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Improving multiline context snippet #2288

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merged 6 commits into from
Feb 20, 2021
Merged

Improving multiline context snippet #2288

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b04dfc1
Improving multiline context snippet
eddynaka Feb 17, 2021
d3886be
changing ConstructMultilineContextSnippet logic
eddynaka Feb 18, 2021
fef1246
updating to charlength property
eddynaka Feb 18, 2021
58cf640
Adding check to verify offset
eddynaka Feb 18, 2021
6f9318c
Reviewing logic to prevent issues
eddynaka Feb 19, 2021
e493b7c
Updating tests.
eddynaka Feb 19, 2021
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33 changes: 30 additions & 3 deletions src/Sarif/FileRegionsCache.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -156,15 +156,42 @@ internal Region ConstructMultilineContextSnippet(Region inputRegion, Uri uri)
return null;
}

const int maxSnippetLength = 512;
const int reasonableSnippetLength = 256;
const int smallSnippetLength = 128;

// If this is big enough, we don't need to create a new snippet.
if (inputRegion.Snippet?.Text.Length >= reasonableSnippetLength)
{
return null;
}
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@michaelcfanning michaelcfanning Feb 18, 2021 •
edited by eddynaka
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shouldn't we actually be checking the region size, not the snippet size? basically, if a region exceeds a certain size, no context region is required. so for this case, the region should have the snippet. your code will permit the following case:

region is 10k in size but has no snippet
we then create a context region + snippet which is smaller than the region! this breaks the SARIF spec. :) #Resolved

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changed to the charLength.

In reply to: 578048420 [](ancestors = 578048420)


int maxLineNumber = newLineIndex.MaximumLineNumber;

// Currently, we just grab a single line before and after the region start
// and end lines, respectively. In the future, we could make this configurable.
var region = new Region()
var region = new Region
{
StartLine = inputRegion.StartLine == 1 ? 1 : inputRegion.StartLine - 1,
EndLine = inputRegion.EndLine == maxLineNumber ? maxLineNumber : inputRegion.EndLine + 1
};

Region multilineContextSnippet = this.PopulateTextRegionProperties(region, uri, populateSnippet: true);

// If the new snippet is big enough, we will use. Otherwise, we will
// generate a new snippet
if (multilineContextSnippet.Snippet.Text.Length <= maxSnippetLength)
{
return multilineContextSnippet;
}

// We are going to grab 128 characters from left and from right if possible.
region.CharOffset = inputRegion.CharOffset < smallSnippetLength
? 0
: inputRegion.CharOffset - smallSnippetLength;

region.CharLength = inputRegion.CharLength + inputRegion.CharOffset + smallSnippetLength < newLineIndex.Text.Length
? inputRegion.CharLength + inputRegion.CharOffset + smallSnippetLength
: newLineIndex.Text.Length - region.CharOffset;

return this.PopulateTextRegionProperties(region, uri, populateSnippet: true);
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@michaelcfanning michaelcfanning Feb 18, 2021 •
edited by eddynaka
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return [](start = 12, length = 6)

the end of this method could be a good place to introduce a debug assert that verifies we have limited the size of the region that we return. #Resolved

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Added the debug.Assert to verify if the new length >= the original

In reply to: 578572270 [](ancestors = 578572270)

}

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33 changes: 33 additions & 0 deletions src/Test.UnitTests.Sarif/FileRegionsCacheTests.cs
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Expand Up @@ -583,5 +583,38 @@ public void FileRegionsCache_PopulatesNullRegion()
region = fileRegionsCache.PopulateTextRegionProperties(inputRegion: null, uri: uri, populateSnippet: true);
region.Should().BeNull();
}

[Fact]
public void FileRegionsCache_PopulatesWithOneLineText()
{
const int maxLength = 128;
Uri uri = new Uri(@"c:\temp\myFile.cpp");
const string fileContent = @"internal Region ConstructMultilineContextSnippet(Region inputRegion, Uri uri){if (inputRegion == null || inputRegion.IsBinaryRegion){return null;}NewLineIndex newLineIndex = GetNewLineIndex(uri, fileText: null);if (newLineIndex == null){return null;}if (inputRegion.Snippet.Text.Length >= 512){return null;}int maxLineNumber = newLineIndex.MaximumLineNumber;var region = new Region{StartLine = inputRegion.StartLine == 1 ? 1 : inputRegion.StartLine - 1,EndLine = inputRegion.EndLine == maxLineNumber ? maxLineNumber : inputRegion.EndLine + 1};Region multilineContextSnippet = this.PopulateTextRegionProperties(region, uri, populateSnippet: true);if (multilineContextSnippet.Snippet.Text.Length <= 512){return multilineContextSnippet;} const int maxLength = 128;region.CharOffset = inputRegion.CharOffset < maxLength? 0: inputRegion.CharOffset - maxLength;region.CharLength = inputRegion.CharLength + inputRegion.CharOffset + maxLength < newLineIndex.Text.Length? inputRegion.CharLength + inputRegion.CharOffset + maxLength: newLineIndex.Text.Length - region.CharOffset;return this.PopulateTextRegionProperties(region, uri, populateSnippet: true);}";

var region = new Region
{
CharOffset = 114,
CharLength = 600,
};

var fileRegionsCache = new FileRegionsCache();
Region newRegion = fileRegionsCache.PopulateTextRegionProperties(region, uri, true, fileContent);
newRegion.Snippet.Text.Should().Be(fileContent.Substring(region.CharOffset, region.CharLength));

Region multilineRegion = fileRegionsCache.ConstructMultilineContextSnippet(newRegion, uri);

// This should be null, since the newRegion already is big enough
multilineRegion.Should().BeNull();

region.CharOffset = 125;
region.CharLength = 22;
newRegion = fileRegionsCache.PopulateTextRegionProperties(region, uri, true, fileContent);
newRegion.Snippet.Text.Should().Be(fileContent.Substring(region.CharOffset, region.CharLength));

multilineRegion = fileRegionsCache.ConstructMultilineContextSnippet(newRegion, uri);

// This should get from 0 -> (125(offset) + 128(maxlength) + 22(charlength))
multilineRegion.Snippet.Text.Should().Be(fileContent.Substring(0, region.CharOffset + region.CharLength + maxLength));
}
}
}