fix: replace cond blocks with pattern matching and case (CSM-021)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CODESMELL.md

@@ -350,9 +350,13 @@
 
 ---
 
-### CSM-021 — `cond` Where Pattern Matching Suffices
-- **Files:** `lib/bds/ai.ex:62-70`, `lib/bds/scripting/api_docs.ex:1345-1398`, `lib/bds/scripting/api_docs.ex:1433-1447`
-- **Fix:** Replace `cond do x == nil -> ...; true -> ... end` with multiple function-head clauses.
+### ~~CSM-021 — `cond` Where Pattern Matching Suffices~~ ✅ FIXED
+- **Fixed:** 2026-05-11
+- **What was done:**
+  - **`lib/bds/ai.ex`** — `get_endpoint/2`: Replaced `cond do is_nil(x) and ...; true -> ... end` with a simple `if/else` since there are only two branches.
+  - **`lib/bds/scripting/api_docs.ex`** — `example_response_value/1`: Extracted `"nil"` literal match into a separate function head. Replaced remaining `cond` with `case` on a tuple of guard results.
+  - **`lib/bds/scripting/api_docs.ex`** — `example_field_value/1`: Replaced `cond` with `case` on a tuple of `String.contains?`/`String.ends_with?` results.
+  - Added 2 source-level tests in `test/bds/csm021_cond_pattern_match_test.exs` asserting no `cond do` blocks remain in either file.
 
 ---
 

lib/bds/ai.ex

@@ -62,14 +62,12 @@ defmodule BDS.AI do
     model = get_setting("ai.#{kind_key}.model")
     encrypted_api_key = get_setting(encrypted_key("ai.#{kind_key}.api_key"))
 
-    cond do
-      is_nil(url) and is_nil(model) and is_nil(encrypted_api_key) ->
-        {:ok, nil}
-
-      true ->
-        with {:ok, api_key} <- get_secret(encrypted_api_key, backend) do
-          {:ok, %{kind: kind, url: url, api_key: api_key, model: model}}
-        end
+    if is_nil(url) and is_nil(model) and is_nil(encrypted_api_key) do
+      {:ok, nil}
+    else
+      with {:ok, api_key} <- get_secret(encrypted_api_key, backend) do
+        {:ok, %{kind: kind, url: url, api_key: api_key, model: model}}
+      end
     end
   end
 

lib/bds/scripting/api_docs.ex

@@ -1434,18 +1434,17 @@ defmodule BDS.Scripting.ApiDocs do
     |> Enum.uniq()
   end
 
-  defp example_response_value(returns) do
-    cond do
-      returns == "nil" ->
-        nil
+  defp example_response_value("nil"), do: nil
 
-      nullable_return?(returns) ->
+  defp example_response_value(returns) do
+    case {nullable_return?(returns), String.ends_with?(returns, "[]")} do
+      {true, _} ->
         {:nullable, example_response_value(non_nil_return(returns))}
 
-      String.ends_with?(returns, "[]") ->
+      {_, true} ->
         [example_value_for_type(String.trim_trailing(returns, "[]"))]
 
-      true ->
+      _ ->
         example_value_for_type(returns)
     end
   end
@@ -1475,10 +1474,10 @@ defmodule BDS.Scripting.ApiDocs do
   end
 
   defp example_field_value(type) do
-    cond do
-      String.contains?(type, " | nil") -> nil
-      String.ends_with?(type, "[]") -> [example_value_for_type(String.trim_trailing(type, "[]"))]
-      true -> example_value_for_type(type)
+    case {String.contains?(type, " | nil"), String.ends_with?(type, "[]")} do
+      {true, _} -> nil
+      {_, true} -> [example_value_for_type(String.trim_trailing(type, "[]"))]
+      _ -> example_value_for_type(type)
     end
   end
 

test/bds/csm021_cond_pattern_match_test.exs

@@ -0,0 +1,15 @@
+defmodule BDS.CSM021CondPatternMatchTest do
+  use ExUnit.Case, async: true
+
+  describe "source-level: no cond blocks in fixed files" do
+    test "ai.ex has no cond do blocks" do
+      source = File.read!("lib/bds/ai.ex")
+      refute source =~ "cond do", "ai.ex should not contain cond do"
+    end
+
+    test "api_docs.ex has no cond do blocks" do
+      source = File.read!("lib/bds/scripting/api_docs.ex")
+      refute source =~ "cond do", "api_docs.ex should not contain cond do"
+    end
+  end
+end