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An extensible config file format

Project description

yay ain't YAML

yay is a configuration file format built on top of YAML based on our experience with the ConfigParser extensions buildout uses. It adds overlays (one config file including and extending another) and variables.

Consider a config file that looks something like this::

- 1
- 2
- 3
qux: wibble.wobble
quux: wobble

- 1
- 2
- 3
- 4
qux: wibble.cobble
quux: cobble

- 1
- 3
qux: wibble.yobble
quux: yobble

With yay, this might look like this::

- 1
- 2
- 3
qux: wibble.{:quux}
quux: wobble

goo.copy: foo
- 4
quux: cobble

hoo.copy: foo
- 2
quux: yobble

Using yay

To load yay config from a string you can use the 'load' function::

>>> from yay import load
>>> load("""
... foo:
... bar: 1
... """)
{"foo": {"bar": 1}}

If you want to load from a URI (file:// and http:// are supported) then use 'load_uri'::

>>> from yay import load_uri
>>> load_uri("/etc/someconfig.yay")
{"foo": {"bar": 1}}

The return value in both cases is a standard python dictionary.

Changelog for yay

0.0.56 (2012-07-31)

- Code paths are now decorated with tracing context. This ``__context__``
metadata gives a sense of what yay was doing when it went off the handle.

0.0.55 (2012-07-25)

- Fix PackageIndex to not warn() on missing package - we capture this

0.0.54 (2012-07-22)

- Line number and file information should be available for nodes that have been
cloned leading to much more useful error output.

- Index errors on Sequence nodes will be properly dealt with

- Treating a sequence as a mapping node will trigger an appropriate Yay error.

0.0.53 (2012-07-21)

- Allow python code using yay to set default configuration for openers

0.0.52 (2012-07-21)

- Fix regression in ``package://`` for existing users..

0.0.51 (2012-07-19)

- Introduce a lazily evaluated mechanism for expanding the search path::

- package://some.egg/

Any subsequent ``.import`` statements will use the modified search path.

- If a package specified either as part of a .include or as part of a .search
is not available on sys.path then an attempt will be made to install it.

- Can pass config to opener backends using ``.config``. For example, you might
want to have the ``package://`` opener to use your internal package

index: https://my-python-mirror/simple/
username: joe
password: penguin55

You can use variable subsitution and to define the password in a GPG
encrypted yay file or to push the variable from application that is using

- Yay openers support basic auth in the url. If used with .include then use of
secrets to concatenate to hide the password is suggsted::

# Define ${password} in a GPG armored file
.include: home://.credentials.yay.gpg

- https://username:${password}

- ``.include`` and ``.search`` may be a single scalar value rather than a list
if you desire.

0.0.50 (2012-07-10)

- Allow expressions to return an empty dictionary::

result: ${site.vhosts else {}}

0.0.49 (2012-06-27)

- Added a string replacement function allowing people to do things like::

something: jolly good show
slug: ${replace(something, " ", "-")}

thereafter the value of ``slug`` will be ``jolly-good-show``.

0.0.48 (2012-04-07)

- Support in operator during foreach::

result.foreach v in somevalues if v in somelist: ${v}.

0.0.47 (2012-04-06)

- Allow expressions to contain literal strings and floats::

result: ${site.description else "No description"}
result2: ${3.212121}

- Allow expressions to return an empty list::

result: ${site.vhosts else []}

- Allow equality checks of undefined keys to pass or fail appropriately without
raising a NoMatching exception::

a: 1
c: 2

res1.foreach p in data if data[p].a = 2: ${p}
res2.foreach p in data if data[p].c != 1: ${p}

res1 will be empty as neither part1 nor part2 have an a field with a value of
2, and res2 will contain part1 and part2 as neither have a c field wth a
value of 1.

- Add an ``undefined`` that raises a NoMatch exception when resolved. This
allows one to filter by whether or not a key is present in a mapping.

a: 1
c: 2

res.foreach p in data if data[p].c = undefined: ${p}

res will contain part1 as part1 doesn't have a c field.

0.0.46 (2012-04-04)

- Fix ``else`` expression inside an ``.include``

0.0.45 (2012-03-22)

- You can now pass an etag to the open method of ``Openers``. This will throw a
NotModified exception if etag matching shows the request URI is unchanged.
This can be used to implement caching strategies and reduce the amount of data
that yay pulls over network connections::

>>> from yay.openers import Openers
>>> fp = Openers().open("/tmp/somefile, etag="1234535462356456fa")
NotModified: File '/tmp/somefile' not modified

- All openers will now have an etag property. This property can be None if a
suitable etag cannot be provided. Otherwise it should be some hash that
guarantees the state of the file so that later requests can just ask "has it
changed since it was in this state". To get an etag::

>>> from yay.openers import Openers
>>> fp = Openers().open("/tmp/somefile")
>>> print fp.etag

0.0.44 (2012-03-17)

- Fix .select when value that is resolved is a complicated expression.

