fix(lifecycle): return correct base when using devel for build-base

get_effective_base() should not return "devel" and pass it to the
PartsLifecycle(), which make the parts think the coreXX is "devel".
Thus checking the wrong path for dynamic linking.

snapcraft/parts/lifecycle.py

@@ -164,7 +164,7 @@ def _run_command(  # noqa PLR0913 # pylint: disable=too-many-branches, too-many-
         project.parts,
         work_dir=work_dir,
         assets_dir=assets_dir,
-        base=project.get_effective_base(),
+        base=project.get_effective_base(allow_return_devel=(project.type == "base")),
         project_base=project.base or "",
         confinement=project.confinement,
         package_repositories=project.package_repositories,
@@ -429,7 +429,7 @@ def _run_in_provider(  # noqa PLR0915
         build_for=project.get_build_for(),
     )
 
-    snapcraft_base = project.get_effective_base()
+    snapcraft_base = project.get_effective_base(allow_return_devel=True)
     build_base = providers.SNAPCRAFT_BASE_TO_PROVIDER_BASE[snapcraft_base]
 
     if snapcraft_base == "devel":

snapcraft/projects.py

@@ -700,7 +700,7 @@ def get_extra_build_snaps(self) -> List[str]:
 
         return extra_build_snaps
 
-    def get_effective_base(self) -> str:
+    def get_effective_base(self, allow_return_devel=False) -> str:
         """Return the base to use to create the snap."""
         base = get_effective_base(
             base=self.base,
@@ -713,6 +713,17 @@ def get_effective_base(self) -> str:
         if base is None:
             raise RuntimeError("cannot determine build base")
 
+        # "devel" is not a valid base but a valid build-base that may returned.
+        # the actual base is the same as the base defined in the project.
+        if base == "devel":
+            if allow_return_devel:
+                return base
+
+            if self.base is None:
+                raise RuntimeError("cannot determine base")
+
+            return self.base
+
         return base
 
     def get_build_on(self) -> str:

snapcraft/utils.py

@@ -218,7 +218,8 @@ def get_effective_base(
 
     Returns build-base if set, but if not, name is returned if the
     snap is of type base. For all other snaps, the base is returned
-    as the build-base.
+    as the build-base. This may return "devel" if the build-base is
+    set it to "devel".
     """
     if build_base is not None:
         return build_base

tests/unit/parts/test_lifecycle.py

@@ -1860,3 +1860,39 @@ def test_lifecycle_write_metadata(
             primed_stage_packages=[],
         )
     ]
+
+
+@pytest.mark.parametrize(
+    "base,build_base,grade,allow_return_devel,expected_base",
+    [
+        ["coreXX", None, "stable", False, "coreXX"],
+        ["coreXX", None, "stable", True, "coreXX"],
+        ["coreXX", None, "devel", False, "coreXX"],
+        ["coreXX", None, "devel", True, "coreXX"],
+        ["coreXX", "coreYY", "stable", False, "coreYY"],
+        ["coreXX", "coreYY", "stable", True, "coreYY"],
+        ["coreXX", "coreYY", "devel", False, "coreYY"],
+        ["coreXX", "coreYY", "devel", True, "coreYY"],
+        ["coreXX", "devel", "devel", False, "coreXX"],
+        ["coreXX", "devel", "devel", True, "devel"],
+    ],
+)
+def test_lifecycle_get_effective_base(
+    emitter,
+    mocker,
+    snapcraft_yaml,
+    tmp_path,
+    base,
+    build_base,
+    grade,
+    allow_return_devel,
+    expected_base,
+):
+    """Get the effective base from the project."""
+    project = Project.unmarshal(
+        snapcraft_yaml(base=base, build_base=build_base, grade=grade)
+    )
+    assert (
+        project.get_effective_base(allow_return_devel=allow_return_devel)
+        == expected_base
+    )