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Switch to iterative algorithm to prevent stack overflows. #40211

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Merged
merged 9 commits into from
Dec 13, 2019
Merged

Switch to iterative algorithm to prevent stack overflows. #40211

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d946407
Switch to iterative algorithm to prevent stack overflows.
CyrusNajmabadi Dec 6, 2019
6a81940
Simplify code
CyrusNajmabadi Dec 6, 2019
b4ac384
Simplify
CyrusNajmabadi Dec 6, 2019
e55e787
Use stack
CyrusNajmabadi Dec 6, 2019
07eb9ba
Simplify
CyrusNajmabadi Dec 6, 2019
e05d90a
Simplify
CyrusNajmabadi Dec 6, 2019
7b2bcfe
Merge remote-tracking branch 'upstream/master' into asyncAwaitIterative
CyrusNajmabadi Dec 13, 2019
4de5af1
Use struct iterator
CyrusNajmabadi Dec 13, 2019
e65968f
reverse
CyrusNajmabadi Dec 13, 2019
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150 changes: 79 additions & 71 deletions src/EditorFeatures/CSharp/Highlighting/KeywordHighlighters/AsyncAwaitHighlighter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,19 +2,23 @@

using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Editor.Implementation.Highlighting;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.Editor.CSharp.KeywordHighlighting.KeywordHighlighters
{
[ExportHighlighter(LanguageNames.CSharp)]
internal class AsyncAwaitHighlighter : AbstractKeywordHighlighter
{
private static readonly ObjectPool<Stack<SyntaxNode>> s_stackPool
= new ObjectPool<Stack<SyntaxNode>>(() => new Stack<SyntaxNode>());

[ImportingConstructor]
public AsyncAwaitHighlighter()
{
Expand All @@ -26,93 +30,97 @@ protected override bool IsHighlightableNode(SyntaxNode node)
protected override IEnumerable<TextSpan> GetHighlightsForNode(SyntaxNode node, CancellationToken cancellationToken)
{
var spans = new List<TextSpan>();
HighlightRelatedKeywords(node, spans);

foreach (var current in WalkChildren(node))
{
cancellationToken.ThrowIfCancellationRequested();
HighlightRelatedKeywords(current, spans);
}

return spans;
}

private static void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
private IEnumerable<SyntaxNode> WalkChildren(SyntaxNode node)
{
// Highlight async keyword
switch (node)
using var pooledObject = s_stackPool.GetPooledObject();

var stack = pooledObject.Object;
stack.Push(node);

while (stack.Count > 0)
{
case MethodDeclarationSyntax methodDeclaration:
{
var asyncModifier = methodDeclaration.Modifiers.FirstOrDefault(m => m.Kind() == SyntaxKind.AsyncKeyword);
if (asyncModifier.Kind() != SyntaxKind.None)
{
spans.Add(asyncModifier.Span);
}
break;
}
case LocalFunctionStatementSyntax localFunction:
{
var asyncModifier = localFunction.Modifiers.FirstOrDefault(m => m.Kind() == SyntaxKind.AsyncKeyword);
if (asyncModifier.Kind() != SyntaxKind.None)
{
spans.Add(asyncModifier.Span);
}
break;
}
case AnonymousFunctionExpressionSyntax anonymousFunction:
if (anonymousFunction.AsyncKeyword.Kind() == SyntaxKind.AsyncKeyword)
{
spans.Add(anonymousFunction.AsyncKeyword.Span);
}
break;

case AwaitExpressionSyntax awaitExpression:
// Note if there is already a highlight for the previous token, merge it
// with this span. That way, we highlight nested awaits with a single span.
var handled = false;
var awaitToken = awaitExpression.AwaitKeyword;
var previousToken = awaitToken.GetPreviousToken();
if (!previousToken.Span.IsEmpty)
{
var index = spans.FindIndex(s => s.Contains(previousToken.Span));
if (index >= 0)
{
var span = spans[index];
spans[index] = TextSpan.FromBounds(span.Start, awaitToken.Span.End);
handled = true;
}
}
var current = stack.Pop();
yield return current;

