control_d_handler: don't mutate eval_string within the handlercontrol-d-ruby-3-friendly

This is a preparational step for #1824
(Enabling `# frozen_string_literal: true` in `~/.pryc` crashes most operations)

Alternative to https://github.com/pry/pry/pull/2030
(config: delete the `control_d_handler` option)

We had to jump a few hoops to change how the handler works. The problem is that
mutation is the default expected behaviour. Therefore, we had to change its
API. There's no need to pass `eval_string` because `pry_instance` already has it
as an attribute.

`config.control_d_handler` is a proxy proc, to preserve backwards compatibility
with users of old signature (one known user is Pry Byebug). The handler will
emit a warning if the old signature is used.

6 files changed, 125 insertions, 18 deletions

diff --git a/lib/pry/config.rb b/lib/pry/config.rb
index 55718200..2ed3542a 100644
--- a/lib/pry/config.rb
+++ b/lib/pry/config.rb
@@ -261,6 +261,33 @@ class Pry
       @custom_attrs = @custom_attrs.dup
     end
 
+    def control_d_handler=(value)
+      proxy_proc =
+        if value.arity == 2
+          Pry::Warning.warn(
+            "control_d_handler's arity of 2 parameters was deprecated. Now it " \
+            'gets passed just 1 parameter (pry_instance). Please update your ' \
+            'handler'
+          )
+          proc do |*args|
+            if args.size == 2
+              value.call(args.first, args[1])
+            else
+              value.call(args.first.eval_string, args.first)
+            end
+          end
+        else
+          proc do |*args|
+            if args.size == 2
+              value.call(args[1])
+            else
+              value.call(args.first)
+            end
+          end
+        end
+      @control_d_handler = proxy_proc
+    end
+
     private
 
     def lazy_readline
diff --git a/lib/pry/control_d_handler.rb b/lib/pry/control_d_handler.rb
index 1021c767..f9b93003 100644
--- a/lib/pry/control_d_handler.rb
+++ b/lib/pry/control_d_handler.rb
@@ -7,9 +7,10 @@ class Pry
     #   1. In an expression behave like `!` command.
     #   2. At top-level session behave like `exit` command.
     #   3. In a nested session behave like `cd ..`.
-    def self.default(eval_string, pry_instance)
-      if !eval_string.empty?
-        eval_string.replace('') # Clear input buffer.
+    def self.default(pry_instance)
+      if !pry_instance.eval_string.empty?
+        # Clear input buffer.
+        pry_instance.eval_string = ''
       elsif pry_instance.binding_stack.one?
         pry_instance.binding_stack.clear
         throw(:breakout)
diff --git a/lib/pry/pry_instance.rb b/lib/pry/pry_instance.rb
index 2aebedc2..41eddb78 100644
--- a/lib/pry/pry_instance.rb
+++ b/lib/pry/pry_instance.rb
@@ -595,7 +595,7 @@ class Pry
 
   def handle_line(line, options)
     if line.nil?
-      config.control_d_handler.call(@eval_string, self)
+      config.control_d_handler.call(self)
       return
     end
 
diff --git a/spec/commands/cd_spec.rb b/spec/commands/cd_spec.rb
index ae715a3a..5ea64861 100644
--- a/spec/commands/cd_spec.rb
+++ b/spec/commands/cd_spec.rb
@@ -129,7 +129,7 @@ describe 'cd' do
     describe 'when using ^D (Control-D) key press' do
       it 'should keep correct old binding' do
         @t.eval 'cd :john_dogg', 'cd :mon_dogg', 'cd :kyr_dogg',
-                'Pry.config.control_d_handler.call("", pry_instance)'
+                'Pry.config.control_d_handler.call(pry_instance)'
         expect(@t.mapped_binding_stack).to eq [@o, :john_dogg, :mon_dogg]
 
