clone;
}
/// <summary>
/// Returns a new instance of this same type.
/// Any properties that cannot be set after creation should be set to copies of values
/// as set for this instance.
/// </summary>
/// <param name="owner">The factory to use for creating the new instance.</param>
protected abstract ProjectElement CreateNewInstance(ProjectRootElement owner);
internal static ProjectElement CreateNewInstance(ProjectElement xml, ProjectRootElement owner)
{
if (xml.Link != null)
{
return xml.Link.CreateNewInstance(owner);
}
return xml.CreateNewInstance(owner);
}
internal ElementLocation GetAttributeLocation(string attributeName)
{
return Link != null ? Link.GetAttributeLocation(attributeName) : XmlElement.GetAttributeLocation(attributeName);
}
internal string GetAttributeValue(string attributeName, bool nullIfNotExists = false)
{
return Link != null ? Link.GetAttributeValue(attributeName, nullIfNotExists) :
ProjectXmlUtilities.GetAttributeValue(XmlElement, attributeName, nullIfNotExists);
}
internal string GetAttributeValue(string attributeName, ref string cache)
{
if (cache != null)
{
return cache;
}
var value = GetAttributeValue(attributeName, false);
if (Link == null)
{
cache = value;
}
return value;
}
internal virtual void ClearAttributeCache()
{
this._condition = null;
}
internal void SetOrRemoveAttributeForLink(string name, string value, bool clearAttributeCache, string reason, string param)
{
SetOrRemoveAttribute(name, value, reason, param);
if (clearAttributeCache)
{
this.ClearAttributeCache();
}
}
internal void SetOrRemoveAttribute(string name, string value, string reason = null, string param = null)
{
if (Link != null)
{
Link.SetOrRemoveAttribute(name, value, false, reason, param);
}
else
{
ProjectXmlUtilities.SetOrRemoveAttribute(XmlElement, name, value);
if (reason != null)
{
MarkDirty(reason, param);
}
}
}
internal void SetOrRemoveAttribute(string name, string value, ref string cache, string reason = null, string param = null)
{
if (Link != null)
{
Link.SetOrRemoveAttribute(name, value, true, reason, param);
}
else
{
ProjectXmlUtilities.SetOrRemoveAttribute(XmlElement, name, value);
cache = value;
if (reason != null)
{
MarkDirty(reason, param);
}
}
}
/// <summary>
/// Special derived variation of ProjectElementContainer used to wrap a ProjectRootElement.
/// This is part of a trick used in ProjectElement to avoid using a separate field for the containing PRE.
/// </summary>
private class WrapperForProjectRootElement : ProjectElementContainer
{
/// <summary>
/// Constructor
/// </summary>
internal WrapperForProjectRootElement(ProjectRootElement containingProject)
{
ErrorUtilities.VerifyThrowInternalNull(containingProject, nameof(containingProject));
ContainingProject = containingProject;
}
/// <summary>
/// Wrapped ProjectRootElement
/// </summary>
internal new ProjectRootElement ContainingProject { get; }
/// <summary>
/// Dummy required implementation
/// </summary>
internal override void VerifyThrowInvalidOperationAcceptableLocation(ProjectElementContainer parent, ProjectElement previousSibling, ProjectElement nextSibling)
{
ErrorUtilities.ThrowInternalErrorUnreachable();
}
/// <inheritdoc />
protected override ProjectElement CreateNewInstance(ProjectRootElement owner)
{
return new WrapperForProjectRootElement(ContainingProject);
}
}
}
}
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