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actions

trestle.core.models.actions ¤

Action wrapper of a command.

Attributes¤

logger = logging.getLogger(__name__) module-attribute ¤

Classes¤

Action ¤

Bases: ABC

Action wrapper of a command.

Source code in trestle/core/models/actions.py 
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class Action(ABC):
    """Action wrapper of a command."""

    def __init__(self, action_type: ActionType, has_rollback: bool) -> None:
        """Initialize an base action."""
        self._type: ActionType = action_type
        self._has_rollback: bool = has_rollback

        # child class must set this flag once it executes
        self._has_executed = False

    def to_string(self) -> str:
        """Return a string representation."""
        return self.__str__()

    def get_type(self) -> ActionType:
        """Return the action type."""
        return self._type

    def _mark_executed(self) -> None:
        """Set flag that the action has been executed."""
        self._has_executed = True

    def has_executed(self) -> bool:
        """Return if the action has been executed."""
        return self._has_executed

    def _mark_rollback(self) -> None:
        """Set flag that the action has been rollbacked."""
        self._has_executed = False

    def has_rollback(self) -> bool:
        """Return if rollback of the action is possible."""
        return self._has_rollback

    def __eq__(self, other: object) -> bool:
        """Check that two actions are equal."""
        if not isinstance(other, Action):
            return False
        if self.get_type() is not other.get_type():
            return False
        is_eq = self.__dict__ == other.__dict__
        return is_eq

    @abstractmethod
    def execute(self) -> None:
        """Execute the action."""

    @abstractmethod
    def rollback(self) -> None:
        """Rollback the action."""
Functions¤
__eq__(other) ¤

Check that two actions are equal.

Source code in trestle/core/models/actions.py 
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def __eq__(self, other: object) -> bool:
    """Check that two actions are equal."""
    if not isinstance(other, Action):
        return False
    if self.get_type() is not other.get_type():
        return False
    is_eq = self.__dict__ == other.__dict__
    return is_eq
__init__(action_type, has_rollback) ¤

Initialize an base action.

Source code in trestle/core/models/actions.py 
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def __init__(self, action_type: ActionType, has_rollback: bool) -> None:
    """Initialize an base action."""
    self._type: ActionType = action_type
    self._has_rollback: bool = has_rollback

    # child class must set this flag once it executes
    self._has_executed = False
execute() abstractmethod ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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@abstractmethod
def execute(self) -> None:
    """Execute the action."""
get_type() ¤

Return the action type.

Source code in trestle/core/models/actions.py 
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def get_type(self) -> ActionType:
    """Return the action type."""
    return self._type
has_executed() ¤

Return if the action has been executed.

Source code in trestle/core/models/actions.py 
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def has_executed(self) -> bool:
    """Return if the action has been executed."""
    return self._has_executed
has_rollback() ¤

Return if rollback of the action is possible.

Source code in trestle/core/models/actions.py 
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def has_rollback(self) -> bool:
    """Return if rollback of the action is possible."""
    return self._has_rollback
rollback() abstractmethod ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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@abstractmethod
def rollback(self) -> None:
    """Rollback the action."""
to_string() ¤

Return a string representation.

Source code in trestle/core/models/actions.py 
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def to_string(self) -> str:
    """Return a string representation."""
    return self.__str__()

ActionType ¤

Bases: Enum

Action type enum for different action type.

File system related actions have code like 1 Model processing related actions have code like 2

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class ActionType(Enum):
    """Action type enum for different action type.

    File system related actions have code like 1*
    Model processing related actions have code like 2*
    """

    # create a file or directory path
    CREATE_PATH = 10

    # remove a file or directory path
    REMOVE_PATH = 12

    # write element to a destination file or stream
    WRITE = 11

    # update or add the element at the path
    UPDATE = 20

    # remove the element at the path
    REMOVE = 21
Attributes¤
CREATE_PATH = 10 class-attribute instance-attribute ¤
REMOVE = 21 class-attribute instance-attribute ¤
REMOVE_PATH = 12 class-attribute instance-attribute ¤
UPDATE = 20 class-attribute instance-attribute ¤
WRITE = 11 class-attribute instance-attribute ¤

CreatePathAction ¤

Bases: Action

Create a file or directory path.

Source code in trestle/core/models/actions.py 
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class CreatePathAction(Action):
    """Create a file or directory path."""

    def __init__(self, sub_path: pathlib.Path, clear_content: bool = False) -> None:
        """Initialize a create path action.

