Actioncable and Actionpack documentation typos [ci skip]

Further investigation seems to disprove that backtracking is the
reason why the positive variant is slower, see

    https://github.com/rails/rails/pull/24658#issuecomment-213079710

so, just say nothing about it, only assert it is slower.

using rails dev:cache instead of rake dev:cache

Log if redis connection is in stale/failed state.

Without the `wdm` gem, it appears that `listen` keeps an open handle to
each of these files, causing them not to be removed when the tempdir
tries to clean iteslf up, and then directory to fail to unlink. In
addition to fixing that particular failure, we now construct OS agnostic
paths, and capture exceptions if the directory fails to unlink so that
minitest will report it rather than crash

Fix ApplicationController.renderer.defaults.merge!

Minor space bump.

use wrapper file to add rake task for engines

When you come here without context, it is important to hightlight that
checking the predicate is worthwhile due to the observation that blank
strings are often empty. So you complicate the code (which has a cost
in terms of readability and aesthetics), but statistically makes sense.

Then, you also need to explain why the second operand is so convoluted.

Otherwise, you wonder why this line is written precisely this way. That
is what code comments are for.

Remove unused `BLANK_RE`

Add #18323 to 5.0 release notes

Update delegate to use newer Ruby syntax

Revert "add doc for `:type` option of `#create_join_table` [ci skip]"

add doc for `:type` option of `#create_join_table` [ci skip]

Follow up to #24221.

This commit updates `delegate` to use the keyword argument syntax added in Ruby 2. I left the `ArgumentError` when `to` is missing, because it better explains how to correctly use `delegate`.  We could instead rely on the default `ArgumentError` that would be raised if `to` were a required keyword argument.

Fix small typos [ci skip]

`bundler` provides wrapper file to add rask tasks.
https://github.com/bundler/bundler/blob/master/lib/bundler/gem_tasks.rb

Instead of directly call method, by which require this file,
it can be used without updating of Rakefile if task has been added.

Follow up to #24658.

Fixes #23643.

[ci skip]

Previously, users were trying to modify a frozen Hash. Includes a
regression test :)

Fixes #22975

Speed up String#blank? Regex

Follow up on https://github.com/rails/rails/commit/697384df36a939e565b7c08725017d49dc83fe40#commitcomment-17184696.

The regex to detect a blank string `/\A[[:space:]]*\z/` will loop through every character in the string to ensure that all of them are a `:space:` type. We can invert this logic and instead look for any non-`:space:` characters. When that happens, we would return on the first character found and the regex engine does not need to keep looking.

Thanks @nellshamrell for the regex talk at LSRC.

By defining a "blank" string as any string that does not have a non-whitespace character (yes, double negative) we can get a substantial speed bump.

Also an inline regex is (barely) faster than a regex in a constant, since it skips the constant lookup. A regex literal is frozen by default.

```ruby
require 'benchmark/ips'

def string_generate
  str = " abcdefghijklmnopqrstuvwxyz\t".freeze
  str[rand(0..(str.length - 1))] * rand(0..23)
end

strings = 100.times.map { string_generate }

ALL_WHITESPACE_STAR = /\A[[:space:]]*\z/

Benchmark.ips do |x|
  x.report('current regex            ') { strings.each {|str| str.empty? || ALL_WHITESPACE_STAR === str } }
  x.report('+ instead of *           ') { strings.each {|str| str.empty? || /\A[[:space:]]+\z/ === str } }
  x.report('not a non-whitespace char') { strings.each {|str| str.empty? || !(/[[:^space:]]/ === str) } }
  x.compare!
end

# Warming up --------------------------------------
# current regex
#                          1.744k i/100ms
# not a non-whitespace char
#                          2.264k i/100ms
# Calculating -------------------------------------
# current regex
#                          18.078k (± 8.9%) i/s -     90.688k
# not a non-whitespace char
#                          23.580k (± 7.1%) i/s -    117.728k

# Comparison:
# not a non-whitespace char:    23580.3 i/s
# current regex            :    18078.2 i/s - 1.30x slower
```

This makes the method roughly 30% faster `(23.580 - 18.078)/18.078 * 100`.

cc/ @fxn

create_join_table should work with uuid

Use of `whether or not` instead of `regardless if ... or not`

Dump indexes in `create_table` for generates SQL in one query

See the rationale in the comment in this patch.

To benchmark this I ran a number of variations, ultimately narrowing to

    require 'benchmark/ips'

    str = ''
    regexp = /\A[[:space:]]*\z/

    Benchmark.ips do |x|
      x.report('regexp') { regexp === str }
      x.report('empty')  { str.empty? || regexp === str }
      x.compare!
    end

This benchmark has consistently reported speedups around 3.5x:

    Calculating -------------------------------------
                  regexp    69.197k i/100ms
                   empty   115.468k i/100ms
    -------------------------------------------------
                  regexp      2. 6.3%) i/s -     13.839M
                   empty      9. 8.8%) i/s -     47.804M

    Comparison:
                   empty:  9642607.6 i/s
                  regexp:  2768351.9 i/s - 3.48x slower

Sometimes even reaching 4x.

Running the same bechmark on strings of 10 or 100 characters (with
whitespace or present) has shown a slowdown of just about 1.01/1.02.
Marginal, we seem to have a worthwhile trade-off here.

use rails command in `time:zones` task desc [ci skip]

Fix example for css_class_attribute and fix indentation

[ci skip] Small grammar fix