docs: update static assets ADR with the new plan #32804
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@@ -5,14 +5,16 @@ Overview | |
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| * edx-platform has a complicated process for managing its static frontend assets. It slows down both developers and site operators. | ||
| * We will deprecate the current paver-based asset processing system in favor of a new implementation based primarily on frontend tools and bash. | ||
| * After one named release, the deprecated paver system will be removed. | ||
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| Status | ||
| ****** | ||
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| **Provisional** | ||
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| This was `originally authored <https://github.com/openedx/edx-platform/pull/31790>`_ in March 2023. We `modified it in July 2023 <https://github.com/openedx/edx-platform/pull/32804>`_ based on learnings from the implementation process. | ||
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| The status will be moved to *Accepted* upon completion of reimplementation. Related work: | ||
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| * `[DEPR]: Asset processing in Paver <https://github.com/openedx/edx-platform/issues/31895>`_ | ||
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@@ -23,8 +25,8 @@ The status will be moved to *Accepted* upon completion of reimplementation. Rela | |
| Context | ||
| ******* | ||
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| State of edx-platform frontends (early 2023) | ||
| ============================================ | ||
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| New Open edX frontend development has largely moved to React-based micro-frontends (MFEs). However, edx-platform still has a few categories of important static frontend assets: | ||
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@@ -98,7 +100,7 @@ We will largely reimplement edx-platform's asset processing system. We will aim | |
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| * Use well-known, npm-installed frontend tooling wherever possible. | ||
| * When bespoke processing is required, use standard POSIX tools like Bash. | ||
| * When Python is absolutely required, minimize the scope of its usage and the set of required Python libraries. | ||
| * Avoid unnecessary indirection or abstraction. For this task, extensibility is a non-goal, and simplicity is a virtue. | ||
| * Provide a clear migration path from the old system to the new one. | ||
| * Enable the future removal of as much legacy frontend tooling code as possible. | ||
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@@ -128,9 +130,11 @@ The three top-level edx-platform asset processing actions are *build*, *collect* | |
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| A Python-defined task that calls out to each build stage. | ||
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| - ``npm clean-install && npm run build`` | ||
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| Simple NPM wrappers around the build stages. The wrappers will be written in Bash and tested on both GNU+Linux and macOS. | ||
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| These commands are a "one stop shop" for building assets, but more efficiency-oriented users may choose to run build stages individually. | ||
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There was a problem hiding this comment. As I moved towards |
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| * - + **Build stage 1: Copy npm-installed assets** from node_modules to other folders in edx-platform. They are used by certain especially-old legacy LMS & CMS frontends that are not set up to work with npm directly. | ||
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@@ -150,54 +154,49 @@ The three top-level edx-platform asset processing actions are *build*, *collect* | |
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| Equivalent paver task and console script, both pointing at to an application-level Python module. That module inspects attributes from legacy XModule-style XBlock classes in order to determine which static assets to copy and what to name them. | ||
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| - (step no longer needed) | ||
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| We will `remove the need for this step entirely <https://github.com/openedx/edx-platform/issues/31624>`_. | ||
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| * - + **Build stage 3: Run Webpack** in order to to shim, minify, otherwise process, and bundle JS modules. This requires a call to the npm-installed ``webpack`` binary. | ||
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| - ``paver webpack`` | ||
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| Python wrapper around a call to webpack. Invokes the ``./manage.py [lms|cms] print_setting`` multiple times in order to determine Django settings, adding which can add 20+ seconds to the build. | ||
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| - ``npm run webpack`` | ||
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| Simple shell script defined in package.json to invoke Webpack in prod or dev mode. The script will look for several environment variables, with a default defined for each one. See **Build Configuration** for details. The script will NOT invoke ``print_setting``; we leave to distributions the tasking of setting environment variables appropriately. | ||
