RCR 188: Remove whitespace before here doc contents

Problem

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When using here docs, there is no good way to indent the here doc the same way as the code surrounding it. For example, the code:

  def foo

    return <<-END
      This is a test.
    END
  end</pre>


results in a function foo() that returns "      This is a test.\n".  This is
probably not what the author intended the result to be.  There are solutions
that use regular expressions at run-time to build a here-doc without leading
whitespace.  For example ,

  def foo

    return %Q{
      This is a test.
    }.gsub!(/^\s*/, '')
  end</pre>


which strips all leading whitespace (and therefore probably undesirable).
Another option :

  def tabto(n)

    if self =~ /^( *)\S/
      tab(n - $1.length)
    else
      self
    end
  end
  def foo
    return %Q{
      This is a test.
    }.tabto(0)
  end</pre>


which is good but IMO is not intuitive when reading code that uses it.

As long as we are missing extended here docs, users will continue to produce
ad-hoc solutions like the above.  we need a solution that occurs at parse time
and is intuitive and easy to use.

Implementation

The patch has already been posted in .

Comments

Current voting

Ummmm... I feel a bit bad (and perhaps a little embarrased) for saying this, but IMO, that looks ugly. It really looks like a hack. If I wanted to program things that looked like that, I'd prefer doing it in Perl. ;)

Perhaps we could have an alternate syntax for here docs that would strip only the *common* whitespace from the beginning of each line. For example: (showing tabs as escaped chars (and noting the *3* lessthans))

n = <<<-EOS
\t\t...line one
\t\s\s...line two
EOS

=> "\t...line one\n ...line two"

This would remove one tab from the front of each line. The goal being to remove as much whitespace as possible, but requiring it to be the same series of whitespace characters from each line.

I've been bitten by the "here doc whitespace problem" myself many times. For me, the problem was that it looked ugly and less readable to have several unindented lines in the midst of (sometimes deeply) indented code.

I don't mean to stir anything up, it's just my opinion. - marc

RabYak: I concur that the leading | notation is non-ideal, IMO. To me the solution is obvious. In the supplied demo code:

 def foo
        return <<-END
                This is a test.
        END
 end

If the user wants their code indented cleanly with respect to their code, they have indented it one tab-stop deeper than the line on which it was called. With some new operator like <<+ (I don't care what it's called) Ruby would see the line on which the <<+ occurred had 1 leading tab character, and would string a single tab from the front of every line within the here doc block.

(Addendum: Uh-oh, I seem to have deleted two people's comments. Where's the history for this Wiki?)

I think it was only one person's comments (I hope :-) and I've restored it. -- David Black

I am going to vote in favor, but I agree that the | notation is not ideal. I prefer the solution proposed by the comment above, where the declaration line determines in the indentation. Nobody is going to want to have to line their HERE document with |s. -- Zachary P. Landau

Strongly opposed	0
Opposed	1
Neutral	1
In favor	12
Strongly advocate	0

RCR 188: Remove whitespace before here doc contents

Abstract

Problem

Proposal

Analysis

Implementation

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