Add source maps support for LESS

Author: Andrey Fedoseev

CHANGES.rst

@@ -6,6 +6,7 @@ Dev
 ===
 
 - Add source maps support for SASS/SCSS
+- Add source maps support for LESS
 
 
 1.0.1

README.rst

@@ -222,10 +222,13 @@ LESS
 ``executable``
   Path to LESS compiler executable. Default: ``"lessc"``.
 
+``sourcemap_enabled``
+  Boolean. Set to ``True`` to enable source maps. Default: ``False``
+
 Example::
 
     STATIC_PRECOMPILER_COMPILERS = (
-        ('static_precompiler.compilers.LESS', {"executable": "/usr/bin/lessc"),
+        ('static_precompiler.compilers.LESS', {"executable": "/usr/bin/lessc", "sourcemap_enabled": True),
     )
 
 

static_precompiler/compilers/less.py

@@ -1,3 +1,4 @@
+import json
 import os
 import posixpath
 import re
@@ -21,8 +22,9 @@ class LESS(base.BaseCompiler):
     IMPORT_RE = re.compile(r"@import\s+(.+?)\s*;", re.DOTALL)
     IMPORT_ITEM_RE = re.compile(r"([\"'])(.+?)\1")
 
-    def __init__(self, executable=settings.LESS_EXECUTABLE):
+    def __init__(self, executable=settings.LESS_EXECUTABLE, sourcemap_enabled=False):
         self.executable = executable
+        self.is_sourcemap_enabled = sourcemap_enabled
         super(LESS, self).__init__()
 
     def should_compile(self, source_path, from_management=False):
@@ -34,20 +36,46 @@ def should_compile(self, source_path, from_management=False):
     def compile_file(self, source_path):
         full_source_path = self.get_full_source_path(source_path)
         full_output_path = self.get_full_output_path(source_path)
-        args = [
-            self.executable,
-            self.get_full_source_path(source_path),
-            full_output_path,
-        ]
+
         # `cwd` is a directory containing `source_path`.
         # Ex: source_path = '1/2/3', full_source_path = '/abc/1/2/3' -> cwd = '/abc'
         cwd = os.path.normpath(os.path.join(full_source_path, *([".."] * len(source_path.split("/")))))
+
+        args = [
+            self.executable
+        ]
+        if self.is_sourcemap_enabled:
+            args.extend([
+                "--source-map"
+            ])
+
+        args.extend([
+            self.get_full_source_path(source_path),
+            full_output_path,
+        ])
         out, errors = utils.run_command(args, cwd=cwd)
         if errors:
             raise exceptions.StaticCompilationError(errors)
 
         utils.convert_urls(full_output_path, source_path)
 
+        if self.is_sourcemap_enabled:
+            sourcemap_full_path = full_output_path + ".map"
+
+            with open(sourcemap_full_path) as sourcemap_file:
+                sourcemap = json.loads(sourcemap_file.read())
+
+            # LESS, unlike SASS, can't add correct relative paths in source map when the compiled file
+            # is not in the same dir as the source file. We fix it here.
+            sourcemap["sources"] = [
+                "../" * len(source_path.split("/")) + posixpath.dirname(source_path) + "/" + source
+                for source in sourcemap["sources"]
+            ]
+            sourcemap["file"] = posixpath.basename(source_path)
+
+            with open(sourcemap_full_path, "w") as sourcemap_file:
+                sourcemap_file.write(json.dumps(sourcemap))
+
         return self.get_output_path(source_path)
 
     def compile_source(self, source):

static_precompiler/tests/test_less.py

@@ -34,6 +34,22 @@ def test_compile_file(monkeypatch, tmpdir):
 """
 
 
+def test_sourcemap(monkeypatch, tmpdir):
+
+    monkeypatch.setattr("static_precompiler.settings.ROOT", tmpdir.strpath)
+    monkeypatch.setattr("static_precompiler.utils.convert_urls", lambda *args: None)
+
+    compiler = compilers.LESS(sourcemap_enabled=False)
+    compiler.compile_file("styles/test.less") == "COMPILED/styles/test.css"
+    full_output_path = compiler.get_full_output_path("styles/test.less")
+    assert not os.path.exists(full_output_path + ".map")
+
+    compiler = compilers.LESS(sourcemap_enabled=True)
+    compiler.compile_file("styles/test.less") == "COMPILED/styles/test.css"
+    full_output_path = compiler.get_full_output_path("styles/test.less")
+    assert os.path.exists(full_output_path + ".map")
+
+
 def test_compile_source():
     compiler = compilers.LESS()