[ruby/irb] Gracefully handle incorrect command aliases

(https://github.com/ruby/irb/pull/1059)

* Gracefully handle incorrect command aliases

Even if the aliased target is a helper method or does not exist, IRB
should not crash.

This commit warns users in such cases and treat the input as normal expression.

* Streamline command parsing and introduce warnings for incorrect command aliases

https://github.com/ruby/irb/commit/9fc14eb74b

1 files changed, 50 insertions, 0 deletions

diff --git a/test/irb/command/test_command_aliasing.rb b/test/irb/command/test_command_aliasing.rb
new file mode 100644
index 0000000000..4ecc88c0aa
--- /dev/null
+++ b/test/irb/command/test_command_aliasing.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require "tempfile"
+require_relative "../helper"
+
+module TestIRB
+  class CommandAliasingTest < IntegrationTestCase
+    def setup
+      super
+      write_rc <<~RUBY
+        IRB.conf[:COMMAND_ALIASES] = {
+          :c => :conf, # alias to helper method
+          :f => :foo
+        }
+      RUBY
+
+      write_ruby <<~'RUBY'
+        binding.irb
+      RUBY
+    end
+
+    def test_aliasing_to_helper_method_triggers_warning
+      out = run_ruby_file do
+        type "c"
+        type "exit"
+      end
+      assert_include(out, "Using command alias `c` for helper method `conf` is not supported.")
+      assert_not_include(out, "Maybe IRB bug!")
+    end
+
+    def test_alias_to_non_existent_command_triggers_warning
+      message = "You're trying to use command alias `f` for command `foo`, but `foo` does not exist."
+      out = run_ruby_file do
+        type "f"
+        type "exit"
+      end
+      assert_include(out, message)
+      assert_not_include(out, "Maybe IRB bug!")
+
+      # Local variables take precedence over command aliases
+      out = run_ruby_file do
+        type "f = 123"
+        type "f"
+        type "exit"
+      end
+      assert_not_include(out, message)
+      assert_not_include(out, "Maybe IRB bug!")
+    end
+  end
+end