lint: Fix or silence 'cyclic-import' errors and enable pylint for it

Cyclic imports can be confusing because the order in which we import
dependencies can make the import fail or not. We should not rely on
ordering of imports for our code. This fixes everywhere possible the
imports and silence explicitely some which are not convenient or would
require big refactors

20 files changed, 38 insertions, 36 deletions

diff --git a/.pylintrc b/.pylintrc
index 0cdb7586e..c47ef92cf 100644
--- a/.pylintrc
+++ b/.pylintrc
@@ -105,11 +105,6 @@ disable=#####################################
 
         unused-argument,
 
-        ###########################################################
-        # Messages that report warnings which should be addressed #
-        ###########################################################
-
-        cyclic-import,
 
 # Enable the message, report, category or checker with the given id(s). You can
 # either give multiple identifier separated by comma (,) or put this option
diff --git a/buildstream/_artifact.py b/buildstream/_artifact.py
index 71b3c6f5c..6d26eb392 100644
--- a/buildstream/_artifact.py
+++ b/buildstream/_artifact.py
@@ -32,9 +32,8 @@ import os
 import shutil
 
 from . import _yaml
-from . import Scope
 from ._exceptions import ArtifactError
-from .types import _KeyStrength
+from .types import Scope, _KeyStrength
 from .storage._casbaseddirectory import CasBasedDirectory
 
 
diff --git a/buildstream/_frontend/app.py b/buildstream/_frontend/app.py
index ebc05e398..d4ea83871 100644
--- a/buildstream/_frontend/app.py
+++ b/buildstream/_frontend/app.py
@@ -41,7 +41,9 @@ from .. import _yaml
 from .._scheduler import ElementJob, JobStatus
 
 # Import frontend assets
-from . import Profile, LogLine, Status
+from .profile import Profile
+from .status import Status
+from .widget import LogLine
 
 # Intendation for all logging
 INDENT = 4
@@ -127,7 +129,7 @@ class App():
     def create(cls, *args, **kwargs):
         if sys.platform.startswith('linux'):
             # Use an App with linux specific features
-            from .linuxapp import LinuxApp
+            from .linuxapp import LinuxApp  # pylint: disable=cyclic-import
             return LinuxApp(*args, **kwargs)
         else:
             # The base App() class is default
diff --git a/buildstream/_frontend/widget.py b/buildstream/_frontend/widget.py
index f092cb5ec..cfe3a06e9 100644
--- a/buildstream/_frontend/widget.py
+++ b/buildstream/_frontend/widget.py
@@ -26,7 +26,7 @@ import textwrap
 from ruamel import yaml
 import click
 
-from . import Profile
+from .profile import Profile
 from .. import Element, Consistency, Scope
 from .. import _yaml
 from .. import __version__ as bst_version
diff --git a/buildstream/_gitsourcebase.py b/buildstream/_gitsourcebase.py
index d4c54fd89..5777d4aed 100644
--- a/buildstream/_gitsourcebase.py
+++ b/buildstream/_gitsourcebase.py
@@ -30,9 +30,10 @@ from tempfile import TemporaryFile
 
 from configparser import RawConfigParser
 
-from buildstream import Source, SourceError, Consistency, SourceFetcher, CoreWarnings
-from buildstream import utils
-from buildstream.utils import move_atomic, DirectoryExistsError
+from .source import Source, SourceError, SourceFetcher
+from .types import Consistency, CoreWarnings
+from . import utils
+from .utils import move_atomic, DirectoryExistsError
 
 GIT_MODULES = '.gitmodules'
 
diff --git a/buildstream/_loader/loader.py b/buildstream/_loader/loader.py
index 965edbee8..6d8310cfa 100644
--- a/buildstream/_loader/loader.py
+++ b/buildstream/_loader/loader.py
@@ -30,8 +30,8 @@ from .._includes import Includes
 
 from .types import Symbol
 from .loadelement import LoadElement, _extract_depends_from_node
-from . import MetaElement
-from . import MetaSource
+from .metaelement import MetaElement
+from .metasource import MetaSource
 from ..types import CoreWarnings
 from .._message import Message, MessageType
 
