add configuration option to trim trailing whitespaces

[bkhouri]

As a software developer using swift format, I would like a configuration to trim trailing whitespaces.

I used swift format to format my entire code base, and it reformatted multi-line comments to include whitespaces on empty lines

        /**
         An argument is an arbitrary key-value entry that adds more information to the remark.
        
         Depending on the key, the value can be interpreted as a string, integer, etc.
        
         The debug location associated with the argument may refer to a separate location in the code.
         */

instead of:

        /**
         An argument is an arbitrary key-value entry that adds more information to the remark.

         Depending on the key, the value can be interpreted as a string, integer, etc.

         The debug location associated with the argument may refer to a separate location in the code.
         */

[bnbarham]

This already exists - indentBlankLines. It defaults to false though, so unless you specifically have it set I wouldn't expect blank lines to be indented (and I did a quick test to check that).

[allevato]

Right, the default behavior should already be doing this. Do you perhaps have an Xcode editor setting that's conflicting with it and adding the whitespace back?

[bkhouri]

was this recently submitted? I don't see it on the night main dev builds.

❯ swift --version                                 
Apple Swift version 6.3-dev (LLVM bff1370bd79c983, Swift 57cf4ce563f700b)
Target: arm64-apple-macosx26.0
Build config: +assertions

❯ swift format dump-configuration | grep -i indent
  "indentConditionalCompilationBlocks" : true,
  "indentSwitchCaseLabels" : false,
  "indentation" : {

[bkhouri]

Right, the default behavior should already be doing this. Do you perhaps have an Xcode editor setting that's conflicting with it and adding the whitespace back?

I'm using VSCode and running swift format via the command line.

[bkhouri]

Also, the indentBlankLines does not appear to take effect in a multi line code block.

[allevato]

Ah, I see what's happening. I've never run into this because I don't use /* or /** comments (they're banned by our style guide), and you're using the form where you don't start each subsequent line with its own *.

If I enter this text (I've replaced spaces with • to make them visible here):

  /**••
      foo bar baz••
••••••
      quxx•••
  */•••

then swift-format outputs:

  /**
      foo bar baz
••
      quxx
  */

In other words, it correctly strips the trailing whitespace from every line except for otherwise blank lines inside a block comment, where it only strips some of it (back to wherever the comment's indentation is, apparently).

This is just a flat-out bug, not something that needs a configuration option. If the default behavior is supposed to strip trailing whitespace, it should do it everywhere.

[bnbarham]

was this recently submitted? I don't see it on the night main dev builds.

indentBlankLines was added by @TTOzzi back in #804, but was missing from the dump. @a7medev fixed this when adding another in #1077. Regardless though, the default has always been to remove.

In other words, it correctly strips the trailing whitespace from every line except for otherwise blank lines inside a block comment, where it only strips some of it (back to wherever the comment's indentation is, apparently).

And this makes me realize my mistake in trying to reproduce this, the important part is:

back to wherever the comment's indentation is, apparently

ie. the following is fine (unindents and results in no extra whitespace):

••/**••
••••••••foo bar baz••
••••••••
••••••••quxx••
••*/••
••func foo() {}

But adding the struct in to give it an indent level then reproduces the issue:

struct Foo {
••/**••
••••••••foo bar baz••
••••••••
••••••••quxx••
••*/••
••func foo() {}
}

->

struct Foo {
••/**
••••••••foo bar baz
••
••••••••quxx
••*/
••func foo() {}
}