feat: Support backlinks

Issue-153: #153

Author: pawamoy

Diff for: mkdocs.yml

@@ -160,6 +160,7 @@ plugins:
         - https://mkdocstrings.github.io/griffe/objects.inv
         - https://python-markdown.github.io/objects.inv
         options:
+          backlinks: flat
           docstring_options:
             ignore_init_summary: true
           docstring_section_style: list

Diff for: src/mkdocstrings_handlers/python/config.py

@@ -386,6 +386,14 @@ class PythonInputOptions:
         ),
     ] = "brief"
 
+    backlinks: Annotated[
+        Literal["flat", "tree", False],
+        Field(
+            group="general",
+            description="Whether to render backlinks, and how.",
+        ),
+    ] = False
+
     docstring_options: Annotated[
         GoogleStyleOptions | NumpyStyleOptions | SphinxStyleOptions | AutoStyleOptions | None,
         Field(

Diff for: src/mkdocstrings_handlers/python/handler.py

@@ -6,6 +6,7 @@
 import os
 import posixpath
 import sys
+from collections.abc import Iterable
 from contextlib import suppress
 from dataclasses import asdict
 from pathlib import Path
@@ -25,6 +26,7 @@
 from mkdocstrings.handlers.base import BaseHandler, CollectionError, CollectorItem, HandlerOptions
 from mkdocstrings.inventory import Inventory
 from mkdocstrings.loggers import get_logger
+from mkdocs_autorefs.plugin import BacklinkCrumb
 
 from mkdocstrings_handlers.python import rendering
 from mkdocstrings_handlers.python.config import PythonConfig, PythonOptions
@@ -33,6 +35,7 @@
     from collections.abc import Iterator, Mapping, MutableMapping, Sequence
 
     from mkdocs.config.defaults import MkDocsConfig
+    from mkdocs_autorefs.plugin import Backlink
 
 
 if sys.version_info >= (3, 11):
@@ -280,6 +283,16 @@ def render(self, data: CollectorItem, options: PythonOptions) -> str:  # noqa: D
             },
         )
 
+    def render_backlinks(self, backlinks: Mapping[str, Iterable[Backlink]]) -> str:  # noqa: D102 (ignore missing docstring)
+        template = self.env.get_template("backlinks.html.jinja")
+        verbose_type = {key: key.capitalize().replace("-by", " by") for key in backlinks.keys()}
+        return template.render(
+            backlinks=backlinks,
+            config=self.get_options({}),
+            verbose_type=verbose_type,
+            default_crumb=BacklinkCrumb(title="", url=""),
+        )
+
     def update_env(self, config: Any) -> None:  # noqa: ARG002
         """Update the Jinja environment with custom filters and tests.
 
@@ -303,6 +316,7 @@ def update_env(self, config: Any) -> None:  # noqa: ARG002
         self.env.filters["as_functions_section"] = rendering.do_as_functions_section
         self.env.filters["as_classes_section"] = rendering.do_as_classes_section
         self.env.filters["as_modules_section"] = rendering.do_as_modules_section
+        self.env.filters["backlink_tree"] = rendering.do_backlink_tree
         self.env.globals["AutorefsHook"] = rendering.AutorefsHook
         self.env.tests["existing_template"] = lambda template_name: template_name in self.env.list_templates()
 

Diff for: src/mkdocstrings_handlers/python/rendering.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from collections.abc import Iterable
 import random
 import re
 import string
@@ -12,7 +13,7 @@
 from functools import lru_cache
 from pathlib import Path
 from re import Match, Pattern
-from typing import TYPE_CHECKING, Any, Callable, ClassVar, Literal
+from typing import TYPE_CHECKING, Any, Callable, ClassVar, Literal, TypeVar
 
 from griffe import (
     Alias,
@@ -26,9 +27,12 @@
     DocstringSectionModules,
     Object,
 )
+from collections import defaultdict
+from typing import Optional, Sequence, Union
+
 from jinja2 import TemplateNotFound, pass_context, pass_environment
 from markupsafe import Markup
-from mkdocs_autorefs import AutorefsHookInterface
+from mkdocs_autorefs import AutorefsHookInterface, Backlink, BacklinkCrumb
 from mkdocstrings.loggers import get_logger
 
 if TYPE_CHECKING:
@@ -210,10 +214,15 @@ def do_format_attribute(
 
     signature = str(attribute_path).strip()
     if annotations and attribute.annotation:
-        annotation = template.render(context.parent, expression=attribute.annotation, signature=True)
+        annotation = template.render(
+            context.parent,
+            expression=attribute.annotation,
+            signature=True,
+            backlink_type="returned-by",
+        )
         signature += f": {annotation}"
     if attribute.value:
-        value = template.render(context.parent, expression=attribute.value, signature=True)
+        value = template.render(context.parent, expression=attribute.value, signature=True, backlink_type="used-by")
         signature += f" = {value}"
 
