build-providers: add support for --shell-after

snapcraft/cli/_options.py

@@ -31,16 +31,18 @@ def get_help_record(self, ctx):
     "--no-parallel-builds",
     "--target-arch",
     "--debug",
+    "--shell-after",
 ]
 
 _BUILD_OPTIONS = [
     dict(
         is_flag=True,
-        help=("Detect best candidate location for stage-packages using geoip"),
+        help="Detect best candidate location for stage-packages using geoip",
     ),
     dict(is_flag=True, help="Force a sequential build."),
     dict(metavar="<arch>", help="Target architecture to cross compile to"),
     dict(is_flag=True, help="Shells into the environment if the build fails."),
+    dict(is_flag=True, help="Shells into the environment after the step has run."),
 ]
 
 

snapcraft/cli/lifecycle.py

@@ -45,6 +45,7 @@ def _execute(
     parts: str,
     pack_project: bool = False,
     output: str = None,
+    shell_after: bool = False,
     **kwargs
 ) -> "Project":
     # fmt: on
@@ -65,6 +66,8 @@ def _execute(
                     instance.pack_project(output=output)
                 else:
                     instance.execute_step(step)
+                if shell_after:
+                    instance.shell()
             except Exception as exc:
                 if project.debug:
                     instance.shell()

tests/unit/commands/test_build_providers.py

@@ -15,6 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from unittest import mock
+from typing import Optional
 
 import fixtures
 from testtools.matchers import Equals
@@ -69,3 +70,61 @@ def test_step_without_debug_using_build_provider_fails_and_does_not_shell(self):
         self.assertRaises(ProviderExecError, self.run_command, ["pull"])
 
         self.shell_mock.assert_not_called()
+
+
+class BuildProviderShellCommandTestCase(LifecycleCommandsBaseTestCase):
+    def setUp(self):
+        super().setUp()
+        self.useFixture(
+            fixtures.EnvironmentVariable("SNAPCRAFT_BUILD_ENVIRONMENT", "multipass")
+        )
+
+        shell_mock = mock.Mock()
+        pack_project_mock = mock.Mock()
+        execute_step_mock = mock.Mock()
+
+        class Provider(ProviderImpl):
+            def pack_project(self, *, output: Optional[str] = None) -> None:
+                pack_project_mock(output)
+
+            def execute_step(self, step: steps.Step) -> None:
+                execute_step_mock(step)
+
+            def shell(self):
+                shell_mock()
+
+        patcher = mock.patch(
+            "snapcraft.internal.build_providers.get_provider_for", return_value=Provider
+        )
+        self.provider = patcher.start()
+        self.addCleanup(patcher.stop)
+
+        self.shell_mock = shell_mock
+        self.pack_project_mock = pack_project_mock
+        self.execute_step_mock = execute_step_mock
+
+        self.make_snapcraft_yaml("pull", base="core18")
+
+    def test_step_with_shell_after(self):
+        result = self.run_command(["pull", "--shell-after"])
+
+        self.assertThat(result.exit_code, Equals(0))
+        self.pack_project_mock.assert_not_called()
+        self.execute_step_mock.assert_called_once_with(steps.PULL)
+        self.shell_mock.assert_called_once_with()
+
+    def test_snap_with_shell_after(self):
+        result = self.run_command(["snap", "--output", "fake.snap", "--shell-after"])
+
+        self.assertThat(result.exit_code, Equals(0))
+        self.pack_project_mock.assert_called_once_with("fake.snap")
+        self.execute_step_mock.assert_not_called()
+        self.shell_mock.assert_called_once_with()
+
+    def test_step_without_shell_after_does_not_enter_shell(self):
+        result = self.run_command(["pull"])
+
+        self.assertThat(result.exit_code, Equals(0))
+        self.pack_project_mock.assert_not_called()
+        self.execute_step_mock.assert_called_once_with(steps.PULL)
+        self.shell_mock.assert_not_called()