4 files changed, 94 insertions, 43 deletions

diff --git a/lib/elixir/lib/code.ex b/lib/elixir/lib/code.ex
index f92da34e5..c5c5b63d2 100644
--- a/lib/elixir/lib/code.ex
+++ b/lib/elixir/lib/code.ex
@@ -194,6 +194,21 @@ defmodule Code do
   """
   @type binding :: [{atom() | tuple(), any}]
 
+  @typedoc """
+  Diagnostics returned by the compiler and code evaluation.
+  """
+  @type diagnostic(severity) :: %{
+          file: Path.t(),
+          severity: severity,
+          message: String.t(),
+          position: position,
+          stacktrace: Exception.stacktrace()
+        }
+
+  @typedoc "The line. 0 indicates no line."
+  @type line() :: non_neg_integer()
+  @type position() :: line() | {pos_integer(), column :: non_neg_integer}
+
   @boolean_compiler_options [
     :docs,
     :debug_info,
@@ -533,6 +548,51 @@ defmodule Code do
     end)
   end
 
+  @doc """
+  Executes the given `fun` and capture all diagnostics.
+
+  Diagnostics are warnings and errors emitted by the compiler
+  and by functions such as `IO.warn/2`.
+
+  ## Options
+
+    * `:log` - if the diagnostics should be logged as they happen.
+      Defaults to `false`.
+
+  """
+  @spec with_diagnostics(keyword(), (-> result)) :: {result, [diagnostic(:warning | :error)]}
+        when result: term()
+  def with_diagnostics(opts \\ [], fun) do
+    value = :erlang.get(:elixir_code_diagnostics)
+    log = Keyword.get(opts, :log, false)
+    :erlang.put(:elixir_code_diagnostics, {[], log})
+
+    try do
+      result = fun.()
+      {diagnostics, _log?} = :erlang.get(:elixir_code_diagnostics)
+      {result, Enum.reverse(diagnostics)}
+    after
+      if value == :undefined do
+        :erlang.erase(:elixir_code_diagnostics)
+      else
+        :erlang.put(:elixir_code_diagnostics, value)
+      end
+    end
+  end
+
+  @doc """
+  Prints a diagnostic into the standard error.
+
+  A diagnostic is either returned by `Kernel.ParallelCompiler`
+  or by `Code.with_diagnostics/2`.
+  """
+  @doc since: "1.15.0"
+  @spec print_diagnostic(diagnostic(:warning | :error)) :: :ok
+  def print_diagnostic(diagnostic) do
+    :elixir_errors.print_diagnostic(diagnostic)
+    :ok
+  end
+
   @doc ~S"""
   Formats the given code `string`.
 
@@ -876,7 +936,7 @@ defmodule Code do
         warn_on_unnecessary_quotes: false,
         literal_encoder: &{:ok, {:__block__, &2, [&1]}},
         token_metadata: true,
-        emit_warnings: false
+        warnings: false
       ] ++ opts
 
     {forms, comments} = string_to_quoted_with_comments!(string, to_quoted_opts)
@@ -1688,7 +1748,7 @@ defmodule Code do
 
   ## Examples
 
-      iex> Code.ensure_loaded?(Atom)
+      iex> Code.ensure_loaded?(String)
       true
 
   """
diff --git a/lib/elixir/lib/code/fragment.ex b/lib/elixir/lib/code/fragment.ex
index 222694fd8..ed30dd3a4 100644
--- a/lib/elixir/lib/code/fragment.ex
+++ b/lib/elixir/lib/code/fragment.ex
@@ -1054,6 +1054,6 @@ defmodule Code.Fragment do
     opts =
       Keyword.take(opts, [:file, :line, :column, :columns, :token_metadata, :literal_encoder])
 
-    Code.string_to_quoted(fragment, [cursor_completion: true, emit_warnings: false] ++ opts)
+    Code.string_to_quoted(fragment, [cursor_completion: true, warnings: false] ++ opts)
   end
 end
diff --git a/lib/elixir/lib/kernel/parallel_compiler.ex b/lib/elixir/lib/kernel/parallel_compiler.ex
index fc9a512d1..a8491220c 100644
--- a/lib/elixir/lib/kernel/parallel_compiler.ex
+++ b/lib/elixir/lib/kernel/parallel_compiler.ex
@@ -3,26 +3,14 @@ defmodule Kernel.ParallelCompiler do
   A module responsible for compiling and requiring files in parallel.
   """
 