     signature = do_format_code(signature, line_length)
@@ -725,3 +734,52 @@ def get_context(self) -> AutorefsHookInterface.Context:
             filepath=str(filepath),
             lineno=lineno,
         )
+
+
+T = TypeVar("T")
+Tree = dict[T, "Tree"]
+CompactTree = dict[tuple[T, ...], "CompactTree"]
+_rtree = lambda: defaultdict(_rtree)
+
+
+def _tree(data: Iterable[tuple[T, ...]]) -> Tree:
+    new_tree = _rtree()
+    for nav in data:
+        *path, leaf = nav
+        node = new_tree
+        for key in path:
+            node = node[key]
+        node[leaf] = _rtree()
+    return new_tree
+
+
+def print_tree(tree: Tree, level: int = 0) -> None:
+    for key, value in tree.items():
+        print("  " * level + str(key))
+        if value:
+            print_tree(value, level + 1)
+
+
+def _compact_tree(tree: Tree) -> CompactTree:
+    new_tree = _rtree()
+    for key, value in tree.items():
+        child = _compact_tree(value)
+        if len(child) == 1:
+            child_key, child_value = next(iter(child.items()))
+            new_key = (key, *child_key)
+            new_tree[new_key] = child_value
+        else:
+            new_tree[(key,)] = child
+    return new_tree
+
+
+def do_backlink_tree(backlinks: list[Backlink]) -> CompactTree[BacklinkCrumb]:
+    """Build a tree of backlinks.
+
+    Parameters:
+        backlinks: The list of backlinks.
+
+    Returns:
+        A tree of backlinks.
+    """
+    return _compact_tree(_tree((backlink.crumbs for backlink in backlinks)))

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/attribute.html.jinja

@@ -113,6 +113,8 @@ Context:
             {% include "docstring"|get_template with context %}
           {% endwith %}
         {% endblock docstring %}
+
+        <backlinks identifier="{{ html_id }}" handler="python" />
       {% endblock contents %}
     </div>
 

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/backlinks.html.jinja

@@ -0,0 +1,65 @@
+{#- Template for backlinks.
+
+This template renders backlinks.
+
+Context:
+  backlinks (Mapping[str, Iterable[str]]): The backlinks to render.
+  config (dict): The configuration options.
+-#}
+
+{% block logs scoped %}
+  {#- Logging block.
+
+  This block can be used to log debug messages, deprecation messages, warnings, etc.
+  -#}
+  {{ log.debug("Rendering backlinks") }}
+{% endblock logs %}
+
+{% macro render_crumb(crumb, last=false) %}
+  <span class="doc doc-backlink-crumb{{ " last" if last else "" }}">
+    {% if crumb.url and crumb.title %}
+      <a href="{{ crumb.url }}">{{ crumb.title | safe }}</a>
+    {% elif crumb.title %}
+      <span>{{ crumb.title | safe }}</span>
+    {% endif %}
+  </span>
+{% endmacro %}
+
+{% macro render_tree(tree) %}
+  <ul class="doc doc-backlink-list">
+    {% for node, child in tree | dictsort %}
+      <li class="doc doc-backlink">
+        {% for crumb in node %}
+          {{ render_crumb(crumb, last=loop.last and not child) }}
+        {% endfor %}
+        {% if child %}
+          {{ render_tree(child) }}
+        {% endif %}
+      </li>
+    {% endfor %}
+  </ul>
+{% endmacro %}
+
+{% if config.backlinks %}
+  <div class="doc doc-backlinks">
+    {% if config.backlinks == "tree" %}
+      {% for backlink_type, backlink_list in backlinks | dictsort %}
+        <b class="doc doc-backlink-type">{{ verbose_type[backlink_type] }}:</b>
+        {{ render_tree(backlink_list|backlink_tree) }}
+      {% endfor %}
+    {% elif config.backlinks == "flat" %}
+      {% for backlink_type, backlink_list in backlinks | dictsort %}
+        <b class="doc doc-backlink-type">{{ verbose_type[backlink_type] }}:</b>
+        <ul class="doc doc-backlink-list">
+          {% for backlink in backlink_list | sort(attribute="crumbs") %}
+            <li class="doc doc-backlink">
+              {% for crumb in backlink.crumbs %}
+                {{ render_crumb(crumb, last=loop.last) }}
+              {% endfor %}
+            </li>
+          {% endfor %}
+        </ul>
+      {% endfor %}
+    {% endif %}
+  </div>
+{% endif %}

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/class.html.jinja

@@ -130,7 +130,11 @@ Context:
           {% if config.show_bases and class.bases %}
             <p class="doc doc-class-bases">
               Bases: {% for expression in class.bases -%}
-                <code>{% include "expression"|get_template with context %}</code>{% if not loop.last %}, {% endif %}
+                <code>
+                  {%- with backlink_type = "subclassed-by" -%}
+                    {%- include "expression"|get_template with context -%}
+                  {%- endwith -%}
+                </code>{% if not loop.last %}, {% endif %}
               {% endfor -%}
             </p>
           {% endif %}
@@ -159,6 +163,8 @@ Context:
           {% endif %}
         {% endblock docstring %}
 
+        <backlinks identifier="{{ html_id }}" handler="python" />
+
         {% block summary scoped %}
           {#- Summary block.
 

