fix: tolerate 3-tuple dep entries in recursively_compose_schema (#372)

`Igniter.Util.Info.recursively_compose_schema/4` merged `installs`
and `adds_deps` with `Keyword.merge/2`, which raises `ArgumentError`
when a dep entry is a 3-tuple like `{:credo, "~> 1.7", only: [:dev,
:test]}`. The type spec at `lib/mix/task/info.ex:129-132` explicitly
allows 3-tuples, and other code in the same module (`add_deps/3`,
installs normalization) already handles them.

Replace both `Keyword.merge/2` calls with a `merge_deps/2` helper
that dedupes by dep name while preserving the tuple shape, keeping
the parent's entry on conflict to match `Keyword.merge/2` semantics.

Co-authored-by: Matt Pruitt <41898282+guitsaru@users.noreply.github.com>

Author: guitsaru

lib/igniter/util/info.ex

@@ -481,8 +481,8 @@ defmodule Igniter.Util.Info do
             alias_conflicts: alias_conflicts(schema, composing_schema, composing_task_name),
             composes: rest,
             extra_args?: schema.extra_args? || composing_schema.extra_args?,
-            installs: Keyword.merge(composing_schema.installs, schema.installs),
-            adds_deps: Keyword.merge(composing_schema.adds_deps, schema.adds_deps)
+            installs: merge_deps(composing_schema.installs, schema.installs),
+            adds_deps: merge_deps(composing_schema.adds_deps, schema.adds_deps)
         },
         argv,
         parent,
@@ -501,6 +501,11 @@ defmodule Igniter.Util.Info do
     end
   end
 
+  defp merge_deps(composed, parent) do
+    names = MapSet.new(parent, &elem(&1, 0))
+    Enum.reject(composed, fn entry -> elem(entry, 0) in names end) ++ parent
+  end
+
   defp flag_conflicts(schema, composing_schema, composing_task_name) do
     Map.merge(
       schema.flag_conflicts,

test/igniter/mix/task_test.exs

@@ -293,6 +293,100 @@ defmodule Igniter.Mix.TaskTest do
     end
   end
 
+  describe "composed schema dep merging" do
+    # Covers every form in the `Igniter.Mix.Task.Info.dep` type:
+    #   {name, version}
+    #   {name, opts}
+    #   {name, version, opts}
+
+    defmodule Elixir.Mix.Tasks.ParentAddsDepsAllFormats do
+      use Igniter.Mix.Task
+
+      def info(_argv, _parent) do
+        %Igniter.Mix.Task.Info{
+          composes: ["child_adds_deps_all_formats"],
+          adds_deps: [
+            {:boundary, "~> 0.10", runtime: false},
+            {:parent_git_dep, git: "https://example.com/parent.git"},
+            {:parent_versioned, "~> 1.0"}
+          ]
+        }
+      end
+
+      def igniter(igniter), do: igniter
+    end
+
+    defmodule Elixir.Mix.Tasks.ChildAddsDepsAllFormats do
+      use Igniter.Mix.Task
+
+      def info(_argv, _parent) do
+        %Igniter.Mix.Task.Info{
+          adds_deps: [
+            {:cloak, "~> 1.1"},
+            {:child_git_dep, git: "https://example.com/child.git"},
+            {:child_with_opts, "~> 2.0", only: :test}
+          ]
+        }
+      end
+
+      def igniter(igniter), do: igniter
+    end
+
+    defmodule Elixir.Mix.Tasks.ParentInstallsAllFormats do
+      use Igniter.Mix.Task
+
+      def info(_argv, _parent) do
+        %Igniter.Mix.Task.Info{
+          composes: ["child_installs_all_formats"],
+          installs: [
+            {:boundary, "~> 0.10", runtime: false},
+            {:parent_git_install, git: "https://example.com/parent.git"},
+            {:parent_versioned_install, "~> 1.0"}
+          ]
+        }
+      end
+
+      def igniter(igniter), do: igniter
+    end
+
+    defmodule Elixir.Mix.Tasks.ChildInstallsAllFormats do
+      use Igniter.Mix.Task
+
+      def info(_argv, _parent) do
+        %Igniter.Mix.Task.Info{
+          installs: [
+            {:credo, "~> 1.7", only: [:dev, :test]},
+            {:child_git_install, git: "https://example.com/child.git"},
+            {:child_versioned_install, "~> 2.0"}
+          ]
+        }
+      end
+
+      def igniter(igniter), do: igniter
+    end
+
+    setup do
+      Elixir.Mix.Task.load_all()
+      :ok
+    end
+
+    test "adds_deps merges cleanly across every supported mix dep format" do
+      Igniter.Util.Info.validate!(
+        [],
+        Mix.Tasks.ParentAddsDepsAllFormats.info(nil, nil),
+        "parent_adds_deps_all_formats"
+      )
+    end
+
+    test "installs merges cleanly across every supported mix dep format" do
+      Igniter.Util.Info.validate!(
+        [],
+        Mix.Tasks.ParentInstallsAllFormats.info(nil, nil),
+        "parent_installs_all_formats"
+      )
+    end
+  end
+
   describe "parse_argv/1" do
     defmodule ExampleTaskWithOverriddenParseArgv do
       use Igniter.Mix.Task