# Upgrading

This section outlines any information and changes that might need to be made in order to update your application built on previous versions of Cement.

## Upgrading from 2.8.x to 2.9.x

Cement 2.9 introduces a few incompatible changes from the previous 2.8 stable release, as noted in the ChangeLog.

### Deprecated: cement.core.interface.list()

This function should no longer be used in favor of `CementApp.handler.list_types()`. It will continue to work throughout Cement 2.x, however is not compatible if `CementApp.Meta.use_backend_globals == False`.

Related:

> - Issue #366
> - Issue #376

## Upgrading from 2.6.x to 2.8.x

Cement 2.8 introduced a few incompatible changes from the previous 2.6 stable release, as noted in the ChangeLog.

### TypeError: my_signal_hook() takes exactly 2 arguments (3 given)

In Cement 2.6, functions registered to the `signal` hook were only expected/required to accept the `signum` and `frame` arguments, however `signal` hook functions must now also accept the `app` object as an argument as well.

After upgrading to Cement 2.8, you might receive something similar to the following exception:

    TypeError: my_signal_hook() takes exactly 2 arguments (3 given)

The fix is to simply prefix any `signal` hook functions with an `app` argument.

For example:

    def my_signal_hook(signum, frame):
        pass

Would need to be:

    def my_signal_hook(app, signum, frame):
        pass

Related:

> - Issue #311

### TypeError: render() got an unexpected keyword argument

In Cement 2.6, output handlers were not required to accept `**kwargs`, however this is now required to allow applications to mix different types of output handlers together that might support different features/usage.

After upgrading to Cement 2.8, you might receive something similar to the following exception:

    TypeError: render() got an unexpected keyword argument

This would most likely be the case because you have created your own custom output handler, or are using a third-party output handler that has not been updated to support Cement 2.8 yet. The fix is to simply add `**kwargs` to the end of the render() method.

For example:

    def render(self, data):
        pass

Would need to be:

    def render(self, data, **kwargs):
        pass

### CementApp.Meta.exit_on_close Defaults to False

In Cement 2.6, the feature to call `sys.exit()` when `app.close()` is called was implemented, however defaulting it to `True` is not the ideal behavior. The default is now `False`, making it the developers option to explicitly enable it.

To revert the change, and default `exit_on_close` to `True`, simply set it in `CementApp.Meta.exit_on_close`:

    from cement.core.foundation import CementApp

    class MyApp(CementApp):
        class Meta:
            label = 'myapp'
            exit_on_close = True

## Upgrading from 2.4.x to 2.6.x

Cement 2.6 introduced a few incompatible changes from the previous 2.4 stable release, as noted in the ChangeLog.

### InterfaceError: Invalid handler … missing ‘_meta.label’.

Prior to Cement 2.5.2, `CementBaseController.Meta.label` defaulted to `base`. The new default is `None`, causing the potential for breakage of a controller that did not explicity set the `label` meta option.

You can resolve this error by explicity setting the `label` meta option:

    class MyBaseController(CementBaseController):
        class Meta:
            label = 'base'

## Upgrading from 2.2.x to 2.4.x

Cement 2.4 introduced a few incompatible changes from the previous 2.2 stable release, as noted in the ChangeLog.

Related:

> - Issue #308

### CementApp.render() Prints Output Without Calling print()

Before Cement 2.3.2 the `app.render()` function did not actually print anything, therefore you would have to call `print app.render()`. This now defaults to writing output to `sys.stdout`, but can be modified for the older behavior by passing `out=None` when calling it:

    app.render(data, out=None)

Additionally, you can also now write directly to a file:

    myfile = open('/path/to/myfile', 'w')
    app.render(data, out=myfile)
    myfile.close()

### error: unrecognized arguments: –json/–yaml

After upgrading to Cement > 2.3.2 you might encounter the error:

    error: unrecognized arguments: --json

Or similar errors like:

    error: unrecognized arguments: --yaml

This is due to a design change, and a new feature allowing the end user to optionally override handlers via command line. Rather than having a unique option for every type of output handler, you now have one option that allows overriding the defined output handler by passing it the handler label.

Note that only handlers that have `overridable = True` in their meta-data will be valid options.

To resolve this issue, you simply need to pass `-o json` or `-o yaml` at command line to override the default output handler.

Related:

> - Issue #229

### NoSectionError: No section: ‘log’

After upgrading to Cement > 2.3.2 you might encounter the error:

    NoSectionError: No section: 'log'

In previous versions of Cement < 2.3.2, the default logging configuration section in the config file was `[log]`. This has been changed to `[log.logging]` in order to be consistent with all other handler configuration sections.

Another issue you might encounter due to the above change is that log related configuration settings read from a configuration file would no longer work. The necessary change to resolve this issue is to change all references of `log` in relation to the log configuration section, to `log.logging`.

Related:

> - Issue #227

### TypeError: load() takes no arguments (1 given)

After upgrading to Cement > 2.3.2 you might encounter the error:

    TypeError: load() takes no arguments (1 given)

Previous versions of Cement < 2.3.2 did not require an app argument to be passed to the load() functions of extensions/plugins/bootstrap modules. In Cement > 2.3.2 all extension/plugins/bootstrap modules must accept a single argument named app which is the application object in its current state when load() is called.

To resolve this issue simply modify all relevant load() functions to accept the app argument. For example:

    def load():
        pass

To:

    def load(app):
        pass

## Upgrading from 2.0.x to 2.2.x

Cement 2.2 introduced a few incompatible changes from the previous 2.0 stable release, as noted in the Changelog.