@@ -562,7 +562,7 @@ class Loader():
         # Load the project
         project_dir = os.path.join(basedir, element.path)
         try:
-            from .._project import Project
+            from .._project import Project  # pylint: disable=cyclic-import
             project = Project(project_dir, self._context, junction=element,
                               parent_loader=self, search_for_project=False)
         except LoadError as e:
diff --git a/buildstream/_platform/darwin.py b/buildstream/_platform/darwin.py
index 8df8cda24..8e08685ec 100644
--- a/buildstream/_platform/darwin.py
+++ b/buildstream/_platform/darwin.py
@@ -19,7 +19,7 @@ import os
 
 from ..sandbox import SandboxDummy
 
-from . import Platform
+from .platform import Platform
 
 
 class Darwin(Platform):
diff --git a/buildstream/_platform/linux.py b/buildstream/_platform/linux.py
index 85e810c26..e4ce02572 100644
--- a/buildstream/_platform/linux.py
+++ b/buildstream/_platform/linux.py
@@ -24,7 +24,7 @@ from .. import _site
 from .. import utils
 from ..sandbox import SandboxDummy
 
-from . import Platform
+from .platform import Platform
 from .._exceptions import PlatformError
 
 
diff --git a/buildstream/_platform/platform.py b/buildstream/_platform/platform.py
index 73ed571fe..eef07812a 100644
--- a/buildstream/_platform/platform.py
+++ b/buildstream/_platform/platform.py
@@ -50,11 +50,11 @@ class Platform():
             backend = 'unix'
 
         if backend == 'linux':
-            from .linux import Linux as PlatformImpl
+            from .linux import Linux as PlatformImpl  # pylint: disable=cyclic-import
         elif backend == 'darwin':
-            from .darwin import Darwin as PlatformImpl
+            from .darwin import Darwin as PlatformImpl  # pylint: disable=cyclic-import
         elif backend == 'unix':
-            from .unix import Unix as PlatformImpl
+            from .unix import Unix as PlatformImpl  # pylint: disable=cyclic-import
         else:
             raise PlatformError("No such platform: '{}'".format(backend))
 
diff --git a/buildstream/_platform/unix.py b/buildstream/_platform/unix.py
index bbc55c3af..d04b0712c 100644
--- a/buildstream/_platform/unix.py
+++ b/buildstream/_platform/unix.py
@@ -21,7 +21,7 @@ import os
 
 from .._exceptions import PlatformError
 
-from . import Platform
+from .platform import Platform
 
 
 class Unix(Platform):
diff --git a/buildstream/buildelement.py b/buildstream/buildelement.py
index eb30d9d31..158f5fc11 100644
--- a/buildstream/buildelement.py
+++ b/buildstream/buildelement.py
@@ -135,8 +135,10 @@ artifact collection purposes.
 """
 
 import os
-from . import Element, Scope
-from . import SandboxFlags
+
+from .element import Element
+from .sandbox import SandboxFlags
+from .types import Scope
 
 
 # This list is preserved because of an unfortunate situation, we
diff --git a/buildstream/element.py b/buildstream/element.py
index 23127d125..2bb492cb3 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -93,16 +93,16 @@ from ._versions import BST_CORE_ARTIFACT_VERSION
 from ._exceptions import BstError, LoadError, LoadErrorReason, ImplError, \
     ErrorDomain, SourceCacheError
 from .utils import UtilError
-from . import Plugin, Consistency, Scope
-from . import SandboxFlags, SandboxCommandError
 from . import utils
 from . import _cachekey
 from . import _signals
 from . import _site
 from ._platform import Platform
+from .plugin import Plugin
+from .sandbox import SandboxFlags, SandboxCommandError
 from .sandbox._config import SandboxConfig
 from .sandbox._sandboxremote import SandboxRemote
-from .types import _KeyStrength, CoreWarnings, _UniquePriorityQueue
+from .types import Consistency, CoreWarnings, Scope, _KeyStrength, _UniquePriorityQueue
 from ._artifact import Artifact
 
 from .storage.directory import Directory
diff --git a/buildstream/sandbox/_sandboxdummy.py b/buildstream/sandbox/_sandboxdummy.py
index 4cc3aae9c..750ddb05d 100644
--- a/buildstream/sandbox/_sandboxdummy.py
+++ b/buildstream/sandbox/_sandboxdummy.py
@@ -17,7 +17,7 @@
 #  Authors:
 
