Add --warnings-as-errors flag for non-zero exit code

.gitignore

@@ -24,6 +24,8 @@ ex_doc-*.tar
 
 node_modules/
 /test/fixtures/umbrella/_build/
+/test/fixtures/single/_build/
+/test/fixtures/single/doc/
 /test/tmp/
 /tmp/
 /npm-debug.log

lib/ex_doc/cli.ex

@@ -35,14 +35,37 @@ defmodule ExDoc.CLI do
           quiet: :boolean,
           source_ref: :string,
           source_url: :string,
-          version: :boolean
+          version: :boolean,
+          warnings_as_errors: :boolean
         ]
       )
 
     if List.keymember?(opts, :version, 0) do
       IO.puts("ExDoc v#{ExDoc.version()}")
     else
-      generate(args, opts, generator)
+      results = generate(args, opts, generator)
+      error_results = Enum.filter(results, &(elem(&1, 0) == :error))
+
+      if error_results == [] do
+        Enum.map(results, fn {:ok, value} -> value end)
+      else
+        formatters = Enum.map(error_results, &elem(&1, 1).formatter)
+
+        format_message =
+          case formatters do
+            [formatter] -> "#{formatter} format"
+            _ -> "#{Enum.join(formatters, ", ")} formats"
+          end
+
+        message =
+          "Documents have been generated, but generation for #{format_message} failed due to warnings while using the --warnings-as-errors option."
+
+        message_formatted = IO.ANSI.format([:red, message, :reset])
+
+        IO.puts(:stderr, message_formatted)
+
+        exit({:shutdown, 1})
+      end
     end
   end
 
@@ -71,7 +94,11 @@ defmodule ExDoc.CLI do
       quiet? ||
         IO.puts(IO.ANSI.format([:green, "View #{inspect(formatter)} docs at #{inspect(index)}"]))
 
-      index
+      if opts[:warnings_as_errors] == true and ExDoc.Utils.warned?() do
+        {:error, %{reason: :warnings_as_errors, formatter: formatter}}
+      else
+        {:ok, index}
+      end
     end
   end
 
@@ -164,29 +191,30 @@ defmodule ExDoc.CLI do
       ex_doc "Project" "1.0.0" "_build/dev/lib/project/ebin" -c "docs.exs"
 
     Options:
-      PROJECT             Project name
-      VERSION             Version number
-      BEAMS               Path to compiled beam files
-          --canonical     Indicate the preferred URL with rel="canonical" link element
-      -c, --config        Give configuration through a file instead of a command line.
-                          See "Custom config" section below for more information.
-      -f, --formatter     Docs formatter to use (html or epub), default: html and epub
-          --homepage-url  URL to link to for the site name
-          --language      Identify the primary language of the documents, its value must be
-                          a valid [BCP 47](https://tools.ietf.org/html/bcp47) language tag, default: "en"
-      -l, --logo          Path to a logo image for the project. Must be PNG, JPEG or SVG. The image will
-                          be placed in the output "assets" directory.
-      -m, --main          The entry-point page in docs, default: "api-reference"
-      -o, --output        Path to output docs, default: "doc"
-          --package       Hex package name
-          --paths         Prepends the given path to Erlang code path. The path might contain a glob
-                          pattern but in that case, remember to quote it: --paths "_build/dev/lib/*/ebin".
-                          This option can be given multiple times
-          --proglang      The project's programming language, default: "elixir"
-      -q, --quiet         Only output warnings and errors
-          --source-ref    Branch/commit/tag used for source link inference, default: "master"
-      -u, --source-url    URL to the source code
-      -v, --version       Print ExDoc version
+      PROJECT                   Project name
+      VERSION                   Version number
+      BEAMS                     Path to compiled beam files
+          --canonical           Indicate the preferred URL with rel="canonical" link element
+      -c, --config              Give configuration through a file instead of a command line.
+                                See "Custom config" section below for more information.
+      -f, --formatter           Docs formatter to use (html or epub), default: html and epub
+          --homepage-url        URL to link to for the site name
+          --language            Identify the primary language of the documents, its value must be
+                                a valid [BCP 47](https://tools.ietf.org/html/bcp47) language tag, default: "en"
+      -l, --logo                Path to a logo image for the project. Must be PNG, JPEG or SVG. The image will
+                                be placed in the output "assets" directory.
+      -m, --main                The entry-point page in docs, default: "api-reference"
+      -o, --output              Path to output docs, default: "doc"
+          --package             Hex package name
+          --paths               Prepends the given path to Erlang code path. The path might contain a glob
+                                pattern but in that case, remember to quote it: --paths "_build/dev/lib/*/ebin".
+                                This option can be given multiple times.
+          --proglang            The project's programming language, default: "elixir".
+      -q, --quiet               Only output warnings and errors.
+          --source-ref          Branch/commit/tag used for source link inference, default: "master".
+      -u, --source-url          URL to the source code.
+      -v, --version             Print ExDoc version.
+          --warnings-as-errors  Exit with non-zero status if doc generation produces warnings.
 