        It creates all the missing directories in the path.
        If it is a file, then it also creates an empty file with the name provided

        Arguments:
            sub_path: this is the desired file or directory path that needs to be created under the project root
        """
        sub_path = sub_path.resolve()

        self._trestle_project_root = file_utils.extract_trestle_project_root(sub_path)
        if self._trestle_project_root is None:
            raise TrestleError(f'Sub path "{sub_path}" should be child of a valid trestle project')

        self._sub_path = sub_path
        self._created_paths: List[pathlib.Path] = []

        # variables for handling with file content
        self._clear_content = clear_content
        self._old_file_content = None

        super().__init__(ActionType.CREATE_PATH, True)

    def get_trestle_project_root(self) -> Optional[pathlib.Path]:
        """Return the trestle workspace root path."""
        return self._trestle_project_root

    def get_created_paths(self) -> List[pathlib.Path]:
        """Get the list of paths that were created after being executed."""
        return self._created_paths

    def execute(self) -> None:
        """Execute the action."""
        # find the start of the sub_path relative to trestle project root
        cur_index = len(self._trestle_project_root.parts)

        # loop through the sub_path parts and create as necessary
        cur_path = self._trestle_project_root
        while cur_index < len(self._sub_path.parts):
            part = self._sub_path.parts[cur_index]

            # create a path relative to the current
            # it starts with the project root, so we shall always create
            # sub directories or files relative to the project root
            cur_path = cur_path / part  # type: ignore

            # create the sub_path file or directory if it does not exists already
            if cur_path.suffix != '':  # suffix will denote a file
                if not cur_path.exists():
                    # create file
                    cur_path.touch()

                    # add in the list for rollback
                    self._created_paths.append(cur_path)
                elif self._clear_content:
                    # read file content for rollback
                    with open(cur_path, 'r+', encoding=const.FILE_ENCODING) as fp:
                        # read all content
                        self._old_file_content = fp.read()

                        # clear file content
                        fp.truncate(0)
            else:
                if not cur_path.exists():
                    # create directory
                    cur_path.mkdir()

                    # add in the list for rollback
                    self._created_paths.append(cur_path)

            # move to the next part of the sub_path parts
            cur_index = cur_index + 1

        self._mark_executed()

    def rollback(self) -> None:
        """Rollback the action."""
        if self.has_executed():
            if len(self._created_paths) > 0:
                for cur_path in reversed(self._created_paths):
                    if cur_path.exists():
                        if cur_path.is_file():
                            cur_path.unlink()
                        elif cur_path.is_dir():
                            cur_path.rmdir()

                self._created_paths.clear()

            # rollback the content of a file if required
            # we should be here only if there were no path created and the sub_part already existed
            elif self._sub_path.is_file() and self._sub_path.exists() and self._clear_content is True:
                if self._old_file_content is not None:
                    with open(self._sub_path, 'w', encoding=const.FILE_ENCODING) as fp:
                        fp.write(self._old_file_content)

        self._mark_rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self._type} {self._sub_path}'
Functions¤
__init__(sub_path, clear_content=False) ¤

Initialize a create path action.

It creates all the missing directories in the path. If it is a file, then it also creates an empty file with the name provided

Parameters:

Name Type Description Default
sub_path Path

this is the desired file or directory path that needs to be created under the project root

 required
Source code in trestle/core/models/actions.py 
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def __init__(self, sub_path: pathlib.Path, clear_content: bool = False) -> None:
    """Initialize a create path action.

    It creates all the missing directories in the path.
    If it is a file, then it also creates an empty file with the name provided

    Arguments:
        sub_path: this is the desired file or directory path that needs to be created under the project root
    """
    sub_path = sub_path.resolve()

    self._trestle_project_root = file_utils.extract_trestle_project_root(sub_path)
    if self._trestle_project_root is None:
        raise TrestleError(f'Sub path "{sub_path}" should be child of a valid trestle project')

    self._sub_path = sub_path
    self._created_paths: List[pathlib.Path] = []

    # variables for handling with file content
    self._clear_content = clear_content
    self._old_file_content = None

    super().__init__(ActionType.CREATE_PATH, True)
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self._type} {self._sub_path}'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    # find the start of the sub_path relative to trestle project root
    cur_index = len(self._trestle_project_root.parts)

    # loop through the sub_path parts and create as necessary
    cur_path = self._trestle_project_root
    while cur_index < len(self._sub_path.parts):
        part = self._sub_path.parts[cur_index]

