feat: support Grass Sass compiler as a fallback

ignis/app.py

@@ -233,16 +233,20 @@ def _setup(self, config_path: str) -> None:
         self._config_path = config_path
 
     def apply_css(
-        self, style_path: str, style_priority: StylePriority = "application"
+        self,
+        style_path: str,
+        style_priority: StylePriority = "application",
+        compiler: Literal["sass", "grass"] | None = None,
     ) -> None:
         """
         Apply a CSS/SCSS/SASS style from a path.
         If ``style_path`` has a ``.sass`` or ``.scss`` extension, it will be automatically compiled.
-        Requires ``dart-sass`` for SASS/SCSS compilation.
+        Requires either ``dart-sass`` or ``grass-sass`` for SASS/SCSS compilation.
 
         Args:
             style_path: Path to the .css/.scss/.sass file.
             style_priority: A priority of the CSS style. More info about style priorities: :obj:`Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION`.
+            compiler: The desired Sass compiler.
 
         .. warning::
             ``style_priority`` won't affect a style applied to widgets using the ``style`` property,
@@ -268,7 +272,7 @@ def apply_css(
             )
 
         if style_path.endswith(".scss") or style_path.endswith(".sass"):
-            css_style = Utils.sass_compile(path=style_path)
+            css_style = Utils.sass_compile(path=style_path, compiler=compiler)
         elif style_path.endswith(".css"):
             with open(style_path) as file:
                 css_style = file.read()

ignis/exceptions.py

@@ -227,7 +227,7 @@ def plugin_package(self) -> str:
 
 class SassCompilationError(Exception):
     """
-    Raised when Dart Sass compilation fails.
+    Raised when the Sass compilation fails.
     """
 
     def __init__(self, stderr: str, *args: object) -> None:
@@ -239,19 +239,20 @@ def stderr(self) -> str:
         """
         - required, read-only
 
-        The stderr output from Dart Sass.
+        The stderr output from the Sass compiler.
         """
         return self._stderr
 
 
-class DartSassNotFoundError(Exception):
+class SassNotFoundError(Exception):
     """
-    Raised when Dart Sass is not found.
+    Raised when a compatible Sass compiler is not found.
     """
 
     def __init__(self, *args: object) -> None:
         super().__init__(
-            "Dart Sass not found! To compile SCSS/SASS, install dart-sass", *args
+            "Sass compiler not found! To compile SCSS/SASS, install either dart-sass or grass-sass",
+            *args,
         )
 
 

ignis/utils/sass.py

@@ -1,14 +1,25 @@
 import os
+import shutil
 import subprocess
-from ignis.exceptions import SassCompilationError, DartSassNotFoundError
+from typing import Literal
+from ignis.exceptions import SassCompilationError, SassNotFoundError
 
 TEMP_DIR = "/tmp/ignis"
 COMPILED_CSS = f"{TEMP_DIR}/compiled.css"
 os.makedirs(TEMP_DIR, exist_ok=True)
 
+# resolve Sass compiler paths and pick a default one
+# "sass" (dart-sass) is the default,
+# "grass" is an API-compatible drop-in replacement
+sass_compilers = {}
+for cmd in ("sass", "grass"):
+    path = shutil.which(cmd)
+    if path:
+        sass_compilers[cmd] = path
 
-def compile_file(path: str) -> str:
-    result = subprocess.run(["sass", path, COMPILED_CSS], capture_output=True)
+
+def compile_file(path: str, compiler_path: str) -> str:
+    result = subprocess.run([compiler_path, path, COMPILED_CSS], capture_output=True)
 
     if result.returncode != 0:
         raise SassCompilationError(result.stderr.decode())
@@ -17,9 +28,9 @@ def compile_file(path: str) -> str:
         return file.read()
 
 
-def compile_string(string: str) -> str:
+def compile_string(string: str, compiler_path: str) -> str:
     process = subprocess.Popen(
-        ["sass", "--stdin"],
+        [compiler_path, "--stdin"],
         stdin=subprocess.PIPE,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
@@ -32,28 +43,42 @@ def compile_string(string: str) -> str:
         return stdout.decode()
 
 
-def sass_compile(path: str | None = None, string: str | None = None) -> str:
+def sass_compile(
+    path: str | None = None,
+    string: str | None = None,
+    compiler: Literal["sass", "grass"] | None = None,
+) -> str:
     """
     Compile a SASS/SCSS file or string.
-    Requires `Dart Sass <https://sass-lang.com/dart-sass/>`_.
+    Requires either `Dart Sass <https://sass-lang.com/dart-sass/>`_
+    or `Grass <https://github.com/connorskees/grass>`_.
 
     Args:
         path: The path to the SASS/SCSS file.
         string: A string with SASS/SCSS style.
+        compiler: The desired Sass compiler, either ``sass`` or ``grass``.
 
     Raises:
         TypeError: If neither of the arguments is provided.
-        DartSassNotFoundError: If Dart Sass not found.
+        SassNotFoundError: If no Sass compiler is available.
         SassCompilationError: If an error occurred while compiling SASS/SCSS.
     """
-    if not os.path.exists("/bin/sass"):
-        raise DartSassNotFoundError()
+    if not sass_compilers:
+        raise SassNotFoundError()
+
+    if compiler and compiler not in sass_compilers:
+        raise SassNotFoundError()
+
+    if compiler:
+        compiler_path = sass_compilers[compiler]
+    else:
+        compiler_path = next(iter(sass_compilers.values()))
 
     if string:
-        return compile_string(string)
+        return compile_string(string, compiler_path)
 
     elif path:
-        return compile_file(path)
+        return compile_file(path, compiler_path)
 
     else:
         raise TypeError("sass_compile() requires at least one positional argument")