diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8dc6451f..6478df6c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,13 +3,30 @@
 Improvements:
 - Add autocompletion of struct fields on a binding when we know for sure what type of struct it is. (thanks [Łukasz Samson](https://github.com/lukaszsamson)) [#202](https://github.com/elixir-lsp/elixir-ls/pull/202)
   - For details see the [Code Completion section of the readme](https://github.com/elixir-lsp/elixir-ls/tree/a2a1f38bf0f47e074ec5d50636d669fae03a3d5e#code-completion)
+- Add all core elixir apps to the Dialyzer PLT. (thanks [Eric Entin](https://github.com/ericentin)) [#225](https://github.com/elixir-lsp/elixir-ls/pull/225)
+- Change "did not receive workspace/didChangeConfiguration" log level from warning to info (thanks [Jason Axelson](https://github.com/axelson)) [#222](https://github.com/elixir-lsp/elixir-ls/pull/222)
+- Automatically create a `.gitignore` file inside the `.elixir-ls` dir so that users do not need to manually add it to their gitignore (thanks [Thanabodee Charoenpiriyakij](https://github.com/wingyplus)) [#232](https://github.com/elixir-lsp/elixir-ls/pull/232)
 
 Bug Fixes:
 - Dialyzer: Get beam file for preloaded modules. (thanks [Łukasz Samson](https://github.com/lukaszsamson)) [#218](https://github.com/elixir-lsp/elixir-ls/pull/218)
 - Warn when using the debugger on Elixir 1.10.0-1.10.2. (thanks [Jason Axelson](https://github.com/axelson)) [#221](https://github.com/elixir-lsp/elixir-ls/pull/221)
+- Don't return snippets to clients that don't declare `snippetSupport` for function completions (thanks [Jeffrey Xiao](https://github.com/jeffrey-xiao)) [#223](https://github.com/elixir-lsp/elixir-ls/pull/223)
 
 VSCode:
 - Add basic support for `.html.leex` files for Phoenix LiveView (thanks [oskarkook](https://github.com/oskarkook)) [#82](https://github.com/elixir-lsp/vscode-elixir-ls/pull/82)
+- Add filetype and watcher for `.html.leex` files for Phoenix LiveView (thanks [Byron Hambly](https://github.com/delta1)) [#83](https://github.com/elixir-lsp/vscode-elixir-ls/pull/83)
+
+VSCode potentially breaking changes:
+- Change language id to be lowercase kebab-case in accordance with [VSCode guidelines](https://code.visualstudio.com/docs/languages/identifiers#_new-identifier-guidelines). This also fixes an issue displaying the elixir logo for html.eex files. (thanks [Matt Furden](https://github.com/zolrath)) [#87](https://github.com/elixir-lsp/vscode-elixir-ls/pull/87)
+  - This changes the language id's `EEx`->`eex` and `HTML (EEx)`->`html-eex`
+  - If you have customized your emmet configuration configuration then you need to update it:
+  - Open VSCode and hit `Ctrl+Shift+P` or `Cmd+Shift+P` and type `"Preference: Open Settings (JSON)"`
+  - Add or edit your `emmet.includedLanguages` to include the new Language Id:
+```json
+"emmet.includeLanguages": {
+  "html-eex": "html"
+}
+```
 
 ### v0.3.3: 15 Apr 2020
 
diff --git a/README.md b/README.md
index 2f0b3b52..979b770c 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,7 @@ You may want to install Elixir and Erlang from source, using the [kiex](https://
 | Neovim   | [coc.nvim](https://github.com/neoclide/coc.nvim)                              | Does not support debugger                      |
 | Emacs    | [lsp-mode](https://github.com/emacs-lsp/lsp-mode) |      Supports debugger via [dap-mode](https://github.com/yyoncho/dap-mode) |
 | Emacs    | [eglot](https://github.com/joaotavora/eglot)                                  |                                                |
+| Kate     | [built-in LSP Client plugin](https://kate-editor.org/post/2020/2020-01-01-kate-lsp-client-status/) | Does not support debugger |
 
 Feel free to create and publish your own client packages and add them to this list!
 
diff --git a/apps/elixir_ls_utils/mix.exs b/apps/elixir_ls_utils/mix.exs
index 45d4d7c0..79d14413 100644
--- a/apps/elixir_ls_utils/mix.exs
+++ b/apps/elixir_ls_utils/mix.exs
@@ -26,7 +26,7 @@ defmodule ElixirLS.Utils.Mixfile do
 
   defp deps do
     [
-      {:jason, "~> 1.1"},
+      {:jason, "~> 1.2"},
       {:mix_task_archive_deps, github: "JakeBecker/mix_task_archive_deps"}
     ]
   end
diff --git a/apps/language_server/lib/language_server/build.ex b/apps/language_server/lib/language_server/build.ex
index ae9ebdf3..d7c2dfc2 100644
--- a/apps/language_server/lib/language_server/build.ex
+++ b/apps/language_server/lib/language_server/build.ex
@@ -1,5 +1,5 @@
 defmodule ElixirLS.LanguageServer.Build do
-  alias ElixirLS.LanguageServer.{Server, JsonRpc, SourceFile}
+  alias ElixirLS.LanguageServer.{Server, JsonRpc, SourceFile, Diagnostics}
 
   def build(parent, root_path, opts) do
     if Path.absname(File.cwd!()) != Path.absname(root_path) do
@@ -13,8 +13,7 @@ defmodule ElixirLS.LanguageServer.Build do
               IO.puts("Compiling with Mix env #{Mix.env()}")
 
               prev_deps = cached_deps()
-              # FIXME: Private API
-              Mix.Dep.clear_cached()
+              :ok = Mix.Project.clear_deps_cache()
 
               case reload_project() do
                 {:ok, mixfile_diagnostics} ->
@@ -29,6 +28,7 @@ defmodule ElixirLS.LanguageServer.Build do
                     load_all_modules()
                   end
 