-  @typedoc "The line. 0 indicates no line."
-  @type line() :: non_neg_integer()
-  @type position() :: line() | {pos_integer(), column :: non_neg_integer}
-
-  @type diagnostic(severity) :: %{
-          file: Path.t(),
-          severity: severity,
-          message: String.t(),
-          position: position,
-          stacktrace: Exception.stacktrace()
-        }
-
   @type info :: %{
-          runtime_warnings: [diagnostic(:warning)],
-          compile_warnings: [diagnostic(:warning)]
+          runtime_warnings: [Code.diagnostic(:warning)],
+          compile_warnings: [Code.diagnostic(:warning)]
         }
 
   # Deprecated types
-  @type warning() :: {file :: Path.t(), position(), message :: String.t()}
-  @type error() :: {file :: Path.t(), position(), message :: String.t()}
+  @type warning() :: {file :: Path.t(), Code.position(), message :: String.t()}
+  @type error() :: {file :: Path.t(), Code.position(), message :: String.t()}
 
   @doc """
   Starts a task for parallel compilation.
@@ -71,7 +59,7 @@ defmodule Kernel.ParallelCompiler do
   resolved.
 
   It returns `{:ok, modules, warnings}` or `{:error, errors, warnings}`
-  by default but we recommend using `return_maps: true` so it returns
+  by default but we recommend using `return_diagnostics: true` so it returns
   diagnostics as maps as well as a map of compilation information.
   The map has the shape of:
 
@@ -115,14 +103,14 @@ defmodule Kernel.ParallelCompiler do
 
     * `:beam_timestamp` - the modification timestamp to give all BEAM files
 
-    * `:return_maps` (since v1.15.0) - returns maps with information instead of
+    * `:return_diagnostics` (since v1.15.0) - returns maps with information instead of
       a list of warnings and returns diagnostics as maps instead of tuples
 
   """
   @doc since: "1.6.0"
   @spec compile([Path.t()], keyword()) ::
           {:ok, [atom], [warning] | info()}
-          | {:error, [error] | [diagnostic(:error)], [warning] | info()}
+          | {:error, [error] | [Code.diagnostic(:error)], [warning] | info()}
   def compile(files, options \\ []) when is_list(options) do
     spawn_workers(files, :compile, options)
   end
@@ -135,7 +123,7 @@ defmodule Kernel.ParallelCompiler do
   @doc since: "1.6.0"
   @spec compile_to_path([Path.t()], Path.t(), keyword()) ::
           {:ok, [atom], [warning] | info()}
-          | {:error, [error] | [diagnostic(:error)], [warning] | info()}
+          | {:error, [error] | [Code.diagnostic(:error)], [warning] | info()}
   def compile_to_path(files, path, options \\ []) when is_binary(path) and is_list(options) do
     spawn_workers(files, {:compile, path}, options)
   end
@@ -147,7 +135,7 @@ defmodule Kernel.ParallelCompiler do
   automatically solved between files.
 
   It returns `{:ok, modules, warnings}` or `{:error, errors, warnings}`
-  by default but we recommend using `return_maps: true` so it returns
+  by default but we recommend using `return_diagnostics: true` so it returns
   diagnostics as maps as well as a map of compilation information.
   The map has the shape of:
 
@@ -172,14 +160,6 @@ defmodule Kernel.ParallelCompiler do
     spawn_workers(files, :require, options)
   end
 
-  @doc """
-  Prints a diagnostic returned by the compiler into stderr.
-  """
-  @doc since: "1.15.0"
-  def print_diagnostic(diagnostic) do
-    :elixir_errors.print_diagnostic(diagnostic)
-  end
-
   @doc false
   # TODO: Deprecate me on Elixir v1.19
   def print_warning({file, location, warning}) do
@@ -239,7 +219,7 @@ defmodule Kernel.ParallelCompiler do
       end
 
