Use the full filename for identifying __init__.py. (#1461)

Previously, `pylint.utils.expand_modules` identified `__init__.py` files by a
substring match, which led to false positives for files with names like
`flycheck__init__.py`. (While users are unlikely to choose such a filename,
tools like flycheck use these sorts of filenames for temporary files.)

The result was that `pylint` would end up linting the entire package, not just
the file in question.

The fix is straightforward -- we use `os.path.basename` instead of a substring
check, and add a test.

3 files changed, 16 insertions, 1 deletions

diff --git a/pylint/test/input/not__init__.py b/pylint/test/input/not__init__.py
new file mode 100644
index 000000000..60e92b76c
--- /dev/null
+++ b/pylint/test/input/not__init__.py
@@ -0,0 +1 @@
+"""test"""
diff --git a/pylint/test/unittest_lint.py b/pylint/test/unittest_lint.py
index a6e401cbb..0c48b49be 100644
--- a/pylint/test/unittest_lint.py
+++ b/pylint/test/unittest_lint.py
@@ -745,3 +745,17 @@ def test_custom_should_analyze_file():
     messages = reporter.messages
     assert len(messages) == 1
     assert 'invalid syntax' in messages[0]
+
+
+def test_filename_with__init__(init_linter):
+    # This tracks a regression where a file whose name ends in __init__.py,
+    # such as flycheck__init__.py, would accidentally lead to linting the
+    # entire containing directory.
+    reporter = testutils.TestReporter()
+    linter = init_linter
+    linter.open()
+    linter.set_reporter(reporter)
+    filepath = join(INPUTDIR, 'not__init__.py')
+    linter.check([filepath])
+    messages = reporter.messages
+    assert len(messages) == 0
diff --git a/pylint/utils.py b/pylint/utils.py
index 1ace59392..4dbfd9e1a 100644
--- a/pylint/utils.py
+++ b/pylint/utils.py
@@ -881,7 +881,7 @@ def expand_modules(files_or_modules, black_list, black_list_re):
                            'basepath': filepath, 'basename': modname})
 
         has_init = (not (modname.endswith('.__init__') or modname == '__init__')
-                    and '__init__.py' in filepath)
+                    and basename(filepath) == '__init__.py')
 
         if has_init or is_namespace or is_directory:
             for subfilepath in modutils.get_module_files(dirname(filepath), black_list,