+                  diagnostics = Diagnostics.normalize(diagnostics, root_path)
                   Server.build_finished(parent, {status, mixfile_diagnostics ++ diagnostics})
 
                 {:error, mixfile_diagnostics} ->
diff --git a/apps/language_server/lib/language_server/diagnostics.ex b/apps/language_server/lib/language_server/diagnostics.ex
new file mode 100644
index 00000000..4a10c3be
--- /dev/null
+++ b/apps/language_server/lib/language_server/diagnostics.ex
@@ -0,0 +1,151 @@
+defmodule ElixirLS.LanguageServer.Diagnostics do
+  def normalize(diagnostics, root_path) do
+    for diagnostic <- diagnostics do
+      {type, file, line, description, stacktrace} =
+        extract_message_info(diagnostic.message, root_path)
+
+      diagnostic
+      |> update_message(type, description, stacktrace)
+      |> maybe_update_file(file)
+      |> maybe_update_position(line, stacktrace)
+    end
+  end
+
+  defp extract_message_info(list, root_path) when is_list(list) do
+    list
+    |> Enum.join()
+    |> extract_message_info(root_path)
+  end
+
+  defp extract_message_info(diagnostic_message, root_path) do
+    {reversed_stacktrace, reversed_description} =
+      diagnostic_message
+      |> String.trim_trailing()
+      |> String.split("\n")
+      |> Enum.reverse()
+      |> Enum.split_while(&is_stack?/1)
+
+    message = reversed_description |> Enum.reverse() |> Enum.join("\n") |> String.trim()
+    stacktrace = reversed_stacktrace |> Enum.map(&String.trim/1) |> Enum.reverse()
+
+    {type, message_without_type} = split_type_and_message(message)
+    {file, line, description} = split_file_and_description(message_without_type, root_path)
+
+    {type, file, line, description, stacktrace}
+  end
+
+  defp update_message(diagnostic, type, description, stacktrace) do
+    description =
+      if type do
+        "(#{type}) #{description}"
+      else
+        description
+      end
+
+    message =
+      if stacktrace != [] do
+        stacktrace =
+          stacktrace
+          |> Enum.map(&"  │ #{&1}")
+          |> Enum.join("\n")
+          |> String.trim_trailing()
+
+        description <> "\n\n" <> "Stacktrace:\n" <> stacktrace
+      else
+        description
+      end
+
+    Map.put(diagnostic, :message, message)
+  end
+
+  defp maybe_update_file(diagnostic, path) do
+    if path do
+      Map.put(diagnostic, :file, path)
+    else
+      diagnostic
+    end
+  end
+
+  defp maybe_update_position(diagnostic, line, stacktrace) do
+    cond do
+      line ->
+        %{diagnostic | position: line}
+
+      diagnostic.position ->
+        diagnostic
+
+      true ->
+        line = extract_line_from_stacktrace(diagnostic.file, stacktrace)
+        %{diagnostic | position: line}
+    end
+  end
+
+  defp split_type_and_message(message) do
+    case Regex.run(~r/^\*\* \(([\w\.]+?)?\) (.*)/s, message) do
+      [_, type, rest] ->
+        {type, rest}
+
+      _ ->
+        {nil, message}
+    end
+  end
+
+  defp split_file_and_description(message, root_path) do
+    with [_, file, line, description] <- Regex.run(~r/^(.*?):(\d+): (.*)/s, message),
+         {:ok, path} <- file_path(file, root_path) do
+      {path, String.to_integer(line), description}
+    else
+      _ ->
+        {nil, nil, message}
+    end
+  end
+
+  defp file_path(nil, _root_path) do
+    {:error, :file_not_found}
+  end
+
+  defp file_path(file, root_path) do
+    path = Path.join([root_path, file])
+
+    if File.exists?(path) do
+      {:ok, path}
+    else
+      file_path_in_umbrella(file, root_path)
+    end
+  end
+
+  defp file_path_in_umbrella(file, root_path) do
+    case [root_path, "apps", "*", file] |> Path.join() |> Path.wildcard() do
+      [] ->
+        {:error, :file_not_found}
+
+      [path] ->
+        {:ok, path}
+
+      _ ->
+        {:error, :more_than_one_file_found}
+    end
+  end
+
+  defp is_stack?("    " <> str) do
+    Regex.match?(~r/.*\.(ex|erl):\d+: /, str) ||
+      Regex.match?(~r/.*expanding macro: /, str)
+  end
+
+  defp is_stack?(_) do
+    false
+  end
+
+  defp extract_line_from_stacktrace(file, stacktrace) do
+    Enum.find_value(stacktrace, fn stack_item ->
+      with [_, _, file_relative, line] <-
+             Regex.run(~r/(\(.+?\)\s+)?(.*\.ex):(\d+): /, stack_item),
+           true <- String.ends_with?(file, file_relative) do
+        String.to_integer(line)
+      else
+        _ ->
+          nil
+      end
+    end)
+  end
+end
diff --git a/apps/language_server/lib/language_server/dialyzer.ex b/apps/language_server/lib/language_server/dialyzer.ex
index a70b3fb2..efa31124 100644
--- a/apps/language_server/lib/language_server/dialyzer.ex
+++ b/apps/language_server/lib/language_server/dialyzer.ex
@@ -374,7 +374,7 @@ defmodule ElixirLS.LanguageServer.Dialyzer do
 
