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pry--pry/lib/pry/pager.rb
Kyrylo Silin edaa1383f2 Require files from pry.rb; deps from each file that uses them
This change brings some order to how we require files. Previously, we required
app files from everywhere, including pry.rb. Now we require app files only from
pry.rb.

External and stdlib dependencies are required at places where they're used, not
globally.
2019-03-10 13:20:03 +02:00

247 lines
6.1 KiB
Ruby

# A pager is an `IO`-like object that accepts text and either prints it
# immediately, prints it one page at a time, or streams it to an external
# program to print one page at a time.
class Pry
class Pager
class StopPaging < StandardError
end
attr_reader :_pry_
def initialize(_pry_)
@_pry_ = _pry_
end
# Send the given text through the best available pager (if
# `Pry.config.pager` is enabled). If you want to send text through in
# chunks as you generate it, use `open` to get a writable object
# instead.
#
# @param [String] text
# Text to run through a pager.
#
def page(text)
open do |pager|
pager << text
end
end
# Yields a pager object (`NullPager`, `SimplePager`, or `SystemPager`).
# All pagers accept output with `#puts`, `#print`, `#write`, and `#<<`.
def open
pager = best_available
yield pager
rescue StopPaging # rubocop:disable Lint/HandleExceptions
ensure
pager.close if pager
end
private
def enabled?
!!@enabled
end
attr_reader :output
# Return an instance of the "best" available pager class --
# `SystemPager` if possible, `SimplePager` if `SystemPager` isn't
# available, and `NullPager` if the user has disabled paging. All
# pagers accept output with `#puts`, `#print`, `#write`, and `#<<`. You
# must call `#close` when you're done writing output to a pager, and
# you must rescue `Pry::Pager::StopPaging`. These requirements can be
# avoided by using `.open` instead.
def best_available
if !_pry_.config.pager
NullPager.new(_pry_.output)
elsif !SystemPager.available? || Helpers::Platform.jruby?
SimplePager.new(_pry_.output)
else
SystemPager.new(_pry_.output)
end
end
# `NullPager` is a "pager" that actually just prints all output as it
# comes in. Used when `Pry.config.pager` is false.
class NullPager
def initialize(out)
@out = out
end
def puts(str)
print "#{str.chomp}\n"
end
def print(str)
write str
end
alias << print
def write(str)
@out.write str
end
def close; end
private
def height
@height ||= Pry::Terminal.height!
end
def width
@width ||= Pry::Terminal.width!
end
end
# `SimplePager` is a straightforward pure-Ruby pager. We use it on
# JRuby and when we can't find a usable external pager.
class SimplePager < NullPager
def initialize(*)
super
@tracker = PageTracker.new(height - 3, width)
end
def write(str)
str.lines.each do |line|
@out.print line
@tracker.record line
next unless @tracker.page?
@out.print "\n"
@out.print "\e[0m"
@out.print "<page break> --- Press enter to continue " \
"( q<enter> to break ) --- <page break>\n"
raise StopPaging if Readline.readline("").chomp == "q"
@tracker.reset
end
end
end
# `SystemPager` buffers output until we're pretty sure it's at least a
# page long, then invokes an external pager and starts streaming output
# to it. If `#close` is called before then, it just prints out the
# buffered content.
class SystemPager < NullPager
def self.default_pager
pager = ENV["PAGER"] || ""
# Default to less, and make sure less is being passed the correct
# options
pager = "less -R -F -X" if pager.strip.empty? || pager =~ /^less\b/
pager
end
@system_pager = nil
def self.available?
if @system_pager.nil?
@system_pager =
begin
pager_executable = default_pager.split(' ').first
if Helpers::Platform.windows? || Helpers::Platform.windows_ansi?
`where /Q #{pager_executable}`
else
`which #{pager_executable}`
end
$CHILD_STATUS.success?
rescue StandardError
false
end
else
@system_pager
end
end
def initialize(*)
super
@tracker = PageTracker.new(height, width)
@buffer = ""
@pager = nil
end
def write(str)
if invoked_pager?
write_to_pager str
else
@tracker.record str
@buffer << str
write_to_pager @buffer if @tracker.page?
end
rescue Errno::EPIPE
raise StopPaging
end
def close
if invoked_pager?
pager.close
else
@out.puts @buffer
end
end
private
def write_to_pager(text)
pager.write @out.decolorize_maybe(text)
end
def invoked_pager?
@pager
end
def pager
@pager ||= IO.popen(self.class.default_pager, 'w')
end
end
# `PageTracker` tracks output to determine whether it's likely to take
# up a whole page. This doesn't need to be super precise, but we can
# use it for `SimplePager` and to avoid invoking the system pager
# unnecessarily.
#
# One simplifying assumption is that we don't need `#page?` to return
# `true` on the basis of an incomplete line. Long lines should be
# counted as multiple lines, but we don't have to transition from
# `false` to `true` until we see a newline.
class PageTracker
def initialize(rows, cols)
@rows = rows
@cols = cols
reset
end
def record(str)
str.lines.each do |line|
if line.end_with? "\n"
@row += ((@col + line_length(line) - 1) / @cols) + 1
@col = 0
else
@col += line_length(line)
end
end
end
def page?
@row >= @rows
end
def reset
@row = 0
@col = 0
end
private
# Approximation of the printable length of a given line, without the
# newline and without ANSI color codes.
def line_length(line)
line.chomp.gsub(/\e\[[\d;]*m/, '').length
end
end
end
end