Trim unnessasary leading lines when removing usings (#60672)

src/Analyzers/CSharp/Tests/RemoveUnnecessaryImports/RemoveUnnecessaryImportsTests.cs

@@ -1984,5 +1984,144 @@ static void Main(string[] args)
                 LanguageVersion = LanguageVersion.CSharp10,
             }.RunAsync();
         }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)]
+        [WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")]
+        public async Task TestUsingGroups_DeleteLeadingBlankLinesIfFirstGroupWasDeleted_SingleUsing()
+        {
+            await new VerifyCS.Test
+            {
+                TestCode =
+@"[|{|IDE0005:using System;|}
+
+using System.Collections.Generic;|]
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+",
+                FixedCode =
+@"using System.Collections.Generic;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+"
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)]
+        [WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")]
+        public async Task TestUsingGroups_DeleteLeadingBlankLinesIfFirstGroupWasDeleted_MultipleUsings()
+        {
+            await new VerifyCS.Test
+            {
+                TestCode =
+@"[|{|IDE0005:using System;
+using System.Threading.Tasks;|}
+
+using System.Collections.Generic;|]
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+",
+                FixedCode =
+@"using System.Collections.Generic;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+"
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)]
+        [WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")]
+        public async Task TestUsingGroups_NotAllFirstGroupIsDeleted()
+        {
+            await new VerifyCS.Test
+            {
+                TestCode =
+@"[|{|IDE0005:using System;|}
+using System.Threading.Tasks;
+
+using System.Collections.Generic;|]
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+        Task task = null;
+    }
+}
+",
+                FixedCode =
+@"using System.Threading.Tasks;
+
+using System.Collections.Generic;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+        Task task = null;
+    }
+}
+"
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)]
+        [WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")]
+        public async Task TestUsingGroups_AllLastGroupIsDeleted()
+        {
+            await new VerifyCS.Test
+            {
+                TestCode =
+@"[|using System.Collections.Generic;
+
+{|IDE0005:using System;
+using System.Threading.Tasks;|}|]
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+",
+                FixedCode =
+@"using System.Collections.Generic;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var argList = new List<string>(args);
+    }
+}
+"
+            }.RunAsync();
+        }
     }
 }

src/Analyzers/VisualBasic/Tests/RemoveUnnecessaryImports/RemoveUnnecessaryImportsTests.vb

@@ -1214,5 +1214,108 @@ Imports System
     Event E()
 End Class|]")
         End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)>
+        <WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")>
+        Public Async Function TestImportGroup_DeleteLeadingBlankLinesIfFirstGroupWasDeleted_SingleImport() As Task
+            Await TestInRegularAndScript1Async(
+"[|Imports System.Threading.Tasks
+
+Imports System|]
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+",
+"Imports System
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)>
+        <WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")>
+        Public Async Function TestImportGroup_DeleteLeadingBlankLinesIfFirstGroupWasDeleted_MultipleImports() As Task
+            Await TestInRegularAndScript1Async(
+"[|Imports System.Threading.Tasks
+Imports System.Collections.Generic
+
+Imports System|]
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+",
+"Imports System
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)>
+        <WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")>
+        Public Async Function TestImportGroup_NotAllFirstGroupIsDeleted() As Task
+            Await TestInRegularAndScript1Async(
+"[|Imports System.Threading.Tasks
+Imports System.Collections.Generic
+
+Imports System|]
+
+Class C
+    Function Test()
+        Console.WriteLine()
+        Dim list As List(Of Integer) = Nothing
+    End Function
+End Class
+",
+"Imports System.Collections.Generic
+
+Imports System
+
+Class C
+    Function Test()
+        Console.WriteLine()
+        Dim list As List(Of Integer) = Nothing
+    End Function
+End Class
+")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryImports)>
+        <WorkItem(45866, "https://github.com/dotnet/roslyn/issues/45866")>
+        Public Async Function TestImportGroup_AllLastGroupIsDeleted() As Task
+            Await TestInRegularAndScript1Async(
+"[|Imports System
+
+Imports System.Threading.Tasks
+Imports System.Collections.Generic|]
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+",
+"Imports System
+
+Class C
+    Function Test()
+        Console.WriteLine()
+    End Function
+End Class
+")
+        End Function
     End Class
 End Namespace

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpRemoveUnnecessaryImportsService.Rewriter.cs

