Handle errors when parsing XML

lib/feed_parser.ex

@@ -23,7 +23,13 @@ defmodule FeedParser do
   """
   @spec parse(data :: String.t(), content_type :: String.t(), parsers :: [module()]) ::
           {:ok, feed :: FeedParser.Feed.t()} | {:error, reason :: String.t()}
-  def parse(data, content_type, parsers \\ @default_parsers) when is_binary(data) do
+  def parse(data, content_type, parsers \\ @default_parsers)
+
+  def parse(nil, _, _) do
+    {:error, "no data"}
+  end
+
+  def parse(data, content_type, parsers) when is_binary(data) do
     parsers
     |> Enum.reduce_while(false, fn parser, acc ->
       case parser.accepts(data, content_type) do

lib/parser/atom.ex

@@ -12,15 +12,22 @@ defmodule FeedParser.Parser.Atom do
   def accepts(data, content_type) do
     case content_type do
       "application/atom+xml" ->
-        {true, XML.parse(data)}
+        case XML.parse(data) do
+          {:error, _} -> false
+          {:ok, doc} -> {true, doc}
+        end
 
       _ when content_type in ["text/xml", "application/xml"] ->
-        doc = XML.parse(data)
+        case XML.parse(data) do
+          {:error, _} ->
+            false
 
-        if XML.xmlElement(doc, :name) == :feed do
-          {true, doc}
-        else
-          false
+          {:ok, doc} ->
+            if XML.xmlElement(doc, :name) == :feed do
+              {true, doc}
+            else
+              false
+            end
         end
 
       _ ->

lib/parser/rss2.ex

@@ -12,15 +12,22 @@ defmodule FeedParser.Parser.RSS2 do
   def accepts(data, content_type) do
     cond do
       content_type in ["application/rss+xml", "text/rss+xml"] ->
-        {true, XML.parse(data)}
+        case XML.parse(data) do
+          {:error, _} -> false
+          {:ok, doc} -> {true, doc}
+        end
 
       content_type in ["text/xml", "application/xml"] ->
-        doc = XML.parse(data)
+        case XML.parse(data) do
+          {:error, _} ->
+            false
 
-        if XML.xmlElement(doc, :name) == :rss do
-          {true, doc}
-        else
-          false
+          {:ok, doc} ->
+            if XML.xmlElement(doc, :name) == :rss do
+              {true, doc}
+            else
+              false
+            end
         end
 
       true ->

lib/xml.ex

@@ -9,12 +9,16 @@ defmodule FeedParser.XML do
   defrecord :xmlAttribute, extract(:xmlAttribute, from_lib: "xmerl/include/xmerl.hrl")
   defrecord :xmlText, extract(:xmlText, from_lib: "xmerl/include/xmerl.hrl")
 
-  @spec parse(data :: String.t()) :: tuple()
+  @spec parse(data :: String.t()) :: {:ok, tuple()} | {:error, String.t()}
   def parse(data) do
     {doc, _} =
-      data
-      |> :binary.bin_to_list()
-      |> :xmerl_scan.string()
+      try do
+        data
+        |> :binary.bin_to_list()
+        |> :xmerl_scan.string()
+      catch
+        :exit, reason -> {:error, "parsing XML failed: #{inspect(reason)}"}
+      end
 
     doc
   end