        # create a path relative to the current
        # it starts with the project root, so we shall always create
        # sub directories or files relative to the project root
        cur_path = cur_path / part  # type: ignore

        # create the sub_path file or directory if it does not exists already
        if cur_path.suffix != '':  # suffix will denote a file
            if not cur_path.exists():
                # create file
                cur_path.touch()

                # add in the list for rollback
                self._created_paths.append(cur_path)
            elif self._clear_content:
                # read file content for rollback
                with open(cur_path, 'r+', encoding=const.FILE_ENCODING) as fp:
                    # read all content
                    self._old_file_content = fp.read()

                    # clear file content
                    fp.truncate(0)
        else:
            if not cur_path.exists():
                # create directory
                cur_path.mkdir()

                # add in the list for rollback
                self._created_paths.append(cur_path)

        # move to the next part of the sub_path parts
        cur_index = cur_index + 1

    self._mark_executed()
get_created_paths() ¤

Get the list of paths that were created after being executed.

Source code in trestle/core/models/actions.py 
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def get_created_paths(self) -> List[pathlib.Path]:
    """Get the list of paths that were created after being executed."""
    return self._created_paths
get_trestle_project_root() ¤

Return the trestle workspace root path.

Source code in trestle/core/models/actions.py 
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def get_trestle_project_root(self) -> Optional[pathlib.Path]:
    """Return the trestle workspace root path."""
    return self._trestle_project_root
rollback() ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Rollback the action."""
    if self.has_executed():
        if len(self._created_paths) > 0:
            for cur_path in reversed(self._created_paths):
                if cur_path.exists():
                    if cur_path.is_file():
                        cur_path.unlink()
                    elif cur_path.is_dir():
                        cur_path.rmdir()

            self._created_paths.clear()

        # rollback the content of a file if required
        # we should be here only if there were no path created and the sub_part already existed
        elif self._sub_path.is_file() and self._sub_path.exists() and self._clear_content is True:
            if self._old_file_content is not None:
                with open(self._sub_path, 'w', encoding=const.FILE_ENCODING) as fp:
                    fp.write(self._old_file_content)

    self._mark_rollback()

RemoveAction ¤

Bases: Action

Remove sub element at the element path in the source element.

Source code in trestle/core/models/actions.py 
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class RemoveAction(Action):
    """Remove sub element at the element path in the source element."""

    def __init__(self, src_element: Element, sub_element_path: ElementPath) -> None:
        """Initialize a remove element action."""
        super().__init__(ActionType.REMOVE, True)

        self._src_element: Element = src_element
        self._sub_element_path: ElementPath = sub_element_path
        self._prev_sub_element = None

    def execute(self) -> None:
        """Execute the action."""
        self._prev_sub_element = self._src_element.get_at(self._sub_element_path)
        self._src_element.set_at(self._sub_element_path, None)
        self._mark_executed()

    def rollback(self) -> None:
        """Rollback the action."""
        if self.has_executed():
            self._src_element.set_at(self._sub_element_path, self._prev_sub_element)
        self._mark_rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self._type} element at {self._sub_element_path} from {self._src_element}'
Functions¤
__init__(src_element, sub_element_path) ¤

Initialize a remove element action.

Source code in trestle/core/models/actions.py 
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def __init__(self, src_element: Element, sub_element_path: ElementPath) -> None:
    """Initialize a remove element action."""
    super().__init__(ActionType.REMOVE, True)

    self._src_element: Element = src_element
    self._sub_element_path: ElementPath = sub_element_path
    self._prev_sub_element = None
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self._type} element at {self._sub_element_path} from {self._src_element}'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    self._prev_sub_element = self._src_element.get_at(self._sub_element_path)
    self._src_element.set_at(self._sub_element_path, None)
    self._mark_executed()
rollback() ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Rollback the action."""
    if self.has_executed():
        self._src_element.set_at(self._sub_element_path, self._prev_sub_element)
    self._mark_rollback()

RemovePathAction ¤

Bases: Action

Remove a file or directory path.

Source code in trestle/core/models/actions.py 
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class RemovePathAction(Action):
    """Remove a file or directory path."""

    def __init__(self, sub_path: pathlib.Path) -> None:
        """Initialize a remove path action.

        It removes the file or directory recursively into trash.