         {active_plt, new_mod_deps, raw_warnings} = Analyzer.analyze(active_plt, files_to_analyze)
 
-        mod_deps = Map.merge(mod_deps, new_mod_deps)
+        mod_deps = update_mod_deps(mod_deps, new_mod_deps, removed_modules)
         warnings = add_warnings(warnings, raw_warnings)
 
         md5 =
@@ -382,6 +382,8 @@ defmodule ElixirLS.LanguageServer.Dialyzer do
             {file, hash}
           end
 
+        md5 = remove_files(md5, removed_files)
+
         {active_plt, mod_deps, md5, warnings}
       end)
 
@@ -393,6 +395,17 @@ defmodule ElixirLS.LanguageServer.Dialyzer do
     analysis_finished(parent, :ok, active_plt, mod_deps, md5, warnings, timestamp, build_ref)
   end
 
+  defp update_mod_deps(mod_deps, new_mod_deps, removed_modules) do
+    mod_deps
+    |> Map.merge(new_mod_deps)
+    |> Map.drop(removed_modules)
+    |> Map.new(fn {mod, deps} -> {mod, deps -- removed_modules} end)
+  end
+
+  defp remove_files(md5, removed_files) do
+    Map.drop(md5, removed_files)
+  end
+
   defp add_warnings(warnings, raw_warnings) do
     new_warnings =
       for {_, {file, line, m_or_mfa}, _} = warning <- raw_warnings,
diff --git a/apps/language_server/lib/language_server/dialyzer/manifest.ex b/apps/language_server/lib/language_server/dialyzer/manifest.ex
index ade00796..e4c7daab 100644
--- a/apps/language_server/lib/language_server/dialyzer/manifest.ex
+++ b/apps/language_server/lib/language_server/dialyzer/manifest.ex
@@ -114,6 +114,8 @@ defmodule ElixirLS.LanguageServer.Dialyzer.Manifest do
     Path.join([Mix.Utils.mix_home(), "elixir-ls-#{otp_vsn()}_elixir-#{System.version()}"])
   end
 
+  @elixir_apps [:elixir, :eex, :ex_unit, :iex, :logger, :mix]
+
   defp build_elixir_plt() do
     JsonRpc.show_message(
       :info,
@@ -121,12 +123,14 @@ defmodule ElixirLS.LanguageServer.Dialyzer.Manifest do
     )
 
     files =
-      Path.join([Application.app_dir(:elixir), "**/*.beam"])
-      |> Path.wildcard()
-      |> Enum.map(&pathname_to_module/1)
-      |> expand_references()
-      |> Enum.map(&Utils.get_beam_file/1)
-      |> Enum.filter(&is_list/1)
+      Enum.flat_map(@elixir_apps, fn app ->
+        Path.join([Application.app_dir(app), "**/*.beam"])
+        |> Path.wildcard()
+        |> Enum.map(&pathname_to_module/1)
+        |> expand_references()
+        |> Enum.map(&Utils.get_beam_file/1)
+        |> Enum.filter(&is_list/1)
+      end)
 
     File.mkdir_p!(Path.dirname(elixir_plt_path()))
 
diff --git a/apps/language_server/lib/language_server/providers/completion.ex b/apps/language_server/lib/language_server/providers/completion.ex
index df0a1fc3..e2bdaf17 100644
--- a/apps/language_server/lib/language_server/providers/completion.ex
+++ b/apps/language_server/lib/language_server/providers/completion.ex
@@ -135,7 +135,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
     items =
       ElixirSense.suggestions(text, line + 1, character + 1)
-      |> Enum.map(&from_completion_item(&1, context))
+      |> Enum.map(&from_completion_item(&1, context, options))
       |> Enum.concat(module_attr_snippets(context))
       |> Enum.concat(keyword_completions(context))
 
@@ -151,12 +151,16 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
   ## Helpers
 
-  defp from_completion_item(%{type: :attribute, name: name}, %{
-         prefix: prefix,
-         def_before: nil,
-         capture_before?: false,
-         pipe_before?: false
-       }) do
+  defp from_completion_item(
+         %{type: :attribute, name: name},
+         %{
+           prefix: prefix,
+           def_before: nil,
+           capture_before?: false,
+           pipe_before?: false
+         },
+         _options
+       ) do
     name_only = String.trim_leading(name, "@")
     insert_text = if String.starts_with?(prefix, "@"), do: name_only, else: name
 
@@ -175,11 +179,15 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     end
   end
 
-  defp from_completion_item(%{type: :variable, name: name}, %{
-         def_before: nil,
-         pipe_before?: false,
-         capture_before?: false
-       }) do
+  defp from_completion_item(
+         %{type: :variable, name: name},
+         %{
+           def_before: nil,
+           pipe_before?: false,
+           capture_before?: false
+         },
+         _options
+       ) do
     %__MODULE__{
       label: to_string(name),
       kind: :variable,
@@ -192,7 +200,8 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
   defp from_completion_item(
          %{type: :return, description: description, spec: spec, snippet: snippet},
-         %{def_before: nil, capture_before?: false, pipe_before?: false}
+         %{def_before: nil, capture_before?: false, pipe_before?: false},
+         _options
        ) do
     snippet = Regex.replace(Regex.recompile!(~r/"\$\{(.*)\}\$"/U), snippet, "${\\1}")
 