### ImportError: cannot import name version

When attempting to install Cement > 2.1 on a system that already has an older version of Cement < 2.1 you will likely run into this error:

    ImportError: cannot import name version

Currently we do not have a way to resolve this programatically in Cement. The resolution is to remove the older version of Cement < 2.1, and then re-install the newer version.

Related:

> - Issue #237

### FrameworkError: Duplicate Arguments/Commands

After upgrading, you might encounter one or both of the following errors related to application controllers:

    cement.core.exc.FrameworkError: Duplicate command named 'mycommand' found
    in controller '<__main__.MySecondController object at 0x10669ab50>'

    cement.core.exc.FrameworkError: argument -f/--foo: conflicting option
    string(s): -f, --foo

This is likely due to a change in how application controllers are configured. By default, all controllers are of type embedded, meaning that their arguments and commands are added to the parent controller. To resolve this issue you can change the stacked_type to nested, meaning that the stacked controller will be an additional sub-command under the parent (nesting a new level commands/arguments).

For example:

    class MyStackedController(CementBaseController):
        class Meta:
            label = 'my_stacked_controller'
            stacked_on = 'base'
            stacked_type = 'nested'

Related:

> - Issue #234

### Discontinued use of Setuptools Namespace Packages

Previous versions of Cement utilitized Setuptools namespace packages in order to allow external libraries (such as optional framework extensions) to use the `cement.ext` namespace. Meaning that an extension packaged separately could use the namespace `cement.ext.ext_myextension` and be imported from the `cement.ext` namespace as if it were shipped with the mainline sources directly. This indirectly caused issues with certain IDE’s due to the fact that namespace packages do not install a proper `__init__.py` and are handled differently by Setuptools.

With the move to merging optional extenions into mainline sources, we no longer require the use of Setuptools namespace packages. That said, if a developer had created their own extension using the `cement.ext` namespace, that extension would no longer work or worse may confusing Python into attempting to load `cement.ext` from the extension and not Cement causing even bigger problems.

To resolve this issue, simply change the extension module to anything other than `cement.ext`, such as `myapp.ext`.

Related:

> - Issue #202

### LoggingLogHandler Changes

The `clear_loggers` meta option is now a `list`, rather than a `boolean`. Therefore, rather than telling LoggingLogHandler to ‘clear all previously defined loggers’, you are telling it to ‘clear only these previously defined loggers’ in the list.

If your application utilizied the `LoggingLogHandler.Meta.clear_loggers` option, you would simply need to change it from a `boolean` to a list of loggers such as `['myapp', 'some_other_logging_namespace']`.

Related:

> - Issue #163

### ConfigParserConfigHandler Changes

The `ConfigParserConfigHandler.has_key()` function has been removed. To update your application for these changes, you would look for all code similar to the following:

    if myapp.config.has_key('mysection', 'mykey'):
        # ...

And modify it to something similar to:

    if 'mykey' in myapp.config.keys('mysection'):
        # ...

Related:

> - Issue #173

### CementApp Changes

The `CementApp.get_last_rendered()` function has been deprected. Developers should now use the `CementApp.last_rendered` property instead. To update your application for these changes, you would look for all code similar to:

    CementApp.get_last_rendered()

And modify it to something similar to:

    CementApp.last_rendered

Related:

> - Issue #201 - Add Deprecation Warning for CementApp.get_last_rendered()

### CementBaseController Changes

All short-cuts such as `log`, `pargs`, etc have been removed from CementBaseController due to the fact that these class members could clash if the developer added a command/function of the same name. To update your application for these changes, in any classes that subclass from `CementBaseController`, you might need to modify references to `self.log`, `self.pargs`, etc to `self.app.log`, `self.app.pargs`, etc.

Additionally, if you wish to re-implement these or other shortcuts, you can do so by overriding `_setup()` in your controller code, and add something similar to the following:

    def _setup(self, *args, **kw):
        res = super(MyClass, self)._setup(*args, **kw)
        self.log = self.app.log
        self.pargs = self.app.pargs
        # etc

        return res

An additional change to `CementBaseController` is that the application’s `base` controller attached to `YourApp.Meta.base_controller` now must have a label of `base`. Previously, the base controller could have any label however this is now a hard requirement. To update your application for these changes, simply change the label of your base controller to `base`.

Finally, the `CementBaseController` used to have members called `hidden`, `visible`, and `exposed` which were each a list of controller functions used for handling dispatch of commands, and how they are displayed in `--help`. These members no longer exist.

These members were never documented, and is very unlikely that anybody has ever used them directly. Updating your application for these changes would be outside the scope of this document.

Related:

> - Issue #141
> - Issue #167
> - Issue #179

### Backend Changes

Several backend pieces have been moved or renamed. For example `cement.core.backend.handlers` is now `cement.core.backend.__handlers__`, etc. The same goes for `cement.core.backend.SAVED_STDOUT` which is now `cement.core.backend.__saved_stdout__`. These are undocumented, and used specifically by Cement. It is unlikely that anyone has used these members directly, and updating your application for these changes is outside the scope of this document. See `cement.core.backend` to assess what, if any, change you may need to change in your code to compensate for these changes.

The `cement.core.backend.defaults()` function has moved to `cement.utils.misc.init_defaults()`. It’s usage is exactly the same.

The `cement.core.backend.minimal_logger()` function has moved to `cement.utils.misc.minimal_logger`. It’s usage is also the same.

Related:

> - Issue #177
> - Issue #178