Store bread crumbs in error context

Some frameworks such as Ash provide bread crumbs in their errors. This
commit records those breadcrumbs and stores them in the occurrence
context.

Author: crbelaus

lib/error_tracker.ex

@@ -120,6 +120,11 @@ defmodule ErrorTracker do
     {:ok, error} = Error.new(kind, reason, stacktrace)
     context = Map.merge(get_context(), given_context)
 
+    context =
+      if bread_crumbs = bread_crumbs(exception),
+        do: Map.put(context, "bread_crumbs", bread_crumbs),
+        else: context
+
     if enabled?() && !ignored?(error, context) do
       sanitized_context = sanitize_context(context)
       {_error, occurrence} = upsert_error!(error, stacktrace, sanitized_context, reason)
@@ -232,6 +237,14 @@ defmodule ErrorTracker do
     end
   end
 
+  defp bread_crumbs(exception) do
+    case exception do
+      {_kind, exception} -> bread_crumbs(exception)
+      %{bread_crumbs: bread_crumbs} -> bread_crumbs
+      _other -> nil
+    end
+  end
+
   defp upsert_error!(error, stacktrace, context, reason) do
     existing_status =
       Repo.one(from e in Error, where: [fingerprint: ^error.fingerprint], select: e.status)

test/error_tracker_test.exs

@@ -99,6 +99,17 @@ defmodule ErrorTrackerTest do
     test "with enabled flag to false it does not store the exception" do
       assert report_error(fn -> raise "Sample error" end) == :noop
     end
+
+    test "includes bread crumbs in the context if present" do
+      bread_crumbs = ["bread crumb 1", "bread crumb 2"]
+
+      occurrence =
+        report_error(fn ->
+          raise ErrorWithBreadcrumbs, message: "test", bread_crumbs: bread_crumbs
+        end)
+
+      assert occurrence.context["bread_crumbs"] == bread_crumbs
+    end
   end
 
   describe inspect(&ErrorTracker.resolve/1) do
@@ -119,3 +130,7 @@ defmodule ErrorTrackerTest do
     end
   end
 end
+
+defmodule ErrorWithBreadcrumbs do
+  defexception [:message, :bread_crumbs]
+end