@@ -212,7 +221,8 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
          %{
            def_before: nil,
            prefix: prefix
-         }
+         },
+         _options
        ) do
     capitalized? = String.first(name) == String.upcase(String.first(name))
 
@@ -252,7 +262,8 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
            origin: origin,
            metadata: metadata
          },
-         context
+         context,
+         options
        ) do
     if (context[:def_before] == :def && String.starts_with?(spec, "@macrocallback")) ||
          (context[:def_before] == :defmacro && String.starts_with?(spec, "@callback")) do
@@ -267,7 +278,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
           end
         end
 
-      full_snippet = "#{def_str}#{snippet(name, args, arity)} do\n\t$0\nend"
+      insert_text = def_snippet(def_str, name, args, arity, options)
       label = "#{def_str}#{function_label(name, args, arity)}"
 
       %__MODULE__{
@@ -275,7 +286,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
         kind: :interface,
         detail: "#{origin} callback",
         documentation: summary,
-        insert_text: full_snippet,
+        insert_text: insert_text,
         priority: 2,
         filter_text: name,
         tags: metadata_to_tags(metadata)
@@ -294,11 +305,12 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
            origin: origin,
            metadata: metadata
          },
-         context
+         context,
+         options
        ) do
     def_str = if(context[:def_before] == nil, do: "def ")
 
-    full_snippet = "#{def_str}#{snippet(name, args, arity)} do\n\t$0\nend"
+    insert_text = def_snippet(def_str, name, args, arity, options)
     label = "#{def_str}#{function_label(name, args, arity)}"
 
     %__MODULE__{
@@ -306,7 +318,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
       kind: :interface,
       detail: "#{origin} protocol function",
       documentation: summary,
-      insert_text: full_snippet,
+      insert_text: insert_text,
       priority: 2,
       filter_text: name,
       tags: metadata_to_tags(metadata)
@@ -315,7 +327,8 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
   defp from_completion_item(
          %{type: :field, subtype: subtype, name: name, origin: origin, call?: call?},
-         _context
+         _context,
+         _options
        ) do
     detail =
       case {subtype, origin} do
@@ -334,7 +347,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     }
   end
 
-  defp from_completion_item(%{type: :param_option} = suggestion, _context) do
+  defp from_completion_item(%{type: :param_option} = suggestion, _context, _options) do
     %{name: name, origin: _origin, doc: doc, type_spec: type_spec, expanded_spec: expanded_spec} =
       suggestion
 
@@ -356,7 +369,11 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     }
   end
 
-  defp from_completion_item(%{type: :type_spec, metadata: metadata} = suggestion, _context) do
+  defp from_completion_item(
+         %{type: :type_spec, metadata: metadata} = suggestion,
+         _context,
+         _options
+       ) do
     %{name: name, arity: arity, origin: _origin, doc: doc, signature: signature, spec: spec} =
       suggestion
 
@@ -387,9 +404,10 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
   defp from_completion_item(
          %{name: name, origin: origin} = item,
-         %{def_before: nil} = context
+         %{def_before: nil} = context,
+         options
        ) do
-    completion = function_completion(item, context)
+    completion = function_completion(item, context, options)
 
     completion =
       if origin == "Kernel" || origin == "Kernel.SpecialForms" do
@@ -405,7 +423,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     end
   end
 
-  defp from_completion_item(_suggestion, _context) do
+  defp from_completion_item(_suggestion, _context, _options) do
     nil
   end
 
@@ -417,30 +435,43 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     end
   end
 
-  defp snippet(name, args, arity, opts \\ []) do
-    if Keyword.get(opts, :capture_before?) && arity <= 1 do
-      Enum.join([name, "/", arity])
+  defp def_snippet(def_str, name, args, arity, opts) do
+    if Keyword.get(opts, :snippets_supported, false) do
+      "#{def_str}#{function_snippet(name, args, arity)} do\n\t$0\nend"
     else
-      args_list =
-        if args && args != "" do
-          split_args(args)
-        else
-          for i <- Enum.slice(0..arity, 1..-1), do: "arg#{i}"
-        end
+      "#{def_str}#{name}"
+    end
+  end
 
-      args_list =
-        if Keyword.get(opts, :pipe_before?) do
-          Enum.slice(args_list, 1..-1)
-        else
-          args_list
-        end
+  defp function_snippet(name, args, arity, opts \\ []) do
+    cond do
+      Keyword.get(opts, :capture_before?) && arity <= 1 ->
+        Enum.join([name, "/", arity])
 
-      tabstops =
-        args_list
-        |> Enum.with_index()
-        |> Enum.map(fn {arg, i} -> "${#{i + 1}:#{arg}}" end)
+      not Keyword.get(opts, :snippets_supported, false) ->
+        name
 
-      Enum.join([name, "(", Enum.join(tabstops, ", "), ")"])
+      true ->
+        args_list =
+          if args && args != "" do
+            split_args(args)
+          else
+            for i <- Enum.slice(0..arity, 1..-1), do: "arg#{i}"
+          end
+
+        args_list =
+          if Keyword.get(opts, :pipe_before?) do
+            Enum.slice(args_list, 1..-1)
+          else
+            args_list
+          end
+
+        tabstops =
+          args_list
+          |> Enum.with_index()
+          |> Enum.map(fn {arg, i} -> "${#{i + 1}:#{arg}}" end)
+
+        Enum.join([name, "(", Enum.join(tabstops, ", "), ")"])
     end
   end
 
@@ -534,7 +565,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     end)
   end
 
