[ruby-core:77192] [Ruby trunk Feature#12694] Want a String method to remove heading substr

[sonots@gmail.com]

Issue #12694 has been updated by Naotoshi Seo.


PHP has ltrim and rtrim (which is an alias of chop) http://php.net/manual/en/function.ltrim.php.
It seems String#ltrim is fine for me. How do you think?

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Feature #12694: Want a String method to remove heading substr
https://bugs.ruby-lang.org/issues/12694#change-60407

* Author: Naotoshi Seo
* Status: Open
* Priority: Normal
* Assignee: 
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I often write codes like:

```ruby
str = 'abcdef'
substr = 'abc'
str[substr.size..-1] if str.start_with?(substr) #=> 'def'
# or
str.sub(/^#{Regexp.escape(substr)}/, '') #=> 'def'
```

I want a short hand which is something like:

```ruby
str = 'abcdef'
substr = 'abc'
str.lstrip(substr) #=> 'def'
```

Having similar argument for `String#rstrip` would be nice for symmetry although we already have `String#chomp(substr)`

My frequent use-case is coming from fluentd. We have `remove_tag_prefix` option to remove a heading substring from a tag. We currently using `String#sub` with a regular expression, but I feel regular expression matching is too much just to remove a heading substring. https://github.com/fluent/fluentd/blob/75005f18d48ed3d416890413fa5f83982b264c71/lib/fluent/compat/handle_tag_name_mixin.rb#L45



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