Fix incorrect configuration mismatch warning when port is specified a…

…s String

I noticed a Ruby app where the configuration mismatch warning was
popping up:

```
W, [2021-10-15T11:44:30.952540 #1]  WARN -- ddtrace: [ddtrace]
Configuration mismatch: values differ between "c.tracer.port" ('8126')
and DD_TRACE_AGENT_PORT environment variable ('8126'). Using '8126'.
```

The warning was being triggered because we convert the values read from
environment variables (`DD_TRACE_AGENT_PORT` or `DD_TRACE_AGENT_URL`)
into integers, but this app had `c.tracer.port` specified as a
string.

Because or that, since we collect all values, call `#uniq` on them
and see if we get more than one, the warning was being triggered
since the `8126` integer is not the same as the `'8126'` string.

lib/ddtrace/configuration/agent_settings_resolver.rb

@@ -130,35 +130,46 @@ def configured_hostname
       def configured_port
         return @configured_port if defined?(@configured_port)
 
-        port_from_env = ENV[Datadog::Ext::Transport::HTTP::ENV_DEFAULT_PORT]
         parsed_port_from_env =
-          if port_from_env
-            begin
-              Integer(port_from_env)
-            rescue ArgumentError
-              log_warning(
-                "Invalid value for #{Datadog::Ext::Transport::HTTP::ENV_DEFAULT_PORT} environment variable " \
-                "('#{port_from_env}'). Ignoring this configuration."
-              )
-            end
-          end
+          try_parsing_as_integer(
+            friendly_name: "#{Datadog::Ext::Transport::HTTP::ENV_DEFAULT_PORT} environment variable",
+            value: ENV[Datadog::Ext::Transport::HTTP::ENV_DEFAULT_PORT],
+          )
+
+        parsed_settings_tracer_port =
+          try_parsing_as_integer(
+            friendly_name: '"c.tracer.port"',
+            value: settings.tracer.port,
+          )
 
         @configured_port = pick_from(
           DetectedConfiguration.new(
             friendly_name: '"c.tracer.port"',
-            value: settings.tracer.port
+            value: parsed_settings_tracer_port,
           ),
           DetectedConfiguration.new(
             friendly_name: "#{Datadog::Ext::Transport::HTTP::ENV_DEFAULT_URL} environment variable",
-            value: parsed_url && parsed_url.port
+            value: parsed_url && parsed_url.port,
           ),
           DetectedConfiguration.new(
             friendly_name: "#{Datadog::Ext::Transport::HTTP::ENV_DEFAULT_PORT} environment variable",
-            value: parsed_port_from_env
+            value: parsed_port_from_env,
           )
         )
       end
 
+      def try_parsing_as_integer(value:, friendly_name:)
+        return unless value
+
+        begin
+          Integer(value)
+        rescue ArgumentError
+          log_warning("Invalid value for #{friendly_name} (#{value.inspect}). Ignoring this configuration.")
+
+          nil
+        end
+      end
+
       def ssl?
         !parsed_url.nil? && parsed_url.scheme == 'https'
       end

spec/ddtrace/configuration/agent_settings_resolver_spec.rb

@@ -199,6 +199,34 @@
           resolver
         end
       end
+
+      context 'when the port is specified as a string instead of a number' do
+        before do
+          ddtrace_settings.tracer.port = '1234'
+        end
+
+        it 'contacts the agent using the http adapter, using the custom port' do
+          expect(resolver).to have_attributes(**settings, port: 1234)
+        end
+      end
+
+      context 'when the port is an invalid value' do
+        before do
+          ddtrace_settings.tracer.port = 'kaboom'
+
+          allow(logger).to receive(:warn)
+        end
+
+        it 'logs a warning' do
+          expect(logger).to receive(:warn).with(/Invalid value/)
+
+          resolver
+        end
+
+        it 'falls back to the defaults' do
+          expect(resolver).to have_attributes settings
+        end
+      end
     end
 
     context 'when a custom port is specified via code using "tracer(port: ...)"' do