Adopt Diataxis

docs/src/_templates/tags_links.need

@@ -0,0 +1,11 @@
+{# Render plain clickable text links for each tag #}
+{% if tags %}
+:strong:`Tags:` {{ " " }} {%- for t in tags -%}
+  {%- if t and t.startswith('topic_') -%}
+    :ref:`{{ t }} <{{ t }}>`
+  {%- else -%}
+    {{ t }}
+  {%- endif -%}
+  {%- if not loop.last %} | {% endif -%}
+{%- endfor %}
+{% endif %}

docs/src/conf.py

@@ -163,6 +163,8 @@ def _dotv(version):
     "sphinx_gallery.gen_gallery",
     "matplotlib.sphinxext.mathmpl",
     "matplotlib.sphinxext.plot_directive",
+    "sphinx_needs",
+    "user_manual_directives",
 ]
 
 if skip_api == "1":
@@ -441,3 +443,57 @@ def reset_modules(gallery_conf, fname):
     "section": "Section %s",
     "table": "Table %s",
 }
+
+# -- sphinx-needs config ------------------------------------------------------
+# See https://sphinx-needs.readthedocs.io/en/latest/configuration.html
+
+# TODO: namespace these types as Diataxis for max clarity?
+needs_types = [
+    {
+        "directive": "tutorial",
+        "title": "Tutorial",
+        "prefix": "",
+        "color": "",
+        "style": "node",
+    },
+    {
+        "directive": "how-to",
+        "title": "How To",
+        "prefix": "",
+        "color": "",
+        "style": "node",
+    },
+    {
+        "directive": "explanation",
+        "title": "Explanation",
+        "prefix": "",
+        "color": "",
+        "style": "node",
+    },
+    {
+        "directive": "reference",
+        "title": "Reference",
+        "prefix": "",
+        "color": "",
+        "style": "node",
+    },
+]
+# The layout whenever a 'need item' directive is used. I.e. at the top of each
+#  user manual page.
+needs_default_layout = "focus"
+# IDs must be used in needtables, as the only way to link to the item. Using
+#  the title makes for the most readable / least jarring links.
+needs_id_from_title = True
+# The `tags_links` jinja template displays a list of tags where every topic_*
+#  tag is a link to the relevant section in user_manual/index.rst.
+needs_template_folder = "_templates"
+needs_global_options = {
+    "post_template": {"default": "tags_links"},
+}
+
+from sphinx_needs.data import NeedsCoreFields
+
+# Known bug in sphinx-needs pre v6.0.
+#  https://github.com/useblocks/sphinx-needs/issues/1420
+if "allow_default" not in NeedsCoreFields["post_template"]:
+    NeedsCoreFields["post_template"]["allow_default"] = "str"

docs/src/further_topics/ux_guide.rst

@@ -3,7 +3,7 @@
 Reviewing the Iris User Experience
 **********************************
 
-.. todo:: https://github.com/SciTools/iris/issues/6511; this page belongs in 'Explanation'
+.. todo:: https://github.com/SciTools/iris/issues/6867; this page belongs in 'Get Involved'
 
 Often, improving and updating the existing user experience can fall behind fixing create new features,
 or quashing pesky bugs. To combat this, we plan to have regular development discussions to ensure

docs/src/index.rst

@@ -45,13 +45,13 @@ For more information see :ref:`why_iris`.
         plotting and more.
 
         +++
-        .. button-ref:: user_guide_index
+        .. button-ref:: user_manual_index
             :ref-type: ref
             :color: primary
             :outline:
             :expand:
 
-                User Guide
+                User Manual
 
     .. grid-item-card::
         :text-align: center
@@ -159,12 +159,12 @@ The legacy support resources:
 
 
 .. toctree::
-   :caption: User Guide
+   :caption: User Manual
    :maxdepth: 1
-   :name: userguide_index
+   :name: user_manual
    :hidden:
 
-   userguide/index
+   user_manual/index
 
 
 .. toctree::
@@ -176,15 +176,6 @@ The legacy support resources:
    developers_guide/contributing_getting_involved
 
