Make flake8 respect configuration

* ensure flake8 is run from the correct directory
* make flake8 aware of the filename being linted

Author: delfick

Diff for: pylsp/plugins/flake8_lint.py

@@ -92,6 +92,9 @@ def run_flake8(flake8_executable, args, document):
     args = [(i if not i.startswith('--ignore=') else FIX_IGNORES_RE.sub('', i))
             for i in args if i is not None]
 
+    if document.path and document.path.startswith(document._workspace.root_path):
+        args.extend(["--stdin-display-name", os.path.relpath(document.path, document._workspace.root_path)])
+
     # if executable looks like a path resolve it
     if not os.path.isfile(flake8_executable) and os.sep in flake8_executable:
         flake8_executable = os.path.abspath(
@@ -102,12 +105,14 @@ def run_flake8(flake8_executable, args, document):
     try:
         cmd = [flake8_executable]
         cmd.extend(args)
-        p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+        p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE, cwd=document._workspace.root_path)
     except IOError:
         log.debug("Can't execute %s. Trying with '%s -m flake8'", flake8_executable, sys.executable)
         cmd = [sys.executable, '-m', 'flake8']
         cmd.extend(args)
-        p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)  # pylint: disable=consider-using-with
+        p = Popen(  # pylint: disable=consider-using-with
+            cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE, cwd=document._workspace.root_path
+        )
     (stdout, stderr) = p.communicate(document.source.encode())
     if stderr:
         log.error("Error while running flake8 '%s'", stderr.decode())

Diff for: test/plugins/test_flake8_lint.py

@@ -3,6 +3,7 @@
 
 import tempfile
 import os
+from textwrap import dedent
 from unittest.mock import patch
 from pylsp import lsp, uris
 from pylsp.plugins import flake8_lint
@@ -59,6 +60,63 @@ def test_flake8_lint(workspace):
         os.remove(name)
 
 
+def test_flake8_respecting_configuration(workspace):
+    docs = [
+        ("src/__init__.py", ""),
+        ("src/a.py", DOC),
+        ("src/b.py", "import os"),
+        ("setup.cfg", dedent("""
+        [flake8]
+        ignore = E302,W191
+        per-file-ignores =
+            src/a.py:F401
+            src/b.py:W292
+        """))
+    ]
+
+    made = {}
+    for rel, contents in docs:
+        location = os.path.join(workspace.root_path, rel)
+        made[rel] = {"uri": uris.from_fs_path(location)}
+
+        os.makedirs(os.path.dirname(location), exist_ok=True)
+        with open(location, "w", encoding="utf-8") as fle:
+            fle.write(contents)
+
+        workspace.put_document(made[rel]["uri"], contents)
+        made[rel]["document"] = workspace._docs[made[rel]["uri"]]
+
+    diags = flake8_lint.pylsp_lint(workspace, made["src/a.py"]["document"])
+    assert diags == [
+        {
+            "source": "flake8",
+            "code": "F841",
+            "range": {
+                "start": {"line": 5, "character": 1},
+                "end": {"line": 5, "character": 11},
+            },
+            "message": "F841 local variable 'a' is assigned to but never used",
+            "severity": 1,
+            "tags": [1],
+        },
+    ]
+
+    diags = flake8_lint.pylsp_lint(workspace, made["src/b.py"]["document"])
+    assert diags == [
+        {
+            "source": "flake8",
+            "code": "F401",
+            "range": {
+                "start": {"line": 0, "character": 0},
+                "end": {"line": 0, "character": 9},
+            },
+            "message": "F401 'os' imported but unused",
+            "severity": 1,
+            "tags": [1],
+        }
+    ]
+
+
 def test_flake8_config_param(workspace):
     with patch('pylsp.plugins.flake8_lint.Popen') as popen_mock:
         mock_instance = popen_mock.return_value
@@ -126,7 +184,9 @@ def test_flake8_multiline(workspace):
         flake8_lint.pylsp_lint(workspace, doc)
 
     call_args = popen_mock.call_args[0][0]
-    assert call_args == ["flake8", "-", "--exclude=blah/,file_2.py"]
+
+    init_file = os.path.join("blah", "__init__.py")
+    assert call_args == ["flake8", "-", "--exclude=blah/,file_2.py", "--stdin-display-name", init_file]
 
     os.unlink(os.path.join(workspace.root_path, "setup.cfg"))