        Arguments:
            sub_path: this is the desired file or directory path that needs to be removed under the project root
        """
        if not isinstance(sub_path, pathlib.Path):
            raise TrestleError('Sub path must be of type pathlib.Path')

        self._trestle_project_root = file_utils.extract_trestle_project_root(sub_path)
        if self._trestle_project_root is None:
            raise TrestleError(f'Sub path "{sub_path}" should be child of a valid trestle project.')

        self._sub_path = sub_path

        super().__init__(ActionType.REMOVE_PATH, True)

    def get_trestle_project_root(self) -> Optional[pathlib.Path]:
        """Return the trestle workspace root path."""
        return self._trestle_project_root

    def execute(self) -> None:
        """Execute the action."""
        if not self._sub_path.exists():
            logger.debug(f'path {self._sub_path} does not exist in remove path action - ignoring.')

        trash.store(self._sub_path, True)

        # check if parent folder is empty and if so delete
        parent_dir = pathlib.Path(os.path.dirname(self._sub_path))
        files = list(parent_dir.iterdir())
        if not files:
            trash.store(parent_dir, True)
        self._mark_executed()

    def rollback(self) -> None:
        """Rollback the action."""
        if self.has_executed():
            trash_path = trash.to_trash_path(self._sub_path)
            if trash_path is None or trash_path.exists() is False:
                # FIXME suppress file contents not found message til trash/rollback behavior is fixed.  # issue 412
                return
            trash.recover(self._sub_path, True)

        self._mark_rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self._type} {self._sub_path}'
Functions¤
__init__(sub_path) ¤

Initialize a remove path action.

It removes the file or directory recursively into trash.

Parameters:

Name Type Description Default
sub_path Path

this is the desired file or directory path that needs to be removed under the project root

 required
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def __init__(self, sub_path: pathlib.Path) -> None:
    """Initialize a remove path action.

    It removes the file or directory recursively into trash.

    Arguments:
        sub_path: this is the desired file or directory path that needs to be removed under the project root
    """
    if not isinstance(sub_path, pathlib.Path):
        raise TrestleError('Sub path must be of type pathlib.Path')

    self._trestle_project_root = file_utils.extract_trestle_project_root(sub_path)
    if self._trestle_project_root is None:
        raise TrestleError(f'Sub path "{sub_path}" should be child of a valid trestle project.')

    self._sub_path = sub_path

    super().__init__(ActionType.REMOVE_PATH, True)
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self._type} {self._sub_path}'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    if not self._sub_path.exists():
        logger.debug(f'path {self._sub_path} does not exist in remove path action - ignoring.')

    trash.store(self._sub_path, True)

    # check if parent folder is empty and if so delete
    parent_dir = pathlib.Path(os.path.dirname(self._sub_path))
    files = list(parent_dir.iterdir())
    if not files:
        trash.store(parent_dir, True)
    self._mark_executed()
get_trestle_project_root() ¤

Return the trestle workspace root path.

Source code in trestle/core/models/actions.py 
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def get_trestle_project_root(self) -> Optional[pathlib.Path]:
    """Return the trestle workspace root path."""
    return self._trestle_project_root
rollback() ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Rollback the action."""
    if self.has_executed():
        trash_path = trash.to_trash_path(self._sub_path)
        if trash_path is None or trash_path.exists() is False:
            # FIXME suppress file contents not found message til trash/rollback behavior is fixed.  # issue 412
            return
        trash.recover(self._sub_path, True)

    self._mark_rollback()

UpdateAction ¤

Bases: Action

Update element at the element path in the destination element with the source element.

Source code in trestle/core/models/actions.py 
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class UpdateAction(Action):
    """Update element at the element path in the destination element with the source element."""

    def __init__(self, sub_element, dest_element: Element, sub_element_path: ElementPath) -> None:
        """Initialize an add element action.

        Sub element can be OscalBaseModel, Element, list or None
        """
        super().__init__(ActionType.UPDATE, True)

        if not Element.is_allowed_sub_element_type(sub_element):
            allowed_types = Element.get_allowed_sub_element_types()
            raise TrestleError(
                f'Sub element "{sub_element.__class__} is not a allowed sub element types in "{allowed_types}"'
            )

        self._sub_element = sub_element
        self._dest_element: Element = dest_element
        self._sub_element_path: ElementPath = sub_element_path
        self._prev_sub_element = None

    def execute(self) -> None:
        """Execute the action."""
        self._prev_sub_element = self._dest_element.get_at(self._sub_element_path)
        self._dest_element.set_at(self._sub_element_path, self._sub_element)
        self._mark_executed()

    def rollback(self) -> None:
        """Rollback the action."""
        if self.has_executed():
            self._dest_element.set_at(self._sub_element_path, self._prev_sub_element)
        self._mark_rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self._type} {self._model_obj.__class__} to {self._dest_element} at {self._sub_element_path}'
Functions¤
__init__(sub_element, dest_element, sub_element_path) ¤

Initialize an add element action.

