Introduce deprecations scheduled for v1.19

Author: josevalim

CHANGELOG.md

@@ -14,6 +14,23 @@
 
 ### 4. Hard deprecations
 
+#### Elixir
+
+  * [Code] The `on_undefined_variable: :warn` is deprecated. Relying on undefined variables becoming function calls will not be supported in the future
+  * [File] Passing a callback as third argument to `File.cp/3` is deprecated, pass it as a `on_conflict: callback` option instead
+  * [File] Passing a callback as third argument to `File.cp_r/3` is deprecated, pass it as a `on_conflict: callback` option instead
+  * [Kernel] Using `size(var)` in bitstrings requires the pin operator on the variable if the variable was defined outside of the current pattern
+  * [Kernel.ParallelCompiler] Passing `return_diagnostics: true` as an option is required on `compile`, `compile_to_path` and `require`
+
+#### Logger
+
+  * [Logger] The `:backends` configuration is deprecated, either set the `:default_handler` to false or start backends in your application start callback
+
+#### Mix
+
+  * [mix] The `:default_task`, `:preferred_cli_env`, and `:preferred_cli_target` configuration inside `def project` in your `mix.exs` has been deprecated in favor of `:default_task`, `:preferred_envs` and `:preferred_targets` inside the `def cli` function
+  * [mix do] Using commas as task separator in `mix do` (such as `mix do foo, bar`) is deprecated, use `+` instead (as in `mix do foo + bar`)
+
 ## v1.18
 
 The CHANGELOG for v1.18 releases can be found [in the v1.18 branch](https://github.com/elixir-lang/elixir/blob/v1.18/CHANGELOG.md).

lib/elixir/lib/code.ex

@@ -1747,6 +1747,17 @@ defmodule Code do
   # TODO: Remove this option on Elixir v2.0
   # TODO: Warn if mode is :warn on Elixir v1.19
   def put_compiler_option(:on_undefined_variable, value) when value in [:raise, :warn] do
+    if value == :warn do
+      IO.warn_once(
+        {__MODULE__, :on_undefined_variable},
+        fn ->
+          "setting :on_undefined_variable to :warn is deprecated. " <>
+            "The warning behaviour will be removed in future releases"
+        end,
+        3
+      )
+    end
+
     :elixir_config.put(:on_undefined_variable, value)
     :ok
   end

lib/elixir/lib/config.ex

@@ -131,15 +131,14 @@ defmodule Config do
 
       config :logger,
         level: :warn,
-        backends: [:console]
 
       config :logger,
         level: :info,
         truncate: 1024
 
   will have a final configuration for `:logger` of:
 
-      [level: :info, backends: [:console], truncate: 1024]
+      [level: :info, truncate: 1024]
 
   """
   @doc since: "1.9.0"

lib/elixir/lib/enum.ex

@@ -2430,7 +2430,7 @@ defmodule Enum do
         {:ok, count, fun} when is_function(fun, 3) ->
           fun.(random_count(count), 1, 1)
 
-        # TODO: Remove deprecation on Elixir v1.20.
+        # TODO: Remove me on v2.0
         {:ok, count, fun} when is_function(fun, 2) ->
           IO.warn(
             "#{inspect(Enumerable.impl_for(enumerable))} must return a three arity function on slice/1"
@@ -4584,7 +4584,7 @@ defmodule Enum do
         amount = Kernel.min(amount, count - start) |> amount_with_step(step)
         fun.(start, amount, step)
 
-      # TODO: Remove me on v2.0.
+      # TODO: Remove me on v2.0
       {:ok, count, fun} when is_function(fun, 2) ->
         IO.warn(
           "#{inspect(Enumerable.impl_for(enumerable))} must return a three arity function on slice/1"

lib/elixir/lib/file.ex

@@ -831,6 +831,14 @@ defmodule File do
 
   # TODO: Deprecate me on Elixir v1.19
   def cp(source_file, destination_file, callback) when is_function(callback, 2) do
+    IO.warn_once(
+      {__MODULE__, :cp},
+      fn ->
+        "passing a callback to File.cp/3 is deprecated, pass it as a on_conflict: callback option instead"
+      end,
+      3
+    )
+
     cp(source_file, destination_file, on_conflict: callback)
   end
 
