.. _classes: ====================== Class Overview ====================== Class Structure ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here's the overview of the essential classes used in the `tmt` project. It should help you to get quickly started and better understand the relation between the individual classes. Basic ------------------------------------------------------------------ The ``Common`` class is the parent of most of the available classes, it provides common methods for logging, running commands and workdir handling. The ``_CommonBase`` class is an actual root of the class tree, makes sure the inheritance works correctly. The ``Core`` class together with its child classes ``Test``, ``Plan`` and ``Story`` cover the :ref:`specification`: .. code-block:: _CommonBase └── Common ├── Core │   ├── Plan │   ├── Story │   └── Test ├── Clean ├── Guest ├── Phase ├── Run ├── Status ├── Step └── Tree Phases ------------------------------------------------------------------ Actions performed during a normal step and plugins for individual step: .. code-block:: Phase ├── Action │   ├── Login │   └── Reboot └── BasePlugin ├── GuestlessPlugin │   ├── DiscoverPlugin │   │   ├── DiscoverFmf │   │   └── DiscoverShell │   ├── ProvisionPlugin │   │   ├── ProvisionArtemis │   │   ├── ProvisionConnect │   │   ├── ProvisionLocal │   │   ├── ProvisionPodman │   │   └── ProvisionTestcloud │   └── ReportPlugin │   ├── ReportDisplay │   ├── ReportHtml │   ├── ReportJUnit │   ├── ReportPolarion │   └── ReportReportPortal └── Plugin ├── ExecutePlugin │   └── ExecuteInternal │   └── ExecuteUpgrade ├── FinishPlugin │   ├── FinishAnsible │   └── FinishShell └── PreparePlugin ├── PrepareAnsible │   └── FinishAnsible ├── PrepareInstall └── PrepareShell Steps ------------------------------------------------------------------ A brief overview of all test steps: .. code-block:: Step ├── Discover ├── Provision ├── Prepare ├── Execute ├── Finish └── Report Containers used for storing configuration data for individual step plugins: .. code-block:: DataContainer └── SpecBasedContainer, SerializableContainer ├── FmfId │   └── DependencyFmfId ├── Link ├── Links └── StepData ├── DiscoverStepData │   ├── DiscoverFmfStepData │   └── DiscoverShellData ├── ExecuteStepData │   ├── ExecuteInternalData │   └── ExecuteUpgradeData ├── FinishStepData │   └── FinishShellData ├── PrepareStepData │   ├── PrepareAnsibleData │   ├── PrepareInstallData │   └── PrepareShellData ├── ProvisionStepData │   ├── ProvisionArtemisData │   ├── ProvisionConnectData │   ├── ProvisionLocalData │   ├── ProvisionPodmanData │   └── ProvisionTestcloudData └── ReportStepData ├── ReportHtmlData ├── ReportJUnitData ├── ReportPolarionData └── ReportReportPortalData Guests ------------------------------------------------------------------ Guests provisioned for test execution: .. code-block:: Guest ├── GuestContainer ├── GuestLocal └── GuestSsh ├── GuestArtemis └── GuestTestcloud Data related to provisioned guests: .. code-block:: GuestData ├── GuestSshData │   ├── ArtemisGuestData │   ├── ConnectGuestData │   └── TestcloudGuestData └── PodmanGuestData Attributes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Hierarchy ------------------------------------------------------------------ Object hierarchy is following: ``Run`` -> ``Plans`` -> ``Steps`` -> ``Plugins``, where the ``Run`` is on the top of this hierarchy. The objects have the ``parent`` attribute, that is pointing to the parent in which the current instance is contained. Nodes, Trees ------------------------------------------------------------------ The ``node`` attribute of ``Test``, ``Plan`` and ``Story`` instances references the original leaf node of the fmf metadata tree from which the respective test, plan or story have been created. In a similar way, the ``tree`` property of the ``Tree`` instance points to the original ``fmf.Tree`` from which it was initialized. Keys, Fields, Options ------------------------------------------------------------------ Configuration options appear throughout the code in several forms, here's a summary of the differences and naming: key a config input coming from the ``fmf`` files, consistently using dashes, example: ``some-thing`` field defined by the ``tmt.utils.field()`` helper, is a python attribute, using underscores, example: ``some_thing`` option coming from the