RSS teasers: After a lot of iterations, a lot of things are working

... so let's finally geta snapshot.

agaric/templates/field/field--field-body-paragraph--rss-teaser.html.twig

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+{#
+/**
+ * @file
+ * Theme override for a field.
+ *
+ * To override output, copy the "field.html.twig" from the templates directory
+ * to your theme's directory and customize it, just like customizing other
+ * Drupal templates such as page.html.twig or node.html.twig.
+ *
+ * Instead of overriding the theming for all fields, you can also just override
+ * theming for a subset of fields using
+ * @link themeable Theme hook suggestions. @endlink For example,
+ * here are some theme hook suggestions that can be used for a field_foo field
+ * on an article node type:
+ * - field--node--field-foo--article.html.twig
+ * - field--node--field-foo.html.twig
+ * - field--node--article.html.twig
+ * - field--field-foo.html.twig
+ * - field--text-with-summary.html.twig
+ * - field.html.twig
+ *
+ * Available variables:
+ * - attributes: HTML attributes for the containing element.
+ * - label_hidden: Whether to show the field label or not.
+ * - title_attributes: HTML attributes for the title.
+ * - label: The label for the field.
+ * - multiple: TRUE if a field can contain multiple items.
+ * - items: List of all the field items. Each item contains:
+ *   - attributes: List of HTML attributes for each item.
+ *   - content: The field item's content.
+ * - entity_type: The entity type to which the field belongs.
+ * - field_name: The name of the field.
+ * - field_type: The type of the field.
+ * - label_display: The display settings for the label.
+ *
+ * @see template_preprocess_field()
+ */
+#}
+<description>
+{% for item in items %}
+  {{ item.content|render|escape }}
+{% endfor %}
+{# the closing description tag is found in the RSS view template so that we can
+   add a Read more link — we don't have the node information to make it here!
+   See views/views-view-row-rss--taxonomy-term--feed-teasers.html.twig #}

agaric/templates/layout/node--rss-teaser.html.twig

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+{#
+/**
+ * @file
+ * Theme override to display a node.
+ *
+ * Available variables:
+ * - node: The node entity with limited access to object properties and methods.
+ *   Only method names starting with "get", "has", or "is" and a few common
+ *   methods such as "id", "label", and "bundle" are available. For example:
+ *   - node.getCreatedTime() will return the node creation timestamp.
+ *   - node.hasField('field_example') returns TRUE if the node bundle includes
+ *     field_example. (This does not indicate the presence of a value in this
+ *     field.)
+ *   - node.isPublished() will return whether the node is published or not.
+ *   Calling other methods, such as node.delete(), will result in an exception.
+ *   See \Drupal\node\Entity\Node for a full list of public properties and
+ *   methods for the node object.
+ * - label: The title of the node.
+ * - content: All node items. Use {{ content }} to print them all,
+ *   or print a subset such as {{ content.field_example }}. Use
+ *   {{ content|without('field_example') }} to temporarily suppress the printing
+ *   of a given child element.
+ * - author_picture: The node author user entity, rendered using the "compact"
+ *   view mode.
+ * - metadata: Metadata for this node.
+ * - date: Themed creation date field.
+ * - author_name: Themed author name field.
+ * - url: Direct URL of the current node.
+ * - display_submitted: Whether submission information should be displayed.
+ * - attributes: HTML attributes for the containing element.
+ *   The attributes.class element may contain one or more of the following
+ *   classes:
+ *   - node: The current template type (also known as a "theming hook").
+ *   - node--type-[type]: The current node type. For example, if the node is an
+ *     "Article" it would result in "node--type-article". Note that the machine
+ *     name will often be in a short form of the human readable label.
+ *   - node--view-mode-[view_mode]: The View Mode of the node; for example, a
+ *     teaser would result in: "node--view-mode-teaser", and
+ *     full: "node--view-mode-full".
+ *   The following are controlled through the node publishing options.
+ *   - node--promoted: Appears on nodes promoted to the front page.
+ *   - node--sticky: Appears on nodes ordered above other non-sticky nodes in
+ *     teaser listings.
+ *   - node--unpublished: Appears on unpublished nodes visible only to site
+ *     admins.
+ * - title_attributes: Same as attributes, except applied to the main title
+ *   tag that appears in the template.
+ * - content_attributes: Same as attributes, except applied to the main
+ *   content tag that appears in the template.
+ * - author_attributes: Same as attributes, except applied to the author of
+ *   the node tag that appears in the template.
+ * - title_prefix: Additional output populated by modules, intended to be
+ *   displayed in front of the main title tag that appears in the template.
+ * - title_suffix: Additional output populated by modules, intended to be
+ *   displayed after the main title tag that appears in the template.
+ * - view_mode: View mode; for example, "teaser" or "full".
+ * - teaser: Flag for the teaser state. Will be true if view_mode is 'teaser'.
+ * - page: Flag for the full page state. Will be true if view_mode is 'full'.
+ * - readmore: Flag for more state. Will be true if the teaser content of the
+ *   node cannot hold the main body content.
+ * - logged_in: Flag for authenticated user status. Will be true when the
+ *   current user is a logged-in member.
+ * - is_admin: Flag for admin user status. Will be true when the current user
+ *   is an administrator.
+ *
+ * @see template_preprocess_node()
+ *
+ * @todo Remove the id attribute (or make it a class), because if that gets
+ *   rendered twice on a page this is invalid CSS for example: two lists
+ *   in different view modes.
+ */
+#}
+
+BOW!  BOW BEFORE MY POWER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+<a class="teaser media content" href="{{ url }}">
+
+{% set has_title_paragraph = false %}
+{% if content.field_body_paragraph %}
+  {% for i, paragraph in content.field_body_paragraph if i|first != '#' %}
+    {% if content.field_body_paragraph['#items'][i].entity.type.0.entity.id == 'title' %}
+      {% set has_title_paragraph = true %}
+      {{ paragraph }}
+    {% endif %}
+  {% endfor %}
+{% endif %}
+
+{% if not has_title_paragraph %}
+  <div class="media-left">
+    {{ content.field_image }}
+    {% if node.bundle == 'blog' and content.field_authors is not empty %}
+      <p class="byline is-mono">
+        By {{ content.field_authors }}<br />
+        On {{ date }}
+      </p>
+    {% endif %}
+  </div>
+  <div class="media-content content">
+    <h3 class="title is-5">{{ label }}</h3>
+    <div class="subtitle is-6">
+      {{ content.field_summary }}
+    </div>
+  </div>
+{% endif %}
+
+</a>
+<!-- Unexpected extra content -->
+{{ content|without('field_body_paragraph', 'field_authors', 'field_image', 'field_summary', 'uid', 'created') }}

