feat(techdocs): add app-config option to disable external font download

Signed-off-by: Karthik <karthik.jk11@gmail.com>

plugins/techdocs-node/src/stages/generate/helpers.test.ts

@@ -37,6 +37,7 @@ import {
   patchMkdocsYmlPreBuild,
   patchMkdocsYmlWithPlugins,
   sanitizeMkdocsYml,
+  patchMkdocsYmlWithFontDisabled
 } from './mkdocsPatchers';
 import yaml from 'js-yaml';
 
@@ -468,6 +469,101 @@ describe('helpers', () => {
     });
   });
 
+  describe('patchMkdocsYmlWithFontDisabled', () => {
+    beforeEach(() => {
+      mockDir.setContent({
+        'mkdocs_without_theme.yml': `site_name: Test Site
+docs_dir: docs
+`,
+        'mkdocs_with_theme_no_font.yml': `site_name: Test Site
+docs_dir: docs
+theme:
+  name: material
+`,
+        'mkdocs_with_theme_font_true.yml': `site_name: Test Site
+docs_dir: docs
+theme:
+  name: material
+  font: true
+`,
+        'mkdocs_with_theme_font_false.yml': `site_name: Test Site
+docs_dir: docs
+theme:
+  name: material
+  font: false
+`,
+      });
+    });
+
+    it('should create theme section with font disabled when no theme exists', async () => {
+      await patchMkdocsYmlWithFontDisabled(
+        mockDir.resolve('mkdocs_without_theme.yml'),
+        mockLogger,
+      );
+
+      const updatedMkdocsYml = await fs.readFile(
+        mockDir.resolve('mkdocs_without_theme.yml'),
+      );
+      const parsedYml = yaml.load(updatedMkdocsYml.toString()) as {
+        theme?: { name?: string; font?: boolean };
+      };
+      expect(parsedYml.theme).toBeDefined();
+      expect(parsedYml.theme?.name).toBe('material');
+      expect(parsedYml.theme?.font).toBe(false);
+    });
+
+    it('should add font: false when theme exists but font is not configured', async () => {
+      await patchMkdocsYmlWithFontDisabled(
+        mockDir.resolve('mkdocs_with_theme_no_font.yml'),
+        mockLogger,
+      );
+
+      const updatedMkdocsYml = await fs.readFile(
+        mockDir.resolve('mkdocs_with_theme_no_font.yml'),
+      );
+      const parsedYml = yaml.load(updatedMkdocsYml.toString()) as {
+        theme?: { name?: string; font?: boolean };
+      };
+      expect(parsedYml.theme).toBeDefined();
+      expect(parsedYml.theme?.name).toBe('material');
+      expect(parsedYml.theme?.font).toBe(false);
+    });
+
+    it('should not override font when font is already set to true', async () => {
+      await patchMkdocsYmlWithFontDisabled(
+        mockDir.resolve('mkdocs_with_theme_font_true.yml'),
+        mockLogger,
+      );
+
+      const updatedMkdocsYml = await fs.readFile(
+        mockDir.resolve('mkdocs_with_theme_font_true.yml'),
+      );
+      const parsedYml = yaml.load(updatedMkdocsYml.toString()) as {
+        theme?: { name?: string; font?: boolean };
+      };
+      expect(parsedYml.theme).toBeDefined();
+      expect(parsedYml.theme?.name).toBe('material');
+      expect(parsedYml.theme?.font).toBe(true);
+    });
+
+    it('should not override font when font is already set to false', async () => {
+      await patchMkdocsYmlWithFontDisabled(
+        mockDir.resolve('mkdocs_with_theme_font_false.yml'),
+        mockLogger,
+      );
+
+      const updatedMkdocsYml = await fs.readFile(
+        mockDir.resolve('mkdocs_with_theme_font_false.yml'),
+      );
+      const parsedYml = yaml.load(updatedMkdocsYml.toString()) as {
+        theme?: { name?: string; font?: boolean };
+      };
+      expect(parsedYml.theme).toBeDefined();
+      expect(parsedYml.theme?.name).toBe('material');
+      expect(parsedYml.theme?.font).toBe(false);
+    });
+  });
+
   describe('patchIndexPreBuild', () => {
     afterEach(() => {
       warn.mockClear();

