Remove the check for a relative path

This isn't a _huge_ perf boost, but every little helps :^)

In the old Pathname method, this if was useful because it was quicker
to skip files that were already resolved, assuming there was a mix of
relative and absolute paths

With File.realpath, however, it's quicker to just run the function as
it does nothing if the path is already resolved. This is roughtly
equal in terms of performance to using the new File.absolute_path?
method (they are so close in benchmarks that it's essentially noise)

CHANGELOG.md

@@ -16,6 +16,7 @@ Changelog
 
 * Improve performance when processing stacktraces
   | [#602](https://github.com/bugsnag/bugsnag-ruby/pull/602)
+  | [#603](https://github.com/bugsnag/bugsnag-ruby/pull/603)
 
 ### Deprecated
 

lib/bugsnag/stacktrace.rb

@@ -27,10 +27,7 @@ def initialize(backtrace, configuration)
         next(nil) if file.nil?
 
         # Expand relative paths
-        p = Pathname.new(file)
-        if p.relative?
-          file = File.realpath(file) rescue file
-        end
+        file = File.realpath(file) rescue file
 
         # Generate the stacktrace line hash
         trace_hash = {}

spec/stacktrace_spec.rb

@@ -95,14 +95,11 @@
       configuration = Bugsnag::Configuration.new
       configuration.send_code = false
 
-      dir = File.dirname(__FILE__)
-
       backtrace = [
         "/foo/bar/app/models/user.rb:1:in `something'",
         "/foo/bar/other_vendor/lib/dont.rb:2:in `to_s'",
         "/foo/bar/vendor/lib/ignore_me.rb:3:in `to_s'",
         "/foo/bar/.bundle/lib/ignore_me.rb:4:in `to_s'",
-        "#{dir}/../spec/stacktrace_spec.rb:5:in `something_else'",
       ]
 
       stacktrace = Bugsnag::Stacktrace.new(backtrace, configuration).to_a
@@ -112,7 +109,6 @@
         { file: "/foo/bar/other_vendor/lib/dont.rb", lineNumber: 2, method: "to_s" },
         { file: "/foo/bar/vendor/lib/ignore_me.rb", lineNumber: 3, method: "to_s" },
         { file: "/foo/bar/.bundle/lib/ignore_me.rb", lineNumber: 4, method: "to_s" },
-        { file: "#{dir}/../spec/stacktrace_spec.rb", lineNumber: 5, method: "something_else" },
       ])
     end
 
@@ -140,20 +136,22 @@
       configuration = Bugsnag::Configuration.new
       configuration.send_code = false
 
+      dir = File.dirname(__FILE__)
+
       backtrace = [
         "./spec/spec_helper.rb:1:in `something'",
         "./lib/bugsnag/breadcrumbs/../configuration.rb:100:in `to_s'",
         "lib/bugsnag.rb:20:in `notify'",
+        "#{dir}/../spec/stacktrace_spec.rb:5:in `something_else'",
       ]
 
       stacktrace = Bugsnag::Stacktrace.new(backtrace, configuration).to_a
 
-      dir = File.dirname(__FILE__)
-
       expect(stacktrace).to eq([
         { file: "#{dir}/spec_helper.rb", lineNumber: 1, method: "something" },
         { file: "#{File.dirname(dir)}/lib/bugsnag/configuration.rb", lineNumber: 100, method: "to_s" },
         { file: "#{File.dirname(dir)}/lib/bugsnag.rb", lineNumber: 20, method: "notify" },
+        { file: "#{dir}/stacktrace_spec.rb", lineNumber: 5, method: "something_else" },
       ])
     end
   end