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There was a problem hiding this comment. Love this, though I know it may feel a bit duplicative to have this info in both an environment variable and in the LMS settings. In the future we could allow the user to override the setting based on a value in the environment as well so I'm not too worried about it for now. There is an implied "We expect Django and Node to put assets in the same place for things to render properly." Is this written down somewhere or should we document it? (Non-blocking thought.) There was a problem hiding this comment. Agreed all around. The specifics of things like the exact env var semantics are still in flux (hence this PR :) so I'm hoping that this ADR will tide over anyone who wants to experiment with the new assets system. Once I'm closer to removing Paver, though, I'll make sure that these sort of settings are either de-duped or documented. |
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| To continue using ``print_setting``, one could run: ``STATIC_ROOT_LMS="$(./manage.py lms print_setting STATIC_ROOT_LMS)" npm run webpack`` | ||
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| * - + **Build stage 4: Compile default SCSS** into CSS for legacy LMS/CMS frontends. | ||
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| - ``paver compile_sass`` | ||
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| Paver task that invokes ``sass.compile`` (from the libsass Python package) and ``rtlcss`` (installed by npm) for several different directories of SCSS. | ||
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| Note: We compile SCSS using ``libsass-python==0.10.0``, a deprecated library from 2015. Installing it requires compiling a large C extension, noticeably affecting Docker image build time. The upgrade path is non-trivial and would require updating many SCSS file in edx-platform. | ||
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| - ``npm run compile-sass`` | ||
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| A functionally equivalent reimplementation, wrapped as an ``npm run`` command in package.json. Due to our SCSS version, the underlying script will be written in Python, although its only Python library requirements will be ``libsass-python`` and ``click``, which will be specified in a new separate edx-platform requirements file. This will be an improvement because the script will not rely on the presence of paver, base Python requirements, or any other edx-platform Python code. | ||
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| If and when `we upgrade from libsass-python <https://github.com/openedx/edx-platform/issues/31616>`_ to a more modern tool like ``node-sass`` or ``dart-sass``, this underlying script could opaquely be rewritten in Bash, removing the Python requirement altogether. | ||
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| * - + **Build stage 5: Compile themes' SCSS** into CSS for legacy LMS/CMS frontends. The default SCSS is used as a base, and theme-provided SCSS files are used as overrides. Themes are searched for from some number of operator-specified theme directories. | ||
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| - ``./manage.py [lms|cms] compile_sass``, or | ||
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| ``paver compile_sass --theme-dirs X Y --themes A B`` | ||
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| The management command is a wrapper around the paver task. The former looks up the list of theme search directories from Django settings and site configuration; the latter requires them to be supplied as arguments. | ||
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| - ``./manage.py [lms|cms] compile_sass``, or | ||
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| ``npm run compile-sass -- --theme-dir X --theme-dir Y --theme A --theme B`` | ||
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| The management command will remain available, but it will be updated to point at ``npm run compile-sass``, which will replace the paver task (see build stage 4 for details). | ||
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| * - **Collect** the built static assets from edx-platform to another location (the ``STATIC_ROOT``) so that they can be efficiently served *without* Django's webserver. This step, by nature, requires Python and Django in order to find and organize the assets, which may come from edx-platform itself or from its many installed Python and NPM packages. This is only needed for **production** environments, where it is usually desirable to serve assets with something efficient like NGINX. | ||
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@@ -217,61 +216,55 @@ The three top-level edx-platform asset processing actions are *build*, *collect* | |
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| Paver task that invokes ``webpack --watch`` for Webpack assets and watchdog (a Python library) for other assets. | ||
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| - ``npm run watch`` | ||
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| Bash wrappers around invocation(s) of `watchman <https://facebook.github.io/watchman/>`_, a popular file-watching library maintained by Meta. Watchman is already installed into edx-platform (and other services) via the pywatchman pip wrapper package. | ||
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There was a problem hiding this comment. This note seemed irrelevant now that |
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| Build Configuration | ||
| ------------------- | ||
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| To facilitate a generally Python-free build reimplementation, we will require that certain Django settings now be specified as environment variables, which can be passed to the build like so:: | ||