@@ -936,6 +944,14 @@ defmodule File do
 
   # TODO: Deprecate me on Elixir v1.19
   def cp_r(source, destination, callback) when is_function(callback, 2) do
+    IO.warn_once(
+      {__MODULE__, :cp_r},
+      fn ->
+        "passing a callback to File.cp_r/3 is deprecated, pass it as a on_conflict: callback option instead"
+      end,
+      3
+    )
+
     cp_r(source, destination, on_conflict: callback)
   end
 

lib/elixir/lib/kernel/cli.ex

@@ -467,7 +467,7 @@ defmodule Kernel.CLI do
 
     if files != [] do
       wrapper(fn ->
-        case Kernel.ParallelCompiler.require(files) do
+        case Kernel.ParallelCompiler.require(files, return_diagnostics: true) do
           {:ok, _, _} -> :ok
           {:error, _, _} -> exit({:shutdown, 1})
         end
@@ -503,7 +503,11 @@ defmodule Kernel.CLI do
 
           opts =
             verbose_opts ++
-              [profile: config.profile, warnings_as_errors: config.warnings_as_errors]
+              [
+                profile: config.profile,
+                warnings_as_errors: config.warnings_as_errors,
+                return_diagnostics: true
+              ]
 
           case Kernel.ParallelCompiler.compile_to_path(files, output, opts) do
             {:ok, _, _} -> :ok

lib/elixir/lib/kernel/parallel_compiler.ex

@@ -222,7 +222,7 @@ defmodule Kernel.ParallelCompiler do
   end
 
   @doc false
-  # TODO: Deprecate me on Elixir v1.19
+  @deprecated "Use Code.print_diagnostic/2 instead"
   def print_warning({file, location, warning}) do
     :elixir_errors.print_warning(location, file, warning)
   end
@@ -284,10 +284,10 @@ defmodule Kernel.ParallelCompiler do
         Module.ParallelChecker.stop(cache)
       end
 
-    # TODO: Require this to be set from Elixir v1.19
     if Keyword.get(options, :return_diagnostics, false) do
       {status, modules_or_errors, info}
     else
+      IO.warn("you must pass return_diagnostics: true when invoking Kernel.ParallelCompiler")
       to_tuples = &Enum.map(&1, fn diag -> {diag.file, diag.position, diag.message} end)
 
       modules_or_errors =

lib/elixir/pages/references/compatibility-and-deprecations.md

@@ -84,6 +84,18 @@ The first column is the version the feature was hard deprecated. The second colu
 
 Version | Deprecated feature                                  | Replaced by (available since)
 :-------| :-------------------------------------------------- | :---------------------------------------------------------------
+[v1.19] | CLI configuration in `def project` inside `mix.exs` | Moving it to `def cli` (v1.14)
+[v1.19] | Using `,` to separate tasks in `mix do`             | Using `+` (v1.14)
+[v1.19] | Logger's `:backends` configuration                  | Logger's `:default_handler` configuration (v1.15)
+[v1.19] | Passing a callback to `File.cp`/`File.cp_r`         | The `:on_conflict` option (v1.14)
+[v1.18] | `<%#` in EEx                                        | `<%!--` (v1.14) or `<% #` (v1.0)
+[v1.18] | `handle_text/2` callback in EEx                     | `handle_text/3` (v1.14)
+[v1.18] | Returning 2-arity fun from `Enumerable.slice/1`     | Returning 3-arity (v1.14)
+[v1.18] | Ranges with negative steps in `Range.new/2`         | Explicit steps in ranges (v1.11)
+[v1.18] | `Tuple.append/2`                                    | `Tuple.insert_at/3` (v1.0)
+[v1.18] | `mix cmd --app APP`                                 | `mix do --app APP` (v1.14)
+[v1.18] | `List.zip/1`                                        | `Enum.zip/1` (v1.0)
+[v1.18] | `Module.eval_quoted/3`                              | `Code.eval_quoted/3` (v1.0)
 [v1.17] | Single-quoted charlists (`'foo'`)                   | `~c"foo"` (v1.0)
 [v1.17] | `left..right` in patterns and guards                | `left..right//step` (v1.11)
 [v1.17] | `ExUnit.Case.register_test/4`                       | `register_test/6` (v1.10)
@@ -216,4 +228,23 @@ Version | Deprecated feature                                  | Replaced by (ava
 [v1.14]: https://github.com/elixir-lang/elixir/blob/v1.14/CHANGELOG.md#4-hard-deprecations
 [v1.15]: https://github.com/elixir-lang/elixir/blob/v1.15/CHANGELOG.md#4-hard-deprecations
 [v1.16]: https://github.com/elixir-lang/elixir/blob/v1.16/CHANGELOG.md#4-hard-deprecations
-[v1.17]: https://github.com/elixir-lang/elixir/blob/main/CHANGELOG.md#4-hard-deprecations
+[v1.17]: https://github.com/elixir-lang/elixir/blob/v1.17/CHANGELOG.md#4-hard-deprecations
+[v1.18]: https://github.com/elixir-lang/elixir/blob/v1.18/CHANGELOG.md#4-hard-deprecations
+[v1.19]: https://github.com/elixir-lang/elixir/blob/main/CHANGELOG.md#4-hard-deprecations
+
+#### Elixir
+
+  * [Code] The `on_undefined_variable: :warn` is deprecated. Relying on undefined variables becoming function calls will not be supported in the future
+
+  * [Kernel] Using `size(var)` in bitstrings requires the pin operator on the variable if the variable was defined outside of the current pattern
+  * [Kernel.ParallelCompiler] Passing `return_diagnostics: true` as an option is required on `compile`, `compile_to_path` and `require`
+
+#### Logger
+
+  * [Logger] `Logger.enable/1` is deprecated in favor of `Logger.delete_process_level/1`
+  * [Logger] The `:backends` configuration is deprecated, either set the `:default_handler` to false or start backends in your application start callback
+
+#### Mix
+
+  * [mix] The `:default_task`, `:preferred_cli_env`, and `:preferred_cli_target` configuration inside `def project` in your `mix.exs` has been deprecated in favor of `:default_task`, `:preferred_envs` and `:preferred_targets` inside the `def cli` function
+  * [mix do] Using commas as task separator in `mix do` (such as `mix do foo, bar`) is deprecated, use `+` instead (as in `mix do foo + bar`)

lib/elixir/src/elixir_expand.erl

@@ -417,9 +417,8 @@ expand({Name, Meta, Kind}, S, E) when is_atom(Name), is_atom(Kind) ->
                 {ok, CurrentVersion};
 
               is_map_key(Pair, Pre) ->
-                %% TODO: Enable this warning on Elixir v1.19
                 %% TODO: Remove me on Elixir 2.0
-                %% elixir_errors:file_warn(Meta, E, ?MODULE, {unpinned_bitsize_var, Name, Kind}),
+                elixir_errors:file_warn(Meta, E, ?MODULE, {unpinned_bitsize_var, Name, Kind}),
                 {ok, CurrentVersion};
 
               not is_map_key(Pair, Original) ->

lib/elixir/test/elixir/file_test.exs

@@ -431,11 +431,13 @@ defmodule FileTest do
       try do
         assert File.exists?(dest)
 
-        assert File.cp(src, dest, fn src_file, dest_file ->
-                 assert src_file == src
-                 assert dest_file == dest
-                 false
-               end) == :ok
+        assert File.cp(src, dest,
+                 on_conflict: fn src_file, dest_file ->
+                   assert src_file == src
+                   assert dest_file == dest
+                   false
+                 end
+               ) == :ok
 
         assert File.read!(dest) == "hello"
       after
@@ -734,11 +736,13 @@ defmodule FileTest do
       try do
         assert File.exists?(tmp_path("tmp/a/1.txt"))
 
-        File.cp_r(src, dest, fn src_file, dest_file ->
-          assert src_file == fixture_path("cp_r/a/1.txt")
-          assert dest_file == tmp_path("tmp/a/1.txt")
-          false
-        end)
+        File.cp_r(src, dest,
+          on_conflict: fn src_file, dest_file ->
+            assert src_file == fixture_path("cp_r/a/1.txt")
+            assert dest_file == tmp_path("tmp/a/1.txt")
+            false
+          end
+        )
 
         assert File.read!(tmp_path("tmp/a/1.txt")) == "hello"
       after
@@ -790,7 +794,7 @@ defmodule FileTest do
       assert src_mode == dest_mode
 
       # On overwrite
-      File.cp!(src, dest, fn _, _ -> true end)
+      File.cp!(src, dest, on_conflict: fn _, _ -> true end)
       %File.Stat{mode: src_mode} = File.stat!(src)
       %File.Stat{mode: dest_mode} = File.stat!(dest)
       assert src_mode == dest_mode