[ruby/irb] Add OMIT_ON_ASSIGNMENT

Omit the results evaluated at assignment if they are too long.

The behavior of ECHO_ON_ASSIGNMENT being on by default is hard to understand,
so I change it to off by default. Instead, we turn OMIT_ON_ASSIGNMENT on by
default. The result is displayed on assignment, but it will always be short
and within one line of the screen.

https://github.com/ruby/irb/commit/c5ea79d5ce

3 files changed, 38 insertions, 4 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index 4f5460a84c..4f001729e1 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -131,7 +131,12 @@ module IRB
 
       @echo_on_assignment = IRB.conf[:ECHO_ON_ASSIGNMENT]
       if @echo_on_assignment.nil?
-        @echo_on_assignment = false
+        @echo_on_assignment = true
+      end
+
+      @omit_on_assignment = IRB.conf[:OMIT_ON_ASSIGNMENT]
+      if @omit_on_assignment.nil?
+        @omit_on_assignment = true
       end
 
       @newline_before_multiline_output = IRB.conf[:NEWLINE_BEFORE_MULTILINE_OUTPUT]
@@ -251,13 +256,27 @@ module IRB
     attr_accessor :echo
     # Whether to echo for assignment expressions
     #
-    # Uses <code>IRB.conf[:ECHO_ON_ASSIGNMENT]</code> if available, or defaults to +false+.
+    # Uses <code>IRB.conf[:ECHO_ON_ASSIGNMENT]</code> if available, or defaults to +true+.
     #
     #     a = "omg"
-    #     IRB.CurrentContext.echo_on_assignment = true
-    #     a = "omg"
     #     #=> omg
+    #     IRB.CurrentContext.echo_on_assignment = false
+    #     a = "omg"
     attr_accessor :echo_on_assignment
+    # Whether to omit echo for assignment expressions
+    #
+    # Uses <code>IRB.conf[:OMIT_ON_ASSIGNMENT]</code> if available, or defaults to +true+.
+    #
+    #     a = [1] * 10
+    #     #=> [1, 1, 1, 1, 1, 1, 1, 1, ...
+    #     [1] * 10
+    #     #=> [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+    #     IRB.CurrentContext.omit_on_assignment = false
+    #     a = [1] * 10
+    #     #=> [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+    #     [1] * 10
+    #     #=> [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+    attr_accessor :omit_on_assignment
     # Whether a newline is put before multiline output.
     #
     # Uses <code>IRB.conf[:NEWLINE_BEFORE_MULTILINE_OUTPUT]</code> if available,
@@ -306,6 +325,7 @@ module IRB
     alias ignore_eof? ignore_eof
     alias echo? echo
     alias echo_on_assignment? echo_on_assignment
+    alias omit_on_assignment? omit_on_assignment
     alias newline_before_multiline_output? newline_before_multiline_output
 
     # Returns whether messages are displayed or not.
diff --git a/lib/irb/init.rb b/lib/irb/init.rb
index da40bee5e1..44383609bd 100644
--- a/lib/irb/init.rb
+++ b/lib/irb/init.rb
@@ -52,6 +52,7 @@ module IRB # :nodoc:
     @CONF[:IGNORE_EOF] = false
     @CONF[:ECHO] = nil
     @CONF[:ECHO_ON_ASSIGNMENT] = nil
+    @CONF[:OMIT_ON_ASSIGNMENT] = nil
     @CONF[:VERBOSE] = nil
 
     @CONF[:EVAL_HISTORY] = nil
@@ -177,6 +178,10 @@ module IRB # :nodoc:
         @CONF[:ECHO_ON_ASSIGNMENT] = true
       when "--noecho-on-assignment"
         @CONF[:ECHO_ON_ASSIGNMENT] = false
+      when "--omit-on-assignment"
+        @CONF[:OMIT_ON_ASSIGNMENT] = true
+      when "--noomit-on-assignment"
+        @CONF[:OMIT_ON_ASSIGNMENT] = false
       when "--verbose"
         @CONF[:VERBOSE] = true
       when "--noverbose"
diff --git a/lib/irb/input-method.rb b/lib/irb/input-method.rb
index 7cb211354b..6e87488753 100644
--- a/lib/irb/input-method.rb
+++ b/lib/irb/input-method.rb
@@ -12,6 +12,7 @@
 require_relative 'src_encoding'
 require_relative 'magic-file'
 require_relative 'completion'
+require 'io/console'
 require 'reline'
 
 module IRB
@@ -36,6 +37,14 @@ module IRB
     end
     public :gets
 
+    def winsize
+      if instance_variable_defined?(:@stdout)
+        @stdout.winsize
+      else
+        [24, 80]
+      end
+    end
+
     # Whether this input method is still readable when there is no more data to
     # read.
     #