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| MY_ENV_VAR="my value" npm run build # Set for the whole build. | ||
| MY_ENV_VAR="my value" npm run webpack # Set for just a single step, like webpack. | ||
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| For Docker-based distributions like Tutor, these environment variables can instead be set in the Dockerfile. | ||
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There was a problem hiding this comment. This whole |
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| Some of these options will remain as Django settings because they are used in edx-platform application code. Others will be removed, as they were only read by the asset build. | ||
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| .. list-table:: | ||
| :header-rows: 1 | ||
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| * - Django Setting (Before) | ||
| - Description | ||
| - Django Setting (After) | ||
| - Environment Variable (After) | ||
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| * - ``WEBPACK_CONFIG_PATH`` | ||
| - Path to Webpack config file. Defaults to ``webpack.prod.config.js``. | ||
| - *removed* | ||
| - ``WEBPACK_CONFIG_PATH`` | ||
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| * - ``STATIC_ROOT`` (LMS) | ||
| - Path to which LMS's static assets will be collected. Defaults to ``test_root/staticfiles``. | ||
| - ``STATIC_ROOT`` (LMS) | ||
| - ``STATIC_ROOT_LMS`` | ||
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| * - ``STATIC_ROOT`` (CMS) | ||
| - Path to which CMS's static assets will be collected. Defaults to ``$STATIC_ROOT_CMS/studio``. | ||
| - ``STATIC_ROOT`` (CMS) | ||
| - ``STATIC_ROOT_CMS`` | ||
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| * - ``JS_ENV_EXTRA_CONFIG`` | ||
| - Global configuration object available to edx-platform JS modules. Specified as a JSON string. Defaults to the empty object (``"{}"``). Only known use as of writing is to add configuration and plugins for the TinyMCE editor. | ||
| - *removed* | ||
| - ``JS_ENV_EXTRA_CONFIG`` | ||
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| * - ``COMPREHENSIVE_THEME_DIRS`` | ||
| - Directories that will be searched when compiling themes. | ||
| - ``COMPREHENSIVE_THEME_DIRS`` | ||
| - ``EDX_PLATFORM_THEME_DIRS`` | ||
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| Migration | ||
| ========= | ||
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@@ -298,19 +291,21 @@ Either way, the migration path is straightforward: | |
| * - Existing Tutor-provided command | ||
| - New upstream command | ||
| * - ``openedx-assets build`` | ||
| - ``npm run build`` | ||
| * - ``openedx-assets npm`` | ||
| - ``scripts/copy-node-modules.sh # (automatically invoked by 'npm install'!)`` | ||
| * - ``openedx-assets xmodule`` | ||
| - (no longer needed) | ||
| * - ``openedx-assets common`` | ||
| - ``npm run compile-sass -- --skip-themes`` | ||
| * - ``openedx-assets themes`` | ||
| - ``npm run compile-sass -- --skip-default`` | ||
| * - ``openedx-assets webpack`` | ||
| - ``npm run webpack`` | ||
| * - ``openedx-assets collect`` | ||
| - ``./manage.py [lms|cms] collectstatic --noinput`` | ||
| * - ``openedx-assets watch-themes`` | ||
| - ``npm run watch`` | ||
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| The options accepted by ``openedx-assets`` will all be valid inputs to ``scripts/build-assets.sh``. | ||
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@@ -334,14 +329,9 @@ Live with the problem | |
| We could avoid committing any work to edx-platform asset tooling, and instead just wait until all frontends have been replatformed into MFEs. See the *Context* section above for why this was rejected. | ||
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| Improve existing system | ||
| ========================== | ||
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There was a problem hiding this comment. We aren't entirely removing Python any more, so I removed this section, but I folded its arguments into the rejection of "Improve existing system" since they are largely the same. |
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| Rather than replace it, we could try to improve the existing Paver-based asset processing system. However, entirely dropping Paver and mostly dropping Python has promising benefits: | ||
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| Asset build independence | ||
| ------------------------ | ||
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@@ -355,10 +345,8 @@ The asset pipeline only needs to perform a handful of simple tasks, primarily co | |
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| However, Python (like any modern application language) encourages developers to modularize, build abstractions, use clever control flow, and employ indirection. This is particularly noticeable with the Paver assets build, which is a thousand lines long and difficult to understand. | ||
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| Better interop with standard tools | ||
| ---------------------------------- | ||
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| It is best if the build can stem from a single call to ``npm install && npm run build`` rather than a call to a bespoke script (whether Paver or Bash). Generally speaking, the more edx-platform can work with standard frontend tooling, the easier it'll be for folks to use, understand, and maintain it. | ||
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Timestamping this since the line between XModule and XBlock has blurred since writing. Still, the table makes sense from the perspective of this ADR.