.. index:: Properties

.. _Properties:

Properties
==========

Build properties are a generalized way to provide configuration information to
build steps; see :ref:`Build-Properties` for the conceptual overview of
properties.

.. contents::
    :depth: 1
    :local:

Some build properties come from external sources and are set before the build
begins; others are set during the build, and available for later steps.  The
sources for properties are:

* :bb:cfg:`global configuration <properties>` -- These properties apply to all
  builds.
* :ref:`schedulers <Configuring-Schedulers>` -- A scheduler can specify
  properties that become available to all builds it starts.
* :ref:`changes <Change-Sources>` -- A change can have properties attached to
  it, supplying extra information gathered by the change source.  This is most
  commonly used with the :bb:cmdline:`sendchange` command.
* :bb:status:`forced builds <WebStatus>` -- The "Force Build" form allows users
  to specify properties
* :bb:cfg:`buildslaves <slaves>` -- A buildslave can pass properties on to
  the builds it performs.
* :ref:`builds <Common-Build-Properties>` -- A build automatically sets a
  number of properties on itself.
* :bb:cfg:`builders <builders>` -- A builder can set properties on all the
  builds it runs.
* :ref:`steps <Build-Steps>` -- The steps of a build can set properties that are available to subsequent steps.
  In particular, source steps set the `got_revision` property.

If the same property is supplied in multiple places, the final appearance takes
precedence.  For example, a property set in a builder configuration will
override one supplied by a scheduler.

Properties are stored internally in JSON format, so they are limited to basic
types of data: numbers, strings, lists, and dictionaries.

.. index:: single: Properties; Common Properties

.. _Common-Build-Properties:

Common Build Properties
-----------------------

The following build properties are set when the build is started, and
are available to all steps.

.. index:: single: Properties; got_revision

``got_revision``
    This property is set when a :class:`Source` step checks out the source tree, and provides the revision that was actually obtained from the VC system.
    In general this should be the same as ``revision``, except for non-absolute sourcestamps, where ``got_revision`` indicates what revision was current when the checkout was performed.
    This can be used to rebuild the same source code later.

    .. note:: For some VC systems (Darcs in particular), the revision is a
       large string containing newlines, and is not suitable for interpolation
       into a filename.

    For multi-codebase builds (where codebase is not the default `''`), this property is a dictionary, keyed by codebase.

.. index:: single: Properties; buildername

``buildername``
    This is a string that indicates which :class:`Builder` the build was a part of.
    The combination of buildername and buildnumber uniquely identify a
    build.

.. index:: single: Properties; buildnumber

``buildnumber``
    Each build gets a number, scoped to the :class:`Builder` (so the first build
    performed on any given :class:`Builder` will have a build number of 0). This
    integer property contains the build's number.

.. index:: single: Properties; slavename

``slavename``
    This is a string which identifies which buildslave the build is
    running on.

.. index:: single: Properties; scheduler

``scheduler``
    If the build was started from a scheduler, then this property will
    contain the name of that scheduler.


``workdir``
    The absolute path of the base working directory on the slave, of the current
    builder.

.. index:: single: Properties; workdir

For single codebase builds, where the codebase is `''`, the following :ref:`Source-Stamp-Attributes` are also available as properties: ``branch``, ``revision``, ``repository``, and ``project`` .

.. _Source-Stamp-Attributes:

Source Stamp Attributes
-----------------------

.. index:: single: Properties; branch

``branch``
``revision``
``repository``
``project``
``codebase``

    For details of these attributes see :doc:`/manual/concepts`.

``changes``

    This attribute is a list of dictionaries reperesnting the changes that make up this sourcestamp.

Using Properties in Steps
-------------------------

For the most part, properties are used to alter the behavior of build steps
during a build.  This is done by annotating the step definition in
``master.cfg`` with placeholders.  When the step is executed, these
placeholders will be replaced using the current values of the build properties.

.. note::

    Properties are defined while a build is in progress; their values are
    not available when the configuration file is parsed.  This can sometimes
    confuse newcomers to Buildbot!  In particular, the following is a common error::

        if Property('release_train') == 'alpha':
            f.addStep(...)

    This does not work because the value of the property is not available when
    the ``if`` statement is executed.  However, Python will not detect this as
    an error - you will just never see the step added to the factory.

You can use build properties in most step parameters.  Please file bugs for any
parameters which do not accept properties.

