Add dependencies between migrations

locales/en.json

@@ -321,6 +321,7 @@
     "migrate_tsig_wait_3": "1min…",
     "migrate_tsig_wait_4": "30 secondes…",
     "migrate_tsig_not_needed": "You do not appear to use a dyndns domain, so no migration is needed!",
+    "migration_backward_impossible": "The migration {name} cannot be reverted.",
     "migration_description_0001_change_cert_group_to_sslcert": "Change certificates group permissions from 'metronome' to 'ssl-cert'",
     "migration_description_0002_migrate_to_tsig_sha256": "Improve security of dyndns TSIG by using SHA512 instead of MD5",
     "migration_description_0003_migrate_to_stretch": "Upgrade the system to Debian Stretch and YunoHost 3.0",
@@ -332,7 +333,6 @@
     "migration_description_0009_decouple_regenconf_from_services": "Decouple the regen-conf mechanism from services",
     "migration_description_0010_migrate_to_apps_json": "Remove deprecated appslists and use the new unified 'apps.json' list instead",
     "migration_description_0011_setup_group_permission": "Setup user group and setup permission for apps and services",
-    "migration_0003_backward_impossible": "The stretch migration cannot be reverted.",
     "migration_0003_start": "Starting migration to Stretch. The logs will be available in {logfile}.",
     "migration_0003_patching_sources_list": "Patching the sources.lists…",
     "migration_0003_main_upgrade": "Starting main upgrade…",

src/yunohost/data_migrations/0003_migrate_to_stretch.py

@@ -31,7 +31,7 @@ class MyMigration(Migration):
 
     def backward(self):
 
-        raise YunohostError("migration_0003_backward_impossible")
+        raise YunohostError("migration_backward_impossible", name=self.name)
 
     def migrate(self):
 

src/yunohost/data_migrations/0004_php5_to_php7_pools.py

@@ -22,6 +22,8 @@ class MyMigration(Migration):
 
     "Migrate php5-fpm 'pool' conf files to php7 stuff"
 
+    dependencies = ["migrate_to_stretch"]
+
     def migrate(self):
 
         # Get list of php5 pool files

src/yunohost/data_migrations/0005_postgresql_9p4_to_9p6.py

@@ -14,6 +14,8 @@ class MyMigration(Migration):
 
     "Migrate DBs from Postgresql 9.4 to 9.6 after migrating to Stretch"
 
+    dependencies = ["migrate_to_stretch"]
+
     def migrate(self):
 
         if not self.package_is_installed("postgresql-9.4"):

src/yunohost/data_migrations/0008_ssh_conf_managed_by_yunohost_step2.py

@@ -33,6 +33,8 @@ class MyMigration(Migration):
     shown - and the user may also choose to skip this migration.
     """
 
+    dependencies = ["ssh_conf_managed_by_yunohost_step1"]
+
     def migrate(self):
         settings_set("service.ssh.allow_deprecated_dsa_hostkey", False)
         regen_conf(names=['ssh'], force=True)
@@ -44,7 +46,7 @@ class MyMigration(Migration):
 
     def backward(self):
 
-        raise YunohostError("migration_0008_backward_impossible")
+        raise YunohostError("migration_backward_impossible", name=self.name)
 
     @property
     def mode(self):

src/yunohost/tools.py

@@ -1052,6 +1052,15 @@ def tools_migrations_migrate(targets=[], skip=False, auto=False, force_rerun=Fal
 
     all_migrations = _get_migrations_list()
 
+    # Small utility that allows up to get a migration given a name, id or number later
+    def get_matching_migration(target):
+        for m in all_migrations:
+            if m.id == target or m.name == target or m.id.split("_")[0] == target:
+                return m
+
+        raise YunohostError("No such migration called %s" % target)
+
+
     # auto, skip, revert and force are exclusive options
     if auto + skip + revert + force_rerun > 1:
         raise YunohostError("--auto, --skip, --revert and --force-rerun are exclusive options.")
@@ -1067,13 +1076,6 @@ def tools_migrations_migrate(targets=[], skip=False, auto=False, force_rerun=Fal
 
     # If explicit targets are provided, we shall validate them
     else:
-        def get_matching_migration(target):
-            for m in all_migrations:
-                if m.id == target or m.name == target or m.id.split("_")[0] == target:
-                    return m
-
-            raise YunohostError("No such migration called %s" % target)
-
         targets = [get_matching_migration(t) for t in targets]
         done = [t.id for t in targets if t.state != "pending"]
         pending = [t.id for t in targets if t.state == "pending"]
@@ -1103,6 +1105,14 @@ def tools_migrations_migrate(targets=[], skip=False, auto=False, force_rerun=Fal
             # We go to the next migration
             continue
 
+        # Check for migration dependencies
+        if not revert and not skip:
+            dependencies = [get_matching_migration(dep) for dep in migration.dependencies]
+            pending_dependencies = [dep.id for dep in dependencies if dep.state == "pending"]
+            if pending_dependencies:
+                logger.error("Can't run migration %s because first you need to run these migrations: %s" % (migration.id, ', '.join(pending_dependencies)))
+                continue
+
         # If some migrations have disclaimers (and we're not trying to skip them)
         if migration.disclaimer and not skip:
             # require the --accept-disclaimer option.
@@ -1308,6 +1318,7 @@ class Migration(object):
     # Those are to be implemented by daughter classes
 
     mode = "auto"
+    dependencies = [] # List of migration ids required before running this migration
 
     def forward(self):
         raise NotImplementedError()