fix: set span name to sinatra.route (#434)

The previous attempt at this failed due to sinatra.route not having been
set yet. This moves the logic for using sinatra.route to later in the
process and only updates the span name if sinatra.route exists.

Author: genebean

instrumentation/sinatra/lib/opentelemetry/instrumentation/sinatra/middlewares/tracer_middleware.rb

@@ -15,10 +15,8 @@ def initialize(app)
           end
 
           def call(env)
-            span_name = env['sinatra.route'] || env['PATH_INFO']
-
             tracer.in_span(
-              span_name,
+              env['PATH_INFO'],
               attributes: { 'http.method' => env['REQUEST_METHOD'],
                             'http.url' => env['PATH_INFO'] },
               kind: :server,
@@ -46,6 +44,7 @@ def trace_response(span, env, resp)
             span.set_attribute('http.status_code', status)
             span.set_attribute('http.status_text', ::Rack::Utils::HTTP_STATUS_CODES[status])
             span.set_attribute('http.route', env['sinatra.route'].split.last) if env['sinatra.route']
+            span.name = env['sinatra.route'] if env['sinatra.route']
             span.status = OpenTelemetry::Trace::Status.http_to_status(status)
           end
         end

instrumentation/sinatra/test/opentelemetry/instrumentation/sinatra_test.rb

@@ -27,6 +27,10 @@
       get '/with_template' do
         erb :foo_template
       end
+
+      get '/api/v1/foo/:myname/?' do
+        'Some name'
+      end
     end
   end
 
@@ -96,14 +100,33 @@
 
       _(exporter.finished_spans.size).must_equal 3
       _(exporter.finished_spans.map(&:name))
-        .must_equal %w[sinatra.render_template
-                       sinatra.render_template
-                       /with_template]
+        .must_equal [
+          'sinatra.render_template',
+          'sinatra.render_template',
+          'GET /with_template'
+        ]
       _(exporter.finished_spans[0..1].map(&:attributes)
         .map { |h| h['sinatra.template_name'] })
         .must_equal %w[layout foo_template]
     end
 
+    it 'correctly name spans' do
+      get '/one//api/v1/foo/janedoe/'
+
+      _(exporter.finished_spans.size).must_equal 1
+      _(exporter.finished_spans.first.attributes).must_equal(
+        'http.method' => 'GET',
+        'http.url' => '/api/v1/foo/janedoe/',
+        'http.status_code' => 200,
+        'http.status_text' => 'OK',
+        'http.route' => '/api/v1/foo/:myname/?'
+      )
+      _(exporter.finished_spans.map(&:name))
+        .must_equal [
+          'GET /api/v1/foo/:myname/?'
+        ]
+    end
+
     it 'does not create unhandled exceptions for missing routes' do
       get '/one/missing_example/not_present'