category with no apps should be ignored, even if defined in config

https://gitlab.com/fdroid/fdroidclient/-/issues/2619#note_1421280589

The test needed to change because the test index files contained category
definitions that were not ever used in the "copy tests/repo, generate java/gpg
keys, update, and gpgsign" test in tests/run-tests.

fdroidserver/index.py

@@ -743,9 +743,16 @@ def make_v2(apps, packages, repodir, repodict, requestsdict, fdroid_signing_key_
 
     if categories_used_by_apps and not output['repo'].get(CATEGORIES_CONFIG_NAME):
         output['repo'][CATEGORIES_CONFIG_NAME] = dict()
+    # include definitions for "auto-defined" categories, e.g. just used in app metadata
     for category in sorted(categories_used_by_apps):
         if category not in output['repo'][CATEGORIES_CONFIG_NAME]:
             output['repo'][CATEGORIES_CONFIG_NAME][category] = dict()
+    # do not include defined categories if no apps use them
+    for category in list(output['repo'].get(CATEGORIES_CONFIG_NAME, list())):
+        if category not in categories_used_by_apps:
+            del output['repo'][CATEGORIES_CONFIG_NAME][category]
+            msg = _('Category "{category}" defined but not used for any apps!')
+            logging.warning(msg.format(category=category))
 
     entry = {}
     entry["timestamp"] = repodict["timestamp"]

tests/metadata.TestCase

@@ -1863,6 +1863,8 @@ class MetadataTest(unittest.TestCase):
                 AntiFeatures:
                   - NonFreeNet
                 Categories:
+                  - Multimedia
+                  - Security
                   - Time
                 License: GPL-3.0-only
                 SourceCode: https://github.com/miguelvps/PoliteDroid

tests/metadata/com.politedroid.yml

@@ -1,6 +1,8 @@
 AntiFeatures:
   - NonFreeNet
 Categories:
+  - Multimedia
+  - Security
   - Time
 License: GPL-3.0-only
 SourceCode: https://github.com/miguelvps/PoliteDroid

tests/metadata/dump/com.politedroid.yaml

@@ -161,6 +161,8 @@ Builds:
   versionCode: 6
   versionName: '1.5'
 Categories:
+- Multimedia
+- Security
 - Time
 Changelog: ''
 CurrentVersion: '1.5'

tests/repo/entry.json

@@ -3,7 +3,7 @@
   "version": 20002,
   "index": {
     "name": "/index-v2.json",
-    "sha256": "b613858aa7a2ec476fcef5c841a5b8ff4b3b0f67f07678da981e2843f49c71ba",
+    "sha256": "5e3c0eaafd99d3518da2bb2bc7565b2ebcb17775a2f4ccc33b7336901ec71a6f",
     "size": 53283,
     "numPackages": 10
   },

tests/repo/index-v1.json

@@ -174,6 +174,8 @@
         "NonFreeNet"
       ],
       "categories": [
+        "Multimedia",
+        "Security",
         "Time"
       ],
       "suggestedVersionName": "1.5",

tests/repo/index-v2.json

@@ -553,6 +553,8 @@
       "metadata": {
         "added": 1498176000000,
         "categories": [
+          "Multimedia",
+          "Security",
           "Time"
         ],
         "issueTracker": "https://github.com/miguelvps/PoliteDroid/issues",

tests/repo/index.xml

@@ -311,8 +311,8 @@ APK is called F-Droid Privileged Extension.</desc>
 		<icon>com.politedroid.6.png</icon>
 		<desc>Activates silent mode during calendar events.</desc>
 		<license>GPL-3.0-only</license>
-		<categories>Time</categories>
+		<categories>Multimedia,Security,Time</categories>
-		<category>Time</category>
+		<category>Multimedia</category>
 		<web></web>
 		<source>https://github.com/miguelvps/PoliteDroid</source>
 		<tracker>https://github.com/miguelvps/PoliteDroid/issues</tracker>

tests/update.TestCase

@@ -1898,6 +1898,30 @@ class UpdateTest(unittest.TestCase):
             index['repo'][CATEGORIES_CONFIG_NAME],
         )
 
+    def test_empty_categories_not_in_index(self):
+        """A category with no apps should be ignored, even if defined in config."""
+        os.chdir(self.testdir)
+        os.mkdir('config')
+        Path('config/categories.yml').write_text('System: {name: S}\nTime: {name: T}\n')
+        os.mkdir('metadata')
+        os.mkdir('repo')
+        Path('config.yml').write_text(
+            'repo_pubkey: ffffffffffffffffffffffffffffffffffffffff'
+        )
+
+        testapk = os.path.join('repo', 'com.politedroid_6.apk')
+        shutil.copy(os.path.join(self.basedir, testapk), testapk)
+        Path('metadata/com.politedroid.yml').write_text('Categories: [Time]')
+
+        with mock.patch('sys.argv', ['fdroid update', '--delete-unknown', '--nosign']):
+            fdroidserver.update.main()
+        with open('repo/index-v2.json') as fp:
+            index = json.load(fp)
+        self.assertEqual(
+            {'Time': {'name': {'en-US': 'T'}}},
+            index['repo'][CATEGORIES_CONFIG_NAME],
+        )
+
 
 if __name__ == "__main__":
     os.chdir(os.path.dirname(__file__))