.. index:: single: Properties; Property

.. _Property:

Property
++++++++

The simplest form of annotation is to wrap the property name with
:class:`Property`::

   from buildbot.steps.shell import ShellCommand
   from buildbot.process.properties import Property

   f.addStep(ShellCommand(command=[ 'echo', 'buildername:', Property('buildername') ]))

You can specify a default value by passing a ``default`` keyword argument::

   f.addStep(ShellCommand(command=[ 'echo', 'warnings:',
                                    Property('warnings', default='none') ]))

The default value is used when the property doesn't exist, or when the value is
something Python regards as ``False``. The ``defaultWhenFalse`` argument can be
set to ``False`` to force buildbot to use the default argument only if the
parameter is not set::

   f.addStep(ShellCommand(command=[ 'echo', 'warnings:',
                    Property('warnings', default='none', defaultWhenFalse=False) ]))

The default value can reference other properties, e.g., ::

    command=Property('command', default=Property('default-command'))

.. index:: single: Properties; Interpolate

.. _Interpolate:

Interpolate
+++++++++++

:class:`Property` can only be used to replace an entire argument: in the
example above, it replaces an argument to ``echo``.  Often, properties need to
be interpolated into strings, instead.  The tool for that job is
:ref:`Interpolate`.

The more common pattern is to use Python dictionary-style string interpolation by using the ``%(prop:<propname>)s`` syntax.
In this form, the property name goes in the parentheses, as above.
A common mistake is to omit the trailing "s", leading to a rather obscure error from Python ("ValueError: unsupported format character"). ::

   from buildbot.steps.shell import ShellCommand
   from buildbot.process.properties import Interpolate
   f.addStep(ShellCommand(command=[ 'make', Interpolate('REVISION=%(prop:got_revision)s'),
                                    'dist' ]))

This example will result in a ``make`` command with an argument like
``REVISION=12098``.

.. _Interpolate-DictStyle:

The syntax of dictionary-style interpolation is a selector, followed by a colon, followed by a selector specific key, optionally followed by a colon and a string indicating how to interpret the value produced by the key.

The following selectors are supported.

``prop``
    The key is the name of a property.

``src``
    The key is a codebase and source stamp attribute, separated by a colon.

``kw``
    The key refers to a keyword argument passed to ``Interpolate``.

``slave``
    The key to the per-buildslave "info" dictionary (e.g., the "Slave information" properties shown
    in the buildslave web page for each buildslave)

The following ways of interpreting the value are available.

``-replacement``
    If the key exists, substitute its value; otherwise,
    substitute ``replacement``. ``replacement`` may be empty
    (``%(prop:propname:-)s``). This is the default.

``~replacement``
    Like ``-replacement``, but only substitutes the value
    of the key if it is something Python regards as ``True``.
    Python considers ``None``, 0, empty lists, and the empty string to be
    false, so such values will be replaced by ``replacement``.

``+replacement``
    If the key exists, substitute ``replacement``; otherwise,
    substitute an empty string.

``?|sub_if_exists|sub_if_missing``

``#?|sub_if_true|sub_if_false``
    Ternary substitution, depending on either the key being present (with
    ``?``, similar to ``+``) or being ``True`` (with ``#?``, like ``~``).
    Notice that there is a pipe immediately following the question mark *and*
    between the two substitution alternatives. The character that follows the
    question mark is used as the delimiter between the two alternatives. In the
    above examples, it is a pipe, but any character other than ``(`` can be used.


Although these are similar to shell substitutions, no other substitutions are currently supported.

Example ::

   from buildbot.steps.shell import ShellCommand
   from buildbot.process.properties import Interpolate
   f.addStep(ShellCommand(command=[ 'make', Interpolate('REVISION=%(prop:got_revision:-%(src::revision:-unknown)s)s'),
                                    'dist' ]))

In addition, ``Interpolate`` supports using positional string interpolation.
Here, ``%s`` is used as a placeholder, and the substitutions (which may themselves be placeholders), are given as subsequent arguments::

  TODO

.. note::

  Like Python, you can use either positional interpolation *or*
  dictionary-style interpolation, not both.  Thus you cannot use a string
  like ``Interpolate("foo-%(src::revision)s-%s", "branch")``.

.. index:: single: Properties; Renderer

.. _Renderer:

Renderer
++++++++

While Interpolate can handle many simple cases, and even some common conditionals, more complex cases are best handled with Python code.
The ``renderer`` decorator creates a renderable object that will be replaced with the result of the function, called when the step it's passed to begins.
The function receives an :class:`~buildbot.interfaces.IProperties` object, which it can use to examine the values of any and all properties.  For example::

    from buildbot.process import properties
    @properties.renderer
    def makeCommand(props):
        command = [ 'make' ]
        cpus = props.getProperty('CPUs')
        if cpus:
            command += [ '-j', str(cpus+1) ]
        else:
            command += [ '-j', '2' ]
        command += [ 'all' ]
        return command
    f.addStep(ShellCommand(command=makeCommand))

You can think of ``renderer`` as saying "call this function when the step starts".

