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Merged
mattwar merged 2 commits into from
Feb 18, 2015
Merged

Improve SyntaxDiffer diffing rules #609

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e90558e
Change SyntaxDiffer matching rules
mattwar Feb 17, 2015
af216b8
Cleanup Test
mattwar Feb 17, 2015
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2 changes: 1 addition & 1 deletion src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxDiffingTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -252,7 +252,7 @@ public void TestDiffClassChangedToStruct()
Assert.Equal("struct", changes[0].NewText);
}

[Fact(Skip = "https://github.com/dotnet/roslyn/issues/320")]
[Fact]
public void TestQualifyWithThis()
{
var original = @"
Expand Down
46 changes: 37 additions & 9 deletions src/Compilers/Core/Portable/Syntax/SyntaxDiffer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -244,9 +244,16 @@ private DiffAction GetNextAction()

if (indexOfOldInNew > 0)
{
return new DiffAction(DiffOp.InsertNew, indexOfOldInNew);
// look ahead to see if the old node also appears again later in its own list
var oldHasIdenticalSibling = FindExactMatch(_oldNodes, _oldNodes.Peek(), 1) >= 1;

if (!oldHasIdenticalSibling)
{
return new DiffAction(DiffOp.InsertNew, indexOfOldInNew);
}
}
else if (!newIsToken)

if (!newIsToken)
{
if (AreSimilar(_oldNodes.Peek(), _newNodes.Peek()))
{
Expand Down Expand Up @@ -324,20 +331,41 @@ private static void ReplaceFirstWithChildren(Stack<SyntaxNodeOrToken> stack)
}
}

private int FindExactMatch(Stack<SyntaxNodeOrToken> stack, SyntaxNodeOrToken node, int startIndex)
{
int i = 0;
foreach (var stackNode in stack)
{
if (i >= MaxSearchLength)
{
break;
}

if (i >= startIndex && AreIdentical(stackNode, node))
{
return i;
}

i++;
}

return -1;
}

private void FindBestMatch(Stack<SyntaxNodeOrToken> stack, SyntaxNodeOrToken node, out int index, out int similarity)
{
index = -1;
similarity = -1;

int i = 0;
foreach (var listNode in stack)
foreach (var stackNode in stack)
{
if (i >= MaxSearchLength)
{
break;
}

if (AreIdentical(listNode, node))
if (AreIdentical(stackNode, node))
{
var sim = node.FullSpan.Length;
if (sim > similarity)
Expand All @@ -347,15 +375,15 @@ private void FindBestMatch(Stack<SyntaxNodeOrToken> stack, SyntaxNodeOrToken nod
return;
}
}
else if (AreSimilar(listNode, node))
else if (AreSimilar(stackNode, node))
{
var sim = GetSimilarity(listNode, node);
var sim = GetSimilarity(stackNode, node);

// Are these really the same? This may be expensive so only check this if
// similarity is rated equal to them being identical.
if (sim == node.FullSpan.Length && node.IsToken)
{
if (listNode.ToFullString() == node.ToFullString())
if (stackNode.ToFullString() == node.ToFullString())
{
index = i;
similarity = sim;
Expand All @@ -373,7 +401,7 @@ private void FindBestMatch(Stack<SyntaxNodeOrToken> stack, SyntaxNodeOrToken nod
{
// check one level deep inside list node's children
int j = 0;
foreach (var child in listNode.ChildNodesAndTokens())
foreach (var child in stackNode.ChildNodesAndTokens())
{
if (j >= MaxSearchLength)
{
Expand Down Expand Up @@ -716,7 +744,7 @@ private static void GetCommonEdgeLengths(StringBuilder oldText, StringBuilder ne
}
}

// don't double count the chars we matches at the start of the strings
// don't double count the chars we matched at the start of the strings
maxChars = maxChars - commonLeadingCount;

commonTrailingCount = 0;
Expand Down