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Package for the integration of RequireJS into a Python environment via the Calmjs framework, to provide a reproducible workflow for the generation of deployable artifacts from JavaScript source code provided by Python packages in conjunction with standard JavaScript or Node.js packages sourced from npm or other similar package repositories.

Project Description


Package for the integration of RequireJS into a Python environment via the Calmjs framework, to provide a reproducible workflow for the generation of deployable artifacts from JavaScript source code provided by Python packages in conjunction with standard JavaScript or Node.js packages sourced from npm or other similar package repositories.


Web applications can be created using any language, however the interactive front-end user interfaces they provide ultimately rely on some form of JavaScript. Python web application frameworks or systems that provide frontend functionalities that bridge the backend have adopted the usage of Node.js for testing the JavaScript code that they may provide, with npm (or bower) being the package manager for the acquisition of JavaScript packages required for the associated functionality. This often resulted in the separation of what would have been a single set of package dependency configuration into multiple different sets; often this also resulted in the package being fractured into two parts to fit in with the distribution channels being used (PyPI vs npm and others).

This outcome ends up being problematic for Python package management due to the increase in difficulty in the propagation of the package’s version and dependency information across all relevant package management channels in a consistent, portable and reproducible manner for downstream packages and their users. The other issue is that the configuration files used for asset management or artifact generation is often coupled tightly to the system at hand, making it rather difficult for their downstream package to reuse these configurations to generate a combined artifacts that work also with their other upstream packages in a consistent manner.

Some other package managers attempt to solve this by being utterly generic, however they lack the awareness of locally available Python packages (such as Python wheels already installed in the local environment not being understood by Bower), thus build processes that involve Bower often end up relying on public infrastructure, and options to move it to a private infrastructure or even reuse locally available artifacts/packages require extra configurations which negate the benefits offered by these systems. Also, these build scripts are tightly coupled to a specific project which are not portable.

The goal of the Calmjs framework is to bring this separation back together by providing the method to expose JavaScript sources included with Python packages, with this package, calmjs.rjs, to provide the facilities to produce deployable artifacts from those exported source files, plus the other declared external bundles to be sourced from npm or other related Node.js package management systems.


How calmjs.rjs works

The Calmjs framework provides the framework to allow Python packages to declare the dependencies they need against npm based packages for the JavaScript code they provide, and also the system that allow Python packages to declare which of their modules export JavaScript sources that can be reused.

The utility included with calmjs.rjs provide the means to consume those declarations, treating the JavaScript files as both source and compilation target, with the final deployable artifact(s) being produced through r.js from the requirejs package.

Currently, the source files could be written in both AMD and CommonJS module formats, although the CommonJS format is recommended due to their wide support under most systems, and that calmjs.rjs provides transpilation and configuration generation utilities that processes the JavaScript source code into a form that is compatible with the r.js optimizer. However, the exports statement in the source file should be not part of module.exports for the mean time. The AMD headers and footers can be absent too, as the calmjs rjs transpiler will add the appropriate headers and footers needed (for example, have require be imported from the correct source, or for mapping exports to module.exports) so that the final script will be usable for the target platform or format.

The resulting sources will be placed in a build directory, along with all the declared bundled sources acquired from the Node.js package managers or repositories. A build file will then be generated that will include all the relevant sources as selected to enable the generation of the final artifact file through r.js. These can then be deployed to the appropriate environment, or the whole above process can be included as part of the functionality of the Python backend at hand.

Ultimately, the goal of calmjs.rjs is to ease the integration and interactions between of client-side JavaScript with server-side Python, by simplifying the task of building, shipping and deployment of the two set of sources in one shared package and environment. The Calmjs framework provides the linkage between these two environment and the tools provided by there will assist with the setup of a common, reproducible local Node.js environments.

Finally, for quality control, this package has integration with, which provides the tools needed to set up the test environment and harnesses for running of JavaScript tests that are part of the Python packages for the associated JavaScript code. However, that package is not declared as a direct dependency, as not all use cases will require the availability of that package. Please refer to installation section for details.

Do note, in the initial implementation, the JavaScript source file supported by this framework loosely follows certain definitions that only mimic what ES6 intends to provide (as outlined earlier). Even with this, as a consequence of treating JavaScript within the Python package as a source file for the compilation target which is the deployable artifact file, the input source files and exported paths generated by calmjs.rjs are NOT meant for direct consumption of web clients such as web browsers. The produced artifact from this framework will be usable through the AMD API.


It is recommended that the local environment already have Node.js and npm installed at the very minimum to enable the installation of requirejs, if it hasn’t already been installed and available. Also, the version of Python must be either 2.7 or 3.3+; PyPy is supported, with PyPy3 version 5.2.0-alpha1 must be used due to a upstream package failing to function in the currently stable PyPy3 version 2.4.

