[ruby-core:77258] [Ruby trunk Feature#12694] Want a String method to remove heading substr

[duerst@it.aoyama.ac.jp]

Issue #12694 has been updated by Martin Dürst.


Naotoshi Seo wrote:

> Python lstrip http://www.tutorialspoint.com/python/string_lstrip.htm takes character classes as an argument, so providing a substring as an argument will introduce confusion.

"character classes" may be confusing. "a list of characters" might be more precise. There are many classes of characters that can't be expressed easily with a list. In particular because Python lstrip doesn't accept hyphens to group characters.

One way to deal with this would be to allow a Regexp that selects a single character, and apply this repeatedly. But we don't have any such concept yet.

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Feature #12694: Want a String method to remove heading substr
https://bugs.ruby-lang.org/issues/12694#change-60490

* 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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