From 32eb779a3923f0f88e8fd9edd7e8e4c352a28948 Mon Sep 17 00:00:00 2001
From: Sergio Schvezov <sergio.schvezov@canonical.com>
Date: Fri, 6 Oct 2023 09:33:58 -0300
Subject: [PATCH] fix(remote-build): warn instead of error when using
 unsupported bases

Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>
---
 snapcraft/commands/remote.py       | 26 ++++++++++++++++++++-
 snapcraft/errors.py                |  1 +
 tests/unit/commands/test_remote.py | 36 ++++++++++++++++++++++++------
 3 files changed, 55 insertions(+), 8 deletions(-)

diff --git a/snapcraft/commands/remote.py b/snapcraft/commands/remote.py
index 61c765a38a..a5bc7ea384 100644
--- a/snapcraft/commands/remote.py
+++ b/snapcraft/commands/remote.py
@@ -135,7 +135,12 @@ def run(self, parsed_args: argparse.Namespace) -> None:
         self._snapcraft_yaml = yaml_utils.get_snap_project().project_file
         self._parsed_args = parsed_args
         # pylint: enable=attribute-defined-outside-init
-        base = self._get_effective_base()
+        try:
+            base = self._get_effective_base()
+        except MaintenanceBase as base_err:
+            base = base_err.base
+            emit.progress(_get_esm_warning_for_base(base), permanent=True)
+
         self._run_new_or_fallback_remote_build(base)
 
     def _run_new_or_fallback_remote_build(self, base: str) -> None:
@@ -279,3 +284,22 @@ def _get_effective_base(self) -> str:
             )
 
         return base
+
+
+def _get_esm_warning_for_base(base: str) -> str:
+    """Return a warning appropriate for the base under ESM."""
+    channel: Optional[str] = None
+    match base:
+        case "core":
+            channel = "4.x"
+            version = "4"
+        case "core18":
+            channel = "7.x"
+            version = "7"
+        case _:
+            raise RuntimeError(f"Unmatched base {base!r}")
+
+    return (
+        f"WARNING: base {base!r} was last supported on Snapcraft {version} available "
+        f"on the {channel!r} channel."
+    )
diff --git a/snapcraft/errors.py b/snapcraft/errors.py
index 18ae86ff93..37148a05ea 100644
--- a/snapcraft/errors.py
+++ b/snapcraft/errors.py
@@ -138,6 +138,7 @@ def __init__(self, base: str) -> None:
             resolution=resolution,
             docs_url="https://snapcraft.io/docs/base-snaps",
         )
+        self.base = base
 
 
 class StoreCredentialsUnauthorizedError(SnapcraftError):
diff --git a/tests/unit/commands/test_remote.py b/tests/unit/commands/test_remote.py
index f03ee82e0e..35403c475f 100644
--- a/tests/unit/commands/test_remote.py
+++ b/tests/unit/commands/test_remote.py
@@ -220,7 +220,7 @@ def test_get_effective_base_with_build_base(
 
 
 @pytest.mark.usefixtures("mock_argv", "mock_confirm")
-@pytest.mark.parametrize("base", CURRENT_BASES | LEGACY_BASES)
+@pytest.mark.parametrize("base", CURRENT_BASES | LEGACY_BASES | ESM_BASES)
 def test_get_effective_base_type(
     base, snapcraft_yaml, mock_run_new_or_fallback_remote_build
 ):
@@ -255,15 +255,37 @@ def test_get_effective_base_none(capsys, snapcraft_yaml):
 
 
 @pytest.mark.usefixtures("mock_argv", "mock_confirm")
-@pytest.mark.parametrize("base", ESM_BASES)
-def test_get_effective_base_esm(base, capsys, snapcraft_yaml):
-    """Raise an error if an ESM base is used."""
-    snapcraft_yaml(base=base)
+def test_get_effective_base_core_esm_warning(
+    emitter, snapcraft_yaml, mock_run_new_or_fallback_remote_build
+):
+    """Warn if core, an ESM base, is used."""
+    snapcraft_yaml(base="core")
 
     cli.run()
 
-    _, err = capsys.readouterr()
-    assert f"{base!r} is not supported on this version of Snapcraft." in err
+    mock_run_new_or_fallback_remote_build.assert_called_once_with("core")
+    emitter.assert_progress(
+        "WARNING: base 'core' was last supported on Snapcraft 4 available on the "
+        "'4.x' channel.",
+        permanent=True,
+    )
+
+
+@pytest.mark.usefixtures("mock_argv", "mock_confirm")
+def test_get_effective_base_core18_esm_warning(
+    emitter, snapcraft_yaml, mock_run_new_or_fallback_remote_build
+):
+    """Warn if core18, an ESM base, is used."""
+    snapcraft_yaml(base="core18")
+
+    cli.run()
+
+    mock_run_new_or_fallback_remote_build.assert_called_once_with("core18")
+    emitter.assert_progress(
+        "WARNING: base 'core18' was last supported on Snapcraft 7 available on the "
+        "'7.x' channel.",
+        permanent=True,
+    )
 
 
 #######################