         @t.eval 'cd -'
diff --git a/spec/config_spec.rb b/spec/config_spec.rb
index a3d38043..0c0e680e 100644
--- a/spec/config_spec.rb
+++ b/spec/config_spec.rb
@@ -28,7 +28,7 @@ RSpec.describe Pry::Config do
   specify { expect(subject.should_load_requires).to be(true).or be(false) }
   specify { expect(subject.should_load_plugins).to be(true).or be(false) }
   specify { expect(subject.windows_console_warning).to be(true).or be(false) }
-  specify { expect(subject.control_d_handler).to be_a(Method) }
+  specify { expect(subject.control_d_handler).to respond_to(:call) }
   specify { expect(subject.memory_size).to be_a(Numeric) }
   specify { expect(subject.extra_sticky_locals).to be_a(Hash) }
   specify { expect(subject.command_completions).to be_a(Proc) }
@@ -171,4 +171,74 @@ RSpec.describe Pry::Config do
       expect(subject[:foo]).to eq(1)
     end
   end
+
+  describe "#control_d_handler=" do
+    context "when the handler expects multiple arguments" do
+      it "prints a warning" do
+        expect(Pry::Warning).to receive(:warn).with(
+          "control_d_handler's arity of 2 parameters was deprecated. Now it " \
+          'gets passed just 1 parameter (pry_instance). Please update your ' \
+          'handler'
+        )
+        subject.control_d_handler = proc { |_arg1, _arg2| }
+      end
+    end
+
+    context "when the handler expects just one argument" do
+      it "doesn't print a warning" do
+        expect(Pry::Warning).not_to receive(:warn)
+        subject.control_d_handler = proc { |_arg1| }
+      end
+    end
+  end
+
+  describe "#control_d_handler" do
+    let(:pry_instance) { Pry.new }
+
+    context "when it returns a callable accepting one argument" do
+      context "and when it is called with one argument" do
+        it "calls the handler with a pry instance" do
+          subject.control_d_handler = proc do |arg|
+            expect(arg).to eql(pry_instance)
+          end
+          subject.control_d_handler.call(pry_instance)
+        end
+      end
+
+      context "and when it is called with multiple arguments" do
+        before { allow(Pry::Warning).to receive(:warn) }
+
+        it "calls the handler with a pry instance" do
+          subject.control_d_handler = proc do |arg|
+            expect(arg).to eql(pry_instance)
+          end
+          subject.control_d_handler.call('', pry_instance)
+        end
+      end
+    end
+
+    context "when it returns a callabale with two arguments" do
+      before { allow(Pry::Warning).to receive(:warn) }
+
+      context "and when it's called with one argument" do
+        it "calls the handler with a eval_string and a pry instance" do
+          subject.control_d_handler = proc do |arg1, arg2|
+            expect(arg1).to eq('')
+            expect(arg2).to eql(pry_instance)
+          end
+          subject.control_d_handler.call(pry_instance)
+        end
+      end
+
+      context "and when it's called with multiple arguments" do
+        it "calls the handler with a eval_string and a pry instance" do
+          subject.control_d_handler = proc do |arg1, arg2|
+            expect(arg1).to eq('')
+            expect(arg2).to eql(pry_instance)
+          end
+          subject.control_d_handler.call('', pry_instance)
+        end
+      end
+    end
+  end
 end
diff --git a/spec/control_d_handler_spec.rb b/spec/control_d_handler_spec.rb
index 5e21ccbe..030cefd6 100644
--- a/spec/control_d_handler_spec.rb
+++ b/spec/control_d_handler_spec.rb
@@ -1,48 +1,57 @@
 RSpec.describe Pry::ControlDHandler do
   context "when given eval string is non-empty" do
-    let(:eval_string) { 'hello' }
-    let(:pry_instance) { Pry.new }
+    let(:pry_instance) do
+      Pry.new.tap do |p|
+        p.eval_string = 'hello'
+      end
+    end
 
     it "clears input buffer" do
-      described_class.default(eval_string, pry_instance)
-      expect(eval_string).to be_empty
+      described_class.default(pry_instance)
+      expect(pry_instance.eval_string).to be_empty
     end
   end
 
   context "when given eval string is empty & pry instance has one binding" do
-    let(:eval_string) { '' }
-    let(:pry_instance) { Pry.new.tap { |p| p.binding_stack = [binding] } }
+    let(:pry_instance) do
+      Pry.new.tap do |p|
+        p.eval_string = ''
+        p.binding_stack = [binding]
+      end
+    end
 
     it "throws :breakout" do
-      expect { described_class.default(eval_string, pry_instance) }
+      expect { described_class.default(pry_instance) }
         .to throw_symbol(:breakout)
     end
 
     it "clears binding stack" do
-      expect { described_class.default(eval_string, pry_instance) }
+      expect { described_class.default(pry_instance) }
         .to throw_symbol
       expect(pry_instance.binding_stack).to be_empty
     end
   end
 
   context "when given eval string is empty & pry instance has 2+ bindings" do
-    let(:eval_string) { '' }
     let(:binding1) { binding }
     let(:binding2) { binding }
     let(:binding_stack) { [binding1, binding2] }
 
     let(:pry_instance) do
-      Pry.new.tap { |p| p.binding_stack = binding_stack }
+      Pry.new.tap do |p|
+        p.eval_string = ''
+        p.binding_stack = binding_stack
+      end
     end
 
     it "saves a dup of the current binding stack in the 'cd' command" do
-      described_class.default(eval_string, pry_instance)
+      described_class.default(pry_instance)
       cd_state = pry_instance.commands['cd'].state
       expect(cd_state.old_stack).to eq([binding1, binding2])
     end
 
     it "pops the binding off the stack" do
-      described_class.default(eval_string, pry_instance)
+      described_class.default(pry_instance)
       expect(pry_instance.binding_stack).to eq([binding1])
     end
   end