@@ -9,7 +9,6 @@
 using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
-using Microsoft.CodeAnalysis.CSharp.Formatting;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Roslyn.Utilities;
@@ -48,6 +47,8 @@ private static void ProcessUsings(
                 out SyntaxTriviaList finalTrivia)
             {
                 var currentUsings = new List<UsingDirectiveSyntax>(usings);
+                var firstUsingNotBeingRemoved = true;
+                var passedLeadngTrivia = false;
 
                 finalTrivia = default;
                 for (var i = 0; i < usings.Count; i++)
@@ -83,13 +84,40 @@ private static void ProcessUsings(
                                     // want to preserve.
                                     currentUsings[nextIndex] = nextUsing.WithLeadingTrivia(leadingTrivia);
                                 }
+
+                                passedLeadngTrivia = true;
                             }
                             else
                             {
                                 finalTrivia = leadingTrivia;
                             }
                         }
                     }
+                    else if (firstUsingNotBeingRemoved)
+                    {
+                        // 1) We only apply this logic for not first using, that is saved:
+                        // ===================
+                        // namespace N;
+                        //
+                        // using System; <- if we save this using, we don't need to cut leading lines
+                        // ===================
+                        // 2) If leading trivia was saved from the previous using, that was removed,
+                        // we don't bother cutting blank lines as well:
+                        // ===================
+                        // namespace N;
+                        //
+                        // using System; <- need to delete this using
+                        // using System.Collections.Generic; <- this using is saved, no need to eat the line,
+                        // otherwise https://github.com/dotnet/roslyn/issues/58972 will happen
+                        if (i > 0 && !passedLeadngTrivia)
+                        {
+                            var currentUsing = currentUsings[i];
+                            var currentUsingLeadingTrivia = currentUsing.GetLeadingTrivia();
+                            currentUsings[i] = currentUsing.WithLeadingTrivia(currentUsingLeadingTrivia.WithoutLeadingBlankLines());
+                        }
+
+                        firstUsingNotBeingRemoved = false;
+                    }
                 }
 
                 finalUsings = currentUsings.WhereNotNull().ToSyntaxList();

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/VisualBasic/LanguageServices/VisualBasicRemoveUnnecessaryImportsService.Rewriter.vb

@@ -39,6 +39,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.RemoveUnnecessaryImports
 
             Private Function ProcessImports(compilationUnit As CompilationUnitSyntax) As CompilationUnitSyntax
                 Dim oldImports = compilationUnit.Imports.ToList()
+                Dim firstImportNotBeingRemoved = True
+                Dim passedLeadingTrivia = False
 
                 Dim remainingTrivia As SyntaxTriviaList = Nothing
                 For i = 0 To oldImports.Count - 1
@@ -65,6 +67,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.RemoveUnnecessaryImports
                                     ' want to preserve.
                                     oldImports(nextIndex) = nextImport.WithLeadingTrivia(leadingTrivia)
                                 End If
+
+                                passedLeadingTrivia = True
                             Else
                                 remainingTrivia = leadingTrivia
                             End If
@@ -85,6 +89,28 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.RemoveUnnecessaryImports
                                 oldImports(index) = previousImport.WithTrailingTrivia(trailingTrivia)
                             End If
                         End If
+                    ElseIf firstImportNotBeingRemoved Then
+                        ' 1) We only apply this logic for Not first using, that is saved:
+                        ' ===================
+                        ' #Const A = 1
+                        '
+                        ' Imports System <- if we save this import, we don't need to cut leading lines
+                        ' ===================
+                        ' 2) If leading trivia was saved from the previous import, that was removed,
+                        ' we don't bother cutting blank lines as well:
+                        ' ===================
+                        ' #Const A = 1
+                        '
+                        ' Imports System <- need to delete this import
+                        ' Imports System.Collections.Generic <- this import is saved, no need to eat the line,
+                        ' otherwise https://github.com/dotnet/roslyn/issues/58972 will happen
+                        If i > 0 AndAlso Not passedLeadingTrivia Then
+                            Dim currentImport = oldImports(i)
+                            Dim currentImportLeadingTrivia = currentImport.GetLeadingTrivia()
+                            oldImports(i) = currentImport.WithLeadingTrivia(currentImportLeadingTrivia.WithoutLeadingWhitespaceOrEndOfLine())
+                        End If
+
+                        firstImportNotBeingRemoved = False
                     End If
                 Next