 
-.. toctree::
-   :caption: Community
-   :maxdepth: 1
-   :name: community_index
-   :hidden:
-
-   Community <community/index>
-
-
 .. toctree::
    :caption: What's New in Iris
    :maxdepth: 1

docs/src/sphinxext/user_manual_directives.py

@@ -0,0 +1,145 @@
+# Copyright Iris contributors
+#
+# This file is part of Iris and is released under the BSD license.
+# See LICENSE in the root of the repository for full licensing details.
+# TODO: header
+# TODO: docstrings/comments. How to document an extension/directive?
+# TODO: linting
+
+# TODO: include a validation routine, calling to sphinx-needs to confirm that
+#  all User Manual pages have the minimum metadata.
+#  - sphinx-need directive
+#    - :tags: including a topic_xxx tag
+#    - think sphinx-needs will already insist on a valid type?
+#    - think sphinx-needs will already insist on a title?
+#    - think sphinx-needs will already insist on a description?
+#  - as it stands this would exclude all section indexes, unless the section
+#    indexes get their own Diataxis tab.
+
+from pathlib import Path
+import enum
+import re
+
+from docutils import nodes  # type: ignore[import-untyped]
+from docutils.parsers.rst import Directive  # type: ignore[import-untyped]
+from docutils.statemachine import StringList  # type: ignore[import-untyped]
+
+
+class Diataxis(enum.StrEnum):
+    # TODO: should user manual section indexes also get their own Diataxis tab?
+    #  This would allow topic-based filtering, and allow all pages to be found
+    #  through the same route.
+
+    ALL = "all"
+    TUTORIAL = "tutorial"
+    HOW_TO = "how-to"
+    REFERENCE = "reference"
+    EXPLANATION = "explanation"
+
+
+DIATAXIS_CAPTIONS = {
+    Diataxis.TUTORIAL: "Guided lessons for understanding a topic. (Supports **study**, via **action**)",
+    Diataxis.HOW_TO: "Step by step instructions for achieving a specific goal. (Supports **work**, via **action**)",
+    Diataxis.EXPLANATION: "In-depth discussion for understanding concepts. (Supports **study**, via **theory**)",
+    Diataxis.REFERENCE: "Concise information to look up when needed. (Supports **work**, via **theory**)",
+}
+
+
+class DiataxisDirective(Directive):
+    has_content = True
+
+    @staticmethod
+    def _indent(text: str) -> str:
+        indented = ["   " + line for line in text.splitlines()]
+        return "\n".join(indented)
+
+    def _needtable(self, types: Diataxis, tags: str) -> str:
+        options = [
+            ':columns: id as "Link";title;content as " "',
+            ":colwidths: 10;30;60",
+            ":style: table",
+            ":filter_warning: No pages for this filter.",
+        ]
+        # TODO: should the table somehow include what section the page belongs
+        #  to? This isn't standard sphinx-needs metadata so would need
+        #  `needs_extra_options` in conf.py.
+        if types is not Diataxis.ALL:
+            options.append(f":types: {types}")
+        # TODO: is looking for `topic_all` brittle hard-coding?
+        if tags != "topic_all":
+            options.append(f":tags: {tags}")
+        options_str = "\n".join(options)
+        needtable = "\n".join([
+            ".. needtable::",
+            self._indent(options_str),
+        ])
+        return needtable
+
+    def _tab_item(self, diataxis: Diataxis, tags: str) -> str:
+        needtable = self._needtable(types=diataxis, tags=tags)
+        tab_item_title = diataxis.capitalize()
+        # TODO: should there be a caption for ALL as well? Even if that's just
+        #  for visual consistency.
+        caption = DIATAXIS_CAPTIONS.get(diataxis, "")
+        if diataxis is not Diataxis.ALL:
+            tab_item_title += "s"
+        content = [
+            f":sync: {diataxis}",
+            "",
+            caption,
+            "",
+            needtable,
+        ]
+        content_str = "\n".join(content)
+        tab_item = "\n".join([
+            f".. tab-item:: {tab_item_title}",
+            self._indent(content_str),
+        ])
+        return tab_item
+
+    def run(self):
+        rst_path = Path(self.state.document['source'])
+        # user_manual.index.rst
+        if not (rst_path.parent.name == "user_manual" and rst_path.name == "index.rst"):
+            message = "Expected directive to only be used in user_manual/index.rst"
+            error = self.state_machine.reporter.error(
+                message, line=self.lineno
+            )
+            return [error]
+        label_pattern = re.compile(r"^\.\. _(topic_.+):$", re.MULTILINE)
+        topic_labels = label_pattern.findall(rst_path.read_text())
+        badges = {
+            label: "bdg-ref-primary" if label == self.content[0] else "bdg-ref-primary-line"
+            for label in topic_labels
+        }
+        # Parse the badges as RST.
+        node = nodes.Element()
+        self.state.nested_parse(
+            StringList([f":{badge}:`{label}`" for label, badge in badges.items()]),
+            self.content_offset,
+            node
+        )
+
+        tab_items = [
+            self._tab_item(diataxis=diataxis, tags=self.content[0])
+            for diataxis in Diataxis
+        ]
+        tab_items_str = "\n\n".join(tab_items)
+        tab_set = "\n".join([
+            ".. tab-set::",
+            "",
+            self._indent(tab_items_str),
+        ])
+        # Parse the tab set as RST.
+        self.state.nested_parse(
+            StringList(tab_set.splitlines()),
+            self.content_offset,
+            node
+        )
+
+        return node.children
+
+
+def setup(app):
+    app.add_directive("diataxis-page-list", DiataxisDirective)
+    return {"version": "0.1"}

