[oe] [RFC] [PATCH 1/2] Implement variable typing

[Chris Larson]

On Tue, Nov 9, 2010 at 4:18 PM, Chris Larson <kergoth at gmail.com> wrote:

> This implementation consists of two components:
>
> - oe.types python module, whose job it is to construct objects of the
> defined
>  type for a given variable in the metadata
> - typecheck.bbclass, which iterates over all configuration variables with a
>  type defined and uses oe.types to check the validity of the values
>
> This gives us a few benefits:
>
> - Automatic sanity checking of all configuration variables with a defined
> type
> - Avoid duplicating the "how do I make use of the value of this variable"
>  logic between its users.  For variables like PATH, this is simply a
> split(),
>  for boolean variables, the duplication can result in confusing, or even
>  mismatched semantics (is this 0/1, empty/nonempty, what?)
> - Make it easier to create a configuration UI, as the type information
> could
>  be used to provide a better interface than a text edit box (e.g checkbox
> for
>  'boolean', dropdown for 'choice')
>
> This functionality is entirely opt-in right now.  To enable the
> configuration
> variable type checking, simply INHERIT += "typecheck".  Example of a
> failing
> type check:
>
> BAZ = "foo"
> BAZ[type] = "boolean"
>
> $ bitbake -p
> FATAL: BAZ: Invalid boolean value 'foo'
> $
>
> Examples of leveraging oe.types in a python snippet:
>
> PACKAGES[type] = "list"
>
> python () {
>    import oe.types
>    for pkg in oe.types.value("PACKAGES", d):
>        bb.note("package: %s" % pkg)
> }
>
> LIBTOOL_HAS_SYSROOT = "yes"
> LIBTOOL_HAS_SYSROOT[type] = "boolean"
>
> python () {
>    import oe.types
>    assert(oe.types.value("LIBTOOL_HAS_SYSROOT", d) == True)
> }
>

See https://github.com/kergoth/openembedded/compare/master...typing for the
current version, just reworked to decouple the types from the metadata to
make their unit testing a bit cleaner.  Note that the __new__ use for Choice
and Regex is pretty ugly, really only using those classes as a container to
make setting the name and flags attributes on the callable less ugly :P
 Comments welcome.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics