/// <summary>
/// Compares two <see cref="ICollection{T}" /> objects to determine if they contain the same objects (by the same rules
/// as <see cref="Compare{T}" /> method)
/// It treats the collections as sets, i.e. does not care about order, just about containing the same objects.
/// </summary>
/// <typeparam name="TElement">Type of the <see cref="ICollection{T}" /> element</typeparam>
/// <param name="first">First collection to compare</param>
/// <param name="second">Second collection to compare with <see cref="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns><c>true</c> if collections contain the same objects, otherwise <c>false</c></returns>
/// <returns></returns>
private static bool CompareAsSets <TElement>(ICollection <TElement> first, ICollection <TElement> second,
CompareOptionsInternal options, PropertyProvider provider, ComparisonContext comparisonContext)
{
// We first look at the difference between first and second
var firstCompare = new HashSet <TElement>(first,
new ProxyEqualityComparer <TElement>(options, provider, comparisonContext));
firstCompare.ExceptWith(second);
foreach (var difference in firstCompare)
{
comparisonContext.AddDifferenceAtCurrentPath(difference, null);
}
// and then at the difference between second and first
var secondCompare = new HashSet <TElement>(second,
new ProxyEqualityComparer <TElement>(options, provider, comparisonContext));
secondCompare.ExceptWith(first);
foreach (var difference in secondCompare)
{
comparisonContext.AddDifferenceAtCurrentPath(null, difference);
}
// NOTE: SymmetricExceptWith COULD be used, but we either would loose the information about which tree (first, second) specific objects exist/don't exist in, or we would have to run 'Contains' checks for each
// Equal if neither of comparison collections has any elements
return(!(firstCompare.Any() || secondCompare.Any()));
}
public ProxyEqualityComparer(CompareOptionsInternal options, PropertyProvider provider,
ComparisonContext comparisonContext)
{
_options = options;
_provider = provider;
// we clone the context, as in multithreaded scenario this would behave very weirdly
_comparisonContext = (ComparisonContext)comparisonContext.Clone();
// and we MUST NOT generate differences, because those are unavoidable during collection comparison, and don't actually mean the entire collections are not equivalent
_comparisonContext.PreventDifferenceGeneration = true;
}
/// <summary>
/// A helper that allows calling one of the generic collection comparers while having the type in a variable
/// </summary>
/// <param name="methodName">Name of the collection comparer to use</param>
/// <param name="first">First object of comparison</param>
/// <param name="second">Second object of comparison, to be compared with <paramref name="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <param name="genericArguments">
/// Generic arguments to pass to the methods (either element type, or key/value types for
/// <see cref="IDictionary{TKey,TValue}" />)
/// </param>
/// <returns>Result of called comparer</returns>
private static bool CallCollectionComparer(string methodName, object first, object second,
CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext, params Type[] genericArguments)
{
// As with CallCompareFor we use name of the method to retrive it from this very class
var method = typeof(ObjectComparer)
.GetMethod(methodName, BindingFlags.NonPublic | BindingFlags.Static) ??
