IDE0304 should preserve the leading comment

[Bartleby2718]

IDE0304 should preserve the leading comment

[DannySliekers]

Hey, can i pick this up if possible?

[CyrusNajmabadi]

@DannySliekers i would just work on a fix that resolves exactly the case reported.

[CyrusNajmabadi]

@DannySliekers Absolutely!

[DannySliekers]

So I did some investigating and found that the issue seems to lie at the removal of the LocalDeclarationStatement, as none of the leading and trailing trivia gets preserved:

roslyn/src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForBuilderCodeFixProvider.cs

Lines 78 to 79 in 2b1fb9b

	// Remove the actual declaration of the builder.
	subEditor.RemoveNode(analysisResult.LocalDeclarationStatement);

For the case of leading trivia i assume we want to include all leading trivia in the fixed code, right?
Example with trivia on same line:

// Code with violation.
/* test */ var builder = ImmutableArray.CreateBuilder<int>();
builder.Add(1);
builder.AddRange(new int[] { 5, 6, 7 });
ImmutableArray<int> i = builder.ToImmutable();

// Desired code
/* test */ ImmutableArray<int> i = [1, .. new int[] { 5, 6, 7 }];

For the case in which the declaration of the builder contains trailing trivia seems to be a little bit more complicated.
This seems like a desired result to me:

// Code with violation.
var builder = ImmutableArray.CreateBuilder<int>(); // test
builder.Add(1);
builder.AddRange(new int[] { 5, 6, 7 });
ImmutableArray<int> i = builder.ToImmutable();

//Desired code
ImmutableArray<int> i = [1, .. new int[] { 5, 6, 7 }]; // test

If the fix in the code above is desired, there is a case where there would be multiple options of preserving trivia:

var builder = ImmutableArray.CreateBuilder<int>(); // test
builder.Add(1);
builder.AddRange(new int[] { 5, 6, 7 });
ImmutableArray<int> i = builder.ToImmutable(); // test2

//Desired code #1? 
ImmutableArray<int> i = [1, .. new int[] { 5, 6, 7 }]; // test2 // test

//Desired code #2? 
ImmutableArray<int> i = [1, .. new int[] { 5, 6, 7 }]; // test // test2

Seems to me like there are multiple options in the case of trailing trivia at the declaration of the builder, and I would like to know what would be desirable.

[CyrusNajmabadi]

For the case of leading trivia i assume we want to include all leading trivia in the fixed code, right?

We try to handle reasonable code patterns, and we don't expend effort on uncommon ones.

So, for example, this is not common: /* test */ var builder = ImmutableArray.CreateBuilder<int>();.