.. index:: single: Properties; WithProperties

.. _WithProperties:

FlattenList
+++++++++++

If nested list should be flatten for some renderables, FlattenList could be used.
For example::

   f.addStep(ShellCommand(command=[ 'make' ], descriptionDone=FlattenList([ 'make ', [ 'done' ]])))

``descriptionDone`` would be set to ``[ 'make', 'done' ]`` when the ``ShellCommand`` executes.
This is useful when a list-returning property is used in renderables.

.. note:: ShellCommand automatically flattens nested lists in its ``command`` argument, so there is no need to use ``FlattenList`` for it.

WithProperties
++++++++++++++

.. warning::

    This placeholder is deprecated. It is an older version of :ref:`Interpolate`.
    It exists for compatibility with older configs.

The simplest use of this class is with positional string interpolation.  Here,
``%s`` is used as a placeholder, and property names are given as subsequent
arguments::

    from buildbot.steps.shell import ShellCommand
    from buildbot.process.properties import WithProperties
    f.addStep(ShellCommand(
              command=["tar", "czf",
                       WithProperties("build-%s-%s.tar.gz", "branch", "revision"),
                       "source"]))

If this :class:`BuildStep` were used in a tree obtained from Git, it would
create a tarball with a name like
:file:`build-master-a7d3a333db708e786edb34b6af646edd8d4d3ad9.tar.gz`.

.. index:: unsupported format character

The more common pattern is to use Python dictionary-style string interpolation
by using the ``%(propname)s`` syntax. In this form, the property name goes in
the parentheses, as above.  A common mistake is to omit the trailing "s",
leading to a rather obscure error from Python ("ValueError: unsupported format
character"). ::

   from buildbot.steps.shell import ShellCommand
   from buildbot.process.properties import WithProperties
   f.addStep(ShellCommand(command=[ 'make', WithProperties('REVISION=%(got_revision)s'),
                                    'dist' ]))

This example will result in a ``make`` command with an argument like
``REVISION=12098``.

.. _WithProperties-DictStyle:

The dictionary-style interpolation supports a number of more advanced
syntaxes in the parentheses.

``propname:-replacement``
    If ``propname`` exists, substitute its value; otherwise,
    substitute ``replacement``. ``replacement`` may be empty
    (``%(propname:-)s``)

``propname:~replacement``
    Like ``propname:-replacement``, but only substitutes the value
    of property ``propname`` if it is something Python regards as ``True``.
    Python considers ``None``, 0, empty lists, and the empty string to be 
    false, so such values will be replaced by ``replacement``.

``propname:+replacement``
    If ``propname`` exists, substitute ``replacement``; otherwise,
    substitute an empty string.
    
Although these are similar to shell substitutions, no other
substitutions are currently supported, and ``replacement`` in the
above cannot contain more substitutions.

Note: like Python, you can use either positional interpolation *or*
dictionary-style interpolation, not both. Thus you cannot use a string like
``WithProperties("foo-%(revision)s-%s", "branch")``.

Custom Renderables
++++++++++++++++++

If the options described above are not sufficient, more complex substitutions can be achieved by writing custom renderables.

Renderables are objects providing the :class:`~buildbot.interfaces.IRenderable` interface.
That interface is simple - objects must provide a `getRenderingFor` method.
The method should take one argument - an :class:`~buildbot.interfaces.IProperties` provider - and should return a string or a deferred firing with a string.
Pass instances of the class anywhere other renderables are accepted.
For example::

    class DetermineFoo(object):
        implements(IRenderable)
        def getRenderingFor(self, props):
            if props.hasProperty('bar'):
                return props['bar']
            elif props.hasProperty('baz'):
                return props['baz']
            return 'qux'
    ShellCommand(command=['echo', DetermineFoo()])

or, more practically, ::

    class Now(object):
        implements(IRenderable)
        def getRenderingFor(self, props):
            return time.clock()
    ShellCommand(command=['make', Interpolate('TIME=%(kw:now)s', now=Now())])

This is equivalent to::

    @renderer
    def now(props):
        return time.clock()
    ShellCommand(command=['make', Interpolate('TIME=%(kw:now)s', now=now)])

Note that a custom renderable must be instantiated (and its constructor can take whatever arguments you'd like), whereas a function decorated with :func:`renderer` can be used directly.