throw new ArgumentNullException(
$"typeof(ObjectComparer).GetMethod({methodName}, BindingFlags.NonPublic | BindingFlags.Static)");
// And again, call generic method while having type argument(s) in a variable
return((bool)method
.MakeGenericMethod(genericArguments)
.Invoke(null, new[] { first, second, options, provider, comparisonContext }));
}
/// <summary>
/// A helper that allows calling the <see cref="Compare{T}" /> method even if we can't explicitly provide type T
/// </summary>
/// <param name="compareType">Type of the objects to compare</param>
/// <param name="first">First object of comparison</param>
/// <param name="second">Second object of comparison, to be compared with <paramref name="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns>Result of <see cref="Compare{T}" /> method called with above parameters</returns>
private static bool CallCompareFor(Type compareType, object first, object second,
CompareOptionsInternal options, PropertyProvider provider, ComparisonContext comparisonContext)
{
// We are using nameof to prevent nasty typos
var method = typeof(ObjectComparer).GetMethod(nameof(Compare), BindingFlags.Static | BindingFlags.NonPublic)
?? throw new ArgumentNullException(
$"typeof(ObjectComparer).GetMethod({nameof(Compare)}, BindingFlags.Static|BindingFlags.NonPublic)");
// This whole thing is so we can do MakeGenericMethod - normally for Method<T>, T must be eitehr explicitly stated, or passed as dynamic for runtime binding, however we know the type - only it's in a variable
return((bool)method
.MakeGenericMethod(compareType)
.Invoke(null,
new[]
{
first, second, options, provider, comparisonContext
})); // we pass the parameters as needed by the Compare method
}
/// <summary>
/// Actual comparisoon implementation that will be called recursively if needed
/// </summary>
/// <typeparam name="T">Type of objects to compare.</typeparam>
/// <param name="first">First object of comparison</param>
/// <param name="second">Second object of comparison to compare with <paramref name="first" /></param>
/// <param name="options">(optional) User-provided settings that customise behaviour of the comparison</param>
/// <param name="provider">Property provider to be reused across the comparison to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns>
/// <c>true</c> if objects are equivalent as understood by provided <paramref name="options" /> (or default
/// <see cref="CompareOptions" />), otherwise <c>false</c>
/// </returns>
private static bool Compare <T>(T first, T second, CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext)
{
// 0. Initial checks
// 0.1 Recursion check
if (!comparisonContext.TryEnterObject(first, second))
{
throw new InvalidOperationException(
$"Detected a circular reference at {comparisonContext.GetCurrentPath()}. Add the property to the blacklist to compare those objects");
}
try
{
// 0.2 Type blacklist check
if (options.TypesToIgnore.Contains(typeof(T)))
{
return(true); // we don't care
}
// 0.3 Path blacklist check
if (options.PathsToIgnore.Contains(comparisonContext.GetCurrentPath()))
{
return(true);
}
// 1. Reference check
if (ReferenceEquals(first, second))
{
return(true); // no need to go deeper, they are at this point SAME object
}
// 2. Null checks
if (first == null || second == null)
{
// oops, we know that they are not BOTH nulls due to check #1
comparisonContext.AddDifferenceAtCurrentPath(first, second);
return
(false); // no need to go deeper, everything deeper down will be a difference, as one of them is null, but not second
}
// 3. Do we have an explicit comparer for this object?
if (options.EqualityComparers.TryGetValue(typeof(T), out var equalityComparerObj) &&
equalityComparerObj is IEqualityComparer <T> equalityComparer)
{
if (equalityComparer.Equals(first, second))
{
return(true);
}
comparisonContext.AddDifferenceAtCurrentPath(first, second);
return(false);
}
// 3.1 Maybe it's strings?
if (first is string firstString &&
second is string secondString)
{
if (string.Equals(firstString, secondString, options.DefaultStringComparison))
{
return(true);
}
comparisonContext.AddDifferenceAtCurrentPath(first, second);
return(false);
}
// 4. Is the object equatable?
if (first is IEquatable <T> equatableFirst)
{
// The type implements IEquatable to itself, so any sub-level comparisons are delegated to this method
if (equatableFirst.Equals(second))
{
return(true);
}
comparisonContext.AddDifferenceAtCurrentPath(first, second);
return(false);
}
// 5. Is the object a collection?
// 5.1 IDictionary
if (typeof(T).TryAsGenericDictionary(out var keyType, out var valueType))
{
return(CallCollectionComparer(nameof(CompareDictionaries), first, second, options,
provider, comparisonContext, keyType, valueType));
}
// 5.2 Set
if (typeof(T).TryAsGenericSet(out var elementType))
{
return(CallCollectionComparer(nameof(CompareSet), first, second, options,
provider, comparisonContext, elementType));
}
// 5.3 List
if (typeof(T).TryAsGenericList(out elementType))
{
return(CallCollectionComparer(nameof(CompareList), first, second, options,
provider, comparisonContext, elementType));
}
// 5.4 Enumerable
if (typeof(T).TryAsGenericEnumerable(out elementType))
{
return(CallCollectionComparer(nameof(CompareEnumerable), first, second, options,
provider, comparisonContext, elementType));
}
// 6. Not enumerable, we don't know how to check it - now the fun starts.