docs/src/user_manual/index.rst

@@ -0,0 +1,83 @@
+.. comment:
+   now that User Manual is the official top-level, and the User Guide is a
+   sub-section, the original labels have been relocated here.
+
+.. _user_guide_index:
+.. _user_guide_introduction:
+.. _user_manual_index:
+
+User Manual
+===========
+
+Welcome to the Iris User Manual!
+
+We encourage exploring our User Manual pages using the tabbed sections below,
+which combine the `Diataxis`_ framework and topic-based filters to find content
+best suited to your purpose today. Alternatively, you can use the sidebar to
+navigate by section.
+
+.. todo:
+   Should the sections also be offered as another Diataxis tab? This would allow
+   topic-based filtering, and allow all pages to be found through the same
+   route.
+
+.. comment:
+   The tree structure for user_manual is specified here. As mentioned in the
+   text, we prefer readers to use the tabbed sections below, so the toctree is
+   hidden - not rendered in the text, only in the sidebar. This toctree is
+   expected to be exclusively section_indexes/* pages; with those pages
+   providing the remaining sub-structure.
+
+
+.. toctree::
+   :maxdepth: 1
+   :hidden:
+
+   section_indexes/userguide
+   section_indexes/dask_best_practices
+   section_indexes/mesh_support
+   section_indexes/metadata_arithmetic
+   section_indexes/community
+   section_indexes/general
+
+.. _topic_all:
+
+All
+---
+
+.. diataxis-page-list:: topic_all
+
+By Topic
+--------
+
+.. _topic_data_model:
+
+topic: ``data_model``
+^^^^^^^^^^^^^^^^^^^^^
+
+Pages about the :class:`~iris.cube.Cube` class and its associated components
+such as :class:`~iris.coords.Coord` and :class:`~iris.mesh.Mesh`.
+
+.. diataxis-page-list:: topic_data_model
+
+.. _topic_load_save:
+
+topic: ``load_save``
+^^^^^^^^^^^^^^^^^^^^
+
+Pages about reading from files into the data model, and writing from the data
+model to files.
+
+.. diataxis-page-list:: topic_load_save
+
+.. _topic_lazy_data:
+
+topic: ``lazy_data``
+^^^^^^^^^^^^^^^^^^^^
+
+Pages about Iris' implementation of parallel and out-of-core data handling, via
+Dask. See :term:`Lazy Data`.
+
+.. diataxis-page-list:: topic_lazy_data
+
+.. _Diataxis: https://diataxis.fr/