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revert: build: remove dependency on Python sass module #34476

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Apr 5, 2024
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revert: build: remove dependency on Python sass module #34476

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124 changes: 28 additions & 96 deletions scripts/compile_sass.py
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Original file line number Diff line number Diff line change
Expand Up @@ -42,9 +42,7 @@
from __future__ import annotations

import glob
import os
import subprocess
import sys
from pathlib import Path

import click
Expand Down Expand Up @@ -155,108 +153,42 @@ def main(

def compile_sass_dir(
message: str,
source_root: Path,
target_root: Path,
source: Path,
dest: Path,
includes: list[Path],
tolerate_missing: bool = False,
) -> None:
"""
Compile a directory of Sass into a target CSS directory, and generate any missing RTL CSS.
Structure of source dir is mirrored in target dir.

IMPLEMENTATION NOTES:
=====================

libsass is a C++ library for compiling Sass (ref: https://github.com/sass/libsass).

libsass-python is a small PyPI package wrapping libsass, including:
* The `_sass` module, which provides direct Python bindings for the C++ library.
(ref: https://github.com/sass/libsass-python/blob/0.10.0/pysass.cpp)
* The `sass` module, which adds some friendly Pythonic wrapper functions around `_sass`,
notably `sass.compile_dirname(...)`.
(ref: https://github.com/sass/libsass-python/blob/0.10.0/sass.py#L198-L201)

Our legacy Sass code only works with a super old version of libsass (3.3.2,) which is provided to us by a super
old version of libsass-python (0.10.0). In this super old libsass-python version:
* the `sass` module DOESN'T support Python 3.11+, but
* the `_sass` module DOES support Python 3.11+.

Upgrading our Sass to work with newer a libsass version would be arduous and would potentially break
comprehensive themes, so we don't want to do that. Forking libsass-python at v0.10.0 and adding Python 3.11+
support would mean adding another repo to the openedx org. Rather than do either of those, we've decided to
hack around the problem by just reimplementing what we need of `sass.compile_dirname` here, directly on top
of the `_sass` C++ binding module.

Eventually, we may eschew libsass-python altogether by switching to [email protected], a direct CLI for [email protected].
(ref: https://github.com/sass/sassc). This would be nice because it would allow us to remove Python from the
Sass build pipeline entirely. However, it would mean explicitly compiling & installing both libsass and SassC
within the edx-platform Dockerfile, which has its own drawbacks.
Structure of source dir is mirrored in target dir.
"""
# Constants from libsass-python
SASS_STYLE_NESTED = 0
_SASS_STYLE_EXPANDED = 1
_SASS_STYLE_COMPACT = 2
SASS_STYLE_COMPRESSED = 3
SASS_COMMENTS_NONE = 0
SASS_COMMENTS_LINE_NUMBERS = 1

# Defaults from libass-python
precision = 5
source_map_filename = None
custom_functions = []
importers = None

use_dev_settings: bool = NORMALIZED_ENVS[env] == "development"
fs_encoding: str = sys.getfilesystemencoding() or sys.getdefaultencoding()
output_style: int = SASS_STYLE_NESTED if use_dev_settings else SASS_STYLE_COMPRESSED
source_comments: int = SASS_COMMENTS_LINE_NUMBERS if use_dev_settings else SASS_COMMENTS_NONE
include_paths: bytes = os.pathsep.join(str(include) for include in includes).encode(fs_encoding)

use_dev_settings = NORMALIZED_ENVS[env] == "development"
click.secho(f" {message}...", fg="cyan")
click.secho(f" Source: {source_root}")
click.secho(f" Target: {target_root}")
if not source_root.is_dir():
click.secho(f" Source: {source}")
click.secho(f" Target: {dest}")
if not source.is_dir():
if tolerate_missing:
click.secho(f" Skipped because source directory does not exist.", fg="yellow")
click.secho(f" Skipped because source directory does not exist.", fg="yellow")
return
else:
raise FileNotFoundError(f"missing Sass source dir: {source_root}")
click.echo(f" Include paths:")
raise FileNotFoundError(f"missing Sass source dir: {source}")
click.echo(f" Include paths:")
for include in includes:
click.echo(f" {include}")

click.echo(f" Files:")
for dirpath, _, filenames in os.walk(str(source_root)):
for filename in filenames:
if filename.startswith('_'):
continue
if not filename.endswith(('.scss', '.sass')):
continue
source = Path(dirpath) / filename
target = (target_root / source.relative_to(source_root)).with_suffix('.css')
click.echo(f" {source} -> {target}")
if not dry:
# Import _sass late so that this script can be dry-run without installing
# libsass, which takes a while as it must be compiled from its C source.
from _sass import compile_filename # pylint: disable=protected-access
success, output, _ = compile_filename(
str(source).encode(fs_encoding),
output_style,
source_comments,
include_paths,
precision,
source_map_filename,
custom_functions,
importers,
)
output_text = output.decode('utf-8')
if not success:
raise Exception(f"Failed to compile {source}: {output_text}")
target.parent.mkdir(parents=True, exist_ok=True)
with open(target, 'w', encoding="utf-8") as target_file:
target_file.write(output_text)

click.secho(f" Done.", fg="green")
click.echo(f" {include}")
if not dry:
# Import sass late so that this script can be dry-run without installing
# libsass, which takes a while as it must be compiled from its C source.
import sass

dest.mkdir(parents=True, exist_ok=True)
sass.compile(
dirname=(str(source), str(dest)),
include_paths=[str(include_path) for include_path in includes],
source_comments=use_dev_settings,
output_style=("nested" if use_dev_settings else "compressed"),
)
click.secho(f" Compiled.", fg="green")
# For Sass files without explicit RTL versions, generate
# an RTL version of the CSS using the rtlcss library.
for sass_path in glob.glob(str(source) + "/**/*.scss"):
Expand All @@ -269,16 +201,16 @@ def compile_sass_dir(
if Path(sass_path.replace(".scss", "-rtl.scss")).exists():
# Don't generate RTL CSS if there is an explicit Sass version for RTL
continue
click.echo(" Generating missing right-to-left CSS:")
click.echo(" Generating missing right-to-left CSS:")
source_css_file = sass_path.replace(str(source), str(dest)).replace(
".scss", ".css"
)
target_css_file = source_css_file.replace(".css", "-rtl.css")
click.echo(f" Source: {source_css_file}")
click.echo(f" Target: {target_css_file}")
click.echo(f" Source: {source_css_file}")
click.echo(f" Target: {target_css_file}")
if not dry:
subprocess.run(["rtlcss", source_css_file, target_css_file])
click.secho(" Generated.", fg="green")
click.secho(" Generated.", fg="green")

# Information
click.secho(f"USING ENV: {NORMALIZED_ENVS[env]}", fg="blue")
Expand Down
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