fix(completions): log source code when env fails to build (#404)

Closes #403

Author: mhanberg

lib/next_ls.ex

@@ -577,18 +577,36 @@ defmodule NextLS do
   def handle_request(%TextDocumentCompletion{params: %{text_document: %{uri: uri}, position: position}}, lsp) do
     document = lsp.assigns.documents[uri]
 
-    env =
+    spliced =
       document
       |> List.update_at(position.line, fn row ->
         {front, back} = String.split_at(row, position.character)
         String.slice(front, -1..1) <> "__cursor__()" <> back
       end)
       |> Enum.join("\n")
+
+    env =
+      spliced
       |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
       |> then(fn
         {:ok, ast} -> ast
         {:error, ast, _} -> ast
       end)
+      |> NextLS.ASTHelpers.find_cursor()
+      |> then(fn
+        {:ok, cursor} ->
+          cursor
+
+        {:error, :not_found} ->
+          NextLS.Logger.warning(lsp.assigns.logger, "Could not locate cursor when building environment")
+
+          NextLS.Logger.warning(
+            lsp.assigns.logger,
+            "Source code that produced the above warning: #{spliced}"
+          )
+
+          nil
+      end)
       |> NextLS.ASTHelpers.Env.build()
 
     document_slice =

lib/next_ls/helpers/ast_helpers.ex

@@ -1,5 +1,6 @@
 defmodule NextLS.ASTHelpers do
   @moduledoc false
+  alias Sourceror.Zipper
 
   defmodule Attributes do
     @moduledoc false
@@ -152,4 +153,18 @@ defmodule NextLS.ASTHelpers do
       end
     end)
   end
+
+  def find_cursor(ast) do
+    with nil <-
+           ast
+           |> Zipper.zip()
+           |> Zipper.find(fn
+             {:__cursor__, _, []} -> true
+             _ -> false
+           end) do
+      {:error, :not_found}
+    else
+      zipper -> {:ok, zipper}
+    end
+  end
 end

lib/next_ls/helpers/ast_helpers/env.ex

@@ -6,15 +6,11 @@ defmodule NextLS.ASTHelpers.Env do
     Sourceror.compare_positions(range.start, position) == :lt && Sourceror.compare_positions(range.end, position) == :gt
   end
 
-  def build(ast) do
-    cursor =
-      ast
-      |> Zipper.zip()
-      |> Zipper.find(fn
-        {:__cursor__, _, _} -> true
-        _ -> false
-      end)
+  def build(nil) do
+    %{variables: []}
+  end
 
+  def build(cursor) do
     position = cursor |> Zipper.node() |> Sourceror.get_range() |> Map.get(:start)
     zipper = Zipper.prev(cursor)
 
@@ -75,7 +71,8 @@ defmodule NextLS.ASTHelpers.Env do
               acc
             end
 
-          {def, _, [{_, _, args} | _]} when def in [:def, :defp, :defmacro, :defmacrop] and args != [] and is_inside ->
+          {def, _, [{_, _, args} | _]}
+          when def in [:def, :defp, :defmacro, :defmacrop] and args != [] and is_inside ->
             {_, vars} =
               Macro.prewalk(args, [], fn node, acc ->
                 case node do

test/next_ls/helpers/ast_helpers/env_test.exs

@@ -19,14 +19,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["foo", "bar"]
     end
@@ -46,14 +39,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["two", "one"]
     end
@@ -76,14 +62,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["baz", "bar", "foo"]
     end
@@ -106,14 +85,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["three", "two", "one"]
     end
@@ -133,14 +105,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["foo", "bar"]
     end
@@ -161,14 +126,7 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["baz", "bar", "big_bar"]
     end
@@ -194,16 +152,22 @@ defmodule NextLS.ASTHelpers.EnvTest do
       end
       """
 
-      actual =
-        code
-        |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
-        |> then(fn
-          {:ok, ast} -> ast
-          {:error, ast, _} -> ast
-        end)
-        |> NextLS.ASTHelpers.Env.build()
+      actual = run(code)
 
       assert actual.variables == ["entries"]
     end
   end
+
+  defp run(code) do
+    {:ok, zip} =
+      code
+      |> Spitfire.parse(literal_encoder: &{:ok, {:__literal__, &2, [&1]}})
+      |> then(fn
+        {:ok, ast} -> ast
+        {:error, ast, _} -> ast
+      end)
+      |> NextLS.ASTHelpers.find_cursor()
+
+    NextLS.ASTHelpers.Env.build(zip)
+  end
 end