From 99bd25d6d88022b8fa501fc62203e13a9fc7dc1d Mon Sep 17 00:00:00 2001
From: Stan Lo <stan.lo@shopify.com>
Date: Sat, 3 Dec 2022 17:35:38 +0000
Subject: [PATCH] Allow using IRB_USE_AUTOCOMPLETE=false to disable
 autocompletion

Currently, the only 2 ways to disable autocompletion are:

1. Create `.irbrc` and set `IRB.conf[:USE_AUTOCOMPLETE] = false`
2. Add the `--noautocomplete` flag when using the `irb` executable

Both of them are less convenient than setting a env var and are
lesser known to devs.

And given the number of problems the autocompletion has (see #445), I
think we should allow disabling it with a simple `IRB_USE_AUTOCOMPLETE=false`.
---
 lib/irb/init.rb       |  2 +-
 test/irb/test_init.rb | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/lib/irb/init.rb b/lib/irb/init.rb
index dd888f372..8e745adbe 100644
--- a/lib/irb/init.rb
+++ b/lib/irb/init.rb
@@ -45,7 +45,7 @@ def IRB.init_config(ap_path)
 
     @CONF[:USE_SINGLELINE] = false unless defined?(ReadlineInputMethod)
     @CONF[:USE_COLORIZE] = (nc = ENV['NO_COLOR']).nil? || nc.empty?
-    @CONF[:USE_AUTOCOMPLETE] = true
+    @CONF[:USE_AUTOCOMPLETE] = !(ENV.fetch("IRB_USE_AUTOCOMPLETE", "true") == "false")
     @CONF[:INSPECT_MODE] = true
     @CONF[:USE_TRACER] = false
     @CONF[:USE_LOADER] = false
diff --git a/test/irb/test_init.rb b/test/irb/test_init.rb
index 9591de158..d9e338da8 100644
--- a/test/irb/test_init.rb
+++ b/test/irb/test_init.rb
@@ -96,6 +96,30 @@ def test_no_color_environment_variable
       IRB.conf[:USE_COLORIZE] = orig_use_colorize
     end
 
+    def test_use_autocomplete_environment_variable
+      orig_use_autocomplete_env = ENV['IRB_USE_AUTOCOMPLETE']
+      orig_use_autocomplete_conf = IRB.conf[:USE_AUTOCOMPLETE]
+
+      ENV['IRB_USE_AUTOCOMPLETE'] = nil
+      IRB.setup(__FILE__)
+      assert IRB.conf[:USE_AUTOCOMPLETE]
+
+      ENV['IRB_USE_AUTOCOMPLETE'] = ''
+      IRB.setup(__FILE__)
+      assert IRB.conf[:USE_AUTOCOMPLETE]
+
+      ENV['IRB_USE_AUTOCOMPLETE'] = 'false'
+      IRB.setup(__FILE__)
+      refute IRB.conf[:USE_AUTOCOMPLETE]
+
+      ENV['IRB_USE_AUTOCOMPLETE'] = 'true'
+      IRB.setup(__FILE__)
+      assert IRB.conf[:USE_AUTOCOMPLETE]
+    ensure
+      ENV["IRB_USE_AUTOCOMPLETE"] = orig_use_autocomplete_env
+      IRB.conf[:USE_AUTOCOMPLETE] = orig_use_autocomplete_conf
+    end
+
     def test_noscript
       argv = %w[--noscript -- -f]
       IRB.setup(eval("__FILE__"), argv: argv)