To install calmjs.rjs into a given Python environment, it may be installed directly from PyPI with the following command:

$ pip install calmjs.rjs

If a local installation of RequireJS into the current directory is desired, it can be done through calmjs with the following command:

$ calmjs npm --install calmjs.rjs

Which does the equivalent of npm install requirejs; while this does not seem immediately advantageous, other Python packages that declared their dependencies for specific sets of tool can be invoked like so, and to follow through on that. As an example, example.package may declare dependencies on RequireJS through npm plus a number of other packages available through requirejs, the process then simply become this:

$ calmjs npm --install example.package

All standard JavaScript and Node.js dependencies for example.package will now be installed into the current directory through the relevant tools. This process will also install all the other dependencies through npm or requirejs that other Python packages depended on by example.package have declared. For more usage please refer to further down this document or the documentation for calmjs.

Alternative installation methods (advanced users)

Development is still ongoing with calmjs.rjs, for the latest features and bug fixes, the development version can be installed through git like so:

$ pip install calmjs
$ pip install git+

Alternatively, the git repository can be cloned directly and execute python develop while inside the root of the source directory.

Keep in mind that calmjs MUST be available before the within the calmjs.rjs source tree is executed, for it needs the package_json writing capabilities in calmjs. Alternatively, please execute python egg_info if any message about Unknown distribution option: is noted during the invocation of

As calmjs is declared as both a namespace and a package, mixing installation methods as described above when installing with other calmjs packages may result in the module importer being unable to look up the target module. While this normally will not affect end users, provided they use the same, standard installation method (i.e. wheel), for developers it can be troublesome. To resolve this, either stick to the same installation method for all packages (i.e. python develop), or import a module from the main calmjs package. Here is an example run:

>>> import calmjs.rjs
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named 'calmjs.rjs'
>>> import calmjs.base
>>> import calmjs.rjs

If this behavior (and workaround) is undesirable, please ensure the installation of all calmjs related packages follow the same method (i.e. either python develop for all packages, or using the wheels acquired through pip).

Testing the installation

Finally, to verify for the successful installation of calmjs.rjs, the included tests may be executed through this command:

$ python -m unittest calmjs.rjs.tests.make_suite

However, if the steps to install external Node.js dependencies to the current directory was followed, the current directory may be specified as the CALMJS_TEST_ENV environment variable. Under POSIX compatible shells this may be executed instead from within that directory:

$ CALMJS_TEST_ENV=. python -m unittest calmjs.rjs.tests.make_suite

Do note that if the package is unavailable, a number of tests will be skipped. To avoid this, either install that package separately, or install calmjs.rjs using its extras dependencies declaration like so:

$ pip install calmjs.rjs[dev]


Any exposed JavaScript code through the calmjs.module registry will be picked up and compiled into a working RequireJS artifact. For details on how the calmjs registry system works please refer to the README included with the calmjs project.

For example, given the following entry points for that registry defined by a package named example:

example.lib = example.lib =

While the import locations declared looks exactly like a Python module (as per the rules of a Python entry point), the calmjs.module registry will present them using the es6 style import paths (i.e. 'example/lib' and 'example/app'), so users of that need those JavaScript modules to be sure they require those strings. Also, the default extractor will extract all source files within those directories. Also, as a consequence of how the imports are done, it is recommended that no relative imports be used.

To extract all JavaScript modules declared within Python packages through this registry can be done like so through the calmjs rjs build tool, which would extract all the relevant sources, create a temporary build directory, generate the build manifest and invoke r.js on that file. An example run:

$ calmjs rjs example

Tracing dependencies for: /home/user/example.js


As the build process used by calmjs.rjs is done in a separate build directory, all imports through the Node.js module system must be declared as extras_calmjs. For instance, if example/app/index need to use the jquery and underscore modules like so:

var $ = require('jquery'),
    _ = require('underscore');

It will need to declare the target location sourced from npm plus the package_json for the dependencies, it will need to declare this in its

    # ...
        "dependencies": {
            "jquery": "~3.1.0",
            "underscore": "~1.8.0",
    extras_calmjs = {
        'node_modules': {
            'jquery': 'jquery/dist/jquery.js',
            'underscore': 'underscore/underscore.js',

Once that is done, rerun python egg_info to write the freshly declared metadata into the package’s egg-info directory, so that it can be used from within the environment. calmjs npm --install can now be invoked to install the npm dependencies into the current directory; to permit calmjs.rjs to find the required files sourced from npm to put into the build directory for r.js to locate them.