- Better validation when you accidentally mix up list and mapping types.

0.0.43 (2012-02-12)

- Fix handling of paths on searchpath without a scheme.

0.0.42 (2012-01-01)

- Change how Django boxing works so that a .bind isn't required for the
boxing mechanism to work. This allows raw Django mdoels to be pushed
into Yay using the ``.add`` API from 0.0.41.

0.0.41 (2011-12-21)

- You can inject Python objects into the Yay Config object, as long as Yay
knows how to box them. If you had a Yay file like this::

hello: abc
result: ${hello}

And the following python code::

from yay.config import Config
c = Config()

Then the following assertion is true::

c.get() == dict(hello="xyz", result="xyz")

0.0.40 (2011-12-13)

- Fixes calling macros defined in other files.

0.0.39 (2011-11-30)

- Fix string builder so that configs containing secrets can be pickled.

0.0.38 (2011-11-22)

- This is a bugfix release to improve existing features, especially boxing of
foreign data.

- Move more code away from direct use of ``Boxed`` to ````

- Wrap any dictionary objects in a Mapping object so they can be merged with
other mappings that come from within Yay.

0.0.37 (2011-11-20)

- Brown paper bag release to remove stray print.

0.0.36 (2011-11-20)

- There is now a ``home://`` URL handler. For my laptop this means::

import yay

Is equivalent to::

import yay

- Improve searchpath handling to better cope with URIs.

- Add support for ``else`` keyword in expressions as per YEP2::

bar: ${foo.baz else 52}

This is useful for providing sensible defaults in your recipes.

- The loop block is now autoflattening. This means that constructs that yield
lists of lists will be turned into 1-dimensional lists by ``.foreach``. For

- - - a
- b
- c
- d

someotherlist.foreach var in somelist: ${var}

The list ``someotherlist`` would now contain::

- a
- b
- c
- d

The previous behaviour can be obtained with the ``chain`` modifier::

somelist.foreach var in somelist chain: ${var}

- Add a simple macro language. This is highly EXPERIMENTAL and subject to
frequent syntax tweaks. You can define a reusable block of configuration
using the .define statement. An example of this in Yaybu to create a reusable
virtualenv step::

.define Virtualenv:
- Directory:
name: ${venv.location}
owner: ${venv.owner}
- Execute:
name: create-virtualenv-${venv.location}
command: virtualenv --no-site-packages ${venv.location}
creates: ${venv.location}/bin/pip
- Execute:
name: install-requirements-${venv.location}
command: ${venv.location}/bin/pip install -r ${venv.requirements}

The macro is callable inline as part of an expression. For example::

.foreach venv in virtualenvs: ${Virtualenv!}

Equally you can do this::

.define Virtualenv:
- Directory:
name: ${location}
owner: ${owner}

location: /tmp/example
owner: dave
requirements: /tmp/requirements.txt

0.0.35 (2011-11-12)

- This release refactors ProtectedString to make it more useful outside Yay.
Instead of importing ``yay.protectedstring.ProtectedString`` you should
import ``yay.String``

- You can now pass strings to the constructor and they will automatically be
wrapped. Previously you had to pass StringPart's to the constructor. That is
now an internal implementation detail.

- There is now an extend() function. This accepts lists that contains a mixture
of raw strings and other ``String`` objects::

s = String("echo")
y = String("supersekritpassword", secret=True)
s.extend(["a", "b", y, "d"])

- There is now an as_list() function. This returns all the parts you have added
to a string. This is useful if you are building a command line to pass to

s.String(["someprogram", "--pasword"])

# Log the obfuscated version but execute with the real password
p = subprocess.Popen(s.as_list(secret=False), cwd="/")

- There is now a ``secret`` call in Yay for exercising secret Yay without
needing to use GPG. This is mainly for test purposes, but might be useful if
you have strings which arent closely guarded secrets yet you dont want them
show in logs. To use it you do something like this::

- Checkout:
name: /checkouts/mycode
scm_password.secret: mypassword

This example is from Yaybu and would stop Yaybu from logging your SVN

0.0.34 (2011-11-10)

- Compose now reuses Opener() rather than creating a new one for each stream

0.0.33 (2011-11-10)

- You can now pass ``searchpath`` to the ``Config`` object.

