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Commit17ad03f

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Smaug123KevinRansom
authored andcommitted
Stop eagerly evaluating seqs (revert parts ofdotnet#5348,dotnet#5370) (dotnet#5947)
* Fix and tests, unbuilt and untested* Correct one of the testsGot the order wrong for the output of `countBy`.* Repair the groupBy testgroupBy test was bad: it assumed (ridiculously) that groupBy wouldn't iterate the original sequence even though it somehow knew the groups in the sequence.
1 parent87ea864 commit17ad03f

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3 files changed

+50
-7
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3 files changed

+50
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‎src/fsharp/FSharp.Core/seq.fs‎

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@@ -1032,8 +1032,6 @@ namespace Microsoft.FSharp.Collections
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let inlinegroupByImpl(comparer:IEqualityComparer<'SafeKey>)(keyf:'T->'SafeKey)(getKey:'SafeKey->'Key)(seq:seq<'T>)=
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checkNonNull"seq" seq
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if isEmpty seqthen emptyelse
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letdict= Dictionary<_,ResizeArray<_>> comparer
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// Previously this was 1, but I think this is rather stingy, considering that we are already paying
@@ -1087,7 +1085,6 @@ namespace Microsoft.FSharp.Collections
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[<CompiledName("Distinct")>]
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letdistinct source=
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checkNonNull"source" source
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if isEmpty sourcethen emptyelse
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seq{lethashSet= HashSet<'T>(HashIdentity.Structural<'T>)
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for vin sourcedo
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if hashSet.Add(v)then
@@ -1096,7 +1093,6 @@ namespace Microsoft.FSharp.Collections
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[<CompiledName("DistinctBy")>]
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letdistinctBy projection source=
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checkNonNull"source" source
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if isEmpty sourcethen emptyelse
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seq{lethashSet= HashSet<_>(HashIdentity.Structural<_>)
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for vin sourcedo
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if hashSet.Add(projection v)then
@@ -1140,7 +1136,6 @@ namespace Microsoft.FSharp.Collections
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let inlinecountByImpl(comparer:IEqualityComparer<'SafeKey>)(keyf:'T->'SafeKey)(getKey:'SafeKey->'Key)(source:seq<'T>)=
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checkNonNull"source" source
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if isEmpty sourcethen emptyelse
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letdict= Dictionary comparer
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‎tests/FSharp.Core.UnitTests/FSharp.Core.UnitTests.fsproj‎

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@@ -52,8 +52,8 @@
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<HintPathCondition="'$(TargetDotnetProfile)' == 'net40'">$(FsCheckLibDir)\net452\FsCheck.dll</HintPath>
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</Reference>
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<ReferenceInclude="System.ValueTuple">
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<HintPath>..\..\packages\System.ValueTuple.$(SystemValueTuplePackageVersion)\lib\portable-net40+sl4+win8+wp8\System.ValueTuple.dll</HintPath>
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<Private>True</Private>
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<HintPath>..\..\packages\System.ValueTuple.$(SystemValueTuplePackageVersion)\lib\portable-net40+sl4+win8+wp8\System.ValueTuple.dll</HintPath>
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<Private>True</Private>
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</Reference>
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</ItemGroup>
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<ItemGroup>
@@ -94,6 +94,7 @@
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<CompileInclude="FSharp.Core\Microsoft.FSharp.Collections\SeqProperties.fs" />
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<CompileInclude="FSharp.Core\Microsoft.FSharp.Collections\CollectionModulesConsistency.fs" />
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<CompileInclude="FSharp.Core\Microsoft.FSharp.Collections\StringModule.fs" />
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<CompileInclude="FSharp.Core\Microsoft.FSharp.Collections\SeqMultipleIteration.fs" />
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<CompileInclude="FSharp.Core\PrimTypes.fs" />
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<CompileInclude="FSharp.Core\ComparersRegression.fs" />
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<CompileInclude="FSharp.Core\DiscrimantedUnionType.fs" />
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@@ -0,0 +1,47 @@
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namespaceFSharp.Core.UnitTests.FSharp_Core.Microsoft_FSharp_Collections
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openNUnit.Framework
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[<TestFixture>]
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moduleSeqMultipleIteration=
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letmakeNewSeq()=
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lethaveCalled=false|> ref
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seq{
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if!haveCalledthen failwith"Should not have iterated this sequence before"
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haveCalled:= true
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yield3
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}, haveCalled
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[<Test>]
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let``Seq.distinct only evaluates the seq once``()=
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lets,haveCalled= makeNewSeq()
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letdistincts= Seq.distinct s
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Assert.IsFalse!haveCalled
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CollectionAssert.AreEqual(distincts|> Seq.toList,[3])
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Assert.IsTrue!haveCalled
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[<Test>]
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let``Seq.distinctBy only evaluates the seq once``()=
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lets,haveCalled= makeNewSeq()
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letdistincts= Seq.distinctBy id s
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Assert.IsFalse!haveCalled
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CollectionAssert.AreEqual(distincts|> Seq.toList,[3])
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Assert.IsTrue!haveCalled
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[<Test>]
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let``Seq.groupBy only evaluates the seq once``()=
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lets,haveCalled= makeNewSeq()
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letgroups:seq<int*seq<int>>= Seq.groupBy id s
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Assert.IsFalse!haveCalled
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letgroups:list<int*seq<int>>= Seq.toList groups
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// Seq.groupBy iterates the entire sequence as soon as it begins iteration.
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Assert.IsTrue!haveCalled
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[<Test>]
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let``Seq.countBy only evaluates the seq once``()=
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lets,haveCalled= makeNewSeq()
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letcounts:seq<int*int>= Seq.countBy id s
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Assert.IsFalse!haveCalled
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letcounts:list<int*int>= Seq.toList counts
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Assert.IsTrue!haveCalled
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CollectionAssert.AreEqual(counts|> Seq.toList,[(3,1)])

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