fix: reprime for try

This solves the case where prime was run before try, where a
subsequent run of try would mask the contents of the existing prime
directory with a newly mounted one from the host. In legacy we had the
concept of `clean --unprime` to solve this.

Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>

snapcraft/parts/lifecycle.py

@@ -346,6 +346,9 @@ def _run_lifecycle_and_pack(
             step_name,
             shell=getattr(parsed_args, "shell", False),
             shell_after=getattr(parsed_args, "shell_after", False),
+            # Repriming needs to happen to take into account any changes to
+            # the actual target directory.
+            rerun_step=command_name == "try",
         )
 
     # Extract metadata and generate snap.yaml

snapcraft/parts/parts.py

@@ -141,10 +141,14 @@ def run(
         *,
         shell: bool = False,
         shell_after: bool = False,
+        rerun_step: bool = False,
     ) -> None:
         """Run the parts lifecycle.
 
         :param target_step: The final step to execute.
+        :param shell: Enter a shell instead of running step_name.
+        :param shell: Enter a shell after running step_name.
+        :param rerun_step: Force running step_name.
 
         :raises PartsLifecycleError: On error during lifecycle.
         :raises RuntimeError: On unexpected error.
@@ -171,6 +175,16 @@ def run(
 
             with self._lcm.action_executor() as aex:
                 for action in actions:
+                    # Workaround until canonical/craft-parts#540 is fixed
+                    if action.step == target_step and rerun_step:
+                        action = craft_parts.Action(
+                            part_name=action.part_name,
+                            step=action.step,
+                            action_type=ActionType.RERUN,
+                            reason="forced rerun",
+                            project_vars=action.project_vars,
+                            properties=action.properties,
+                        )
                     message = _action_message(action)
                     emit.progress(f"Executing parts lifecycle: {message}")
                     with emit.open_stream("Executing action") as stream:

tests/spread/core22/try/task.yaml

@@ -7,11 +7,14 @@ execute: |
   chmod a+w prime
   
   unset SNAPCRAFT_BUILD_ENVIRONMENT
+  # Prime first to regression test snapcore/snapcraft#4219
+  snapcraft prime --use-lxd
+  # Followed by the actual try
   snapcraft try --use-lxd
   
   find prime/meta/snap.yaml
   find prime/usr/bin/hello
   
   snap try prime
   hello-try | MATCH "Hello, world"
-  snap remove hello-try
+  snap remove hello-try

tests/unit/parts/test_lifecycle.py

@@ -299,13 +299,45 @@ def test_lifecycle_run_command_step(
         parsed_args=parsed_args,
     )
 
-    call_args = {"shell": False, "shell_after": False}
+    call_args = {"shell": False, "shell_after": False, "rerun_step": False}
     if debug_shell:
         call_args[debug_shell] = True
 
     assert run_mock.mock_calls == [call(step, **call_args)]
 
 
+def test_lifecycle_run_try_command(snapcraft_yaml, project_vars, new_dir, mocker):
+    project = Project.unmarshal(snapcraft_yaml(base="core22"))
+    run_mock = mocker.patch("snapcraft.parts.PartsLifecycle.run")
+    mocker.patch("snapcraft.meta.snap_yaml.write")
+    mocker.patch("snapcraft.pack.pack_snap")
+
+    parsed_args = argparse.Namespace(
+        debug=False,
+        destructive_mode=True,
+        enable_manifest=False,
+        shell=False,
+        shell_after=False,
+        use_lxd=False,
+        ua_token=None,
+        parts=[],
+    )
+
+    parts_lifecycle._run_command(
+        "try",
+        project=project,
+        parse_info={},
+        assets_dir=Path(),
+        start_time=datetime.now(),
+        parallel_build_count=8,
+        parsed_args=parsed_args,
+    )
+
+    assert run_mock.mock_calls == [
+        call("prime", shell=False, shell_after=False, rerun_step=True)
+    ]
+
+
 @pytest.mark.parametrize("cmd", ["pack", "snap"])
 def test_lifecycle_run_command_pack(cmd, snapcraft_yaml, project_vars, new_dir, mocker):
     project = Project.unmarshal(snapcraft_yaml(base="core22"))
@@ -333,7 +365,9 @@ def test_lifecycle_run_command_pack(cmd, snapcraft_yaml, project_vars, new_dir,
         ),
     )
 
-    assert run_mock.mock_calls == [call("prime", shell=False, shell_after=False)]
+    assert run_mock.mock_calls == [
+        call("prime", shell=False, shell_after=False, rerun_step=False)
+    ]
     assert pack_mock.mock_calls[:1] == [
         call(
             new_dir / "prime",
@@ -382,7 +416,9 @@ def test_lifecycle_pack_destructive_mode(
     )
 
     assert run_in_provider_mock.mock_calls == []
-    assert run_mock.mock_calls == [call("prime", shell=False, shell_after=False)]
+    assert run_mock.mock_calls == [
+        call("prime", shell=False, shell_after=False, rerun_step=False)
+    ]
     assert pack_mock.mock_calls[:1] == [
         call(
             new_dir / "home/prime",
@@ -432,7 +468,9 @@ def test_lifecycle_pack_managed(cmd, snapcraft_yaml, project_vars, new_dir, mock
     )
 
     assert run_in_provider_mock.mock_calls == []
-    assert run_mock.mock_calls == [call("prime", shell=False, shell_after=False)]
+    assert run_mock.mock_calls == [
+        call("prime", shell=False, shell_after=False, rerun_step=False)
+    ]
     assert pack_mock.mock_calls[:1] == [
         call(
             new_dir / "home/prime",
@@ -525,7 +563,9 @@ def test_lifecycle_pack_metadata_error(cmd, snapcraft_yaml, new_dir, mocker):
     assert str(raised.value) == (
         "error setting grade: unexpected value; permitted: 'stable', 'devel'"
     )
-    assert run_mock.mock_calls == [call("prime", shell=False, shell_after=False)]
+    assert run_mock.mock_calls == [
+        call("prime", shell=False, shell_after=False, rerun_step=False)
+    ]
     assert pack_mock.mock_calls == []