Make the composers designate their output extension.

This will be used for file resolving later.

handroll/composers/__init__.py

@@ -23,6 +23,11 @@ def compose(self, catalog, source_file, out_dir):
         """
         raise NotImplementedError
 
+    @property
+    def output_extension(self):
+        """Get the extension of the output file generated by this composer."""
+        raise NotImplementedError
+
 
 class Composers(object):
     """A collection of available composers"""
@@ -96,3 +101,10 @@ def compose(self, catalog, source_file, out_dir):
         logger.info(_('Copying {filename} to {out_dir} ...').format(
             filename=filename, out_dir=out_dir))
         shutil.copy(source_file, out_dir)
+
+    @property
+    def output_extension(self):
+        raise AttributeError(
+            'The output extension of the CopyComposer is dependent '
+            'on the source file extension. This property should not '
+            'be invoked for this composer.')

handroll/composers/atom.py

@@ -30,10 +30,11 @@ class AtomComposer(Composer):
 
     .. literalinclude:: ../sample/atom_sample.atom
     """
+    output_extension = '.xml'
 
     def compose(self, catalog, source_file, out_dir):
         root, ext = os.path.splitext(os.path.basename(source_file))
-        filename = root + '.xml'
+        filename = root + self.output_extension
         output_file = os.path.join(out_dir, filename)
         if self._needs_update(source_file, output_file):
             logger.info(_('Generating Atom XML for {source_file} ...').format(

handroll/composers/generic.py

@@ -21,6 +21,7 @@ class GenericHTMLComposer(Composer):
     The title will be extracted from the first line and the remaining source
     lines will be passed to a template method for further processing.
     """
+    output_extension = '.html'
 
     # A pattern to get source content from a file with YAML front matter.
     yaml_scanner = re.compile(r""".*?    # YAML header
@@ -40,7 +41,7 @@ def compose(self, catalog, source_file, out_dir):
 
         # Determine the output filename.
         root, ext = os.path.splitext(os.path.basename(source_file))
-        filename = root + '.html'
+        filename = root + self.output_extension
         output_file = os.path.join(out_dir, filename)
 
         if self._needs_update(template, source_file, output_file):

handroll/composers/sass.py

@@ -21,6 +21,7 @@ class SassComposer(Composer):
     installed separately before it can be used. Check out the `installation
     options <http://sass-lang.com/install>`_.
     """
+    output_extension = '.css'
 
     def __init__(self, path=None):
         self.sass = spawn.find_executable('sass', path)
@@ -29,7 +30,7 @@ def __init__(self, path=None):
 
     def compose(self, catalog, source_file, out_dir):
         root, ext = os.path.splitext(os.path.basename(source_file))
-        filename = root + '.css'
+        filename = root + self.output_extension
         output_file = os.path.join(out_dir, filename)
 
         logger.info(_('Generating CSS for {source_file} ...').format(

handroll/tests/test_composers.py

@@ -27,6 +27,11 @@ def test_compose_not_implemented(self):
         self.assertRaises(
             NotImplementedError, composer.compose, None, None, None)
 
+    def test_output_extension_not_implemented(self):
+        composer = Composer()
+        self.assertRaises(
+            NotImplementedError, lambda: composer.output_extension)
+
 
 class TestComposers(unittest.TestCase):
 
@@ -81,6 +86,10 @@ def test_skips_up_to_date(self, json):
         composer.compose(None, self.source_file, self.outdir)
         self.assertFalse(json.loads.called)
 
+    def test_output_extension(self):
+        composer = AtomComposer()
+        self.assertEqual('.xml', composer.output_extension)
+
 
 class TestCopyComposer(unittest.TestCase):
 
@@ -109,6 +118,15 @@ def test_copies_when_content_differs(self, shutil):
         composer.compose(None, source_file, outdir)
         self.assertTrue(shutil.copy.called)
 
+    def test_output_extension(self):
+        """The copy composer takes the extension of the source file.
+
+        This composer is the fallback composer and resolution should
+        never rely on this composer's output extension.
+        """
+        composer = CopyComposer()
+        self.assertRaises(AttributeError, lambda: composer.output_extension)
+
 
 class TestGenericHTMLComposer(unittest.TestCase):
 
@@ -189,6 +207,10 @@ def test_needs_update(self):
         self.assertFalse(
             composer._needs_update(template, source_file, output_file))
 
+    def test_output_extension(self):
+        composer = GenericHTMLComposer()
+        self.assertEqual('.html', composer.output_extension)
+
 
 class TestMarkdownComposer(unittest.TestCase):
 
@@ -274,6 +296,10 @@ def test_failed_sass_aborts(self, subprocess):
         self.assertRaises(
             AbortError, composer.compose, None, source_file, output_dir)
 
+    def test_output_extension(self):
+        composer = SassComposer()
+        self.assertEqual('.css', composer.output_extension)
+
 
 class TestTextileComposer(unittest.TestCase):