Rework completion resolution #2126

333fred · 2021-04-02T05:22:06Z

Recently, Roslyn undeprecated the CompletionChange.TextChanges API. This API gives changes in a significantly simpler manner for us to deal with, as it splits up things like imports and the actual main change element, so we can remove a whole bunch of code dedicated to finding the changed elements and mapping original source locations to the new document. The new pattern is much simpler: except for import completion, we always resolve the change up front. For most providers, this is an extremely quick call, as most providers just return the label, and for the ones that don't we can't do much about it anyway. We can then loop through the individual changes, putting changes that are not touching the current cursor location into AdditionalTextChanges. This shrinks the completion payload pretty significantly for many scenarios, and gets rid of a bunch of special handling around it. The only remaining special handling is adjusting the filter texts and snippitizing completions that want to move the cursor. I've also aligned the behavior of the Preselect flag with Roslyn's completion handler, and removed additional filtering of completion items so that they can be filtered by the client instead.

Fixes #2123 as well.

Recently, Roslyn undeprecated the CompletionChange.TextChanges API. This API gives changes in a significantly simpler manner for us to deal with, as it splits up things like imports and the actual main change element, so we can remove a whole bunch of code dedicated to finding the changed elements and mapping original source locations to the new document. The new pattern is much simpler: except for import completion, we always resolve the change up front. For most providers, this is an extremely quick call, as most providers just return the label, and for the ones that don't we can't do much about it anyway. We can then loop through the individual changes, putting changes that are not touching the current cursor location into AdditionalTextChanges. This shrinks the completion payload pretty significantly for many scenarios, and gets rid of a bunch of special handling around it. The only remaining special handling is adjusting the filter texts and snippitizing completions that want to move the cursor. I've also aligned the behavior of the Preselect flag with Roslyn's completion handler, and removed additional filtering of completion items so that they can be filtered by the client instead. Fixes OmniSharp#2123 as well.

333fred · 2021-04-02T05:23:05Z

src/OmniSharp.Roslyn.CSharp/Services/Completion/CompletionService.cs

@@ -509,86 +455,17 @@ public async Task<CompletionResolveResponse> Handle(CompletionResolveRequest req
            };
        }

-        private (IReadOnlyList<LinePositionSpanTextChange>? edits, int endOffset) GetAdditionalTextEdits(


Man am I happy to delete this method :).

333fred · 2021-04-02T05:23:55Z

tests/OmniSharp.Roslyn.CSharp.Tests/CompletionFacts.cs

-                        Assert.False(c.Preselect);
-                        break;
-                }
+                if (c.Label == "ToString")


I honestly can't tell you why Roslyn wants to preselect this, but it does. The behavior in VSCode is that ToString is filtered out because of the prefix mismatch.

333fred · 2021-04-02T05:27:38Z

tests/OmniSharp.Roslyn.CSharp.Tests/CompletionFacts.cs

@@ -270,12 +270,34 @@ public static void Test(this object o)

            Assert.Single(resolved.Item.AdditionalTextEdits);
            var additionalEdit = resolved.Item.AdditionalTextEdits[0];
-            Assert.Equal(NormalizeNewlines("using N2;\n\nnamespace N1\r\n{\r\n    public class C1\r\n    {\r\n        public void M(object o)\r\n        {\r\n            o"),
+            Assert.Equal(NormalizeNewlines("using N2;\n\n"),


@bjorkstromm @NTaylorMullen this change will, I think, make import completion easier to support from Cake/Razor, as we're not sending the whole document anymore. Just the import changes.

filipw · 2021-04-02T07:36:15Z

tests/OmniSharp.Roslyn.CSharp.Tests/CompletionFacts.cs

+        [Theory]
+        [InlineData("dummy.cs")]
+        [InlineData("dummy.csx")]
+        public async Task ImportCompletion_OnLine0(string filename)


thanks for fixing this!

filipw · 2021-04-02T07:49:44Z

src/OmniSharp.Roslyn.CSharp/Services/Completion/CompletionService.cs

+                        {
+                            // Except for import completion, we just resolve the change up front in the sync version. It's only expensive
+                            // for override completion, but there's not a heck of a lot we can do about that for the sync scenario
+                            var change = await completionService.GetChangeAsync(document, completion);


does it now make sense to update the client to not call resolve on the server for each item except in specific cases?

No, because resolve will still fill in documentation for all items.

Any benefit (or problems!) with using Task.WhenAll to group all the async operations. Not that we were doing this before anyway.

I'd need to get a real benchmark setup to determine this. A quick test didn't show any obvious impact either way.

I've created a benchmark project using benchmarkdotnet and included in this PR. Some statistics from running it with and without Task.WhenAll:

Method Mean Error StdDev

ImportCompletionListAsyncOriginal 3.715 ms 0.0203 ms 0.0190 ms

ImportCompletionListAsyncWhenAll 4.232 ms 0.0200 ms 0.0178 ms

Method NumOverrides Mean Error StdDev Median

OverrideCompletionAsyncOriginal 10 11.54 ms 0.051 ms 0.045 ms 11.53 ms

OverrideCompletionAsyncOriginal 100 34.25 ms 0.681 ms 1.852 ms 35.29 ms

OverrideCompletionAsyncOriginal 250 65.92 ms 1.312 ms 3.194 ms 67.20 ms

OverrideCompletionAsyncOriginal 500 111.92 ms 0.566 ms 0.529 ms 111.89 ms

OverrideCompletionAsyncWhenAll 10 6.769 ms 0.1011 ms 0.0945 ms

OverrideCompletionAsyncWhenAll 100 16.147 ms 0.3139 ms 0.2936 ms

OverrideCompletionAsyncWhenAll 250 28.739 ms 0.4544 ms 0.3547 ms

OverrideCompletionAsyncWhenAll 500 73.618 ms 1.4516 ms 1.7827 ms

filipw · 2021-04-02T07:49:56Z

looks very nice, thank you

david-driscoll · 2021-04-02T14:34:20Z

Timeout of 2400000ms hit 😱

david-driscoll

Not sure what's causing the issues with GitHub Actions, but that's concerning at least because Azure Devops was just fine.

