Treat Stripe charge_already_captured as successful capture

app/models/spree/gateway/stripe_gateway.rb

@@ -37,7 +37,19 @@ def authorize(money, creditcard, gateway_options)
     end
 
     def capture(money, response_code, gateway_options)
-      provider.capture(money, response_code, gateway_options)
+      response = provider.capture(money, response_code, gateway_options)
+      return response if response.success?
+
+      if response.params.is_a?(Hash) && response.params.dig('error', 'code') == 'charge_already_captured'
+        return ActiveMerchant::Billing::Response.new(
+          true,
+          'Charge was already captured on Stripe',
+          response.params,
+          authorization: response_code
+        )
+      end
+
+      response
     end
 
     def credit(money, creditcard, response_code, gateway_options)

spec/models/gateway/stripe_gateway_spec.rb

@@ -143,11 +143,11 @@
     end
 
     it 'convert the amount to cents' do
-      provider.should_receive(:capture).with(1234,anything,anything)
+      provider.should_receive(:capture).with(1234,anything,anything).and_return(double(success?: true))
     end
 
     it 'use the response code as the authorization' do
-      provider.should_receive(:capture).with(anything,'response_code',anything)
+      provider.should_receive(:capture).with(anything,'response_code',anything).and_return(double(success?: true))
     end
   end
 
@@ -198,3 +198,74 @@
     end
   end
 end
+
+# Regression for spree/spree#11974: when a charge is captured directly on the
+# Stripe dashboard and then captured again from Spree, ActiveMerchant returns
+# an error with code 'charge_already_captured'. We treat this as a successful
+# capture so the Spree payment transitions to completed instead of failed.
+#
+# This describe intentionally sits outside the block above so it does not
+# inherit the legacy `.stub` syntax used in the older specs.
+describe Spree::Gateway::StripeGateway, '#capture when Stripe already captured the charge' do
+  let(:provider) { double('provider') }
+
+  let(:gateway) do
+    described_class.new.tap do |g|
+      g.preferences = { secret_key: 'key' }
+      allow(g).to receive(:provider).and_return(provider)
+    end
+  end
+
+  let(:already_captured_response) do
+    ActiveMerchant::Billing::Response.new(
+      false,
+      'Charge ch_123 has already been captured.',
+      {
+        'error' => {
+          'code' => 'charge_already_captured',
+          'message' => 'Charge ch_123 has already been captured.',
+          'type' => 'invalid_request_error'
+        }
+      },
+      {}
+    )
+  end
+
+  before do
+    allow(provider).to receive(:capture).and_return(already_captured_response)
+  end
+
+  subject(:capture_result) { gateway.capture(1234, 'ch_123', {}) }
+
+  it 'returns a successful response' do
+    expect(capture_result.success?).to be true
+  end
+
+  it 'uses the original response_code as the authorization' do
+    expect(capture_result.authorization).to eq('ch_123')
+  end
+
+  it 'preserves the Stripe error params on the response' do
+    expect(capture_result.params.dig('error', 'code')).to eq('charge_already_captured')
+  end
+
+  context 'when Stripe returns a different error' do
+    let(:other_error_response) do
+      ActiveMerchant::Billing::Response.new(
+        false,
+        'Your card was declined.',
+        { 'error' => { 'code' => 'card_declined' } },
+        {}
+      )
+    end
+
+    before do
+      allow(provider).to receive(:capture).and_return(other_error_response)
+    end
+
+    it 'returns the original failed response untouched' do
+      expect(capture_result.success?).to be false
+      expect(capture_result.params.dig('error', 'code')).to eq('card_declined')
+    end
+  end
+end