 from .._exceptions import SandboxError
-from . import Sandbox
+from .sandbox import Sandbox
 
 
 class SandboxDummy(Sandbox):
diff --git a/buildstream/sandbox/_sandboxremote.py b/buildstream/sandbox/_sandboxremote.py
index f7ee6471f..14e160dc5 100644
--- a/buildstream/sandbox/_sandboxremote.py
+++ b/buildstream/sandbox/_sandboxremote.py
@@ -28,8 +28,7 @@ import grpc
 
 from .. import utils
 from .._message import Message, MessageType
-from . import Sandbox, SandboxCommandError
-from .sandbox import _SandboxBatch
+from .sandbox import Sandbox, SandboxCommandError, _SandboxBatch
 from ..storage._casbaseddirectory import CasBasedDirectory
 from .. import _signals
 from .._protos.build.bazel.remote.execution.v2 import remote_execution_pb2, remote_execution_pb2_grpc
diff --git a/buildstream/scriptelement.py b/buildstream/scriptelement.py
index 3327f818e..dfdbb45c0 100644
--- a/buildstream/scriptelement.py
+++ b/buildstream/scriptelement.py
@@ -35,7 +35,9 @@ implementations.
 import os
 from collections import OrderedDict
 
-from . import Element, ElementError, Scope, SandboxFlags
+from .element import Element, ElementError
+from .sandbox import SandboxFlags
+from .types import Scope
 
 
 class ScriptElement(Element):
diff --git a/buildstream/source.py b/buildstream/source.py
index 36885ee2a..6f4ff575b 100644
--- a/buildstream/source.py
+++ b/buildstream/source.py
@@ -165,8 +165,9 @@ import os
 from collections.abc import Mapping
 from contextlib import contextmanager
 
-from . import Plugin, Consistency
 from . import _yaml, utils
+from .plugin import Plugin
+from .types import Consistency
 from ._exceptions import BstError, ImplError, ErrorDomain
 from ._loader.metasource import MetaSource
 from ._projectrefs import ProjectRefStorage
diff --git a/buildstream/storage/_filebaseddirectory.py b/buildstream/storage/_filebaseddirectory.py
index 742200379..9a746f731 100644
--- a/buildstream/storage/_filebaseddirectory.py
+++ b/buildstream/storage/_filebaseddirectory.py
@@ -79,7 +79,7 @@ class FileBasedDirectory(Directory):
                      can_link=False):
         """ See superclass Directory for arguments """
 
-        from ._casbaseddirectory import CasBasedDirectory
+        from ._casbaseddirectory import CasBasedDirectory  # pylint: disable=cyclic-import
 
         if isinstance(external_pathspec, CasBasedDirectory):
             if can_link and not update_mtime:
diff --git a/buildstream/utils.py b/buildstream/utils.py
index f4a329210..e730dc2a9 100644
--- a/buildstream/utils.py
+++ b/buildstream/utils.py
@@ -485,7 +485,7 @@ def get_bst_version():
        (int): The minor version
     """
     # Import this only conditionally, it's not resolved at bash complete time
-    from . import __version__
+    from . import __version__  # pylint: disable=cyclic-import
     versions = __version__.split('.')[:2]
 
     if versions[0] == '0+untagged':
diff --git a/tests/testutils/element_generators.py b/tests/testutils/element_generators.py
index 448c8571a..4461e4b7f 100644
--- a/tests/testutils/element_generators.py
+++ b/tests/testutils/element_generators.py
@@ -3,7 +3,7 @@ import os
 from buildstream import _yaml
 from buildstream import utils
 
-from . import create_repo
+from .repo import create_repo
 
 
 # create_element_size()
diff --git a/tests/testutils/junction.py b/tests/testutils/junction.py
index 01c76d14a..e0db8fcfb 100644
--- a/tests/testutils/junction.py
+++ b/tests/testutils/junction.py
@@ -1,6 +1,7 @@
-from tests.testutils import create_repo
 from buildstream import _yaml
 
+from .repo import create_repo
+
 
 # generate_junction()
 #