Fix to skip terminal size detection from readline on non-TTY output

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 * Fix ioctl call test to stub terminal size encoding for big-endian systems
+* Fix to skip terminal size detection from readline on non-TTY output
 
 ## [v0.8.1] - 2020-07-17
 

lib/tty/screen.rb

@@ -229,8 +229,9 @@ def size_from_ioctl; nil end
     #
     # @api private
     def size_from_readline(verbose: false)
-      require "readline" unless defined?(::Readline)
+      return unless output.tty?
 
+      require "readline" unless defined?(::Readline)
       return unless ::Readline.respond_to?(:get_screen_size)
 
       size = ::Readline.get_screen_size

spec/unit/screen_spec.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "delegate"
+require "readline"
 require "stringio"
 
 RSpec.describe TTY::Screen do
@@ -122,6 +123,59 @@ def ioctl(_control, buf)
     end
   end
 
+  describe "#size_from_readline" do
+    it "doesn't detect size on non-tty output" do
+      allow(screen.output).to receive(:tty?).and_return(false)
+
+      expect(screen.size_from_readline).to eq(nil)
+      expect(screen.output).to have_received(:tty?)
+    end
+
+    it "doesn't detect size when the readline fails to load" do
+      undefine_const(:Readline) do
+        allow(screen.output).to receive(:tty?).and_return(true)
+        allow(screen).to receive(:require).with("readline").and_raise(LoadError)
+
+        expect(screen.size_from_readline).to eq(nil)
+        expect(screen).to have_received(:require).with("readline")
+      end
+    end
+
+    it "warns in verbose mode when the readline fails to load" do
+      undefine_const(:Readline) do
+        allow(screen.output).to receive(:tty?).and_return(true)
+        allow(screen).to receive(:require).with("readline").and_raise(LoadError)
+
+        expect {
+          screen.size_from_readline(verbose: true)
+        }.to output("no readline gem\n").to_stderr
+      end
+    end
+
+    it "doesn't detect size when the get_screen_size method is missing" do
+      allow(screen.output).to receive(:tty?).and_return(true)
+      allow(Readline).to receive(:respond_to?)
+        .with(:get_screen_size).and_return(false)
+
+      expect(screen.size_from_readline).to eq(nil)
+      expect(Readline).to have_received(:respond_to?).with(:get_screen_size)
+    end
+
+    it "detects no columns", if: Readline.respond_to?(:get_screen_size) do
+      allow(screen.output).to receive(:tty?).and_return(true)
+      allow(Readline).to receive(:get_screen_size).and_return([51, 0])
+
+      expect(screen.size_from_readline).to eq(nil)
+    end
+
+    it "detects size", if: Readline.respond_to?(:get_screen_size) do
+      allow(screen.output).to receive(:tty?).and_return(true)
+      allow(Readline).to receive(:get_screen_size).and_return([51, 211])
+
+      expect(screen.size_from_readline).to eq([51, 211])
+    end
+  end
+
   describe "#size_from_tput" do
     it "doesn't run command if outside of terminal" do
       allow(screen.output).to receive(:tty?).and_return(false)