!

david-driscoll · 2021-04-02T14:38:11Z

src/OmniSharp.Roslyn.CSharp/Services/Completion/CompletionService.cs

+                        {
+                            // Except for import completion, we just resolve the change up front in the sync version. It's only expensive
+                            // for override completion, but there's not a heck of a lot we can do about that for the sync scenario
+                            var change = await completionService.GetChangeAsync(document, completion);


Any benefit (or problems!) with using Task.WhenAll to group all the async operations. Not that we were doing this before anyway.

333fred · 2021-04-02T15:56:23Z

I'll try to look into the timeouts sometime this weekend.

david-driscoll · 2021-04-02T20:16:53Z

Oh wait, azure devops doesn't run tests anymore, so never mind there may be something there. I'll try and run them on my machines later as well.

333fred · 2021-04-04T06:07:53Z

I'll try to look into the timeouts sometime this weekend.

So, I have no idea why the tests failing is causing the github action runner to take so long (perhaps all the output?), but the main issue is that I forgot I cloned all the tests for the lsp handler when I updated LSP to use the new service, and they're of course now all failing.

… in the override completion case, while having a minimal cost for the non-override case.

filipw · 2021-04-06T12:15:55Z

src/OmniSharp.LanguageServerProtocol/Handlers/OmniSharpCompletionHandler.cs

@@ -112,7 +112,7 @@ private static void VerifyEnumsInSync(Type enum1, Type enum2)
            Debug.Assert(lspValues.Length == modelValues.Length);
            for (int i = 0; i < lspValues.Length; i++)
            {
-                Debug.Assert((int?)lspValues.GetValue(i) == (int?)modelValues.GetValue(i));
+                Debug.Assert((int)lspValues.GetValue(i) == (int)modelValues.GetValue(i));


I changed this to int? because I noticed on the .NET 5.0 branch that it reports CS8605 "Unboxing possibly null value" there - and since we have TreatWarningsAsErrors enabled, it wouldn't build

Well, if it's int? the assert fails because these are ints, not nullable ints :)

filipw · 2021-04-06T12:32:39Z

OmniSharp.sln

-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OmniSharp.Lsp.Tests", "tests\OmniSharp.Lsp.Tests\OmniSharp.Lsp.Tests.csproj", "{D67AA10B-8DB6-408D-A4C5-0B1DDCF5B3CC}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OmniSharp.Lsp.Tests", "tests\OmniSharp.Lsp.Tests\OmniSharp.Lsp.Tests.csproj", "{D67AA10B-8DB6-408D-A4C5-0B1DDCF5B3CC}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OmniSharp.Benchmarks", "src\OmniSharp.Benchmarks\OmniSharp.Benchmarks.csproj", "{6F5B209E-8DD3-4E90-A1F3-D85E7AF56588}"


thank you for adding this... It has been long long long overdue ✨

333fred commented Apr 2, 2021

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filipw reviewed Apr 2, 2021

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david-driscoll approved these changes Apr 2, 2021

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333fred added 6 commits April 3, 2021 23:37

Adjust LSP tests as well.

99e805d

Use Task.WhenAll for completion resolution. This can provide benefits…

3c95dbd

… in the override completion case, while having a minimal cost for the non-override case.

Add Benchmarking project.

185e9f5

Some additional adjustments based on benchmarking.

127e565

Remove unneeded tuple.

afcd88a

Fix default rules

21faedb

filipw reviewed Apr 6, 2021

View reviewed changes

Merge branch 'master' into completion-improvements

f81588e

filipw enabled auto-merge April 8, 2021 14:20

filipw merged commit 38dbed5 into OmniSharp:master Apr 8, 2021

333fred deleted the completion-improvements branch April 8, 2021 14:40

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Rework completion resolution #2126

Rework completion resolution #2126

333fred commented Apr 2, 2021

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Method	Mean	Error	StdDev
ImportCompletionListAsyncOriginal	3.715 ms	0.0203 ms	0.0190 ms
ImportCompletionListAsyncWhenAll	4.232 ms	0.0200 ms	0.0178 ms

Method	NumOverrides	Mean	Error	StdDev	Median
OverrideCompletionAsyncOriginal	10	11.54 ms	0.051 ms	0.045 ms	11.53 ms
OverrideCompletionAsyncOriginal	100	34.25 ms	0.681 ms	1.852 ms	35.29 ms
OverrideCompletionAsyncOriginal	250	65.92 ms	1.312 ms	3.194 ms	67.20 ms
OverrideCompletionAsyncOriginal	500	111.92 ms	0.566 ms	0.529 ms	111.89 ms
OverrideCompletionAsyncWhenAll	10	6.769 ms	0.1011 ms	0.0945 ms
OverrideCompletionAsyncWhenAll	100	16.147 ms	0.3139 ms	0.2936 ms
OverrideCompletionAsyncWhenAll	250	28.739 ms	0.4544 ms	0.3547 ms
OverrideCompletionAsyncWhenAll	500	73.618 ms	1.4516 ms	1.7827 ms

Rework completion resolution #2126

Rework completion resolution #2126

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