feat(remote-build): check base before executing (#4343)

Only core20 and core22 bases can use the fallback remote build behavior.

Signed-off-by: Callahan Kovacs <callahan.kovacs@canonical.com>

snapcraft/commands/remote.py

@@ -24,8 +24,9 @@
 from craft_cli.helptexts import HIDDEN
 from overrides import overrides
 
+from snapcraft.errors import MaintenanceBase, SnapcraftError
 from snapcraft.legacy_cli import run_legacy
-from snapcraft.parts.yaml_utils import get_snap_project, process_yaml
+from snapcraft.parts import yaml_utils
 from snapcraft.utils import confirm_with_user
 from snapcraft_legacy.internal.remote_build.errors import AcceptPublicUploadError
 
@@ -88,15 +89,58 @@ def fill_parser(self, parser: argparse.ArgumentParser) -> None:
             help="acknowledge that uploaded code will be publicly available.",
         )
 
+    def _get_effective_base(self) -> str:
+        """Get a valid effective base from the project's snapcraft.yaml.
+
+        :returns: The project's effective base.
+
+        :raises SnapcraftError: If the base is unknown or missing or if the
+        snapcraft.yaml cannot be loaded.
+        :raises MaintenanceBase: If the base is not supported
+        """
+        snapcraft_yaml = yaml_utils.get_snap_project().project_file
+
+        with open(snapcraft_yaml, encoding="utf-8") as file:
+            base = yaml_utils.get_base(file)
+
+        if base is None:
+            raise SnapcraftError(
+                f"Could not determine base from {str(snapcraft_yaml)!r}."
+            )
+
+        emit.debug(f"Got base {base!r} from {str(snapcraft_yaml)!r}.")
+
+        if base in yaml_utils.ESM_BASES:
+            raise MaintenanceBase(base)
+
+        if base not in yaml_utils.BASES:
+            raise SnapcraftError(f"Unknown base {base!r} in {str(snapcraft_yaml)!r}.")
+
+        return base
+
+    def _run_remote_build(self, base: str) -> None:
+        # bases newer than core22 must use the new remote-build
+        if base in yaml_utils.CURRENT_BASES - {"core22"}:
+            emit.debug(
+                "Using fallback remote-build because new remote-build is not available."
+            )
+            # TODO: use new remote-build code (#4323)
+            run_legacy()
+            return
+
+        emit.debug("Running fallback remote-build.")
+        run_legacy()
+
     @overrides
-    def run(self, parsed_args):
+    def run(self, parsed_args) -> None:
         if os.getenv("SUDO_USER") and os.geteuid() == 0:
             emit.message(
                 "Running with 'sudo' may cause permission errors and is discouraged."
             )
 
         emit.message(
-            "snapcraft remote-build is experimental and is subject to change - use with caution."
+            "snapcraft remote-build is experimental and is subject to change "
+            "- use with caution."
         )
 
         if parsed_args.build_on:
@@ -108,14 +152,5 @@ def run(self, parsed_args):
         ):
             raise AcceptPublicUploadError()
 
-        snap_project = get_snap_project()
-        # TODO proper core22 support would mean we need to load the project
-        # yaml_data = process_yaml(snap_project.project_file)
-        # for now, only log explicitly that we are falling back to legacy to
-        # remote build for core22
-        process_yaml(snap_project.project_file)
-
-        emit.debug(
-            "core22 not yet supported in new code base: re-executing into legacy for remote-build"
-        )
-        run_legacy()
+        base = self._get_effective_base()
+        self._run_remote_build(base)

snapcraft/parts/yaml_utils.py

@@ -31,8 +31,15 @@
 
 _CORE_PART_KEYS = ["build-packages", "build-snaps"]
 _CORE_PART_NAME = "snapcraft/core"
-_ESM_BASES = {"core", "core18"}
-_LEGACY_BASES = {"core20"}
+
+# All bases recognized by snapcraft
+BASES = {"core", "core18", "core20", "core22", "devel"}
+# Bases no longer supported by the current version of snapcraft
+ESM_BASES = {"core", "core18"}
+# Bases handled by the legacy snapcraft codebase
+LEGACY_BASES = {"core20"}
+# Bases handled by the current snapcraft codebase
+CURRENT_BASES = BASES - ESM_BASES - LEGACY_BASES
 
 
 @dataclass
@@ -133,9 +140,9 @@ def load(filestream: TextIO) -> Dict[str, Any]:
 
     if build_base is None:
         raise errors.LegacyFallback("no base defined")
-    if build_base in _ESM_BASES:
+    if build_base in ESM_BASES:
         raise errors.MaintenanceBase(build_base)
-    if build_base in _LEGACY_BASES:
+    if build_base in LEGACY_BASES:
         raise errors.LegacyFallback(f"base is {build_base}")
 
     filestream.seek(0)