[ruby-core:71773] [Ruby trunk - Feature #9098] Indent heredoc against the left margin by default when "indented closing identifier" is turned on.

Issue #9098 has been updated by Nobuyoshi Nakada.


"8 spaces for tab stops" is not enough to make the spec.

When tabs and spaces are mixed, e.g., there are`"\t"*2+"2 tabs"` line and `" "*10+"10 spaces"` line, what should be expected?

1. dedent at the greatest indent column where all lines have a white space.

    a tab which includes the column will remain, but spaces between previous tab stop and the column will be removed.
    this is the implementation by @bjmllr, and results
    `"\t"+"2 tabs"` line and `" "*2+"10 spaces"` line.

2. dedent at the greatest indent column exclusively tabs

    a tab which includes the column will remain, and also spaces before the column will be removed.
    this is like `kill-rectangle` of Emacs, and I've thought this, and results
    `"\t"+"2 tabs"` line and `"10 spaces"` line.

3. expand tabs first

    tabs are expanded first before dedent, and results
    `" "*6+"2 tabs"` line and `"10 spaces"` line.

4. or, like Andrew M claims, dedent of byte-wise common parts can be an option, I think now.

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Feature #9098: Indent heredoc against the left margin by default when "indented closing identifier" is turned on.
https://bugs.ruby-lang.org/issues/9098#change-55183

* Author: Prem Sichanugrist
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
----------------------------------------
tl;dr: I would like to port +String#strip_heredoc+ (http://api.rubyonrails.org/classes/String.html#method-i-strip_heredoc) from Rails and enable it on `<<-` heredoc.

Hi,

I've been using here document (heredoc) for a while, and I've found out that it's very annoying that the content is always treated as flushed left. Per syntax doc:

    Note that the while the closing identifier may be indented, the content is
    always treated as if it is flush left.  If you indent the content those spaces
    will appear in the output.

So, this is the current result if you use heredoc in Ruby:

    class FancyHello
      def self.hello
        puts <<-README.inspect
          Hello
            World!
        README
      end
    end
    
    FancyHello.hello # => "      Hello\n        World!\n"

In Rails, the core team has implemented +String#strip_heredoc+, which handles this scenario by remove leading white spaces  from the string. However, not many user know that Rails has that method, and instead doing this to get around it:

    class FancyHello
      def self.hello
        puts <<-README.inspect
    Hello
      World!
        README
      end
    end
    
    FancyHello.hello # => "Hello\n  World!\n"

I really think that we could do better on this by removing the leading white spaces, matching +String#strip_heredoc+ method.

So, after the change, I want to be able to do this, and get this result:

    class FancyHello
      def self.hello
        puts <<-README.inspect
          Hello
            World!
        README
      end
    end
    
    FancyHello.hello # => "Hello\n  World!\n"

Note: the behavior on `<<HEREDOC` will stay the same, as I feel like in that case you really want the input to be flushed left.

I'll write up a patch and submit it if you think this is a good idea. Please let me know any question or concern you may have.

Thank you,

Prem

---Files--------------------------------
dedent_heredoc.patch (12.8 KB)


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