Fix crash on error detail page when using MySQL/MariaDB

Instead of using `{:array, :string}` for the `:breadcrumbs` field in `ErrorTracker.Occurrence` we use a new custom field type `ErrorTracker.Types.StringArray`.
It uses `Jason` to decode arrays when retrieving data from MySQL/MariaDB. Therefore it works very similarly to the `:array` type but without crashing on retrieval.
This fix does not make a schema migration necessary. An additional test module `ErrorTracker.StoreFetchTest` was implemented to avoid regreessions in the future.

Fixes #150.

Author: phihos

.github/workflows/elixir.yml

@@ -47,6 +47,16 @@ jobs:
           --health-interval 10s
           --health-timeout 5s
           --health-retries 5
+      mysql:
+        image: mysql:9
+        ports: ["3307:3306"]
+        env:
+          MYSQL_ROOT_PASSWORD: root
+        options: >-
+          --health-cmd "mysqladmin ping --password=root"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
     name: Elixir v${{ matrix.elixir }}, Erlang v${{ matrix.erlang }}
     steps:
       - uses: actions/checkout@v4
@@ -96,7 +106,12 @@ jobs:
         env:
           DB: postgres
 
-      - name: Run Tests - MySQL/MariaDB
+      - name: Run Tests - MariaDB
+        run: mix test
+        env:
+          DB: mariadb
+
+      - name: Run Tests - MySQL
         run: mix test
         env:
-          DB: mysql
+          DB: mysql

config/test.example.exs

@@ -5,8 +5,15 @@ config :error_tracker, ErrorTracker.Test.Repo,
   pool: Ecto.Adapters.SQL.Sandbox,
   log: false
 
+config :error_tracker, ErrorTracker.Test.MariaDBRepo,
+  url: "ecto://root:root@127.0.0.1:3306/error_tracker_test",
+  pool: Ecto.Adapters.SQL.Sandbox,
+  log: false,
+  # Use the same migrations as the PostgreSQL repo
+  priv: "priv/repo"
+
 config :error_tracker, ErrorTracker.Test.MySQLRepo,
-  url: "ecto://root:root@127.0.0.1/error_tracker_test",
+  url: "ecto://root:root@127.0.0.1:3307/error_tracker_test",
   pool: Ecto.Adapters.SQL.Sandbox,
   log: false,
   # Use the same migrations as the PostgreSQL repo

lib/error_tracker/schemas/occurrence.ex

@@ -18,7 +18,7 @@ defmodule ErrorTracker.Occurrence do
     field :reason, :string
 
     field :context, :map
-    field :breadcrumbs, {:array, :string}
+    field :breadcrumbs, ErrorTracker.Types.StringArray
 
     embeds_one :stacktrace, ErrorTracker.Stacktrace
     belongs_to :error, ErrorTracker.Error

lib/error_tracker/schemas/types/string_array.ex

@@ -0,0 +1,36 @@
+defmodule ErrorTracker.Types.StringArray do
+  @moduledoc """
+  Custom Ecto type for lists.
+
+  The built-in `:array` type is not properly implemented for the Ecto adapter `Ecto.Adapters.MyXQL`.
+  Therefore we can not use it and have to impelement our own.
+  """
+  use Ecto.Type
+
+  def type, do: {:array, :string}
+
+  def cast(list) when is_list(list) do
+    {:ok, list}
+  end
+
+  def cast(_), do: :error
+
+  def load(list) when is_binary(list) do
+    Jason.decode(list)
+  end
+
+  def load(list) when is_nil(list) do
+    []
+  end
+
+  def load(list), do: {:ok, list}
+
+  def dump(list) when is_list(list) do
+    ErrorTracker.Repo.with_adapter(fn
+      :mysql -> Jason.encode(list)
+      _ -> {:ok, list}
+    end)
+  end
+
+  def dump(_), do: :error
+end

test/error_tracker/store_fetch_test.exs

@@ -0,0 +1,15 @@
+defmodule ErrorTracker.StoreFetchTest do
+  @moduledoc """
+  Test if simple store-retrieve operations are successful.
+
+  This is necessary, because some Ecto adapters like `Ecto.Adapters.MyXQL` may successfully store a field, but crash on retrieval.
+  """
+  use ErrorTracker.Test.Case
+
+  test "after reporting an error its occurrence should be retrievable from DB" do
+    assert %ErrorTracker.Occurrence{id: occurrence_id} =
+             report_error(fn -> raise "BOOM" end)
+
+    assert %ErrorTracker.Occurrence{} = repo().get!(ErrorTracker.Occurrence, occurrence_id)
+  end
+end

test/support/mariadb_repo.ex

@@ -0,0 +1,4 @@
+defmodule ErrorTracker.Test.MariaDBRepo do
+  @moduledoc false
+  use Ecto.Repo, otp_app: :error_tracker, adapter: Ecto.Adapters.MyXQL
+end

test/test_helper.exs

@@ -7,11 +7,14 @@ repo =
     "mysql" ->
       ErrorTracker.Test.MySQLRepo
 
+    "mariadb" ->
+      ErrorTracker.Test.MariaDBRepo
+
     "postgres" ->
       ErrorTracker.Test.Repo
 
     _other ->
-      raise "Please run either `DB=sqlite mix test`, `DB=postgres mix test` or `DB=mysql mix test`"
+      raise "Please run either `DB=sqlite mix test`, `DB=postgres mix test`, `DB=mariadb mix test` or `DB=mysql mix test`"
   end
 
 Application.put_env(:error_tracker, :repo, repo)