plugins/techdocs-node/src/stages/generate/mkdocsPatchers.ts

@@ -25,11 +25,17 @@ import { assertError } from '@backstage/errors';
 import { ScmIntegrationRegistry } from '@backstage/integration';
 import { LoggerService } from '@backstage/backend-plugin-api';
 
+const MATERIAL_THEME = 'material';
+
 type MkDocsObject = {
   plugins?: string[];
   docs_dir: string;
   repo_url?: string;
   edit_uri?: string;
+  theme?: {
+    name?: string;
+    font?: boolean;
+  };
 };
 
 const patchMkdocsFile = async (
@@ -185,6 +191,39 @@ export const patchMkdocsYmlWithPlugins = async (
   });
 };
 
+/**
+ * Disable external font download for the material theme.
+ * @param mkdocsYmlPath - Absolute path to mkdocs.yml or equivalent of a docs site
+ * @param logger
+ */
+export const patchMkdocsYmlWithFontDisabled = async (
+  mkdocsYmlPath: string,
+  logger: LoggerService,
+) => {
+  await patchMkdocsFile(mkdocsYmlPath, logger, mkdocsYml => {
+    if (!('theme' in mkdocsYml)) {
+      // No theme section exists, create it with font disabled
+      mkdocsYml.theme = {
+        name: MATERIAL_THEME,
+        font: false,
+      };
+      return true;
+    }
+
+    // Theme section exists, check if font is not configured, add font: false
+    if (
+      mkdocsYml.theme &&
+      typeof mkdocsYml.theme === 'object' &&
+      !('font' in mkdocsYml.theme)
+    ) {
+      mkdocsYml.theme.font = false;
+      return true;
+    }
+
+    return false;
+  });
+};
+
 /**
  * Sanitize mkdocs.yml by keeping only allowed configuration keys.
  *
@@ -249,3 +288,4 @@ export const sanitizeMkdocsYml = async (
     return true;
   });
 };
+

plugins/techdocs-node/src/stages/generate/techdocs.ts

@@ -32,6 +32,7 @@ import {
 
 import {
   patchMkdocsYmlPreBuild,
+  patchMkdocsYmlWithFontDisabled,
   patchMkdocsYmlWithPlugins,
   sanitizeMkdocsYml,
 } from './mkdocsPatchers';
@@ -150,6 +151,9 @@ export class TechdocsGenerator implements GeneratorBase {
     }
 
     await patchMkdocsYmlWithPlugins(mkdocsYmlPath, childLogger, defaultPlugins);
+    if (this.options.disableExternalFonts) {
+      await patchMkdocsYmlWithFontDisabled(mkdocsYmlPath, childLogger);
+    }
 
     // Directories to bind on container
     const mountDirs = {
@@ -264,5 +268,8 @@ export function readGeneratorConfig(
     dangerouslyAllowAdditionalKeys: config.getOptionalStringArray(
       'techdocs.generator.mkdocs.dangerouslyAllowAdditionalKeys',
     ),
+    disableExternalFonts: config.getOptionalBoolean(
+      'techdocs.generator.mkdocs.disableExternalFonts'
+    ),
   };
 }

plugins/techdocs-node/src/stages/generate/types.ts

@@ -46,6 +46,7 @@ export type GeneratorConfig = {
   legacyCopyReadmeMdToIndexMd?: boolean;
   defaultPlugins?: string[];
   dangerouslyAllowAdditionalKeys?: string[];
+  disableExternalFonts?: boolean;
 };
 
 /**