     ## Custom config
 

lib/ex_doc/config.ex

@@ -49,7 +49,8 @@ defmodule ExDoc.Config do
             source_url: nil,
             source_url_pattern: nil,
             title: nil,
-            version: nil
+            version: nil,
+            warnings_as_errors: false
 
   @type t :: %__MODULE__{
           annotations_for_docs: (map() -> list()),
@@ -88,7 +89,8 @@ defmodule ExDoc.Config do
           source_url: nil | String.t(),
           source_url_pattern: nil | String.t(),
           title: nil | String.t(),
-          version: nil | String.t()
+          version: nil | String.t(),
+          warnings_as_errors: boolean()
         }
 
   @spec build(String.t(), String.t(), Keyword.t()) :: ExDoc.Config.t()

lib/ex_doc/formatter/epub.ex

@@ -5,12 +5,15 @@ defmodule ExDoc.Formatter.EPUB do
   @assets_dir "OEBPS/assets"
   alias __MODULE__.{Assets, Templates}
   alias ExDoc.Formatter.HTML
+  alias ExDoc.Utils
 
   @doc """
-  Generate EPUB documentation for the given modules.
+  Generates EPUB documentation for the given modules.
   """
   @spec run([ExDoc.ModuleNode.t()], [ExDoc.ModuleNode.t()], ExDoc.Config.t()) :: String.t()
   def run(project_nodes, filtered_modules, config) when is_map(config) do
+    Utils.unset_warned()
+
     config = normalize_config(config)
     File.rm_rf!(config.output)
     File.mkdir_p!(Path.join(config.output, "OEBPS"))
@@ -66,7 +69,7 @@ defmodule ExDoc.Formatter.EPUB do
         html = Templates.extra_template(config, title, title_content, content)
 
         if File.regular?(output) do
-          ExDoc.Utils.warn("file #{Path.relative_to_cwd(output)} already exists", [])
+          Utils.warn("file #{Path.relative_to_cwd(output)} already exists", [])
         end
 
         File.write!(output, html)

lib/ex_doc/formatter/html.ex

@@ -8,10 +8,12 @@ defmodule ExDoc.Formatter.HTML do
   @assets_dir "assets"
 
   @doc """
-  Generate HTML documentation for the given modules.
+  Generates HTML documentation for the given modules.
   """
   @spec run([ExDoc.ModuleNode.t()], [ExDoc.ModuleNode.t()], ExDoc.Config.t()) :: String.t()
   def run(project_nodes, filtered_modules, config) when is_map(config) do
+    Utils.unset_warned()
+
     config = normalize_config(config)
     config = %{config | output: Path.expand(config.output)}
 
@@ -528,7 +530,7 @@ defmodule ExDoc.Formatter.HTML do
 
   defp generate_redirect(filename, config, redirect_to) do
     unless case_sensitive_file_regular?("#{config.output}/#{redirect_to}") do
-      ExDoc.Utils.warn("#{filename} redirects to #{redirect_to}, which does not exist", [])
+      Utils.warn("#{filename} redirects to #{redirect_to}, which does not exist", [])
     end
 
     content = Templates.redirect_template(config, redirect_to)

lib/ex_doc/utils.ex

@@ -1,19 +1,49 @@
 defmodule ExDoc.Utils do
   @moduledoc false
 
+  @elixir_gte_1_14? Version.match?(System.version(), ">= 1.14.0")
+
   @doc """
   Emits a warning.
   """
-  if Version.match?(System.version(), ">= 1.14.0") do
-    def warn(message, stacktrace_info) do
+  def warn(message, stacktrace_info) do
+    set_warned()
+
+    # TODO: remove check when we require Elixir v1.14
+    if @elixir_gte_1_14? do
       IO.warn(message, stacktrace_info)
-    end
-  else
-    def warn(message, _stacktrace_info) do
+    else
       IO.warn(message, [])
     end
   end
 
+  @doc """
+  Stores that a warning has been generated.
+  """
+  def set_warned() do
+    unless warned?() do
+      :persistent_term.put({__MODULE__, :warned?}, true)
+    end
+
+    true
+  end
+
+  @doc """
+  Removes that a warning has been generated.
+  """
+  def unset_warned() do
+    if warned?() do
+      :persistent_term.put({__MODULE__, :warned?}, false)
+    end
+  end
+
+  @doc """
+  Returns `true` if any warning has been generated during the document building. Otherwise returns `false`.
+  """
+  def warned?() do
+    :persistent_term.get({__MODULE__, :warned?}, false)
+  end
+
   @doc """
   Runs the `before_closing_head_tag` callback.
   """

lib/mix/tasks/docs.ex

@@ -27,6 +27,8 @@ defmodule Mix.Tasks.Docs do
     * `--proglang` - Chooses the main programming language: `elixir`
       or `erlang`
 
+    * `--warnings-as-errors` - Exits with non-zero exit code if any warnings are found
+
   The command line options have higher precedence than the options
   specified in your `mix.exs` file below.
 
