Merge ~ogayot/curtin:fix-curthooks-no-kernel into curtin:master

[Olivier Gayot]

curthooks: fix exception when passing 'kernel: null'

When we don't want curthooks to install a kernel, we can pass:

  kernel: null

However, currently, it makes the code raise an exception because we run
.get() on the kernel object even if it is None.

 config.merge_config(mapping, kernel_cfg.get('mapping', {}))
 AttributeError: 'NoneType' object has no attribute 'get'
 'NoneType' object has no attribute 'get'

Fixed by returning gracefully without installing any kernel upon
encountering this configuration.

LP: #2026225

Signed-off-by: Olivier Gayot <email address hidden>

When we specify 'kernel: null' in the curthooks configuration, curtin raises an exception:

builtin_curthooks
     install_kernel(cfg, target)
   File "/snap/ubuntu-desktop-installer/x1/lib/python3.10/site-packages/curtin/commands/curthooks.py", line 375, in install_kernel
     config.merge_config(mapping, kernel_cfg.get('mapping', {}))
 AttributeError: 'NoneType' object has no attribute 'get'
 'NoneType' object has no attribute 'get'
 curtin: Installation failed with exception: Unexpected error while running command.

[Server Team CI bot (server-team-bot)]

FAILED: Continuous integration, rev:66606faddb99576a72e8e2818f05c40905641410
https://jenkins.canonical.com/server-team/job/curtin-ci/154/
Executed test runs:
    FAILURE: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-amd64/154/
    FAILURE: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-arm64/154/
    FAILURE: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-ppc64el/154/
    FAILURE: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-s390x/154/

Click here to trigger a rebuild:
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review: Needs Fixing (continuous-integration)

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:93d47e95859fc92d5108913fc15b98a0ad56234e
https://jenkins.canonical.com/server-team/job/curtin-ci/155/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-amd64/155/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-arm64/155/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-ppc64el/155/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-s390x/155/

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

[Dan Bungert (dbungert)]

Please mention the LP in the commit message then LGTM. Thanks!

review: Approve

[Server Team CI bot (server-team-bot)]

Autolanding: FAILED
More details in the following jenkins job:
https://jenkins.canonical.com/server-team/job/curtin-autoland-test/90/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-autoland-test/nodes=metal-amd64/90/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-autoland-test/nodes=metal-arm64/90/
    FAILURE: https://jenkins.canonical.com/server-team/job/curtin-autoland-test/nodes=metal-ppc64el/90/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-autoland-test/nodes=metal-s390x/90/

review: Needs Fixing (continuous-integration)

[Server Team CI bot (server-team-bot)]

review: Approve (continuous-integration)

diff --git a/curtin/commands/curthooks.py b/curtin/commands/curthooks.py
index c52d5ab..b0844d5 100644
--- a/curtin/commands/curthooks.py
+++ b/curtin/commands/curthooks.py
@@ -365,12 +365,13 @@ def install_kernel(cfg, target):
     kernel_cfg = cfg.get('kernel', {'package': None,
                                     'fallback-package': "linux-generic",
                                     'mapping': {}})
-    if kernel_cfg is not None:
-        kernel_package = kernel_cfg.get('package')
-        kernel_fallback = kernel_cfg.get('fallback-package')
-    else:
-        kernel_package = None
-        kernel_fallback = None
+
+    if kernel_cfg is None:
+        LOG.debug("Not installing any kernel since kernel: null was specified")
+        return
+
+    kernel_package = kernel_cfg.get('package')
+    kernel_fallback = kernel_cfg.get('fallback-package')
 
     mapping = copy.deepcopy(KERNEL_MAPPING)
     config.merge_config(mapping, kernel_cfg.get('mapping', {}))
diff --git a/tests/unittests/test_curthooks.py b/tests/unittests/test_curthooks.py
index d6b5445..a67bc81 100644
--- a/tests/unittests/test_curthooks.py
+++ b/tests/unittests/test_curthooks.py
@@ -94,6 +94,15 @@ class TestCurthooksInstallKernel(CiTestCase):
             self.mock_instpkg.assert_called_with(
                 [kernel_package], target=self.target, env=env)
 
+    def test__installs_kernel_null(self):
+        kernel_cfg = {'kernel': None}
+        self.mock_get_flash_kernel_pkgs.return_value = None
+
+        with patch.dict(os.environ, clear=True):
+            curthooks.install_kernel(kernel_cfg, self.target)
+
+            self.mock_instpkg.assert_not_called()
+
 
 class TestEnableDisableUpdateInitramfs(CiTestCase):