Sub element can be OscalBaseModel, Element, list or None

Source code in trestle/core/models/actions.py 
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def __init__(self, sub_element, dest_element: Element, sub_element_path: ElementPath) -> None:
    """Initialize an add element action.

    Sub element can be OscalBaseModel, Element, list or None
    """
    super().__init__(ActionType.UPDATE, True)

    if not Element.is_allowed_sub_element_type(sub_element):
        allowed_types = Element.get_allowed_sub_element_types()
        raise TrestleError(
            f'Sub element "{sub_element.__class__} is not a allowed sub element types in "{allowed_types}"'
        )

    self._sub_element = sub_element
    self._dest_element: Element = dest_element
    self._sub_element_path: ElementPath = sub_element_path
    self._prev_sub_element = None
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self._type} {self._model_obj.__class__} to {self._dest_element} at {self._sub_element_path}'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    self._prev_sub_element = self._dest_element.get_at(self._sub_element_path)
    self._dest_element.set_at(self._sub_element_path, self._sub_element)
    self._mark_executed()
rollback() ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Rollback the action."""
    if self.has_executed():
        self._dest_element.set_at(self._sub_element_path, self._prev_sub_element)
    self._mark_rollback()

WriteAction ¤

Bases: Action

Write the element to a destination stream.

Source code in trestle/core/models/actions.py 
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class WriteAction(Action):
    """Write the element to a destination stream."""

    def __init__(self, writer: Optional[io.TextIOWrapper], element: Element, content_type: FileContentType) -> None:
        """Initialize an write file action."""
        super().__init__(ActionType.WRITE, True)

        if writer is not None and not issubclass(io.TextIOWrapper, writer.__class__):
            raise TrestleError(f'Writer must be of io.TextIOWrapper, given f{writer.__class__}')

        self._writer: Optional[io.TextIOWrapper] = writer
        self._element: Element = element
        self._content_type: FileContentType = content_type
        self._lastStreamPos = -1
        if self._writer is not None:
            self._lastStreamPos = self._writer.tell()

    def _is_writer_valid(self) -> bool:
        if self._writer is not None and isinstance(self._writer, io.TextIOWrapper) and not self._writer.closed:
            return True

        return False

    def _encode(self) -> str:
        """Encode the element to appropriate content type."""
        if self._content_type == FileContentType.YAML:
            return self._element.to_yaml()
        if self._content_type == FileContentType.JSON:
            return self._element.to_json()

        raise TrestleError(f'Invalid content type {self._content_type}')

    def execute(self) -> None:
        """Execute the action."""
        if self._element is None:
            raise TrestleError('Element is empty and cannot write')

        if not self._is_writer_valid():
            raise TrestleError('Writer is not provided or closed')

        self._writer.write(self._encode())
        self._writer.flush()
        self._mark_executed()

    def rollback(self) -> None:
        """Rollback the action."""
        if not self._is_writer_valid():
            raise TrestleError('Writer is not provided or closed')

        if self._lastStreamPos < 0:
            raise TrestleError('Last stream position is not available to rollback to')

        if self.has_executed():
            self._writer.seek(self._lastStreamPos)
            self._writer.truncate()

        self._mark_rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self.get_type()} {self._element}'
Functions¤
__init__(writer, element, content_type) ¤

Initialize an write file action.

Source code in trestle/core/models/actions.py 
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def __init__(self, writer: Optional[io.TextIOWrapper], element: Element, content_type: FileContentType) -> None:
    """Initialize an write file action."""
    super().__init__(ActionType.WRITE, True)

    if writer is not None and not issubclass(io.TextIOWrapper, writer.__class__):
        raise TrestleError(f'Writer must be of io.TextIOWrapper, given f{writer.__class__}')

    self._writer: Optional[io.TextIOWrapper] = writer
    self._element: Element = element
    self._content_type: FileContentType = content_type
    self._lastStreamPos = -1
    if self._writer is not None:
        self._lastStreamPos = self._writer.tell()
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self.get_type()} {self._element}'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    if self._element is None:
        raise TrestleError('Element is empty and cannot write')

    if not self._is_writer_valid():
        raise TrestleError('Writer is not provided or closed')

    self._writer.write(self._encode())
    self._writer.flush()
    self._mark_executed()
rollback() ¤

