Resources fixes and improvements

- Fix getting page description
- Fix fetching metadata from Twitter (thx @marienfressinaud)
- Improve error handling

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/views/Resources/ResourceFolder.vue

@@ -190,6 +190,9 @@
     <b-modal :active.sync="createLinkResourceModal" has-modal-card>
       <div class="modal-card">
         <section class="modal-card-body">
+          <b-message type="is-danger" v-if="modalError">
+            {{ modalError }}
+          </b-message>
           <form @submit.prevent="createResource">
             <b-field :label="$t('URL')">
               <b-input
@@ -317,6 +320,8 @@ export default class Resources extends Mixins(ResourceMixin) {
 
   renameModal = false;
 
+  modalError = "";
+
   groupObject: Record<string, unknown> = {
     name: "resources",
     pull: "clone",
@@ -341,6 +346,7 @@ export default class Resources extends Mixins(ResourceMixin) {
 
   async createResource(): Promise<void> {
     if (!this.resource.actor) return;
+    this.modalError = "";
     try {
       await this.$apollo.mutate({
         mutation: CREATE_RESOURCE,
@@ -364,10 +370,13 @@ export default class Resources extends Mixins(ResourceMixin) {
       this.newResource.resourceUrl = "";
     } catch (err) {
       console.error(err);
+      this.modalError = err.graphQLErrors[0].message;
     }
   }
 
   async previewResource(): Promise<void> {
+    this.modalError = "";
+    try {
       if (this.newResource.resourceUrl === "") return;
       const { data } = await this.$apollo.mutate({
         mutation: PREVIEW_RESOURCE_LINK,
@@ -379,6 +388,10 @@ export default class Resources extends Mixins(ResourceMixin) {
       this.newResource.summary = data.previewResourceLink.description;
       this.newResource.metadata = data.previewResourceLink;
       this.newResource.type = "link";
+    } catch (err) {
+      console.error(err);
+      this.modalError = err.graphQLErrors[0].message;
+    }
   }
 
   createSentenceForType(type: string): string {

lib/graphql/resolvers/resource.ex

@@ -118,6 +118,9 @@ defmodule Mobilizon.GraphQL.Resolvers.Resource do
            ) do
       {:ok, resource}
     else
+      {:error, _} ->
+        {:error, dgettext("errors", "Error while creating resource")}
+
       {:own_check, _} ->
         {:error, dgettext("errors", "Parent resource doesn't belong to this group")}
 
@@ -201,8 +204,12 @@ defmodule Mobilizon.GraphQL.Resolvers.Resource do
       {:ok, data} when is_map(data) ->
         {:ok, struct(Metadata, data)}
 
-      {:error, _err} ->
+      {:error, :invalid_parsed_data} ->
+        {:error, dgettext("errors", "Unable to fetch resource details from this URL.")}
+
+      {:error, err} ->
         Logger.warn("Error while fetching preview from #{inspect(resource_url)}")
+        Logger.debug(inspect(err))
         {:error, :unknown_resource}
     end
   end

lib/service/rich_media/parser.ex

@@ -57,7 +57,7 @@ defmodule Mobilizon.Service.RichMedia.Parser do
 
   @spec parse_url(String.t(), Enum.t()) :: {:ok, map()} | {:error, any()}
   defp parse_url(url, options \\ []) do
-    user_agent = Keyword.get(options, :user_agent, Config.instance_user_agent())
+    user_agent = Keyword.get(options, :user_agent, default_user_agent(url))
     headers = [{"User-Agent", user_agent}]
     Logger.debug("Fetching content at address #{inspect(url)}")
 
@@ -212,7 +212,8 @@ defmodule Mobilizon.Service.RichMedia.Parser do
   end
 
   defp check_parsed_data(data) do
-    {:error, "Found metadata was invalid or incomplete: #{inspect(data)}"}
+    Logger.debug("Found metadata was invalid or incomplete: #{inspect(data)}")
+    {:error, :invalid_parsed_data}
   end
 
   defp clean_parsed_data(data) do
@@ -293,4 +294,17 @@ defmodule Mobilizon.Service.RichMedia.Parser do
   end
 
   defp check_remote_picture_path(data), do: data
+
+  # Twitter requires a well-know crawler user-agent to show server-rendered data
+  defp default_user_agent("https://twitter.com/" <> _) do
+    "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
+  end
+
+  defp default_user_agent("https://mobile.twitter.com/" <> _) do
+    "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
+  end
+
+  defp default_user_agent(_url) do
+    Config.instance_user_agent()
+  end
 end

lib/service/rich_media/parsers/meta_tags_parser.ex

@@ -70,8 +70,14 @@ defmodule Mobilizon.Service.RichMedia.Parsers.MetaTagsParser do
 
   defp maybe_put_description(meta, html) when meta != %{} do
     case get_page_description(html) do
-      "" -> meta
+      "" ->
-      description -> Map.put_new(meta, :description, description)
+        meta
+
+      descriptions when is_list(descriptions) and length(descriptions) > 0 ->
+        Map.put_new(meta, :description, hd(descriptions))
+
+      description ->
+        Map.put_new(meta, :description, description)
     end
   end