Suggest a module name for defmodule completion (#338)

* Suggest module name for defmodule

The defmodule completion snippet now does a best-effort attempt to
guess the module name.

The guessing takes into account lib, test and test/support
directories, and if it doesn't detect any of them, just uses the file name.

apps/server/lib/lexical/server/code_intelligence/completion/translations/macro.ex

@@ -1,4 +1,5 @@
 defmodule Lexical.Server.CodeIntelligence.Completion.Translations.Macro do
+  alias Lexical.Document
   alias Lexical.RemoteControl.Completion.Candidate
   alias Lexical.Server.CodeIntelligence.Completion.Env
   alias Lexical.Server.CodeIntelligence.Completion.Translatable
@@ -52,9 +53,10 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.Macro do
 
   def translate(%Candidate.Macro{name: "defmodule"} = macro, builder, env) do
     label = "defmodule (Define a module)"
+    suggestion = suggest_module_name(env.document)
 
     snippet = """
-    defmodule ${1:module name} do
+    defmodule ${1:#{suggestion}} do
       $0
     end
     """
@@ -561,4 +563,44 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.Macro do
   def translate(%Candidate.Macro{}, _builder, _env) do
     :skip
   end
+
+  def suggest_module_name(%Document{} = document) do
+    result =
+      document.path
+      |> Path.split()
+      |> Enum.reduce(false, fn
+        "lib", _ ->
+          {:lib, []}
+
+        "test", _ ->
+          {:test, []}
+
+        "support", {:test, _} ->
+          {:lib, []}
+
+        _, false ->
+          false
+
+        element, {type, elements} ->
+          camelized =
+            element
+            |> Path.rootname()
+            |> Macro.camelize()
+
+          {type, [camelized | elements]}
+      end)
+
+    case result do
+      {_, parts} ->
+        parts
+        |> Enum.reverse()
+        |> Enum.join(".")
+
+      false ->
+        document.path
+        |> Path.basename()
+        |> Path.rootname()
+        |> Macro.camelize()
+    end
+  end
 end

apps/server/test/lexical/server/code_intelligence/completion/translations/macro_test.exs

@@ -107,7 +107,7 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.MacroTest do
       assert %Completion.Item{} = completion
     end
 
-    test "defmodule", %{project: project} do
+    test "defmodule for lib paths", %{project: project} do
       assert {:ok, completion} =
                project
                |> complete("defmodule|")
@@ -118,7 +118,58 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.MacroTest do
       assert completion.insert_text_format == :snippet
 
       assert completion.insert_text == """
-             defmodule ${1:module name} do
+             defmodule ${1:File} do
+               $0
+             end
+             """
+    end
+
+    test "defmodule for test paths", %{project: project} do
+      assert {:ok, completion} =
+               project
+               |> complete("defmodule|", path: "test/foo/project/my_test.exs")
+               |> fetch_completion("defmodule ")
+
+      assert completion.detail
+      assert completion.label == "defmodule (Define a module)"
+      assert completion.insert_text_format == :snippet
+
+      assert completion.insert_text == """
+             defmodule ${1:Foo.Project.MyTest} do
+               $0
+             end
+             """
+    end
+
+    test "defmodule for test/support paths", %{project: project} do
+      assert {:ok, completion} =
+               project
+               |> complete("defmodule|", path: "test/support/path/to/file.ex")
+               |> fetch_completion("defmodule ")
+
+      assert completion.detail
+      assert completion.label == "defmodule (Define a module)"
+      assert completion.insert_text_format == :snippet
+
+      assert completion.insert_text == """
+             defmodule ${1:Path.To.File} do
+               $0
+             end
+             """
+    end
+
+    test "defmodule for other paths", %{project: project} do
+      assert {:ok, completion} =
+               project
+               |> complete("defmodule|", path: "/this/is/another/path.ex")
+               |> fetch_completion("defmodule ")
+
+      assert completion.detail
+      assert completion.label == "defmodule (Define a module)"
+      assert completion.insert_text_format == :snippet
+
+      assert completion.insert_text == """
+             defmodule ${1:Path} do
                $0
              end
              """

apps/server/test/lexical/server/code_intelligence/completion/translations/struct_test.exs

@@ -131,7 +131,7 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.StructTest do
     test "when using %, child structs are returned", %{project: project} do
       assert [account, order, order_line, user] =
                project
-               |> complete("%Project.Structs.|", "%")
+               |> complete("%Project.Structs.|", trigger_character: "%")
                |> Enum.sort_by(& &1.label)
 
       assert account.label == "Account"
@@ -150,7 +150,7 @@ defmodule Lexical.Server.CodeIntelligence.Completion.Translations.StructTest do
     test "when using % and child is not a struct, just `more` snippet is returned", %{
       project: project
     } do
-      assert [more] = complete(project, "%Project.|", "%")
+      assert [more] = complete(project, "%Project.|", trigger_character: "%")
       assert more.label == "Structs...(4 more structs)"
       assert more.detail == "Project.Structs."
     end

apps/server/test/support/lexical/test/completion_case.ex

@@ -40,13 +40,27 @@ defmodule Lexical.Test.Server.CompletionCase do
     Document.to_string(edited_document)
   end
 
-  def complete(project, text, trigger_character \\ nil) do
+  def complete(project, text, opts \\ []) do
+    trigger_character = Keyword.get(opts, :trigger_character)
     {line, column} = cursor_position(text)
 
     text = strip_cursor(text)
 
     root_path = Project.root_path(project)
-    file_path = Path.join([root_path, "lib", "file.ex"])
+
+    file_path =
+      case Keyword.fetch(opts, :path) do
+        {:ok, path} ->
+          if Path.expand(path) == path do
+            # it's absolute
+            path
+          else
+            Path.join(root_path, path)
+          end
+
+        :error ->
+          Path.join([root_path, "lib", "file.ex"])
+      end
 
     document =
       file_path
@@ -59,7 +73,7 @@ defmodule Lexical.Test.Server.CompletionCase do
       if is_binary(trigger_character) do
         CompletionContext.new(
           trigger_kind: :trigger_character,
-          trigger_character: trigger_character
+          trigger_character: nil
         )
       else
         CompletionContext.new(trigger_kind: :trigger_character)