Use add_error in report_error helper

Within the `report_error` helper, use `add_error` instead of the
`set_error` method, so that multiple errors can be reported from
the same transaction.

.changesets/support-adding-multiple-errors-to-a-transaction.md

@@ -0,0 +1,10 @@
+---
+bump: patch
+type: add
+---
+
+Support adding multiple errors to a transaction.
+
+Using the `Appsignal.report_error` helper, you can now report more than one error within the same transaction context, up to a maximum of ten errors per transaction. Each error will be reported as a separate sample in the AppSignal UI.
+
+Before this change, using `Appsignal.report_error` or `Appsignal.set_error` helpers, adding a new error within the same transaction would overwrite the previous one.

lib/appsignal/helpers/instrumentation.rb

@@ -362,7 +362,7 @@ def set_error(exception)
       # @since 3.10.0
       def report_error(exception)
         unless exception.is_a?(Exception)
-          internal_logger.error "Appsignal.report_error: Cannot set error. " \
+          internal_logger.error "Appsignal.report_error: Cannot add error. " \
             "The given value is not an exception: #{exception.inspect}"
           return
         end
@@ -379,7 +379,7 @@ def report_error(exception)
             )
           end
 
-        transaction.set_error(exception)
+        transaction.add_error(exception)
         yield transaction if block_given?
 
         return if has_parent_transaction

spec/lib/appsignal_spec.rb

@@ -1345,7 +1345,7 @@ def on_start
           logs = capture_logs { Appsignal.report_error(error) }
           expect(logs).to contains_log(
             :error,
-            "Appsignal.report_error: Cannot set error. " \
+            "Appsignal.report_error: Cannot add error. " \
               "The given value is not an exception: #{error.inspect}"
           )
         end
@@ -1392,7 +1392,7 @@ def on_start
           expect(last_transaction).to eq(transaction)
           transaction._sample
           expect(transaction).to have_namespace(Appsignal::Transaction::HTTP_REQUEST)
-          expect(transaction).to have_error("ExampleException", "error message")
+          expect(transaction.errors).to eq([error])
         end
 
         it "does not complete the transaction" do
@@ -1412,7 +1412,7 @@ def on_start
             transaction._sample
             expect(transaction).to have_namespace("my_namespace")
             expect(transaction).to have_action("my_action")
-            expect(transaction).to have_error("ExampleException", "error message")
+            expect(transaction.errors).to eq([error])
             expect(transaction).to include_tags("tag1" => "value1")
             expect(transaction).to_not be_completed
           end