Colour language tag using GitHub's linguist colours

dev-requirements.txt

@@ -17,3 +17,4 @@ flake8-mutable==1.2.0
 flake8-print==5.0.0
 flake8-tuple==0.4.1
 djlint==1.19.2
+types-pyyaml==6.0.12.9

static/src/scss/_blocks.scss

@@ -80,6 +80,14 @@ div.block-tangent {
 div.block-code {
   position: relative;
 
+  .highlight {
+    pre,
+    span,
+    & {
+      @include dark-mode;
+    }
+  }
+
   .code-header {
     position: absolute;
     font-family: $family-code;
@@ -103,19 +111,17 @@ div.block-code {
 
     .language-tag {
       background-color: $primary-light;
+      font-weight: $weight-medium;
 
       @include dark-mode {
         background-color: $primary-dark;
         color: $white;
       }
-    }
-  }
 
-  .highlight {
-    pre,
-    span,
-    & {
-      @include dark-mode;
+      &.linguist-color span {
+        // HACK: Naive inverse threshold of the colour for optimum contrast
+        filter: contrast(1000) grayscale(100) invert(1);
+      }
     }
   }
 }

static/src/scss/_bulma_overrides.scss

@@ -22,4 +22,4 @@ $code-padding: 0;
 $code: inherit;
 $pre: unset;
 $content-heading-weight: $weight-medium;
-$content-pre-padding: 1.5em 1.25em 1.25em;
+$content-pre-padding: 1.5em;

website/contrib/code_block/blocks.py

@@ -1,13 +1,17 @@
 from typing import Iterator
 
+from django.utils.functional import cached_property
 from django.utils.safestring import mark_safe
 from pygments import highlight
 from pygments.formatters.html import HtmlFormatter
 from pygments.lexers import find_lexer_class, get_all_lexers
 from pygments.lexers.python import PythonConsoleLexer, PythonLexer
+from pygments.lexers.shell import BashLexer, BashSessionLexer
 from pygments.lexers.special import TextLexer
 from wagtail.blocks import CharBlock, ChoiceBlock, StructBlock, StructValue, TextBlock
 
+from .utils import get_linguist_colours
+
 
 def get_language_choices() -> Iterator[tuple[str, str]]:
     for name, _, _, _ in sorted(get_all_lexers()):
@@ -17,6 +21,8 @@ def get_language_choices() -> Iterator[tuple[str, str]]:
 class CodeStructValue(StructValue):
     LANGUAGE_DISPLAY_MAPPING = {PythonConsoleLexer.name: PythonLexer.name}
 
+    LINGUIST_MAPPING = {BashLexer.name: "Shell", BashSessionLexer.name: "Shell"}
+
     def code(self) -> str:
         lexer = find_lexer_class(self["language"])()
         formatter = HtmlFormatter(
@@ -39,6 +45,25 @@ class CodeStructValue(StructValue):
         """
         return self.LANGUAGE_DISPLAY_MAPPING.get(self["language"], self["language"])
 
+    @cached_property
+    def colour(self) -> str | None:
+        """
+        Expose the colour denoted by GitHub's linguist.
+        """
+        linguist_colours = get_linguist_colours()
+
+        language = self.LINGUIST_MAPPING.get(self["language"], self["language"])
+
+        if exact_match := linguist_colours.get(language.lower()):
+            return exact_match
+
+        if language_display_match := linguist_colours.get(
+            self.LANGUAGE_DISPLAY_MAPPING.get(language, "").lower()
+        ):
+            return language_display_match
+
+        return None
+
 
 class CodeBlock(StructBlock):
     filename = CharBlock(max_length=128, required=False)

website/contrib/code_block/templates/contrib/blocks/code.html

@@ -1,6 +1,10 @@
 {% if value.header_text %}
-  <div class="code-header tags">
-    {% if value.header_text %}<span class="tag ml-auto mr-5 language-tag" title="{{ value.language }}">{{ value.header_text }}</span>{% endif %}
+  <div class="code-header">
+    {% if value.header_text %}
+      <span class="tag ml-auto mr-5 language-tag {% if value.colour %}linguist-color{% endif %}" title="{{ value.language }}" {% if value.colour %}style="background-color: {{ value.colour }}"{% endif %}>
+        <span {% if value.colour %}style="color: {{ value.colour }}"{% endif %}>{{ value.header_text }}</span>
+      </span>
+    {% endif %}
     <span class="tag code-copy-tag">
       <i class="fa-regular fa-clipboard is-clickable code-copy" title="Copy to clipboard"></i>
     </span>

website/contrib/code_block/utils.py

@@ -1,4 +1,25 @@
 from importlib.metadata import version
 
+import requests
+import yaml
+from django_cache_decorator import django_cache_decorator
+
 PYGMENTS_VERSION = version("pygments")
 PYGMENTS_VERSION_SLUG = PYGMENTS_VERSION.replace(".", "-")
+
+LINGUIST_DATA_URL = "https://raw.githubusercontent.com/github/linguist/master/lib/linguist/languages.yml"
+
+
+@django_cache_decorator(time=21600)
+def get_linguist_colours() -> dict[str, str]:
+    response = requests.get(LINGUIST_DATA_URL)
+
+    response.raise_for_status()
+
+    linguist_data = yaml.safe_load(response.text)
+
+    return {
+        language.lower(): l["color"]
+        for language, l in linguist_data.items()
+        if l.get("color")
+    }