yak(credo-strict-tuned-config-both-apps-x02d): credo strict, tuned config (both apps)

blogex/test/credo_config_test.exs

@@ -0,0 +1,66 @@
+defmodule Blogex.CredoConfigTest do
+  @moduledoc """
+  Pins the *policy* in `.credo.exs`, not just the file's presence.
+
+  The gate is `mix credo --strict` (see the `credo` target in `Makefile`), so
+  the config is load-bearing: a check silently re-enabled here changes what
+  every future commit has to satisfy. These assertions are deliberately coarse
+  - "this check sits in that list", "the disable says why" - so they survive
+  credo's own boilerplate churn but not a policy change.
+  """
+  use ExUnit.Case, async: true
+
+  @config_path ".credo.exs"
+  @complexity_check "Credo.Check.Refactor.CyclomaticComplexity"
+
+  test "cyclomatic complexity is disabled in favour of CRAP" do
+    checks = default_config()[:checks]
+
+    assert @complexity_check in check_modules(checks[:disabled])
+    refute @complexity_check in check_modules(checks[:enabled])
+  end
+
+  test "the disable carries a rationale comment" do
+    rationale = rationale_above(@complexity_check)
+
+    refute rationale == [], "no comment block above the #{@complexity_check} entry"
+    assert Enum.join(rationale, "\n") =~ ~r/crap/i
+  end
+
+  defp default_config do
+    {config, _bindings} = Code.eval_file(@config_path)
+    Enum.find(config.configs, &(&1.name == "default"))
+  end
+
+  defp check_modules(checks) do
+    Enum.map(checks, fn
+      {module, _opts} -> module_name(module)
+      module -> module_name(module)
+    end)
+  end
+
+  # `Atom.to_string/1` keeps the "Elixir." prefix that `inspect/1` drops; the
+  # assertions read better (and diff better) without it.
+  defp module_name(module) do
+    module |> Atom.to_string() |> String.replace_prefix("Elixir.", "")
+  end
+
+  # The contiguous `#` block immediately above the check's own line. The entry
+  # line is the one that is not itself a comment: a comment mentioning the
+  # check by name must not be mistaken for the entry.
+  defp rationale_above(check_name) do
+    lines = @config_path |> File.read!() |> String.split("\n")
+
+    index =
+      Enum.find_index(lines, fn line ->
+        String.contains?(line, check_name) and not comment?(line)
+      end)
+
+    lines
+    |> Enum.take(index)
+    |> Enum.reverse()
+    |> Enum.take_while(&comment?/1)
+  end
+
+  defp comment?(line), do: line |> String.trim() |> String.starts_with?("#")
+end