System locale manipulation wired into Subiquity.

- We don't have cloud-init in WSL.
- Subiquity must perform any actions to support the choosen locale.

system_setup/server/controllers/locale.py

@@ -14,7 +14,9 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import logging
+import os
 from subiquity.server.controllers.locale import LocaleController
+from subiquitycore.utils import arun_command
 
 log = logging.getLogger('system_setup.server.controllers.locale')
 
@@ -30,3 +32,62 @@ class WSLLocaleController(LocaleController):
                           .format(self.model.selected_language))
 
         super().start()
+
+    async def _run_locale_support_cmds(self, lang: str):
+        """ Final commands to be ran when a valid language is POST'ed. """
+
+        env = os.environ.copy()
+        # Ensure minimal console translation is enabled.
+        cmds = (["locale-gen"],
+                ["update-locale", "LANG={}".format(lang)],
+                ["bash", "-c", "\"apt", "install", "$(check-language-support",
+                 "-l", lang[0:2], ")\""])
+        if self.app.opts.dry_run:
+            for cmd in cmds:
+                log.debug('Would run: ' + ' '.join(cmd))
+        else:
+            for cmd in cmds:
+                cp = await arun_command(cmd, env=env)
+                if cp.returncode:
+                    log.debug('Command \"%s\" failed with return code %d',
+                              cp.args, cp.returncode)
+
+    async def POST(self, data: str):
+        if data == self.autoinstall_default or data == os.environ.get("LANG"):
+            await super().POST(data)
+            return
+
+        fileContents: str
+        fname = "locale.gen"
+        env = os.environ.copy()
+        if self.app.opts.dry_run:
+            # For debug purposes.
+            fname = ".subiquity/" + fname
+            await arun_command(['cp', '/etc/locale.gen', '.subiquity/'],
+                               env=env)
+        else:
+            fname = "/etc/" + fname
+
+        pendingWrite = False
+        with open(fname, "r") as localeGen:
+            # locale.gen is not so big.
+            fileContents = localeGen.read()
+            lineFound = fileContents.find(data)
+            if lineFound == -1:
+                # An unsupported locale coming from our UI is a bug.
+                raise AssertionError("Selected language {} not supported."
+                                     " Rolling back.".format(data))
+
+            commented = "# {}".format(data)
+            lineFound = fileContents.find(commented)
+            if lineFound != -1:
+                fileContents = fileContents.replace(commented, data)
+                pendingWrite = True
+
+        if pendingWrite:
+            with open(fname, "wt") as f:
+                f.write(fileContents)
+
+        # If we arrive here, data is a supported language.
+        await self._run_locale_support_cmds(data)
+        await super().POST(data)