-  defp function_completion(info, context) do
+  defp function_completion(info, context, options) do
     %{
       type: type,
       args: args,
@@ -555,7 +586,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
       text_after_cursor: text_after_cursor
     } = context
 
-    {label, snippet} =
+    {label, insert_text} =
       cond do
         match?("sigil_" <> _, name) ->
           "sigil_" <> sigil_name = name
@@ -568,16 +599,19 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
         true ->
           label = function_label(name, args, arity)
 
-          snippet =
-            snippet(
+          insert_text =
+            function_snippet(
               name,
               args,
               arity,
-              pipe_before?: pipe_before?,
-              capture_before?: capture_before?
+              Keyword.merge(
+                options,
+                pipe_before?: pipe_before?,
+                capture_before?: capture_before?
+              )
             )
 
-          {label, snippet}
+          {label, insert_text}
       end
 
     detail =
@@ -597,7 +631,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
       kind: :function,
       detail: detail,
       documentation: summary,
-      insert_text: snippet,
+      insert_text: insert_text,
       priority: 7,
       tags: metadata_to_tags(metadata)
     }
@@ -670,7 +704,7 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
   end
 
   defp snippet?(item) do
-    item.kind == :snippet || String.match?(item.insert_text, ~r/\$\d/)
+    item.kind == :snippet || String.match?(item.insert_text, ~r/\${?\d/)
   end
 
   # As defined by CompletionItemTag in https://microsoft.github.io/language-server-protocol/specifications/specification-current/
diff --git a/apps/language_server/lib/language_server/providers/formatting.ex b/apps/language_server/lib/language_server/providers/formatting.ex
index 4534cf59..43dfa9c7 100644
--- a/apps/language_server/lib/language_server/providers/formatting.ex
+++ b/apps/language_server/lib/language_server/providers/formatting.ex
@@ -79,7 +79,9 @@ defmodule ElixirLS.LanguageServer.Providers.Formatting do
       if char == "\n" do
         {line + 1, 0}
       else
-        {line, col + 1}
+        # LSP contentChanges positions are based on UTF-16 string representation
+        # https://microsoft.github.io/language-server-protocol/specification#textDocuments
+        {line, col + byte_size(:unicode.characters_to_binary(char, :utf8, :utf16)) / 2}
       end
     end)
   end
diff --git a/apps/language_server/lib/language_server/server.ex b/apps/language_server/lib/language_server/server.ex
index 593b8818..734ada13 100644
--- a/apps/language_server/lib/language_server/server.ex
+++ b/apps/language_server/lib/language_server/server.ex
@@ -144,7 +144,9 @@ defmodule ElixirLS.LanguageServer.Server do
     JsonRpc.register_capability_request("workspace/didChangeWatchedFiles", %{
       "watchers" => [
         %{"globPattern" => "**/*.ex"},
-        %{"globPattern" => "**/*.exs"}
+        %{"globPattern" => "**/*.exs"},
+        %{"globPattern" => "**/*.eex"},
+        %{"globPattern" => "**/*.leex"}
       ]
     })
 
@@ -157,7 +159,7 @@ defmodule ElixirLS.LanguageServer.Server do
       case state do
         %{settings: nil} ->
           JsonRpc.show_message(
-            :warning,
+            :info,
             "Did not receive workspace/didChangeConfiguration notification after 5 seconds. " <>
               "Using default settings."
           )
@@ -730,6 +732,7 @@ defmodule ElixirLS.LanguageServer.Server do
       |> set_project_dir(project_dir)
       |> set_dialyzer_enabled(enable_dialyzer)
 
+    state = create_gitignore(state)
     trigger_build(%{state | settings: settings})
   end
 
@@ -796,4 +799,24 @@ defmodule ElixirLS.LanguageServer.Server do
   defp set_project_dir(state, _) do
     state
   end
+
+  defp create_gitignore(%{project_dir: project_dir} = state) do
+    with gitignore_path <- Path.join([project_dir, ".elixir_ls", ".gitignore"]),
+         false <- File.exists?(gitignore_path),
+         :ok <- gitignore_path |> Path.dirname() |> File.mkdir_p(),
+         :ok <- File.write(gitignore_path, "*", [:write]) do
+      state
+    else
+      true ->
+        state
+
+      {:error, err} ->
+        JsonRpc.log_message(
+          :warning,
+          "Cannot create .elixir_ls/.gitignore, cause: #{Atom.to_string(err)}"
+        )
+
+        state
+    end
+  end
 end
diff --git a/apps/language_server/lib/language_server/source_file.ex b/apps/language_server/lib/language_server/source_file.ex
index da2162f4..ace92dea 100644
--- a/apps/language_server/lib/language_server/source_file.ex
+++ b/apps/language_server/lib/language_server/source_file.ex
@@ -83,7 +83,14 @@ defmodule ElixirLS.LanguageServer.SourceFile do
             [[line, ?\n] | acc]
 
           idx == start_line ->
-            [String.slice(line, 0, start_character) | acc]
+            # LSP contentChanges positions are based on UTF-16 string representation
+            # https://microsoft.github.io/language-server-protocol/specification#textDocuments
+            beginning_utf8 =
+              :unicode.characters_to_binary(line, :utf8, :utf16)
+              |> binary_part(0, start_character * 2)
+              |> :unicode.characters_to_binary(:utf16, :utf8)
+
+            [beginning_utf8 | acc]
 
           idx > start_line ->
             acc
@@ -99,7 +106,18 @@ defmodule ElixirLS.LanguageServer.SourceFile do
             acc
 
