Add a function for creating cache dirs according to aboutcode-org#357

Signed-off-by: Haiko Schol <[email protected]>

src/commoncode/fileutils.py

@@ -98,6 +98,9 @@ def logger_debug(*args):
 # DIRECTORIES
 #
 
+TMP_DIR_ENV = 'SCANCODE_TMP'
+
+
 def create_dir(location):
     """
     Create directory and all sub-directories recursively at location ensuring these
@@ -141,7 +144,7 @@ def system_temp_dir():
     """
     Return the global temp directory for the current user.
     """
-    temp_dir = os.getenv('SCANCODE_TMP')
+    temp_dir = os.getenv(TMP_DIR_ENV)
     if not temp_dir:
         sc = text.python_safe_name('scancode_' + system.username)
         temp_dir = os.path.join(tempfile.gettempdir(), sc)
@@ -164,6 +167,40 @@ def get_temp_dir(base_dir, prefix=''):
     create_dir(base)
     return tempfile.mkdtemp(prefix=prefix, dir=base)
 
+
+def create_cache_dir(dir_name, dev_mode=False):
+    """
+    Create directory `dir_name` and return it as an absolute path.
+
+    If `dev_mode` is True, the cache directory will be created in the
+    root directory of the source tree (e.g. the git repo root). If it
+    is False, it will be created in the current users home directory.
+
+    This location can be overridden by setting the environment variable
+    SCANCODE_TMP_DIR.
+    """
+    cache_path = build_cache_path(dir_name, dev_mode=dev_mode)
+    create_dir(cache_path)
+    return cache_path
+
+
+def build_cache_path(dir_name, dev_mode=False):
+    from os.path import abspath, expanduser, dirname, join
+
+    cache_root = os.environ.get(TMP_DIR_ENV)
+
+    if cache_root and not os.path.exists(cache_root):
+        raise OSError('{} is set to non-existent directory: {}'.format(TMP_DIR_ENV, cache_root))
+
+    if not cache_root:
+        if dev_mode:
+            cache_root = dirname(dirname(dirname(abspath(__file__))))
+        else:
+            cache_root = expanduser('~')
+
+    return join(cache_root, '.cache', 'scancode', dir_name)
+
+
 #
 # FILE READING
 #

tests/commoncode/test_fileutils.py

@@ -25,9 +25,13 @@
 from __future__ import absolute_import, print_function
 
 import os
+import tempfile
+from os.path import abspath
+from os.path import dirname
 from os.path import join
 from os.path import sep
-from unittest.case import skipIf
+from unittest import TestCase
+from unittest import skipIf
 
 from commoncode import filetype
 from commoncode import fileutils
@@ -970,3 +974,41 @@ def test_parent_directory_on_path_and_location_10(self):
         result = fileutils.parent_directory((os.path.join(test_dir, test_file)))
         result = fileutils.as_posixpath(result)
         assert result.endswith(expected_name)
+
+
+class TestBuildCachePath(TestCase):
+
+    def setUp(self):
+        self._old_val = os.environ.get(fileutils.TMP_DIR_ENV)
+        if self._old_val:
+            del os.environ[fileutils.TMP_DIR_ENV]
+
+    def tearDown(self):
+        if self._old_val:
+            os.environ[fileutils.TMP_DIR_ENV] = self._old_val
+        elif fileutils.TMP_DIR_ENV in os.environ:
+            del os.environ[fileutils.TMP_DIR_ENV]
+
+    def test_in_dev_mode(self):
+        root_dir = dirname(dirname(dirname(abspath(__file__))))
+        expected_path = join(root_dir, '.cache', 'scancode', 'testing')
+        cache_path = fileutils.build_cache_path('testing', dev_mode=True)
+        assert expected_path == cache_path
+
+    def test_not_in_dev_mode(self):
+        expected_path = join(os.path.expanduser('~'), '.cache', 'scancode', 'testing')
+        cache_path = fileutils.build_cache_path('testing', dev_mode=False)
+        assert expected_path == cache_path
+
+    def test_env_var_overrides(self):
+        root_dir = tempfile.gettempdir()
+        os.environ[fileutils.TMP_DIR_ENV] = root_dir
+        expected_path = join(root_dir, '.cache', 'scancode', 'testing')
+        cache_path = fileutils.build_cache_path('testing', dev_mode=True)
+        assert cache_path == expected_path
+
+    def test_raises_on_invalid_env_var(self):
+        root_dir = '/nosuchdir'
+        os.environ[fileutils.TMP_DIR_ENV] = root_dir
+        expected_path = join(root_dir, '.cache', 'scancode', 'testing')
+        self.assertRaises(OSError, fileutils.build_cache_path, 'testing', dev_mode=True)