// We are actually going to get the properties and compare them one to one
var properties = provider.GetAllProperties <T>();
var propertyEqual = true;
foreach (var propertyInfo in properties)
{
// This will note that we have entered a property of given name
comparisonContext.Enter(propertyInfo.Name);
// TODO: add multithreading, remember to clone context to prevent messing up the path stacks
propertyEqual = CallCompareFor(propertyInfo.PropertyType, propertyInfo.GetValue(first),
propertyInfo.GetValue(second), options, provider, comparisonContext);
// Unless full diff requested by user - bail, we have our answer
if (!propertyEqual && options.StopAtFirstDifference)
{
return(false);
}
// property comparison finished, remove from stack
comparisonContext.Exit();
}
return(propertyEqual);
}
finally
{
// ALWAYS run this, because if we got to this point we have called TryEnterObject (and it returned true).
comparisonContext.ExitObject <T>();
}
}
/// <summary>
/// Compares two <see cref="IEnumerable{T}" /> objects to determine if they contain the same objects (by the same rules
/// as <see cref="Compare{T}" /> method) in the same order
/// </summary>
/// <typeparam name="TElement">Type of the <see cref="IEnumerable{T}" /> element</typeparam>
/// <param name="first">First enumerabe to compare</param>
/// <param name="second">Second enumerable to compare with <see cref="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns><c>true</c> if enumerable contain the same objects in the same order, otherwise <c>false</c></returns>
private static bool CompareAsEnumeration <TElement>(IEnumerable <TElement> first, IEnumerable <TElement> second,
CompareOptionsInternal options, PropertyProvider provider, ComparisonContext comparisonContext)
{
// it will iterate at equal pace both lists, and run Compare - if a difference is found, it will be noted. Also, if nulls occur in a non-symmetric manner.
var iterationContext = (ComparisonContext)comparisonContext.Clone();
iterationContext.PreventDifferenceGeneration = true;
return(first
.ZipFullLength(second, (f, s) => Compare(f, s, options, provider, iterationContext))
.All(x => x));
}
/// <summary>
/// Compares two <see cref="IEnumerable{T}" /> objects to determine if they contain the same objects (by the same rules
/// as <see cref="Compare{T}" /> method) in the same order
/// </summary>
/// <typeparam name="TElement">Type of the <see cref="IEnumerable{T}" /> element</typeparam>
/// <param name="first">First enumerabe to compare</param>
/// <param name="second">Second enumerable to compare with <see cref="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns><c>true</c> if enumerable contain the same objects in the same order, otherwise <c>false</c></returns>
private static bool CompareEnumerable <TElement>(IEnumerable <TElement> first,
IEnumerable <TElement> second, CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext) =>
!options.EnumerateEnumerables || // we might be prohibited from enumerating enumerables
CompareAsEnumeration(first, second, options, provider, comparisonContext);
// ReSharper enable SuggestBaseTypeForParameter
/// <summary>
/// Compares two <see cref="IList{T}" /> objects to determine if they contain the same objects (by the same rules as
/// <see cref="Compare{T}" /> method), and possibly in the same order, as determined by <paramref name="options" />
/// </summary>
/// <typeparam name="TElement">Type of the <see cref="IList{T}" /> element</typeparam>
/// <param name="first">First list to compare</param>
/// <param name="second">Second list to compare with <see cref="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns>
/// <c>true</c> if lists contain the same objects (and possibly in the same order as determined by
/// <paramref name="options" />), otherwise <c>false</c>
/// </returns>
private static bool CompareList <TElement>(IList <TElement> first,
IList <TElement> second, CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext) => options.VerifyListOrder
? CompareAsEnumeration(first, second, options, provider, comparisonContext)
: CompareAsSets(first, second, options, provider, comparisonContext);
