improvement: support non-literal/non-standard deps lists

lib/igniter/code/common.ex

@@ -24,6 +24,14 @@ defmodule Igniter.Code.Common do
     end
   end
 
+  @doc "Returns true if the node represents a variable assignment"
+  @spec variable_assignment?(zipper :: Zipper.t(), name :: atom) :: boolean()
+  def variable_assignment?(%{node: {:=, _, [{name, _, ctx}, _]}}, name) when is_atom(ctx) do
+    true
+  end
+
+  def variable_assignment?(_, _), do: false
+
   @doc """
   Moves to the last node that matches the predicate.
 

lib/igniter/project/deps.ex

@@ -23,11 +23,26 @@ defmodule Igniter.Project.Deps do
         add_dependency(igniter, name, version, opts)
 
       {name, version, version_opts} ->
-        if Keyword.keyword?(version) do
-          add_dependency(igniter, name, version ++ version_opts, opts)
-        else
-          add_dependency(igniter, name, version, Keyword.put(opts, :dep_opts, version_opts))
-        end
+        new_igniter =
+          if Keyword.keyword?(version) do
+            add_dependency(igniter, name, version ++ version_opts, opts)
+          else
+            add_dependency(igniter, name, version, Keyword.put(opts, :dep_opts, version_opts))
+          end
+
+        new_igniter =
+          if Enum.count(igniter.issues) != Enum.count(new_igniter.issues) ||
+               Enum.count(igniter.warnings) != Enum.count(new_igniter.warnings) do
+            Igniter.assign(
+              new_igniter,
+              :failed_to_add_deps,
+              [name | igniter.assigns[:failed_to_add_deps] || []]
+            )
+          else
+            new_igniter
+          end
+
+        new_igniter
 
       other ->
         raise ArgumentError, "Invalid dependency: #{inspect(other)}"
@@ -197,73 +212,123 @@ defmodule Igniter.Project.Deps do
   end
 
   defp do_add_dependency(igniter, name, version, opts) do
+    error_tag =
+      if opts[:error?] do
+        :error
+      else
+        :warning
+      end
+
+    quoted =
+      if opts[:dep_opts] do
+        quote do
+          {unquote(name), unquote(version), unquote(opts[:dep_opts])}
+        end
+      else
+        {:__block__, [],
+         [
+           {{:__block__, [], [name]}, {:__block__, [], [version]}}
+         ]}
+      end
+
     igniter
     |> Igniter.update_elixir_file("mix.exs", fn zipper ->
       with {:ok, zipper} <- Igniter.Code.Module.move_to_module_using(zipper, Mix.Project),
-           {:ok, zipper} <- Igniter.Code.Function.move_to_defp(zipper, :deps, 0),
-           true <- Igniter.Code.List.list?(zipper) do
-        match =
-          Igniter.Code.List.move_to_list_item(zipper, fn zipper ->
-            if Igniter.Code.Tuple.tuple?(zipper) do
-              case Igniter.Code.Tuple.tuple_elem(zipper, 0) do
-                {:ok, first_elem} ->
-                  Common.nodes_equal?(first_elem, name)
-
-                :error ->
-                  false
-              end
+           {:ok, zipper} <- Igniter.Code.Function.move_to_defp(zipper, :deps, 0) do
+        case igniter.assigns[:igniter_exs][:deps_location] || :last_list_literal do
+          {m, f, a} ->
+            with {:ok, zipper} <- apply(m, f, [a] ++ [igniter, zipper]) do
+              add_to_deps_list(zipper, name, quoted, opts)
+            else
+              _ ->
+                {error_tag,
+                 """
+                 Could not add dependency #{inspect({name, version})}
+
+                 #{inspect(m)}.#{f}/#{Enum.count(a) + 2} did not find a deps location
+
+                 Please add the dependency manually.
+                 """}
             end
-          end)
 
-        quoted =
-          if opts[:dep_opts] do
-            quote do
-              {unquote(name), unquote(version), unquote(opts[:dep_opts])}
+          {:variable, name} ->
+            with {:ok, zipper} <-
+                   Igniter.Code.Common.move_to(
+                     zipper,
+                     &Igniter.Code.Common.variable_assignment?(&1, name)
+                   ),
+                 {:ok, zipper} <- Igniter.Code.Function.move_to_nth_argument(zipper, 1),
+                 true <- Igniter.Code.List.list?(zipper) do
+              add_to_deps_list(zipper, name, quoted, opts)
+            else
+              _ ->
+                {error_tag,
+                 """
+                 Could not add dependency #{inspect({name, version})}
+
+                 `deps/0` does not contain an assignment of the `#{name}` variable to a literal list
+
+                 Please add the dependency manually.
+                 """}
             end
-          else
-            {:__block__, [],
-             [
-               {{:__block__, [], [name]}, {:__block__, [], [version]}}
-             ]}
-          end
 
-        case match do
-          {:ok, zipper} ->
-            Igniter.Code.Common.replace_code(zipper, quoted)
+          :last_list_literal ->
+            zipper = Zipper.rightmost(zipper)
 
-          _ ->
-            if Keyword.get(opts, :append?, false) do
-              Igniter.Code.List.append_to_list(zipper, quoted)
+            if Igniter.Code.List.list?(zipper) do
+              add_to_deps_list(zipper, name, quoted, opts)
             else
-              Igniter.Code.List.prepend_to_list(zipper, quoted)
+              {error_tag,
+               """
+               Could not add dependency #{inspect({name, version})}
+
+               `deps/0` does not end in a list literal that can be added to.
+
+               Please add the dependency manually.
+               """}
             end
         end
       else
         _ ->
-          if opts[:error?] do
-            {:error,
-             """
-             Could not add dependency #{inspect({name, version})}
-
-             `mix.exs` file does not contain a simple list of dependencies in a `deps/0` function.
-             Please add it manually and run the installer again.
-             """}
-          else
-            {:warning,
-             [
-               """
-               Could not add dependency #{inspect({name, version})}
+          {error_tag,
+           """
+           Could not add dependency #{inspect({name, version})}
 
-               `mix.exs` file does not contain a simple list of dependencies in a `deps/0` function.
+           `mix.exs` file does not contain a `deps/0` function.
 