@@ -325,7 +327,8 @@ defmodule Mix.Tasks.Docs do
     language: :string,
     open: :boolean,
     output: :string,
-    proglang: :string
+    proglang: :string,
+    warnings_as_errors: :boolean
   ]
 
   @aliases [
@@ -383,17 +386,52 @@ defmodule Mix.Tasks.Docs do
       |> normalize_formatters()
       |> put_package(config)
 
+    Code.prepend_path(options[:source_beam])
+
+    for path <- Keyword.get_values(options, :paths),
+        path <- Path.wildcard(path) do
+      Code.prepend_path(path)
+    end
+
     Mix.shell().info("Generating docs...")
 
-    for formatter <- options[:formatters] do
-      index = generator.(project, version, Keyword.put(options, :formatter, formatter))
-      Mix.shell().info([:green, "View #{inspect(formatter)} docs at #{inspect(index)}"])
+    results =
+      for formatter <- options[:formatters] do
+        index = generator.(project, version, Keyword.put(options, :formatter, formatter))
+        Mix.shell().info([:green, "View #{inspect(formatter)} docs at #{inspect(index)}"])
 
-      if cli_opts[:open] do
-        browser_open(index)
+        if cli_opts[:open] do
+          browser_open(index)
+        end
+
+        if options[:warnings_as_errors] == true and ExDoc.Utils.warned?() do
+          {:error, %{reason: :warnings_as_errors, formatter: formatter}}
+        else
+          {:ok, index}
+        end
       end
 
-      index
+    error_results = Enum.filter(results, &(elem(&1, 0) == :error))
+
+    if error_results == [] do
+      Enum.map(results, fn {:ok, value} -> value end)
+    else
+      formatters = Enum.map(error_results, &elem(&1, 1).formatter)
+
+      format_message =
+        case formatters do
+          [formatter] -> "#{formatter} format"
+          _ -> "#{Enum.join(formatters, ", ")} formats"
+        end
+
+      message =
+        "Documents have been generated, but generation for #{format_message} failed due to warnings while using the --warnings-as-errors option."
+
+      message_formatted = IO.ANSI.format([:red, message, :reset])
+
+      IO.puts(:stderr, message_formatted)
+
+      exit({:shutdown, 1})
     end
   end
 

test/ex_doc/formatter/epub_test.exs

@@ -1,5 +1,9 @@
 defmodule ExDoc.Formatter.EPUBTest do
-  use ExUnit.Case, async: true
+  use ExUnit.Case, async: false
+
+  import ExUnit.CaptureIO
+
+  alias ExDoc.Utils
 
   @moduletag :tmp_dir
 
@@ -237,4 +241,47 @@ defmodule ExDoc.Formatter.EPUBTest do
   after
     File.rm_rf!("test/tmp/epub_assets")
   end
+
+  describe "warnings" do
+    @describetag :warnings
+
+    test "multiple warnings are registered when using warnings_as_errors: true", context do
+      Utils.unset_warned()
+
+      output =
+        capture_io(:stderr, fn ->
+          generate_docs(
+            doc_config(context,
+              skip_undefined_reference_warnings_on: [],
+              warnings_as_errors: true
+            )
+          )
+        end)
+
+      # TODO: remove check when we require Elixir v1.16
+      if Version.match?(System.version(), ">= 1.16.0-rc") do
+        assert output =~ ~S|moduledoc `Warnings.bar/0`|
+        assert output =~ ~S|typedoc `Warnings.bar/0`|
+        assert output =~ ~S|doc callback `Warnings.bar/0`|
+        assert output =~ ~S|doc `Warnings.bar/0`|
+      end
+
+      assert Utils.warned?() == true
+    end
+
+    test "warnings are registered even with warnings_as_errors: false", context do
+      Utils.unset_warned()
+
+      capture_io(:stderr, fn ->
+        generate_docs(
+          doc_config(context,
+            skip_undefined_reference_warnings_on: [],
+            warnings_as_errors: false
+          )
+        )
+      end)
+
+      assert Utils.warned?() == true
+    end
+  end
 end