raise on Money.new is attempting to change currency of an existing mo…

…ney object

lib/money/money.rb

@@ -45,6 +45,8 @@ def configure
     end
 
     def new(value = 0, currency = nil)
+      return new_from_money(value, currency) if value.is_a?(Money)
+
       value = Helpers.value_to_decimal(value)
       currency = Helpers.value_to_currency(currency)
 
@@ -100,6 +102,20 @@ def with_currency(new_currency)
         Money.current_currency = old_currency
       end
     end
+
+    private
+
+    def new_from_money(amount, currency)
+      return amount if amount.currency.compatible?(Helpers.value_to_currency(currency))
+
+      msg = "Money.new is attempting to change currency of an existing money object"
+      if Money.config.legacy_deprecations
+        Money.deprecate("#{msg}. A Money::IncompatibleCurrencyError will raise in the next major release")
+        return Money.new(amount.value, currency)
+      else
+        raise Money::IncompatibleCurrencyError, msg
+      end
+    end
   end
   configure
 

spec/money_spec.rb

@@ -60,6 +60,29 @@
     expect(Money.new('')).to eq(Money.new(0))
   end
 
+  it "can be constructed with a string" do
+    expect(Money.new('1')).to eq(Money.new(1))
+  end
+
+  it "can be constructed with a numeric" do
+    expect(Money.new(1.00)).to eq(Money.new(1))
+  end
+
+  it "can be constructed with a money object" do
+    expect(Money.new(Money.new(1))).to eq(Money.new(1))
+  end
+
+  it "constructor raises when changing currency" do
+    expect { Money.new(Money.new(1, 'USD'), 'CAD') }.to raise_error(Money::IncompatibleCurrencyError)
+  end
+
+  it "legacy_deprecations constructor with money used the constructor currency" do
+    configure(legacy_deprecations: true) do
+     expect(Money).to receive(:deprecate).with(match(/Money.new is attempting to change currency of an existing money object/)).once
+      expect(Money.new(Money.new(1, 'USD'), 'CAD')).to eq(Money.new(1, 'CAD'))
+    end
+  end
+
   it "legacy_deprecations defaults to 0 when constructed with an invalid string" do
     configure(legacy_deprecations: true) do
       expect(Money).to receive(:deprecate).once