command line, defined using the ``tmt.options.option()`` helper, includes the ``--`` prefix, example: ``--some-thing`` Class Conversions ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Various internal objects and classes often need to be converted from their Python nature to data that can be saved, loaded or exported in different form. To facilitate these conversions, three families of helper methods are provided, each with its own set of use cases. ``to_spec``/``to_minimal_spec``/``from_spec`` ------------------------------------------------------------------ This family of methods works with tmt *specification*, i.e. raw user-provided data coming from fmf files describing plans, tests, stories, or from command-line options. ``from_spec()`` shall be called to spawn objects representing the user input, while ``to_spec()`` should produce output one could find in fmf files. The default implementation comes from ``tmt.utils.SpecBasedContainer`` class, all classes based on user input data should include this class among their bases. ``to_minimal_spec`` performs the identical operation as ``to_spec``, but its result should not include keys that are optional and not set, while ``to_spec`` should always include all keys, even when set to default values or not set at all. .. code-block:: python # Create an fmf id object from raw data fmf_id = tmt.base.FmfId.from_spec({'url': ..., 'ref': ...}) ``to_serialized``/``from_serialized``/``unserialize`` ------------------------------------------------------------------ This family of methods is aiming at runtime objects that may be saved into and loaded from tmt working files, i.e. files tmt uses to store a state in its workdir, like `step.yaml` or `guests.yaml`. Third member of this family, ``unserialize``, is similar to ``from_serialized`` - both create an object from its serialized form, only ``unserialize`` is capable of detecting the class to instantiate while for using ``from_serialized``, one must already know which class to work with. ``unserialize`` then uses ``from_serialized`` under the hood to do the heavy lifting when correct class is identified. The default implementation comes from ``tmt.utils.SerializableContainer`` class, all classes that are being saved and loaded during tmt run should include this class among their bases. See https://en.wikipedia.org/wiki/Serialization for more details on the concept of serialization. .. code-block:: python # tmt.steps.discover.shell.DiscoverShellData wishes to unserialize its # `tests` a list of `TestDescription` objects rather than a list of # dictionaries (the default implementation). @classmethod def from_serialized(cls, serialized: Dict[str, Any]) -> 'DiscoverShellData': obj = super().from_serialized(serialized) obj.tests = [TestDescription.from_serialized( serialized_test) for serialized_test in serialized['tests']] return obj # A step saving its state... content: Dict[str, Any] = { 'status': self.status(), 'data': [datum.to_serialized() for datum in self.data] } self.write('step.yaml', tmt.utils.dict_to_yaml(content)) # ... and loading it back. # Note the use of unserialize(): step data may have been serialized from # various different classes (derived from tmt.steps.provision.Guest), # and unserialize() will detect the correct class. raw_step_data: Dict[Any, Any] = tmt.utils.yaml_to_dict(self.read('step.yaml')) self.data = [ StepData.unserialize(raw_datum) for raw_datum in raw_step_data['data'] ] ``to_dict``/``to_minimal_dict`` ------------------------------------------------------------------ Very special helper methods: its use cases are not related to any input or output data, and most of the time, when in need of iterating over object's keys and/or values, one can use ``keys()``, ``values()`` or ``items()`` methods. They are used as sources of data for serialization and validation, but they usually have no use outside of default implementations. .. warning:: If you think of using ``to_dict()``, please, think again and be sure you know what are you doing. Despite its output being sometimes perfectly compatible with output of ``to_serialized()`` or ``to_spec()``, it is not generaly true, and using it instead of proper methods may lead to unexpected exceptions. The same applies to ``to_minimal_dict()``. .. code-block:: python # tmt.base.FmfId's specification is basically just a mapping, # therefore `to_dict()` is good enough to produce a specification. def to_spec(self) -> Dict[str, Any]: return self.to_dict() Commands vs. shell scripts ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ tmt internals makes distinction between a command and a shell script. This is important to enforce proper handling of shell scripts specified by users - ``prepare`` and ``finish`` scripts, test commands, etc. There are two basic types for describing commands: * ``tmt.utils.Command`` - a list of "command elements" representing an executable followed by its arguments. Common throughout tmt's code, never used with ``shell=True``. This is the only form accepted by ``tmt.utils.Common.run()`` method. * ``tmt.utils.ShellScript`` - a free-form string containing a shell script, from a single built-in command to multiline complex scripts. Traditionally, this kind of "commands" is accompanied by ``shell=True``, tmt code converts ``ShellScript`` values into ``Command`` elements, e.g. with the help of the ``ShellScript.to_element()`` method. Following rules apply: * tmt code shall stick to ``Command`` and ``ShellScript`` types when passing commands between functions and classes. There should be no need for custom types like ``List[str]`` or ``str``, the preferred types are equipped with necessary conversion helpers. * in most cases, tmt is given **scripts** by users, not executable commands with options. Plugin writers should avoid using bare ``str`` or ``Command`` types when annotating this kind of input. For example: .. code-block:: python class FooStepData(tmt.steps.StepData): # `--script ...` option dictates step data to have a field of correct type script: List[tmt.utils.ShellScript] ... def go(self): ... # When calling `get()`, hint type linters with the right type scripts: List[tmt.utils.ShellScript] = self.get('script') * ``shell=True`` should not be needed, use ``ShellScript.to_shell_command()`` instead. Both ``ShellScript`` and ``Command`` support addition, therefore it's possible to build up commands and scripts from smaller building blocks: .. code-block:: python >>> command = Command('ls') >>> command += Command('-al') >>> command += ['/'] >>> str(command) 'ls -al /' >>> script = ShellScript('ls -al') >>> script += ShellScript('ls -al $HOME') >>> str(script) 'ls -al; ls -al $HOME' There are several functions available to help with conversion between command and shell script format: ``Command.to_element`` ------------------------------------------------------------------ Convert a command - or possibly just command options - to a command element. Useful when you got a list of command options that another command is expecting as its options: .. code-block:: python >>> ssh_command = Command('ssh', '-o', 'ForwardX11=yes', '-o', 'IdentitiesOnly=yes') >>> command = Command('rsync', '-e', ssh_command.to_element()) >>> str(command) "rsync -e 'ssh -o ForwardX11=yes -o IdentitiesOnly=yes'" ``Command.to_script`` ------------------------------------------------------------------ Convert a command to a shell script: .. code-block:: python >>> command1 = Command('ls', '-al', '/') >>> command2 = Command('bash', '-c', command1.to_script().to_element()) >>> str(command2) "bash -c 'ls -al /'" ``Script.to_element`` ------------------------------------------------------------------ Convert a shell script to a command element: .. code-block:: python >>> command = Command('bash', '-c', ShellScript('ls -al /').to_element()) >>> str(command) "bash -c 'ls -al /'" ``Script.from_scripts`` ------------------------------------------------------------------ Convert a list of shell scripts into a single script. Useful when building a script from multiple steps: .. code-block:: python >>> scripts: List[ShellScript] = [ ... ShellScript('cd $HOME'), ... ShellScript('ls -al') ... ] >>> >>> if True: ... scripts.append(ShellScript('rm -f bar')) ... >>> script = ShellScript.from_scripts(scripts) >>> str(script) 'cd $HOME; ls -al; rm -f bar' ``Script.to_shell_command`` ------------------------------------------------------------------ Convert a shell script into a shell-driven command. This is what ``shell=True`` would do, but it makes it explicit and involves correct type conversion: .. code-block:: python >>> script = ShellScript(""" ... cd $HOME ... ls -al ... """) >>> command = script.to_shell_command() >>> str(command) "/bin/bash -c '\ncd $HOME\nls -al\n'"