Add tests for BaseFormatter

flake8/formatting/base.py

@@ -55,7 +55,7 @@ class BaseFormatter(object):
     def handle(self, error):
         """Handle an error reported by Flake8.
 
-        This defaults to calling :meth:`format`, :meth:`format_source`, and
+        This defaults to calling :meth:`format`, :meth:`show_source`, and
         then :meth:`write`. To extend how errors are handled, override this
         method.
 
@@ -65,7 +65,7 @@ class BaseFormatter(object):
             flake8.style_guide.Error
         """
         line = self.format(error)
-        source = self.format_source(error)
+        source = self.show_source(error)
         self.write(line, source)
 
     def format(self, error):
@@ -85,11 +85,19 @@ class BaseFormatter(object):
         raise NotImplementedError('Subclass of BaseFormatter did not implement'
                                   ' format.')
 
-    def format_source(self, error):
-        """Format the physical line generating the error.
+    def show_benchmarks(self, benchmarks):
+        pass
+
+    def show_source(self, error):
+        """Show the physical line generating the error.
+
+        This also adds an indicator for the particular part of the line that
+        is reported as generating the problem.
 
         :param error:
             This will be an instance of :class:`~flake8.style_guide.Error`.
+        :type error:
+            flake8.style_guide.Error
         :returns:
             The formatted error string if the user wants to show the source.
             If the user does not want to show the source, this will return
@@ -104,6 +112,13 @@ class BaseFormatter(object):
         # one
         return error.physical_line + pointer
 
+    def _write(self, output):
+        """Handle logic of whether to use an output file or print()."""
+        if self.output_fd is not None:
+            self.output_fd.write(output + self.newline)
+        else:
+            print(output)
+
     def write(self, line, source):
         """Write the line either to the output file or stdout.
 
@@ -113,16 +128,13 @@ class BaseFormatter(object):
 
         :param str line:
             The formatted string to print or write.
+        :param str source:
+            The source code that has been formatted and associated with the
+            line of output.
         """
-        if self.output_fd is not None:
-            write = self.output_fd.write
-            output_func = lambda line: write(line + self.newline)
-        else:
-            output_func = print
-
-        output_func(line)
+        self._write(line)
         if source:
-            output_func(source)
+            self._write(source)
 
     def stop(self):
         """Clean up after reporting is finished."""

tests/unit/test_base_formatter.py

@@ -0,0 +1,103 @@
+"""Tests for the BaseFormatter object."""
+import optparse
+
+import mock
+import pytest
+
+from flake8.formatting import base
+from flake8 import style_guide
+
+
+def options(**kwargs):
+    """Create an optparse.Values instance."""
+    kwargs.setdefault('output_file', None)
+    return optparse.Values(kwargs)
+
+
+@pytest.mark.parametrize('filename', [None, 'out.txt'])
+def test_start(filename):
+    """Verify we open a new file in the start method."""
+    mock_open = mock.mock_open()
+    formatter = base.BaseFormatter(options(output_file=filename))
+    with mock.patch('flake8.formatting.base.open', mock_open):
+        formatter.start()
+
+    if filename is None:
+        assert mock_open.called is False
+    else:
+        mock_open.assert_called_once_with(filename, 'w')
+
+
+def test_stop():
+    """Verify we close open file objects."""
+    filemock = mock.Mock()
+    formatter = base.BaseFormatter(options())
+    formatter.output_fd = filemock
+    formatter.stop()
+
+    filemock.close.assert_called_once_with()
+    assert formatter.output_fd is None
+
+
+def test_format_needs_to_be_implemented():
+    """Ensure BaseFormatter#format raises a NotImplementedError."""
+    formatter = base.BaseFormatter(options())
+    with pytest.raises(NotImplementedError):
+        formatter.format('foo')
+
+
+def test_show_source_returns_nothing_when_not_showing_source():
+    """Ensure we return nothing when users want nothing."""
+    formatter = base.BaseFormatter(options(show_source=False))
+    assert formatter.show_source(
+        style_guide.Error('A000', 'file.py', 1, 1, 'error text', 'line')
+    ) is None
+
+
+@pytest.mark.parametrize('line, column', [
+    ('x=1\n', 2),
+    ('    x=(1\n       +2)\n', 5),
+    # TODO(sigmavirus24): Add more examples
+])
+def test_show_source_updates_physical_line_appropriately(line, column):
+    """Ensure the error column is appropriately indicated."""
+    formatter = base.BaseFormatter(options(show_source=True))
+    error = style_guide.Error('A000', 'file.py', 1, column, 'error', line)
+    output = formatter.show_source(error)
+    _, pointer = output.rsplit('\n', 1)
+    assert pointer.count(' ') == column
+
+
+def test_write_uses_an_output_file():
+    """Verify that we use the output file when it's present."""
+    line = 'Something to write'
+    source = 'source'
+    filemock = mock.Mock()
+
+    formatter = base.BaseFormatter(options())
+    formatter.output_fd = filemock
+    formatter.write(line, source)
+
+    assert filemock.write.called is True
+    assert filemock.write.call_count == 2
+    assert filemock.write.mock_calls == [
+        mock.call(line + formatter.newline),
+        mock.call(source + formatter.newline),
+    ]
+
+
+@mock.patch('flake8.formatting.base.print')
+def test_write_uses_print(print_function):
+    """Verify that we use the print function without an output file."""
+    line = 'Something to write'
+    source = 'source'
+
+    formatter = base.BaseFormatter(options())
+    formatter.write(line, source)
+
+    assert print_function.called is True
+    assert print_function.call_count == 2
+    assert print_function.mock_calls == [
+        mock.call(line),
+        mock.call(source),
+    ]