           idx == end_line ->
-            [[String.slice(line, end_character..-1), ?\n] | acc]
+            # LSP contentChanges positions are based on UTF-16 string representation
+            # https://microsoft.github.io/language-server-protocol/specification#textDocuments
+            ending_utf8 =
+              :unicode.characters_to_binary(line, :utf8, :utf16)
+              |> (&binary_part(
+                    &1,
+                    end_character * 2,
+                    byte_size(&1) - end_character * 2
+                  )).()
+              |> :unicode.characters_to_binary(:utf16, :utf8)
+
+            [[ending_utf8, ?\n] | acc]
 
           idx > end_line ->
             [[line, ?\n] | acc]
diff --git a/apps/language_server/test/diagnostics_test.exs b/apps/language_server/test/diagnostics_test.exs
new file mode 100644
index 00000000..d8aac1c2
--- /dev/null
+++ b/apps/language_server/test/diagnostics_test.exs
@@ -0,0 +1,147 @@
+defmodule ElixirLS.LanguageServer.DiagnosticsTest do
+  alias ElixirLS.LanguageServer.Diagnostics
+  use ExUnit.Case
+
+  describe "normalize/2" do
+    test "extract the stacktrace from the message and format it" do
+      root_path = Path.join(__DIR__, "fixtures/build_errors")
+      file = Path.join(root_path, "lib/has_error.ex")
+      position = 2
+
+      message = """
+      ** (CompileError) some message
+
+          Hint: Some hint
+          (elixir 1.10.1) lib/macro.ex:304: Macro.pipe/3
+          (stdlib 3.7.1) lists.erl:1263: :lists.foldl/3
+          (elixir 1.10.1) expanding macro: Kernel.|>/2
+          expanding macro: SomeModule.sigil_L/2
+          lib/my_app/my_module.ex:10: MyApp.MyModule.render/1
+      """
+
+      [diagnostic | _] =
+        [build_diagnostic(message, file, position)]
+        |> Diagnostics.normalize(root_path)
+
+      assert diagnostic.message == """
+             (CompileError) some message
+
+                 Hint: Some hint
+
+             Stacktrace:
+               │ (elixir 1.10.1) lib/macro.ex:304: Macro.pipe/3
+               │ (stdlib 3.7.1) lists.erl:1263: :lists.foldl/3
+               │ (elixir 1.10.1) expanding macro: Kernel.|>/2
+               │ expanding macro: SomeModule.sigil_L/2
+               │ lib/my_app/my_module.ex:10: MyApp.MyModule.render/1\
+             """
+    end
+
+    test "update file and position if file is present in the message" do
+      root_path = Path.join(__DIR__, "fixtures/build_errors")
+      file = Path.join(root_path, "lib/has_error.ex")
+      position = 2
+
+      message = """
+      ** (CompileError) lib/has_error.ex:3: some message
+          lib/my_app/my_module.ex:10: MyApp.MyModule.render/1
+      """
+
+      [diagnostic | _] =
+        [build_diagnostic(message, file, position)]
+        |> Diagnostics.normalize(root_path)
+
+      assert diagnostic.message == """
+             (CompileError) some message
+
+             Stacktrace:
+               │ lib/my_app/my_module.ex:10: MyApp.MyModule.render/1\
+             """
+
+      assert diagnostic.position == 3
+    end
+
+    test "update file and position if file is present in the message (umbrella)" do
+      root_path = Path.join(__DIR__, "fixtures/umbrella")
+      file = Path.join(root_path, "lib/file_to_be_replaced.ex")
+      position = 3
+
+      message = """
+      ** (CompileError) lib/app2.ex:5: some message
+          (elixir 1.10.1) lib/macro.ex:304: Macro.pipe/3
+          lib/my_app/my_module.ex:10: MyApp.MyModule.render/1
+      """
+
+      [diagnostic | _] =
+        [build_diagnostic(message, file, position)]
+        |> Diagnostics.normalize(root_path)
+
+      assert diagnostic.message =~ "(CompileError) some message"
+      assert diagnostic.file =~ "umbrella/apps/app2/lib/app2.ex"
+      assert diagnostic.position == 5
+    end
+
+    test "don't update file nor position if file in message does not exist" do
+      root_path = Path.join(__DIR__, "fixtures/build_errors_on_external_resource")
+      file = Path.join(root_path, "lib/has_error.ex")
+      position = 2
+
+      message = """
+      ** (CompileError) lib/non_existing.ex:3: some message
+          lib/my_app/my_module.ex:10: MyApp.MyModule.render/1
+      """
+
+      [diagnostic | _] =
+        [build_diagnostic(message, file, position)]
+        |> Diagnostics.normalize(root_path)
+
+      assert diagnostic.message == """
+             (CompileError) lib/non_existing.ex:3: some message
+
+             Stacktrace:
+               │ lib/my_app/my_module.ex:10: MyApp.MyModule.render/1\
+             """
+
+      assert diagnostic.position == 2
+    end
+
+    test "if position is nil, try to retrieve it info from the stacktrace" do
+      root_path = Path.join(__DIR__, "fixtures/build_errors")
+      file = Path.join(root_path, "lib/demo_web/router.ex")
+      position = nil
+
+      message = """
+      ** (FunctionClauseError) no function clause matching in Phoenix.Router.Scope.pipeline/2
+
+      The following arguments were given to Phoenix.Router.Scope.pipeline/2:
+
+          # 1
+          DemoWeb.Router
+
+          # 2
+          "api"
+
+          (phoenix 1.5.1) lib/phoenix/router/scope.ex:66: Phoenix.Router.Scope.pipeline/2
+          lib/demo_web/router.ex:13: (module)
+          (stdlib 3.7.1) erl_eval.erl:680: :erl_eval.do_apply/6
+      """
+
+      [diagnostic | _] =
+        [build_diagnostic(message, file, position)]
+        |> Diagnostics.normalize(root_path)
+
+      assert diagnostic.position == 13
+    end
+
+    defp build_diagnostic(message, file, position) do
+      %Mix.Task.Compiler.Diagnostic{
+        compiler_name: "Elixir",
+        details: nil,
+        file: file,
+        message: message,
+        position: position,
+        severity: :error
+      }
+    end
+  end
+end
diff --git a/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/has_error.ex b/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/has_error.ex
new file mode 100644
index 00000000..fbd93fc9
--- /dev/null
+++ b/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/has_error.ex
@@ -0,0 +1,3 @@
+defmodule ElixirLS.LanguageServer.Fixtures.BuildErrorsOnExternalResource.HasError do
+  EEx.compile_file("lib/template.eex", line: 1)
+end
diff --git a/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/template.eex b/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/template.eex
new file mode 100644
index 00000000..e1b53702
--- /dev/null
+++ b/apps/language_server/test/fixtures/build_errors_on_external_resource/lib/template.eex
@@ -0,0 +1,3 @@
+line 1
+<%= , %>
+line 3
\ No newline at end of file
diff --git a/apps/language_server/test/fixtures/build_errors_on_external_resource/mix.exs b/apps/language_server/test/fixtures/build_errors_on_external_resource/mix.exs
new file mode 100644
index 00000000..4e4d39da
--- /dev/null
+++ b/apps/language_server/test/fixtures/build_errors_on_external_resource/mix.exs
@@ -0,0 +1,11 @@
+defmodule ElixirLS.LanguageServer.Fixtures.BuildErrorsOnExternalResource.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :els_build_errors_test, version: "0.1.0"]
+  end
+
+  def application do
+    []
+  end
+end
diff --git a/apps/language_server/test/providers/completion_test.exs b/apps/language_server/test/providers/completion_test.exs
index 95c8e515..d5172b05 100644
--- a/apps/language_server/test/providers/completion_test.exs
+++ b/apps/language_server/test/providers/completion_test.exs
@@ -87,6 +87,35 @@ defmodule ElixirLS.LanguageServer.Providers.CompletionTest do
     assert length(items) == 0
   end
 
