bridge: Drop translations from manifests.js, introduce m-i18n.js

Pages don't (shouldn't) care about manifest translations when including
`manifests.js` -- they usually do that to query for a package's
existence or some feature flags.

Only the Shell cares about the translations. So drop translations from
`manifests.js`, and support a new `manifests-i18n.js` which only the
shell uses.

This isolates translations from different pages from another.
Concretely, subscription-manager-cockpit and our systemd page both
translate "$0 important hit" differently, and even to different data
types (in s-m it results in an array, in systemd in a normal string).
This caused a page crash, and also wrong strings, as s-m's translations
are really not expected to be used on the Overview page.

This also speeds up the loading of frames, as they now don't have to go
through umpteen `cockpit.locale()` calls any more.

Note that this still leaves i18n conflicts in the shell itself, so this
isn't a full fix, just an "80%" mitigation.

Fixes #21486

pkg/shell/index.html

@@ -7,7 +7,7 @@
     <link href="shell.css" rel="stylesheet" />
     <link href="../../static/branding.css" rel="stylesheet" />
     <script src="../base1/cockpit.js"></script>
-    <script src="../manifests.js"></script>
+    <script src="../manifests-i18n.js"></script>
     <script src="po.js"></script>
     <script src="shell.js"></script>
   </head>

src/cockpit/packages.py

@@ -516,26 +516,27 @@ def reload_hint(self):
             self.reload()
         self.saw_first_reload_hint = True
 
-    def load_manifests_js(self, headers: JsonObject) -> Document:
+    def load_manifests_js(self, headers: JsonObject, *, i18n: bool) -> Document:
         logger.debug('Serving /manifests.js')
 
         chunks: List[bytes] = []
 
         # Send the translations required for the manifest files, from each package
-        locales = parse_accept_language(get_str(headers, 'Accept-Language', ''))
-        for name, package in self.packages.items():
-            if name in ['static', 'base1']:
-                continue
+        if i18n:
+            locales = parse_accept_language(get_str(headers, 'Accept-Language', ''))
+            for name, package in self.packages.items():
+                if name in ['static', 'base1']:
+                    continue
 
-            # find_translation will always find at least 'en'
-            translation = package.load_translation('po.manifest.js', locales)
-            with translation.data:
-                if translation.content_encoding == 'gzip':
-                    data = gzip.decompress(translation.data.read())
-                else:
-                    data = translation.data.read()
+                # find_translation will always find at least 'en'
+                translation = package.load_translation('po.manifest.js', locales)
+                with translation.data:
+                    if translation.content_encoding == 'gzip':
+                        data = gzip.decompress(translation.data.read())
+                    else:
+                        data = translation.data.read()
 
-            chunks.append(data)
+                chunks.append(data)
 
         chunks.append(b"""
             (function (root, data) {
@@ -573,7 +574,9 @@ def load_path(self, path: str, headers: JsonObject) -> Document:
         if packagename is not None:
             return self.packages[packagename].load_path(filename, headers)
         elif filename == 'manifests.js':
-            return self.load_manifests_js(headers)
+            return self.load_manifests_js(headers, i18n=False)
+        elif filename == 'manifests-i18n.js':
+            return self.load_manifests_js(headers, i18n=True)
         elif filename == 'manifests.json':
             return self.load_manifests_json()
         else:

test/pytest/test_packages.py

@@ -233,7 +233,7 @@ def test_translation(pkgdir):
     assert document.data.read() == b''
 
     # make sure the manifest translations get sent along with manifests.js
-    document = packages.load_path('/manifests.js', {'Accept-Language': 'de'})
+    document = packages.load_path('/manifests-i18n.js', {'Accept-Language': 'de'})
     contents = document.data.read()
     assert b'eins\n' in contents
     assert b'zwo\n' in contents