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# frozen_string_literal: true
# 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_instance
def initialize(pry_instance)
@pry_instance = pry_instance
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_instance.config.pager
NullPager.new(pry_instance.output)
elsif !SystemPager.available? || Helpers::Platform.jruby?
SimplePager.new(pry_instance.output)
else
SystemPager.new(pry_instance.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 ||= @out.height
end
def width
@width ||= @out.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 = Pry::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
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