[ruby-core:86254] [Ruby trunk Bug#14363] each_grapheme_cluster.size returns the wrong size

Issue #14363 has been updated by naruse (Yui NARUSE).

Backport changed from 2.3: DONTNEED, 2.4: DONTNEED, 2.5: REQUIRED to 2.3: DONTNEED, 2.4: DONTNEED, 2.5: DONE

ruby_2_5 r62896 merged revision(s) 62892,62893.

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Bug #14363: each_grapheme_cluster.size returns the wrong size
https://bugs.ruby-lang.org/issues/14363#change-71163

* Author: sos4nt (Stefan Schüßler)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin15]
* Backport: 2.3: DONTNEED, 2.4: DONTNEED, 2.5: DONE
----------------------------------------
Ruby 2.5 adds `String#each_grapheme_cluster` to enumerate the string's grapheme clusters:

```ruby
str = "a\u0300i\u0301"          #=> "àí"
str.each_grapheme_cluster.to_a  #=> ["à", "í"]
```

Unfortunately, the enumerator's `size` doesn't work as expected:

```ruby
str.each_grapheme_cluster.size  #=> 4
```

The source code reveals that it invokes `rb_str_each_char_size`, so it is equivalent to `each_char.size`:

```c
static VALUE
rb_str_each_grapheme_cluster(VALUE str)
{
    RETURN_SIZED_ENUMERATOR(str, 0, 0, rb_str_each_char_size);
    return rb_str_enumerate_grapheme_clusters(str, 0);
}
```

If the grapheme enumerator's size cannot be calculated lazily, `each_grapheme_cluster.size` should return `nil` to indicate that.

---Files--------------------------------
each_grapheme_cluster_size_nil.patch (921 Bytes)
each_grapheme_cluster_size_real.patch (3.03 KB)


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