+  test "function with snippets not supported does not have argument placeholders" do
+    text = """
+    defmodule MyModule do
+      def add(a, b), do: a + b
+
+      def dummy_function() do
+        ad
+        # ^
+      end
+    end
+    """
+
+    {line, char} = {4, 6}
+    TestUtils.assert_has_cursor_char(text, line, char)
+
+    {:ok, %{"items" => [item]}} = Completion.completion(text, line, char, @supports)
+    assert item["insertText"] == "add(${1:a}, ${2:b})"
+
+    {:ok, %{"items" => [item]}} =
+      Completion.completion(
+        text,
+        line,
+        char,
+        @supports |> Keyword.put(:snippets_supported, false)
+      )
+
+    assert item["insertText"] == "add"
+  end
+
   test "provides completions for protocol functions" do
     text = """
     defimpl ElixirLS.LanguageServer.Fixtures.ExampleProtocol, for: MyModule do
diff --git a/apps/language_server/test/providers/formatting_test.exs b/apps/language_server/test/providers/formatting_test.exs
index 956efaf1..2e10450b 100644
--- a/apps/language_server/test/providers/formatting_test.exs
+++ b/apps/language_server/test/providers/formatting_test.exs
@@ -67,4 +67,109 @@ defmodule ElixirLS.LanguageServer.Providers.FormattingTest do
     assert {:error, :internal_error, msg} = Formatting.format(source_file, uri, project_dir)
     assert String.contains?(msg, "Unable to format")
   end
+
+  test "Proper utf-16 format: emoji 😀" do
+    uri = "file://project/file.ex"
+
+    text = """
+    IO.puts "😀"
+    """
+
+    source_file = %ElixirLS.LanguageServer.SourceFile{
+      text: text,
+      version: 1,
+      dirty?: true
+    }
+
+    project_dir = "/project"
+
+    assert {:ok, changes} = Formatting.format(source_file, uri, project_dir)
+
+    assert changes == [
+             %{
+               "newText" => ")",
+               "range" => %{
+                 "end" => %{"character" => 12, "line" => 0},
+                 "start" => %{"character" => 12, "line" => 0}
+               }
+             },
+             %{
+               "newText" => "(",
+               "range" => %{
+                 "end" => %{"character" => 8, "line" => 0},
+                 "start" => %{"character" => 7, "line" => 0}
+               }
+             }
+           ]
+  end
+
+  test "Proper utf-16 format: emoji 🏳️‍🌈" do
+    uri = "file://project/file.ex"
+
+    text = """
+    IO.puts "🏳️‍🌈"
+    """
+
+    source_file = %ElixirLS.LanguageServer.SourceFile{
+      text: text,
+      version: 1,
+      dirty?: true
+    }
+
+    project_dir = "/project"
+
+    assert {:ok, changes} = Formatting.format(source_file, uri, project_dir)
+
+    assert changes == [
+             %{
+               "newText" => ")",
+               "range" => %{
+                 "end" => %{"character" => 16, "line" => 0},
+                 "start" => %{"character" => 16, "line" => 0}
+               }
+             },
+             %{
+               "newText" => "(",
+               "range" => %{
+                 "end" => %{"character" => 8, "line" => 0},
+                 "start" => %{"character" => 7, "line" => 0}
+               }
+             }
+           ]
+  end
+
+  test "Proper utf-16 format: zalgo" do
+    uri = "file://project/file.ex"
+
+    text = """
+    IO.puts "ẕ̸͇̞̲͇͕̹̙̄͆̇͂̏̊͒̒̈́́̕͘͠͝à̵̢̛̟̞͚̟͖̻̹̮̘͚̻͍̇͂̂̅́̎̉͗́́̃̒l̴̻̳͉̖̗͖̰̠̗̃̈́̓̓̍̅͝͝͝g̷̢͚̠̜̿̊́̋͗̔ȍ̶̹̙̅̽̌̒͌͋̓̈́͑̏͑͊͛͘ ̸̨͙̦̫̪͓̠̺̫̖͙̫̏͂̒̽́̿̂̊́͂͋͜͠͝͝ṭ̴̜͎̮͉̙͍͔̜̾͋͒̓̏̉̄͘͠͝ͅę̷̡̭̹̰̺̩̠͓͌̃̕͜͝ͅͅx̵̧͍̦͈͍̝͖͙̘͎̥͕̾̾̍̀̿̔̄̑̈͝t̸̛͇̀̕"
+    """
+
+    source_file = %ElixirLS.LanguageServer.SourceFile{
+      text: text,
+      version: 1,
+      dirty?: true
+    }
+
+    project_dir = "/project"
+
+    assert {:ok, changes} = Formatting.format(source_file, uri, project_dir)
+
+    assert changes == [
+             %{
+               "newText" => ")",
+               "range" => %{
+                 "end" => %{"character" => 213, "line" => 0},
+                 "start" => %{"character" => 213, "line" => 0}
+               }
+             },
+             %{
+               "newText" => "(",
+               "range" => %{
+                 "end" => %{"character" => 8, "line" => 0},
+                 "start" => %{"character" => 7, "line" => 0}
+               }
+             }
+           ]
+  end
 end
diff --git a/apps/language_server/test/server_test.exs b/apps/language_server/test/server_test.exs
index b91f96fe..719c78d5 100644
--- a/apps/language_server/test/server_test.exs
+++ b/apps/language_server/test/server_test.exs
@@ -259,7 +259,7 @@ defmodule ElixirLS.LanguageServer.ServerTest do
                        "diagnostics" => [
                          %{
                            "message" =>
-                             "** (CompileError) lib/has_error.ex:4: undefined function does_not_exist" <>
+                             "(CompileError) undefined function does_not_exist" <>
                                _,
                            "range" => %{"end" => %{"line" => 3}, "start" => %{"line" => 3}},
                            "severity" => 1
@@ -269,6 +269,27 @@ defmodule ElixirLS.LanguageServer.ServerTest do
     end)
   end
 
