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[Blazor] Fix ExpressionFormatter sometimes generating malformed expression strings #58799

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Merged
merged 1 commit into from
Nov 5, 2024
Merged

[Blazor] Fix ExpressionFormatter sometimes generating malformed expression strings #58799

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18 changes: 18 additions & 0 deletions src/Components/Forms/test/ReverseStringBuilderTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,24 @@ public void ToString_Works_AfterExceedingStackAllocatedBuffer()
Assert.Equal(1, builder.SequenceSegmentCount);
}

[Fact]
public void ToString_Works_AfterExceedingStackAllocatedBuffer_WithUnusedSpaceInInitialBuffer()
{
const int InitialBufferSize = 64;
var builder = new ReverseStringBuilder(stackalloc char[InitialBufferSize]);

var firstChunk = new string('A', InitialBufferSize - 10);
var secondChunk = new string('B', 20);

builder.InsertFront(firstChunk);
builder.InsertFront(secondChunk);

var expected = secondChunk + firstChunk;
var actual = builder.ToString();

Assert.Equal(expected, actual);
}

[Fact]
public void ToString_Works_AfterExpandingIntoMultipleBuffersFromEstimatedStringSize()
{
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16 changes: 8 additions & 8 deletions src/Components/Shared/src/ExpressionFormatting/ReverseStringBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ internal ref struct ReverseStringBuilder
private SequenceSegment? _fallbackSequenceSegment;

// For testing.
internal int SequenceSegmentCount => _fallbackSequenceSegment?.Count() ?? 0;
internal readonly int SequenceSegmentCount => _fallbackSequenceSegment?.Count() ?? 0;

public ReverseStringBuilder(int conservativeEstimatedStringLength)
{
Expand All @@ -33,7 +33,7 @@ public ReverseStringBuilder(Span<char> initialBuffer)
_nextEndIndex = _currentBuffer.Length;
}

public bool Empty => _nextEndIndex == _currentBuffer.Length;
public readonly bool Empty => _nextEndIndex == _currentBuffer.Length;

public void InsertFront(scoped ReadOnlySpan<char> span)
{
Expand All @@ -60,13 +60,13 @@ public void InsertFront(scoped ReadOnlySpan<char> span)
var newBuffer = s_arrayPool.Rent(sizeToRent);
_fallbackSequenceSegment = new(newBuffer);

_nextEndIndex = newBuffer.Length - _currentBuffer.Length;
_currentBuffer.CopyTo(newBuffer.AsSpan()[_nextEndIndex..]);
_currentBuffer = newBuffer;
var newEndIndex = newBuffer.Length - _currentBuffer.Length + _nextEndIndex;
_currentBuffer[_nextEndIndex..].CopyTo(newBuffer.AsSpan(newEndIndex));
newEndIndex -= span.Length;
span.CopyTo(newBuffer.AsSpan(newEndIndex));

startIndex = _nextEndIndex - span.Length;
span.CopyTo(_currentBuffer[startIndex..]);
_nextEndIndex = startIndex;
_currentBuffer = newBuffer;
_nextEndIndex = newEndIndex;
}
else
{
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