Fixes: #403;

RELEASE.md

@@ -8,16 +8,18 @@
 
 - fixing picture links in README.eex
 
+- [403-warn-if-illegal-keyword-options-are-provided](https://github.com/robertdober/earmark_parser/issues/403)
+
 - [401-option-to-disable-html-escapes](https://github.com/robertdober/earmark_parser/pull/401-to-disable-html-escapes)
     Kudos to [paradox460](https://github.com/paradox460)
 
-- [397-typo fix](https://github.com/robertdober/earmark_parser/pull/397)
-    Kudos to [rubysolo](https://github.com/rubysolo)  
-
+- [398-walk-ast-helper-and-ast-postprocessing-option](https://github.com/robertdober/earmark_parser/issues/398)
 
+- [397-typo fix](https://github.com/robertdober/earmark_parser/pull/397)
+    Kudos to [rubysolo](https://github.com/rubysolo)
 
 # 1.4.13   2020-12-03
- 
+
 - A minor fix for the compact output option , Noo Issue, OMG ;)
 
 # 1.4.12   2020-11-27
@@ -27,10 +29,10 @@ Adapted the CLI to accept the wikilinks switch for `EarmarkParser`
 # 1.4.11   2020-11-26
 
 - [394-compact-html-output](https://github.com/robertdober/earmark_parser/pull/394)
-    Kudos and Спасибо to [rinpatch](https://github.com/rinpatch)  
+    Kudos and Спасибо to [rinpatch](https://github.com/rinpatch)
 
 - [387-treat-del-tag-as-compact-tag](https://github.com/pragdave/earmark/pull/387)
-    Kudos to [Médi-Rémi Hashim](https://github.com/mediremi)  
+    Kudos to [Médi-Rémi Hashim](https://github.com/mediremi)
 
 - [383-smartyants-inside-code-blocks](https://github.com/robertdober/earmark_parser/issues/-)
     Kudos to [David Bernheisel](https://github.com/dbernheisel)

lib/earmark.ex

@@ -186,7 +186,10 @@ defmodule Earmark do
   def as_html(lines, options \\ %Options{})
 
   def as_html(lines, options) when is_list(options) do
-    as_html(lines, struct(Options, options))
+    case  Options.make_options(options) do
+      {:ok, options1} -> as_html(lines, options1)
+      {:error, messages} -> {:error, "", messages}
+    end
   end
 
   def as_html(lines, options) do
@@ -225,12 +228,7 @@ defmodule Earmark do
   Otherwise it behaves exactly as `as_html`.
   """
   def as_html!(lines, options \\ %Options{})
-
-  def as_html!(lines, options) when is_list(options) do
-    as_html!(lines, struct(Options, options))
-  end
-
-  def as_html!(lines, options = %Options{}) do
+  def as_html!(lines, options) do
     {_status, html, messages} = as_html(lines, options)
     emit_messages(messages, options)
     html

lib/earmark/message.ex

@@ -37,6 +37,10 @@ defmodule Earmark.Message do
     messages
     |> Enum.each(&emit_message(file, &1))
   end
+  def emit_messages(messages, _) do
+    messages
+    |> Enum.each(&emit_message("<args>", &1))
+  end
 
   @doc """
   For final output

lib/earmark/options.ex

@@ -65,10 +65,43 @@ defmodule Earmark.Options do
     end
   end
 
+  @doc false
+  def make_options(options) do
+    legal_keys =
+      __MODULE__
+      |> struct()
+      |> Map.keys
+      |> MapSet.new
+
+    given_keys =
+      options
+      |> Keyword.keys
+      |> MapSet.new
+
+    violators =
+      MapSet.difference(given_keys, legal_keys)
+
+    if MapSet.size(violators) == 0 do
+      {:ok, struct(__MODULE__, options)}
+    else
+      {:error, _format_errors(violators, options)}
+    end
+  end
+
   @doc false
   def plugin_for_prefix(options, plugin_name) do
     Map.get(options.plugins, plugin_name, false)
   end
+
+  defp _format_error(violator, options) do
+    {:warning, 0, "Unrecognized option #{violator}: #{Keyword.get(options, violator) |> inspect()} ignored"}
+  end
+
+  defp _format_errors(violators, options) do
+    violators
+    |> Enum.map(&_format_error(&1, options))
+  end
+
 end
 
 # SPDX-License-Identifier: Apache-2.0

test/acceptance/html/illegal_options_test.exs

@@ -0,0 +1,30 @@
+defmodule Test.Acceptance.Html.IllegalOptionsTest do
+  use ExUnit.Case
+
+  import ExUnit.CaptureIO
+  import Earmark, only: [as_html: 2, as_html!: 2]
+
+  describe "unrecognized options" do
+    test "with empty" do
+      messages = [
+        {:warning, 0, "Unrecognized option no_such_option: true ignored"}
+      ]
+      assert as_html("", no_such_option: true) == {:error, "", messages}
+    end
+    test "with non empty" do
+      messages = [
+        {:warning, 0, "Unrecognized option hello: 42 ignored"},
+        {:warning, 0, "Unrecognized option no_such_option: true ignored"},
+      ]
+      assert as_html("hello", no_such_option: true, hello: 42) == {:error, "", messages}
+    end
+  end
+
+  test "with as_html!" do
+    error_messages =
+      capture_io(:stderr, fn ->
+        as_html!("hello", oops: Earmark) 
+      end)
+    assert error_messages == "<args>:0: warning: Unrecognized option oops: Earmark ignored\n"
+  end 
+end