Rollback the action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Rollback the action."""
    if not self._is_writer_valid():
        raise TrestleError('Writer is not provided or closed')

    if self._lastStreamPos < 0:
        raise TrestleError('Last stream position is not available to rollback to')

    if self.has_executed():
        self._writer.seek(self._lastStreamPos)
        self._writer.truncate()

    self._mark_rollback()

WriteFileAction ¤

Bases: WriteAction

Write the element to a destination file.

Source code in trestle/core/models/actions.py 
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class WriteFileAction(WriteAction):
    """Write the element to a destination file."""

    def __init__(self, file_path: pathlib.Path, element: Element, content_type: FileContentType) -> None:
        """Initialize a write file action.

        It opens the file in append mode. Therefore the file needs to exist even if it is a new file.
        """
        if not isinstance(file_path, pathlib.Path):
            raise TrestleError('file_path should be of type pathlib.Path')

        inferred_content_type = FileContentType.to_content_type(file_path.suffix)
        if inferred_content_type != content_type:
            raise TrestleError(f'Mismatch between stated content type {content_type.name} and file path {file_path}')

        self._file_path = file_path

        # initialize super without writer for now
        # Note, execute and rollback sets the writer as appropriate
        super().__init__(None, element, content_type)

    def execute(self) -> None:
        """Execute the action."""
        if not self._file_path.exists():
            raise TrestleError(f'File at {self._file_path} does not exist')

        with open(self._file_path, 'a+', encoding=const.FILE_ENCODING) as writer:
            if self._lastStreamPos < 0:
                self._lastStreamPos = writer.tell()
            else:
                writer.seek(self._lastStreamPos)

            self._writer = writer
            super().execute()

    def rollback(self) -> None:
        """Execute the rollback action."""
        if not self._file_path.exists():
            raise TrestleError(f'File at {self._file_path} does not exist')

        with open(self._file_path, 'a+', encoding=const.FILE_ENCODING) as writer:
            self._writer = writer
            super().rollback()

    def __str__(self) -> str:
        """Return string representation."""
        return f'{self._type} {self._element} to "{self._file_path}"'
Functions¤
__init__(file_path, element, content_type) ¤

Initialize a write file action.

It opens the file in append mode. Therefore the file needs to exist even if it is a new file.

Source code in trestle/core/models/actions.py 
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def __init__(self, file_path: pathlib.Path, element: Element, content_type: FileContentType) -> None:
    """Initialize a write file action.

    It opens the file in append mode. Therefore the file needs to exist even if it is a new file.
    """
    if not isinstance(file_path, pathlib.Path):
        raise TrestleError('file_path should be of type pathlib.Path')

    inferred_content_type = FileContentType.to_content_type(file_path.suffix)
    if inferred_content_type != content_type:
        raise TrestleError(f'Mismatch between stated content type {content_type.name} and file path {file_path}')

    self._file_path = file_path

    # initialize super without writer for now
    # Note, execute and rollback sets the writer as appropriate
    super().__init__(None, element, content_type)
__str__() ¤

Return string representation.

Source code in trestle/core/models/actions.py 
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def __str__(self) -> str:
    """Return string representation."""
    return f'{self._type} {self._element} to "{self._file_path}"'
execute() ¤

Execute the action.

Source code in trestle/core/models/actions.py 
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def execute(self) -> None:
    """Execute the action."""
    if not self._file_path.exists():
        raise TrestleError(f'File at {self._file_path} does not exist')

    with open(self._file_path, 'a+', encoding=const.FILE_ENCODING) as writer:
        if self._lastStreamPos < 0:
            self._lastStreamPos = writer.tell()
        else:
            writer.seek(self._lastStreamPos)

        self._writer = writer
        super().execute()
rollback() ¤

Execute the rollback action.

Source code in trestle/core/models/actions.py 
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def rollback(self) -> None:
    """Execute the rollback action."""
    if not self._file_path.exists():
        raise TrestleError(f'File at {self._file_path} does not exist')

    with open(self._file_path, 'a+', encoding=const.FILE_ENCODING) as writer:
        self._writer = writer
        super().rollback()

handler: python