Fix Oban.PerformError grouping (#92)

This change improves how we store data from `Oban.PerformError` errors.

Those errors don't come from exceptions, as they are delivered via
Telemetry when the worker ends up with an `:error` or an `{:error,
any()}` tuple.

As they are not exceptions, there is no stack trace, and they were been
detected as the same error by our fingerprinting algo.

This changes introduces an fix that adds the worker module as the only
stacktrace of the occurrence, so the error can populate the
`source_function` attribute and different workers generate different
error groupings.

We cannot generate different error groups per different outputs of a
worker. In that case, you should use `raise`, that generates a full
stack trace and works as expected.

Closes #87

lib/error_tracker/integrations/oban.ex

@@ -12,6 +12,20 @@ defmodule ErrorTracker.Integrations.Oban do
   It works using Oban's Telemetry events, so you don't need to modify anything
   on your application.
 
+  > #### A note on errors grouping {: .warning}
+  >
+  > All errors reported using `:error` or `{:error, any()}` as the output of
+  > your `perform/2` worker function are going to be grouped together (one group
+  > of those of errors per worker).
+  >
+  > The reason of that behaviour is that those errors do not generate an exception,
+  > so no stack trace is detected and they are stored as happening in the same
+  > place.
+  >
+  > If you want errors of your workers to be grouped as you may expect on other
+  > integrations, you should raise exceptions to report errors instead of gracefully
+  > returning an error value.
+
   ### Default context
 
   By default we store some context for you on errors generated in an Oban
@@ -58,9 +72,14 @@ defmodule ErrorTracker.Integrations.Oban do
   end
 
   def handle_event([:oban, :job, :exception], _measurements, metadata, :no_config) do
-    %{reason: exception, stacktrace: stacktrace} = metadata
+    %{reason: exception, stacktrace: stacktrace, job: job} = metadata
     state = Map.get(metadata, :state, :failure)
 
+    stacktrace =
+      if stacktrace == [],
+        do: [{String.to_existing_atom("Elixir." <> job.worker), :perform, 2, []}],
+        else: stacktrace
+
     ErrorTracker.report(exception, stacktrace, %{state: state})
   end
 end

lib/error_tracker/schemas/error.ex

@@ -32,7 +32,7 @@ defmodule ErrorTracker.Error do
 
     {source_line, source_function} =
       if source do
-        source_line = if source.line, do: "#{source.file}:#{source.line}", else: "nofile"
+        source_line = if source.line, do: "#{source.file}:#{source.line}", else: "(nofile)"
         source_function = "#{source.module}.#{source.function}/#{source.arity}"
 
         {source_line, source_function}

lib/error_tracker/web/live/show.html.heex

@@ -48,7 +48,7 @@
                 <td class="px-2 align-top"><pre>(<%= line.application || @app %>)</pre></td>
                 <td>
                   <pre><%= "#{sanitize_module(line.module)}.#{line.function}/#{line.arity}" %>
-                <%= if line.line, do: "#{line.file}:#{line.line}", else: "nofile" %></pre>
+                <%= if line.line, do: "#{line.file}:#{line.line}", else: "(nofile)" %></pre>
                 </td>
               </tr>
             </tbody>

test/error_tracker_test.exs

@@ -40,7 +40,7 @@ defmodule ErrorTrackerTest do
         assert error.source_line =~ @relative_file_path
       else
         assert error.source_function == "erlang.+/2"
-        assert error.source_line == "nofile"
+        assert error.source_line == "(nofile)"
       end
     end
 
@@ -54,7 +54,7 @@ defmodule ErrorTrackerTest do
       assert error.kind == to_string(UndefinedFunctionError)
       assert error.reason =~ "is undefined or private"
       assert error.source_function == Exception.format_mfa(m, f, Enum.count(a))
-      assert error.source_line == "nofile"
+      assert error.source_line == "(nofile)"
     end
 
     test "reports throws" do