Flake8 plugin for linting (#656)

pyls/config/flake8_conf.py

@@ -19,6 +19,13 @@
     ('ignore', 'plugins.pycodestyle.ignore', list),
     ('max-line-length', 'plugins.pycodestyle.maxLineLength', int),
     ('select', 'plugins.pycodestyle.select', list),
+    # flake8
+    ('exclude', 'plugins.flake8.exclude', list),
+    ('filename', 'plugins.flake8.filename', list),
+    ('hang-closing', 'plugins.flake8.hangClosing', bool),
+    ('ignore', 'plugins.flake8.ignore', list),
+    ('max-line-length', 'plugins.flake8.maxLineLength', int),
+    ('select', 'plugins.flake8.select', list),
 ]
 
 

pyls/plugins/flake8_lint.py

@@ -0,0 +1,99 @@
+# Copyright 2019 Palantir Technologies, Inc.
+"""Linter pluging for flake8"""
+import logging
+from flake8.api import legacy as flake8
+from pyls import hookimpl, lsp
+
+log = logging.getLogger(__name__)
+
+
+@hookimpl
+def pyls_settings():
+    # Default flake8 to disabled
+    return {'plugins': {'flake8': {'enabled': False}}}
+
+
+@hookimpl
+def pyls_lint(config, document):
+    settings = config.plugin_settings('flake8')
+    log.debug("Got flake8 settings: %s", settings)
+
+    opts = {
+        'exclude': settings.get('exclude'),
+        'filename': settings.get('filename'),
+        'hang_closing': settings.get('hangClosing'),
+        'ignore': settings.get('ignore'),
+        'max_line_length': settings.get('maxLineLength'),
+        'select': settings.get('select'),
+    }
+
+    # Build the flake8 checker and use it to generate a report from the document
+    kwargs = {k: v for k, v in opts.items() if v}
+    style_guide = flake8.get_style_guide(quiet=4, verbose=0, **kwargs)
+    report = style_guide.check_files([document.path])
+
+    return parse_report(document, report)
+
+
+def parse_report(document, report):
+    """
+    Build a diagnostics from a report, it should extract every result and format
+    it into a dict that looks like this:
+        {
+            'source': 'flake8',
+            'code': code, # 'E501'
+            'range': {
+                'start': {
+                    'line': start_line,
+                    'character': start_column,
+                },
+                'end': {
+                    'line': end_line,
+                    'character': end_column,
+                },
+            },
+            'message': msg,
+            'severity': lsp.DiagnosticSeverity.*,
+        }
+
+    Args:
+        document: The document to be linted.
+        report: A Report object returned by checking the document.
+    Returns:
+        A list of dictionaries.
+    """
+
+    file_checkers = report._application.file_checker_manager.checkers
+    # No file have been checked
+    if not file_checkers:
+        return []
+    # There should be only a filechecker since we are parsing using a path and not a pattern
+    if len(file_checkers) > 1:
+        log.error("Flake8 parsed more than a file for '%s'", document.path)
+
+    diagnostics = []
+    file_checker = file_checkers[0]
+    for error in file_checker.results:
+        code, line, character, msg, physical_line = error
+        diagnostics.append(
+            {
+                'source': 'flake8',
+                'code': code,
+                'range': {
+                    'start': {
+                        'line': line,
+                        'character': character
+                    },
+                    'end': {
+                        'line': line,
+                        # no way to determine the column
+                        'character': len(physical_line)
+                    }
+                },
+                'message': msg,
+                # no way to determine the severity using the legacy api
+                'severity': lsp.DiagnosticSeverity.Warning,
+            }
+        )
+
+    return diagnostics

setup.py

@@ -48,6 +48,7 @@
     extras_require={
         'all': [
             'autopep8',
+            'flake8',
             'mccabe',
             'pycodestyle',
             'pydocstyle>=2.0.0',
@@ -57,6 +58,7 @@
             'yapf',
         ],
         'autopep8': ['autopep8'],
+        'flake8': ['flake8'],
         'mccabe': ['mccabe'],
         'pycodestyle': ['pycodestyle'],
         'pydocstyle': ['pydocstyle>=2.0.0'],
@@ -76,6 +78,7 @@
         ],
         'pyls': [
             'autopep8 = pyls.plugins.autopep8_format',
+            'flake8 = pyls.plugins.flake8_lint',
             'jedi_completion = pyls.plugins.jedi_completion',
             'jedi_definition = pyls.plugins.definition',
             'jedi_hover = pyls.plugins.hover',

test/plugins/test_flake8_lint.py

@@ -0,0 +1,52 @@
+# Copyright 2019 Palantir Technologies, Inc.
+import tempfile
+import os
+from pyls import lsp, uris
+from pyls.plugins import flake8_lint
+from pyls.workspace import Document
+
+DOC_URI = uris.from_fs_path(__file__)
+DOC = """import pyls
+
+t = "TEST"
+
+def using_const():
+\ta = 8 + 9
+\treturn t
+"""
+
+
+def temp_document(doc_text):
+    temp_file = tempfile.NamedTemporaryFile(mode='w', delete=False)
+    name = temp_file.name
+    temp_file.write(doc_text)
+    temp_file.close()
+    doc = Document(uris.from_fs_path(name))
+
+    return name, doc
+
+
+def test_flake8_no_checked_file(config):
+    # A bad uri or a non-saved file may cause the flake8 linter to do nothing.
+    # In this situtation, the linter will return an empty list.
+
+    doc = Document('', DOC)
+    diags = flake8_lint.pyls_lint(config, doc)
+    assert diags == []
+
+
+def test_flake8_lint(config):
+    try:
+        name, doc = temp_document(DOC)
+        diags = flake8_lint.pyls_lint(config, doc)
+        msg = 'local variable \'a\' is assigned to but never used'
+        unused_var = [d for d in diags if d['message'] == msg][0]
+
+        assert unused_var['source'] == 'flake8'
+        assert unused_var['code'] == 'F841'
+        assert unused_var['range']['start'] == {'line': 6, 'character': 1}
+        assert unused_var['range']['end'] == {'line': 6, 'character': 11}
+        assert unused_var['severity'] == lsp.DiagnosticSeverity.Warning
+
+    finally:
+        os.remove(name)