The resulting calmjs run may then end up looking something like this:

$ calmjs rjs example

Tracing dependencies for: /home/user/example.js


The transpiler will add the appropriate boilerplates and thus the require statements through requirejs will import from node_modules if the extras_calmjs have been declared. However, there are cases where the desired artifact should only contain the sources from the Python package without the extras or vice versa (due to the library being available via another deployed artifact), this is supported by the empty: scheme by r.js, and to enable it for calmjs rjs it can be done like so:

$ calmjs rjs example --bundle-map-method empty --export-filename main.js

Tracing dependencies for: /home/user/main.js


$ calmjs rjs example --source-map-method empty --export-filename deps.js

Tracing dependencies for: /home/user/deps.js


The above example shows the generation of two separate artifacts, one containing just the sources from the Python package example that had been declared in the calmjs.module registry, and the other contains only the external extra sources.

If the above triggers a dependency trace error for r.js, there is a last resort --empty flag that can be applied; do note that this completely disables the trace functionality for r.js as this initiates a similar trace process to locate all the imported module names for stubbing them out with the empty: scheme within the generated configuration file. Ensure that the modules required by the resulting artifact has all its required modules provided elsewhere.

The explicit extras_calmjs declaration also supports the usage through bower (supported via calmjs.bower); instead of using node_modules as the key, bower_components should be used instead.

Alternative registries aside from calmjs.module can be specified with the --source-registry flag. Assuming there are registries in the current environment registered as myreg1 and myreg2 and the example package has registered sources to both of them, the command to build a bundle from both those registries into one artifact can be triggered like so:

$ calmjs rjs --source-registry=myreg1,myreg2 example

Handling of RequireJS loader plugins

The AMD system as defined by RequireJS has the concept of loader plugins, where the module name provided may be suffixed with a ! as arguments for handling by the plugin. As the string provided after is opaque to the requirejs system as a whole and thus handled directly by the preceding plugin, the resources that it need will be specific to the plugin itself. As it may load resources through the requirejs system, any paths that require configuration will need to be done.

To account for this issue, calmjs.rjs introduces the concept of loader plugin handlers and a registry system for dealing with this. A given RJSToolchain will have a default loader plugin registry assigned, but this can be overridden by specifying a custom identifier (overriding the default 'calmjs.rjs.loader_plugin') for the registry to be used, which will allow the handling of very customized loaders for a given project. Please refer to the calmjs.rjs.registry module for more details on how this is constructed and set up for usage.

By default, the text handler is registered to the default loader plugin registry, which should cover the most common use case encountered by the calmjs framework.


The following are some known issues with regards to this package and its integration with other Python/Node.js packages.

When calling calmjs rjs on a package, got ENOENT

Typically this is caused by source files from the source package or registry invoking require a JavaScript module that is not available in the build directory. One possible cause through the calmjs framework is that the Python package failed to declare extras_calmjs that it might require, or that explicit map method and/or source registry that was selected did not result in all required sources be loaded into the build directory.

If the missing source files are intended, applying the --empty or the -e flag to the rjs tool will stub out all the missing modules from the bundle; do note that this will result in the generated artifact bundle not having all the required modules for its execution. The resulting artifact bundle should be used in conjunction with the other artifact bundles that provide the result of the required dependencies.

WARNING: Couldn’t write lextab module <module ‘slimit.lextab’ …>

This is due to the slimit module shipping outdated table files. Try removing the file from that module (the path indicated) which should permit the ply library to regenerate the relevant files to remove the exception, and to speed up execution as generating the JavaScript parser without these precompiled tables in place for operations that involve working with the JavaScript source tree has significant performance penalties. This information also applies for the slimit.yacctab module.

RJSRuntimeError: unable to locate ‘r.js’

This means the current Node.js environment is missing the requirejs package from npm; either install it manually with it or through calmjs on this package. If a given Python package is required to use requirejs to generate the package, its package_json should declare that, or declare dependency on calmjs.rjs.

UserWarning: Unknown distribution option:

During setup and installation using the development method, if this warning message is shown, please ensure the egg metadata is correctly generated by running python egg_info in the source directory, as the package calmjs was not available when the setup script was initially executed.


1.0.2 (2017-05-22)

  • Corrected the issue where plugins that have been unmapped using the empty: scheme triggering FileNotFoundError.

1.0.1 (2017-01-27)

  • Load the non-test files in deps also, instead as part of the tests to avoid automatic inclusion.
  • Test files should start with the name test as per convention.

1.0.0 (2016-11-18)

  • Initial implementation that brings in the support of the production of AMD artifacts (bundles) from JavaScript sources included with Python packages (along with their declared dependencies through npm or other supported tools) through the calmjs framework.
  • Enabled the calmjs rjs tool entry point.
  • Also provide integration with 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.
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