Add a helper for executing test code in the given directory

Use a context manager instead of writing try/finally in several places.

No real changes, this just (slightly) simplifies the existing tests and
will make adding new ones less painful.

tests/conftest.py

@@ -26,8 +26,9 @@
 def pytest_configure(config):
     import sys, os.path
 
-    bkl_path = os.path.normpath(os.path.join(os.path.dirname(__file__), '..', 'src'))
-    sys.path = [bkl_path] + sys.path
+    tests_path = os.path.dirname(__file__)
+    bkl_path = os.path.normpath(os.path.join(tests_path, '..', 'src'))
+    sys.path = [bkl_path, tests_path] + sys.path
 
     import logging
     log_level = logging.DEBUG if config.getvalue("debug") else logging.WARNING

tests/indir.py

@@ -0,0 +1,35 @@
+#  This file is part of Bakefile (http://bakefile.org)
+#
+#  Copyright (C) 2018 Vadim Zeitlin
+#
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to
+#  deal in the Software without restriction, including without limitation the
+#  rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+#  sell copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#
+#  The above copyright notice and this permission notice shall be included in
+#  all copies or substantial portions of the Software.
+#
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+#  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+#  IN THE SOFTWARE.
+#
+
+import os
+from contextlib import contextmanager
+
+@contextmanager
+def in_directory(path):
+    """
+    Context manager for temporarily changing the current directory.
+    """
+    cwd_orig = os.getcwd()
+    os.chdir(path)
+    yield
+    os.chdir(cwd_orig)

tests/test_builder.py

@@ -28,6 +28,7 @@
 
 import bkl.parser, bkl.interpreter, bkl.error
 import bkl.dumper
+from indir import in_directory
 
 @pytest.fixture(scope='session')
 def testdirs():
@@ -59,12 +60,8 @@ def test_builder(testdir, model_file):
     input = os.path.splitext(model_file)[0] + '.bkl'
 
     f = input[len(testdir)+1:]
-    cwd = os.getcwd()
-    os.chdir(testdir)
-    try:
+    with in_directory(testdir):
         _do_test_builder_on_file(f, model_file)
-    finally:
-        os.chdir(cwd)
 
 def _do_test_builder_on_file(input, model_file):
     print 'interpreting %s' % input

tests/test_full.py

@@ -30,6 +30,8 @@
 import bkl.parser, bkl.interpreter, bkl.error
 import bkl.dumper
 
+from indir import in_directory
+
 @pytest.fixture(scope='session')
 def testdir():
     import projects
@@ -64,12 +66,8 @@ def test_full(testdir, project_file):
     model_file = os.path.splitext(project_file)[0] + '.model'
 
     f = project_file[len(testdir)+1:]
-    cwd = os.getcwd()
-    os.chdir(testdir)
-    try:
+    with in_directory(testdir):
         _do_test_on_file(f, model_file)
-    finally:
-        os.chdir(cwd)
 
 def _do_test_on_file(input, model_file):
     print 'interpreting %s' % input
@@ -116,9 +114,8 @@ def test_unicode_filename():
     import tempfile
     cwd = os.getcwd()
     tmpdir = tempfile.mkdtemp(prefix=u"Üñîçöḍè".encode('utf-8'))
-    os.chdir(tmpdir)
     try:
-        i.process(t)
+        with in_directory(tmpdir):
+            i.process(t)
     finally:
-        os.chdir(cwd)
         shutil.rmtree(tmpdir)

tests/test_parser.py

@@ -27,6 +27,7 @@
 from glob import glob
 
 import bkl.parser, bkl.error
+from indir import in_directory
 
 @pytest.fixture(scope='session')
 def testdir():
@@ -52,12 +53,8 @@ def test_parser(testdir, ast_file):
     input = os.path.splitext(ast_file)[0] + '.bkl'
 
     f = input[len(testdir)+1:]
-    cwd = os.getcwd()
-    os.chdir(testdir)
-    try:
+    with in_directory(testdir):
         _do_test_parser_on_file(f, ast_file)
-    finally:
-        os.chdir(cwd)
 
 
 def _do_test_parser_on_file(input, ast_file):