Fix forced cache miss for fetch.

[mechanicles]

As per given document, if we call fetch method with 'force: true' option without
the block, it should force a cache miss. But it was happening properly,
so added this fix.

https://github.com/rails/rails/blob/master/activesupport/lib/active_support/cache.rb#L200-L204

# You may also specify additional options via the +options+ argument.
# Setting <tt>force: true</tt> will force a cache miss:
#
#   cache.write('today', 'Monday')
#   cache.fetch('today', force: true)  # => nil

UPDATE

Based on the discussion with Jeremy. Now we have only raised argument error if no block is passed to fetch method with option force: true is set.

r? @jeremy

[jeremy]

Why are we adding force: true to #read? We already skip read_entry in #fetch if force is true.

[mechanicles]

@jeremy We are skipping read_entry when the block is passed. If the block is not passed then it goes to else part and code in that section don't consider force: true.

I think I should move handling of force: true from #read method to #fetch method's else part like below

  ...
  else
    options && options[:force] ? nil : read(name, options)
  end

Let me know your thoughts.

[jeremy]

I see. That would make sense, yes.

However, does this make sense overall? Forcing a cache miss only makes sense when a block is provided to write the new value. When no block is provided, fetch is a cache read where :force is meaningless.

I think it'd make sense to raise an ArgumentError instead. Note, the docs show an example of calling fetch force: true with no block—let's change that too.

[mechanicles]

@jeremy Please check. I have raised an argument error if no block is passed to fetch method with option force: true is set. Also, updated doc and tests and refactored the code.

[jeremy]

I think we can get away without extracting separate implementation methods.

if block_given?
  # fetch = write if not present
elsif options[:force]
  raise ArgumentError, "…"
else
  # read …
end

[mechanicles]

@jeremy I updated the code as per your suggestions.

[mechanicles]

Thanks, @jeremy 😃