+  test "reports build diagnostics on external resources", %{server: server} do
+    in_fixture(__DIR__, "build_errors_on_external_resource", fn ->
+      error_file = SourceFile.path_to_uri("lib/template.eex")
+
+      initialize(server)
+
+      assert_receive notification("textDocument/publishDiagnostics", %{
+                       "uri" => ^error_file,
+                       "diagnostics" => [
+                         %{
+                           "message" =>
+                             "(SyntaxError) syntax error before: ','" <>
+                               _,
+                           "range" => %{"end" => %{"line" => 1}, "start" => %{"line" => 1}},
+                           "severity" => 1
+                         }
+                       ]
+                     })
+    end)
+  end
+
   test "reports error if no mixfile", %{server: server} do
     in_fixture(__DIR__, "no_mixfile", fn ->
       mixfile_uri = SourceFile.path_to_uri("mix.exs")
diff --git a/mix.lock b/mix.lock
index 9af1d9e4..1745dd85 100644
--- a/mix.lock
+++ b/mix.lock
@@ -6,7 +6,7 @@
   "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "forms": {:hex, :forms, "0.0.1", "45f3b10b6f859f95f2c2c1a1de244d63855296d55ed8e93eb0dd116b3e86c4a6", [:rebar3], [], "hexpm", "530f63ed8ed5a171f744fc75bd69cb2e36496899d19dbef48101b4636b795868"},
   "getopt": {:hex, :getopt, "1.0.1", "c73a9fa687b217f2ff79f68a3b637711bb1936e712b521d8ce466b29cbf7808a", [:rebar3], [], "hexpm", "53e1ab83b9ceb65c9672d3e7a35b8092e9bdc9b3ee80721471a161c10c59959c"},
-  "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fdf843bca858203ae1de16da2ee206f53416bbda5dc8c9e78f43243de4bc3afe"},
+  "jason": {:hex, :jason, "1.2.1", "12b22825e22f468c02eb3e4b9985f3d0cb8dc40b9bd704730efa11abd2708c44", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "b659b8571deedf60f79c5a608e15414085fa141344e2716fbd6988a084b5f993"},
   "mix_task_archive_deps": {:git, "https://github.com/JakeBecker/mix_task_archive_deps.git", "50301a4314e3cc1104f77a8208d5b66ee382970b", []},
   "providers": {:hex, :providers, "1.8.1", "70b4197869514344a8a60e2b2a4ef41ca03def43cfb1712ecf076a0f3c62f083", [:rebar3], [{:getopt, "1.0.1", [hex: :getopt, repo: "hexpm", optional: false]}], "hexpm", "e45745ade9c476a9a469ea0840e418ab19360dc44f01a233304e118a44486ba0"},
 }