/// <summary>
/// Compares two <see cref="ISet{T}" /> objects to determine if they contain the same objects (by the same rules as
/// <see cref="Compare{T}" /> method)
/// </summary>
/// <typeparam name="TElement">Type of the <see cref="ISet{T}" /> element</typeparam>
/// <param name="first">First set to compare</param>
/// <param name="second">Second set to compare with <see cref="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns><c>true</c> if sets contain the same objects, otherwise <c>false</c></returns>
// ReSharper disable SuggestBaseTypeForParameter - I know it doesn't need to be a set, because we rewrite it into another set anyway, but it communicates the purpose better and it does not mess with MakeGenericMethod
private static bool CompareSet <TElement>(ISet <TElement> first,
ISet <TElement> second, CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext) =>
CompareAsSets(first, second, options, provider, comparisonContext);
/// <summary>
/// Compares two <see cref="IDictionary{TKey,TValue}" /> objects to determine whether they have the same keys and
/// contain the same objects under said keys
/// </summary>
/// <typeparam name="TKey">Key type of the <see cref="IDictionary{TKey,TValue}" /></typeparam>
/// <typeparam name="TValue">Value type of the <see cref="IDictionary{TKey,TValue}" /></typeparam>
/// <param name="first">First dictionary for comparison</param>
/// <param name="second">Second dictionary for comparison, to be compared with <paramref name="first" /></param>
/// <param name="options">Options of the comparison</param>
/// <param name="provider">PropertyProvider, reused to take advantage of caching</param>
/// <param name="comparisonContext">Current context of the comparison</param>
/// <returns><c>true</c> if dictionaries contain the same objects under the same keys, otherwise <c>false</c></returns>
private static bool CompareDictionaries <TKey, TValue>(IDictionary <TKey, TValue> first,
IDictionary <TKey, TValue> second, CompareOptionsInternal options,
PropertyProvider provider, ComparisonContext comparisonContext)
{
var equal = true;
// NOTE: this indeed could be simpler if we cared only about equivalence, but we might also want all the differences
// TODO: this smells superfluous as it repeates the logic from Compare method
var keys = first.Keys.Concat(second.Keys);
// if we can distinct the keys by any known means, we should
if (options.EqualityComparers.TryGetValue(typeof(TKey), out var keyComparerObj) &&
keyComparerObj is IEqualityComparer <TKey> keyComparer)
{
keys = keys.Distinct(keyComparer); // we have our custom comparer to use
}
else if (typeof(TKey) == typeof(string))
{
keys = keys
.Cast <string>()
.Distinct(StringComparisonToStringComparer[
options.DefaultStringComparison]) // it's string, use string equality
.Cast <TKey>();
}
else if (typeof(IEquatable <TKey>).IsAssignableFrom(typeof(TKey)))
{
keys = keys.Distinct(); // we can use default, as it will use IEquatable interface
}
// else: we can't distinct it, because we would have to run Compare on them and it would be painful
// but fear not: the dictionaries have their own comparers they use, so whatever was used, we will use
// the only downside: some keys, or even all keys could be duplicated - but well, this is only if you use some non-IEquatable keys
foreach (var key in keys)
{
comparisonContext.Enter($"[{key}]");
var firstHas = first.TryGetValue(key, out var firstValue);
var secondHas = second.TryGetValue(key, out var secondValue);
if (firstHas && secondHas)
{
// This will save the difference for us
if (!Compare(firstValue, secondValue, options, provider, comparisonContext))
{
equal = false;
}
}
else
{
equal = false;
// We could just use first/second value, but if type is int, and one dict has under 'key'
// value '0', then it would show as if both of them have 0, due to default(int) = 0
comparisonContext.AddDifferenceAtCurrentPath(
firstHas ? (object)firstValue : null,
secondHas ? (object)secondValue : null);
}
comparisonContext.Exit();
if (!equal && options.StopAtFirstDifference)
{
return(false);
}
}
return(equal);
}