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/docstring/other_parameters.html.jinja

@@ -36,7 +36,7 @@ Context:
             <td><code>{{ parameter.name }}</code></td>
             <td>
               {% if parameter.annotation %}
-                {% with expression = parameter.annotation %}
+                {% with expression = parameter.annotation, backlink_type = "used-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               {% endif %}
@@ -60,7 +60,7 @@ Context:
         <li class="doc-section-item field-body">
           <b><code>{{ parameter.name }}</code></b>
           {% if parameter.annotation %}
-            {% with expression = parameter.annotation %}
+            {% with expression = parameter.annotation, backlink_type = "used-by" %}
               (<code>{% include "expression"|get_template with context %}</code>)
             {% endwith %}
           {% endif %}
@@ -94,7 +94,7 @@ Context:
                 {% if parameter.annotation %}
                   <span class="doc-param-annotation">
                     <b>{{ lang.t("TYPE:") }}</b>
-                    {% with expression = parameter.annotation %}
+                    {% with expression = parameter.annotation, backlink_type = "used-by" %}
                       <code>{% include "expression"|get_template with context %}</code>
                     {% endwith %}
                   </span>

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/docstring/parameters.html.jinja

@@ -51,7 +51,7 @@ Context:
             </td>
             <td>
               {% if parameter.annotation %}
-                {% with expression = parameter.annotation %}
+                {% with expression = parameter.annotation, backlink_type = "used-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               {% endif %}
@@ -63,7 +63,7 @@ Context:
             </td>
             <td>
               {% if parameter.default %}
-                {% with expression = parameter.default %}
+                {% with expression = parameter.default, backlink_type = "used-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               {% else %}
@@ -96,10 +96,10 @@ Context:
             <b><code>{{ parameter.name }}</code></b>
           {% endif %}
           {% if parameter.annotation %}
-            {% with expression = parameter.annotation %}
+            {% with expression = parameter.annotation, backlink_type = "used-by" %}
               (<code>{% include "expression"|get_template with context %}</code>
               {%- if parameter.default %}, {{ lang.t("default:") }}
-                {% with expression = parameter.default %}
+                {% with expression = parameter.default, backlink_type = "used-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               {% endif %})
@@ -149,15 +149,15 @@ Context:
                 {% if parameter.annotation %}
                   <span class="doc-param-annotation">
                     <b>{{ lang.t("TYPE:") }}</b>
-                    {% with expression = parameter.annotation %}
+                    {% with expression = parameter.annotation, backlink_type = "used-by" %}
                       <code>{% include "expression"|get_template with context %}</code>
                     {% endwith %}
                   </span>
                 {% endif %}
                 {% if parameter.default %}
                   <span class="doc-param-default">
                     <b>{{ lang.t("DEFAULT:") }}</b>
-                    {% with expression = parameter.default %}
+                    {% with expression = parameter.default, backlink_type = "used-by" %}
                       <code>{% include "expression"|get_template with context %}</code>
                     {% endwith %}
                   </span>

Diff for: src/mkdocstrings_handlers/python/templates/material/_base/docstring/raises.html.jinja

@@ -34,7 +34,7 @@ Context:
           <tr class="doc-section-item">
             <td>
               {% if raises.annotation %}
-                {% with expression = raises.annotation %}
+                {% with expression = raises.annotation, backlink_type = "raised-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               {% endif %}
@@ -57,7 +57,7 @@ Context:
       {% for raises in section.value %}
         <li class="doc-section-item field-body">
           {% if raises.annotation %}
-            {% with expression = raises.annotation %}
+            {% with expression = raises.annotation, backlink_type = "raised-by" %}
               <code>{% include "expression"|get_template with context %}</code>
             {% endwith %}
             –
@@ -84,7 +84,7 @@ Context:
           <tr class="doc-section-item">
             <td>
               <span class="doc-raises-annotation">
-                {% with expression = raises.annotation %}
+                {% with expression = raises.annotation, backlink_type = "raised-by" %}
                   <code>{% include "expression"|get_template with context %}</code>
                 {% endwith %}
               </span>