-               Please add it manually.
-               """
-             ]}
-          end
+           Please add the dependency manually.
+           """}
       end
     end)
   end
 
+  defp add_to_deps_list(zipper, name, quoted, opts) do
+    match =
+      Igniter.Code.List.move_to_list_item(zipper, fn zipper ->
+        if Igniter.Code.Tuple.tuple?(zipper) do
+          case Igniter.Code.Tuple.tuple_elem(zipper, 0) do
+            {:ok, first_elem} ->
+              Common.nodes_equal?(first_elem, name)
+
+            :error ->
+              false
+          end
+        end
+      end)
+
+    case match do
+      {:ok, zipper} ->
+        Igniter.Code.Common.replace_code(zipper, quoted)
+
+      _ ->
+        if Keyword.get(opts, :append?, false) do
+          Igniter.Code.List.append_to_list(zipper, quoted)
+        else
+          Igniter.Code.List.prepend_to_list(zipper, quoted)
+        end
+    end
+  end
+
   @doc false
   def determine_dep_type_and_version(requirement) do
     case String.split(requirement, "@", trim: true, parts: 2) do

lib/igniter/project/igniter_config.ex

@@ -20,6 +20,18 @@ defmodule Igniter.Project.IgniterConfig do
       default: [],
       doc: "A list of extensions to use in the project."
     ],
+    deps_location: [
+      type: {:or, [:last_list_literal, {:tagged_tuple, :variable, :atom}, :mfa]},
+      default: :last_list_literal,
+      doc: """
+      The strategy for finding the `deps` list to add new dependencies to, in your `deps/0` function in `mix.exs`
+
+      - `:last_list_literal` expects your deps function to return a literal list which will be prepended to
+      - `{:variable, :name}` expects to find an assignment from the given variable to a list literal, i.e `deps = [...]`, and prepends to that
+      - `:mfa` will call the given mfa with the igniter and the zipper within the `deps/0` function. It should return `{:ok, zipper}`
+         at the position where the dep should be prepended, or :error if the location could not be found.
+      """
+    ],
     source_folders: [
       type: {:list, :string},
       default: ["lib", "test/support"],
@@ -114,6 +126,33 @@ defmodule Igniter.Project.IgniterConfig do
     end)
   end
 
+  def configure(igniter, key, value) do
+    value =
+      value
+      |> Macro.escape()
+      |> Sourceror.to_string()
+      |> Sourceror.parse_string!()
+
+    igniter
+    |> setup()
+    |> Igniter.update_elixir_file(".igniter.exs", fn zipper ->
+      rightmost = Igniter.Code.Common.rightmost(zipper)
+
+      if Igniter.Code.List.list?(rightmost) do
+        Igniter.Code.Keyword.set_keyword_key(
+          zipper,
+          key,
+          [value],
+          fn zipper ->
+            {:ok, Igniter.Code.Common.replace_code(zipper, value)}
+          end
+        )
+      else
+        {:warning, "Failed to modify `.igniter.exs` when configuring #{inspect(key)}"}
+      end
+    end)
+  end
+
   def dont_move_file_pattern(igniter, pattern) do
     quoted =
       case pattern do

lib/igniter/util/info.ex

@@ -168,10 +168,15 @@ defmodule Igniter.Util.Info do
 
   defp add_deps(igniter, add_deps, opts) do
     Enum.reduce(add_deps, igniter, fn dependency, igniter ->
-      with {_, _, dep_opts} <- dependency,
+      with {name, _, dep_opts} <- dependency,
            only when not is_nil(only) <- dep_opts[:only],
            false <- Mix.env() in only do
-        Igniter.add_warning(igniter, """
+        igniter
+        |> Igniter.assign(
+          :failed_to_add_deps,
+          [name | igniter.assigns[:failed_to_add_deps] || []]
+        )
+        |> Igniter.add_warning("""
         Dependency #{inspect(dependency)} could not be installed,
         because it is configured to be installed with `only: #{inspect(only)}`.
 

lib/igniter/util/install.ex

@@ -99,6 +99,23 @@ defmodule Igniter.Util.Install do
         append?: Keyword.get(opts, :append?, false)
       )
 
+    if igniter.assigns[:failed_to_add_deps] do
+      Mix.shell().error("""
+      Failed to add dependencies to the `mix.exs` file.
+
+      Igniter may not be able to find where to modify your `deps/0` function.
+      To address this, modify your `.igniter.exs` file's `deps_location` option.
+
+      If you don't yet have a `.igniter.exs`, run `mix igniter.setup`.
+
+      For more information, see: 
+
+      https://hexdocs.pm/igniter/Igniter.Project.IgniterConfig.html
+      """)
+
+      exit({:shutdown, 1})
+    end
+
     installing_names = Enum.join(installing, ", ")
 
     igniter =