This is a re-factor of element_dependencies to achieve two things --
centralising override policy and storing path names.
Firstly we want to make the override policy for elements completely
explicit. Currently, elements that wish to copy parts of other
elements walk ELEMENTS_PATH themselves and look for elements in
IMAGE_ELEMENT. How they handle duplicate elements can differ, leading
to inconsistent behaviour.
We introduce logic in element-info to find elements in each of the
directories in ELEMENT_PATHS in *reverse* order -- that is to say,
earlier entries in the paths will overwrite later ones.
For example
ELEMENT_PATHS=foo:bar:baz
will mean that "foo/element" will override "baz/element", since "foo"
is first. This should be sane to anyone familiar with $PATH.
Documentation is clarified around this point and a test-case is added.
The second thing is that we want to keep the complete path of the
elements we have chosen. We want the aforementioned elements that
walk the element list to use these canonical paths to pickup files;
this way they don't need to make local decisions about element
overrides, but can simply iterate a list and copy/merge files if they
exist.
A follow-on change (I7092e1845942f249175933d67ab121188f3511fd) will
expose this data in a separate variable that can be parsed by elements
(a further follow-on I0a64b45e9f2cfa28e84b2859d76b065a6c4590f0
modifies the elements to use this information). Thus this does not
change the status-quo -- elements that are walking ELEMENTS_PATH
themselves and can/will continue doing that.
Change-Id: I2a29861c67de2d25c595cb35d850e92807d26ac6
I got quite confused what this was trying to tell me at first. It's
saying that you requested an element but another element already
provides that element, so we don't know which one to choose.
To help clarify the situation to the user, keep track of what is
providing elements so we can describe where the conflict came from.
Change-Id: Ie7471ac900a8cbee5684c928badd1b8ce6d3e3cf
Use standard logging module for output. Add some basic testing of
error messages to the unit-tests. Use the logging_config module to
setup the logging for interactive use.
Change-Id: Ia23722a7bd00aba336118edb155356a3b3ef6926
The phrase is no longer needed as of August 23, 2000 with Nicaragua's
joining of the Berne Convention.
Additionally, in at least one instance,
elements/cache-url/bin/cache-url, its existence in the file between
Copyright lines is just weird and feels misleading, even though it is
not.
Remove all of the lines, because sanity.
Change-Id: I24fd76c2b4f66b8036010b5079db39ead729abee
To ensure that we have the list of provided elements from the
command line before looking up dependencies, use a deque and
popleft() to take the elements on a first-in/first-out basis.
Change-Id: I0a2c21fa081763fd3cc8358be25dafeee1ed4718
Closes-Bug: #1303911
An element can define a list of elements provided by itself. This allows
using an alternative element and keeping element dependencies at the
same time. This will be needed for example for mariadb element which will be
an alternative to mysql element - mysql dependency can be kept everywhere
but user can choose mariadb explicitly as a replacement by putting "mysql"
into "element-provides" file.
Change-Id: I7f193612f279dd71d9f1f1edfc60009838a00c5a
This commit refactors the python code in diskimage_builder slightly. This is
in preparation for a larger review that adds more functionality to the python
code, namely the ability to apply elements to the current system as opposed to
a chroot. Further, the refactorings can stand on their own for better clarity.
They include:
- renaming elements.py to element_dependencies.py. Adds clarity about the
purpose of this module.
- updating other code for this rename.
- move tests into a tests submodule.
Change-Id: I5519cc52398e442b24e33802bae42070d64b0c1d