     # TODO: Require this to be set from Elixir v1.19
-    if Keyword.get(options, :return_maps, false) do
+    if Keyword.get(options, :return_diagnostics, false) do
       {status, modules_or_errors, info}
     else
       to_tuples = &Enum.map(&1, fn diag -> {diag.file, diag.position, diag.message} end)
diff --git a/lib/elixir/lib/module/parallel_checker.ex b/lib/elixir/lib/module/parallel_checker.ex
index 20f146931..f5e93a25f 100644
--- a/lib/elixir/lib/module/parallel_checker.ex
+++ b/lib/elixir/lib/module/parallel_checker.ex
@@ -48,7 +48,7 @@ defmodule Module.ParallelChecker do
   @doc """
   Spawns a process that runs the parallel checker.
   """
-  def spawn({pid, checker}, module, info) do
+  def spawn({pid, checker}, module, info, log?) do
     ref = make_ref()
 
     spawned =
@@ -79,7 +79,7 @@ defmodule Module.ParallelChecker do
 
                 warnings =
                   if module_map do
-                    check_module(module_map, {checker, ets})
+                    check_module(module_map, {checker, ets}, log?)
                   else
                     []
                   end
@@ -143,12 +143,23 @@ defmodule Module.ParallelChecker do
   """
   @spec verify(pid(), [{module(), Path.t()}]) :: [warning()]
   def verify(checker, runtime_files) do
+    value = :erlang.get(:elixir_code_diagnostics)
+    log? = not match?({_, false}, value)
+
     for {module, file} <- runtime_files do
-      spawn({self(), checker}, module, file)
+      spawn({self(), checker}, module, file, log?)
     end
 
     count = :gen_server.call(checker, :start, :infinity)
-    collect_results(count, [])
+    diagnostics = collect_results(count, [])
+
+    case :erlang.get(:elixir_code_diagnostics) do
+      :undefined -> :ok
+      {tail, true} -> :erlang.put(:elixir_code_diagnostics, {diagnostics ++ tail, true})
+      {tail, false} -> :erlang.put(:elixir_code_diagnostics, {diagnostics ++ tail, false})
+    end
+
+    diagnostics
   end
 
   defp collect_results(0, diagnostics) do
@@ -221,7 +232,7 @@ defmodule Module.ParallelChecker do
 
   ## Module checking
 
-  defp check_module(module_map, cache) do
+  defp check_module(module_map, cache, log?) do
     %{
       module: module,
       file: file,
@@ -252,7 +263,7 @@ defmodule Module.ParallelChecker do
       |> Module.Types.warnings(file, definitions, no_warn_undefined, cache)
       |> Kernel.++(behaviour_warnings)
       |> group_warnings()
-      |> emit_warnings()
+      |> emit_warnings(log?)
 
     module_map
     |> Map.get(:after_verify, [])
@@ -278,7 +289,7 @@ defmodule Module.ParallelChecker do
 
   ## Warning helpers
 
-  def group_warnings(warnings) do
+  defp group_warnings(warnings) do
     warnings
     |> Enum.reduce(%{}, fn {module, warning, location}, acc ->
       locations = MapSet.new([location])
@@ -288,11 +299,11 @@ defmodule Module.ParallelChecker do
     |> Enum.sort()
   end
 
-  def emit_warnings(warnings) do
+  defp emit_warnings(warnings, log?) do
     Enum.flat_map(warnings, fn {module, warning, locations} ->
       message = module.format_warning(warning)
       diagnostics = Enum.map(locations, &to_diagnostic(message, &1))
-      :elixir_errors.print_warning([message, ?\n, format_stacktraces(diagnostics)])
+      log? and :elixir_errors.print_warning([message, ?\n, format_stacktraces(diagnostics)])
       diagnostics
     end)
   end
@@ -317,7 +328,7 @@ defmodule Module.ParallelChecker do
       severity: :warning,
       file: file,
       position: line,
-      message: message,
+      message: IO.iodata_to_binary(message),
       stacktrace: [to_stacktrace(file, line, mfa)]
     }
   end