if (!handled)
// 'Reverse' isn't really necessary, but it means we walk the nodes in document
// order, which is nicer when debugging and understanding the results produced.
foreach (var child in current.ChildNodesAndTokens().Reverse())
{
if (child.IsNode)
{
spans.Add(awaitToken.Span);
}
break;
var childNode = child.AsNode();

case UsingStatementSyntax usingStatement:
if (usingStatement.AwaitKeyword.Kind() == SyntaxKind.AwaitKeyword)
{
spans.Add(usingStatement.AwaitKeyword.Span);
// Only process children if they're not the start of another construct
// that async/await would be related to.
if (!childNode.IsReturnableConstruct())
{
stack.Push(childNode);
}
}
break;
}
}
}

case LocalDeclarationStatementSyntax localDeclaration:
if (localDeclaration.AwaitKeyword.Kind() == SyntaxKind.AwaitKeyword && localDeclaration.UsingKeyword.Kind() == SyntaxKind.UsingKeyword)
{
spans.Add(localDeclaration.AwaitKeyword.Span);
}
break;
private static bool HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
=> node switch
{
MethodDeclarationSyntax methodDeclaration => TryAddAsyncModifier(methodDeclaration.Modifiers, spans),
LocalFunctionStatementSyntax localFunction => TryAddAsyncModifier(localFunction.Modifiers, spans),
AnonymousFunctionExpressionSyntax anonymousFunction => TryAddAsyncOrAwaitKeyword(anonymousFunction.AsyncKeyword, spans),
UsingStatementSyntax usingStatement => TryAddAsyncOrAwaitKeyword(usingStatement.AwaitKeyword, spans),
LocalDeclarationStatementSyntax localDeclaration =>
localDeclaration.UsingKeyword.Kind() == SyntaxKind.UsingKeyword && TryAddAsyncOrAwaitKeyword(localDeclaration.AwaitKeyword, spans),
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@CyrusNajmabadi CyrusNajmabadi Dec 6, 2019

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i preserved this logic. But i dont' actually think it's necessary. this basically ensures that we only highlight await in await using var whatever and not in await var whatever. However, the latter is broken code, so it would be fine IMO to highlight there.

CommonForEachStatementSyntax forEachStatement => TryAddAsyncOrAwaitKeyword(forEachStatement.AwaitKeyword, spans),
AwaitExpressionSyntax awaitExpression => TryAddAsyncOrAwaitKeyword(awaitExpression.AwaitKeyword, spans),
_ => false,
};

case CommonForEachStatementSyntax forEachStatement:
if (forEachStatement.AwaitKeyword.Kind() == SyntaxKind.AwaitKeyword)
{
spans.Add(forEachStatement.AwaitKeyword.Span);
}
break;
private static bool TryAddAsyncModifier(SyntaxTokenList modifiers, List<TextSpan> spans)
{
foreach (var mod in modifiers)
{
if (TryAddAsyncOrAwaitKeyword(mod, spans))
{
return true;
}
}

foreach (var child in node.ChildNodes())
return false;
}

private static bool TryAddAsyncOrAwaitKeyword(SyntaxToken mod, List<TextSpan> spans)
{
if (mod.IsKind(SyntaxKind.AsyncKeyword, SyntaxKind.AwaitKeyword))
{
// Only recurse if we have anything to do
if (!child.IsReturnableConstruct())
// Note if there is already a highlight for the previous token, merge it with this
// span. That way, we highlight nested awaits with a single span.

if (spans.Count > 0)
{
HighlightRelatedKeywords(child, spans);
var previousToken = mod.GetPreviousToken();
var lastSpan = spans[spans.Count - 1];
if (lastSpan == previousToken.Span)
{
spans[spans.Count - 1] = TextSpan.FromBounds(lastSpan.Start, mod.Span.End);
return true;
}
}
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@CyrusNajmabadi CyrusNajmabadi Dec 6, 2019

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i preserved this logic (just in O(1) time instead of O(n)). But, overall, i think preserving this logic is pretty unnecessary. i don't see why we actually need it.

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@AdamSpeight2008 AdamSpeight2008 Dec 7, 2019

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It highlights the entire async code section rather than the highlighting the nested inside keywords Async and Await.
Personally i prefer the latter.


spans.Add(mod.Span);
return true;
}

return false;
}
}
}