0.0.32 (2011-11-10)

- Working package:// imports

0.0.31 (2011-11-10)

- Better absolute path handling

0.0.30 (2011-11-10)

- Any stream objects returned by the ``Openers()`` API now have a ``len`` property.

- The internal ``Openers()`` API can now load from any package on the Python path::

fp = Openers().open("package://some.egg/hello.txt")

0.0.29 (2011-11-10)

- The internal ``Openers()`` API now has support for a search path::

fp = Openers(searchpath=['file:///home/john', '']).open("foo.txt")

- The ``Openers()`` API now supports https://

0.0.28 (2011-11-07)

- Fully remove all Mapping default crud

0.0.27 (2011-11-03)

- Fix ${django.SomeModel} to properly resolve

0.0.26 (2011-11-03)

- Add support for a Django DataStore
- Allow objects exposed from Python, including simple method calls

0.0.25 (2011-10-28)

- Fix regression in .append

0.0.24 (2011-10-22)

- Can now foreach over a mapping
- Add ``.foreach x in y if x.z = a``
- Add '.with expression as foo:'
- Add chain and nochain mode to foreach. chain is the default.
- Major refactoring, context variable is no longer needed to resolve the graph
- The 'semi_resolve' API is now more correctly named 'expand'

0.0.23 (2011-07-26)

- $$ escapes $ - so $${foo} is treated as a string, not a variable lookup

0.0.22 (2011-07-19)

- Remove spurious debug messages
- Fix .import on a .foreach

0.0.21 (2011-07-19)

- New .include directive that can use variables and appear anywhere in file

0.0.20 (2011-06-29)

- Change ProtectedString to inherit from basestring

0.0.19 (2011-06-29)

- Concept of a protected yay file, where any strings that end up containing
secrets will be obscured
- ProtectedString that handles concatenation of protected and unprocted strings
- GPG used to decrypt .yay.gpg files, any variables they spawn are protected

0.0.18 (2011-06-10)

- Brown paper bag to remove stray debugging scaffold

0.0.17 (2011-06-10)

- Fix appending to None
- Fix list access where list has already been partially resolved

0.0.16 (2011-06-10)

- Add range tests, fixed range() as a ${} expansion
- Added sum() (but no syntax sugar)
- Allow index operations against filters
- Fix iterating over Flatten() nodes
- Fix iterating over ForEach() nodes
- Add test for empty documents that got away

0.0.15 (2011-05-18)

- Raise an error if field access is invalid
- Add a LanguageError for displaying helpful messages when yay files
are wrong
- It is now a bug if we raise an error that doesn't descend from

0.0.14 (2011-05-12)

- Don't break on empty (e.g. {})

0.0.13 (2011-03-06)

- Fix Append nodes

0.0.12 (2011-03-03)

- Export that method ;)

0.0.11 (2011-03-03)

- Don't be unicode unless needed
- Add a dump() method

0.0.10 (2011-02-22)

- Don't chomp whitespace in bracketed_expression

0.0.9 (2011-02-22)

- Don't chomp whitespace in templated_string

0.0.8 (2011-02-18)

- Replace 'foreach bar as foo' with 'foreach foo in bar'

0.0.7 (2011-02-16)

- Numbers starting 0 are treated as base 8.

0.0.6 (2011-02-13)

- Avoid unicode mapping keys where possible - they break **kwargs in Py2.x

0.0.5 (2011-02-09)

- Add support for nested foreach

- At least for now, support a ruby style .flatten

0.0.4 (2011-02-04)

- {foo} can be interpreted as a map by YAML. For now, we will use ${foo} to avoid this

- Function calls to python are implemented - there is now range()

- There is now a key so switch statements can be used

0.0.3 (2011-01-24)

- Egg packaging fixes

0.0.2 (2011-01-24)

- Lots more unittests for expression evaluation and expression parsing

- Drop dependency on OrderedDict


- This is still pre-release, no API or language stability guarantees

- Variable resolving is now done in expression tree without a seperate resolve stage

- Uses pyparsing to parse {foo[bar][@.baz > 5]} type syntax


- This is a pre-alpha release to experiment with what we can and can't do.

- New PyYAML Loader subclass for getting ordered maps without ugly !!omap markup

- Resolves {} markup within YAML nodes

- Lazily evaluates .copy, .append and .remove instructions

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