agaric/templates/views/views-view-row-rss--taxonomy-term--feed-teasers.html.twig

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+{#
+/**
+ * @file
+ * Theme override to display an item in a views RSS feed.
+ *
+ * Available variables:
+ * - title: RSS item title.
+ * - link: RSS item link.
+ * - description: RSS body text.
+ * - item_elements: RSS item elements to be rendered as XML (pubDate, creator,
+ *   guid).
+ *
+ * @see template_preprocess_views_view_row_rss()
+ *
+ * web/core/modules/node/src/Plugin/views/row/Rss.php manages to process the
+ * node rendering without a node template being involved, and i'm not exactly
+ * sure how, but we work around it by taking each field we enable in the RSS
+ * Teaser view mode and overriding the field template, so go see various
+ * field--*--rss-teaser.html.twig templates to see inside 'description'.
+ */
+#}
+<item>
+  <title>{{ title }}</title>
+  <link>{{ link }}</link>
+  <guid isPermaLink="true">{{ link }}</guid>
+  <comments>{{ link }}#comments</comments>
+  {# The RSS Teaser view mode *must* be configured to output the body paragraph
+     (summary) LAST; see below for why. #}
+  {{ description|render|raw }}
+    <a href="{{ item.node.url }}">Read more and discuss at agaric.coop.</a>
+    {# Opening description tag is in paragraph template used for description,
+       see field/field--field-body-paragraph--rss-teaser.html.twig and only the
+       closing description tag is here so that we can have the read more link
+       here (the node info isn't available in the paragraph field template, ugh.
+       Also this is horrific and don't try this at home, kids. #}
+    </description>
+</item>

agaric/templates/views/views-view-row-rss.html.twig

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+{#
+/**
+ * @file
+ * Theme override to display an item in a views RSS feed.
+ *
+ * Available variables:
+ * - title: RSS item title.
+ * - link: RSS item link.
+ * - description: RSS body text.
+ * - item_elements: RSS item elements to be rendered as XML (pubDate, creator,
+ *   guid).
+ *
+ * @see template_preprocess_views_view_row_rss()
+ */
+#}
+<item>
+  <title>{{ title }}</title>
+  <link>{{ link }}</link>
+  <description>{{ description }}</description>
+  {% for item in item_elements -%}
+    <{{ item.key }}{{ item.attributes -}}
+    {% if item.value -%}
+      >{{ item.value }}</{{ item.key }}>
+    {% else -%}
+      {{ ' />' }}
+    {% endif %}
+  {%- endfor %}
+</item>