Calmjs.webpack

------------------

- Various changes to enable the support of webpack 3 and 4. [
`6 <https://github.com/calmjs/calmjs.webpack/issues/6>`_
]

- Substantial modification to the generation of webpack configuration
scripts, as they are constructed through helpers that construct an
abstract syntax tree through ``calmjs.parse``. This is done so that
webpack version specific incompatibilities can be added/removed into
the generated script as executable Node.js code.
- A kill plugin is provided to karma by default; if webpack fails to
build, the karma process will halt, as the ``singleRun: true`` flag
no longer does the job for webpack.

- Provide the ability to interrogate artifacts that simply have their
function scope variable names mangled. [
`8 <https://github.com/calmjs/calmjs.webpack/issues/8>`_
]

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- Ensure the line-continuation mark is filtered out in the to_identifier
helper function as the values of String node object included that mark
as of ``calmjs.parse-1.1.0``. [
`7 <https://github.com/calmjs/calmjs.webpack/issues/7>`_
]

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- Provide support of prefix-free loaders through a customized webpack
loader module registry; this one also works in tandem with the
``calmjs.module`` registry. [
`5 <https://github.com/calmjs/calmjs.webpack/issues/5>`_
]

- Integrate the support of the package resource loader registry
introduced by ``calmjs-3.3.0``.
- Bumped supported ``calmjs.dev`` to version 2.2.0 such that the
correct test loader registries can be automatically acquired. This
also makes it possible to declare test data files as resources for
JavaScript tests in the most straightforward manner as possible

- The base loader plugin handler will also generate a modname prefixed
with ``./``, in an attempt to provide a more natural include mechanism
from within certain webpack loader contexts, as a number of them will
implicitly resolve by relative path for a bare import, and the goal is
to avoid further proprietary webpack syntaxes (e.g. the usage of the
``~`` prefixes to some ``namespace/package`` import/inclusions done
inside the loader context). [
`4 <https://github.com/calmjs/calmjs.webpack/issues/4>`_
]

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- Provide a builder that will generate an artifact with the supported
optimize flags enabled. [
`3 <https://github.com/calmjs/calmjs.webpack/issues/3>`_
]

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- Update the export_target production and usage of working_dir to be
inline with what is expected by ``calmjs-3.1.0``. [
`2 <https://github.com/calmjs/calmjs.webpack/issues/2>`_
]

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- Initial implementation of the Calmjs integration tool that enable the
production of webpack artifacts from JavaScript sources that are
included with Python packages, that also allow import of their
dependencies sourced through ``npm`` through the Calmjs framework.
- Enabled the ``calmjs webpack`` tool entry point.
- Also provide integration with ``calmjs.dev`` by correcting the correct
hooks so that this package can be used as an advice package for the
execution of tests against artifacts generated through this package,
through the usage of ``calmjs karma webpack``.
- Support for prebuilt artifacts for packages is provided through
``calmjs.artifacts`` registry; default complete builders for both
building and testing are available via the ``calmjs.webpack.artifact``
module.
- Webpack is pinned to ~2.6.0, as that is the current stable version
that is verified to work with building and testing of artifacts.