Configure linters.

Introduce flake8 and mypy for better error checking.
Fix all errors and warnings emitted by those.
Also fix type error with `url_for`.

9 files changed, 87 insertions, 39 deletions

diff --git a/Makefile b/Makefile
index b615b65..4ba0066 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,8 @@
-.PHONY: tags
+.PHONY: tags check
 
 tags:
 	ctags `find mu4web -type f -name \*.py `
+
+check:
+	mypy -p mu4web
+	flake8 mu4web
diff --git a/mu4web/maildir.py b/mu4web/maildir.py
index c2abc16..dd5be1c 100644
--- a/mu4web/maildir.py
+++ b/mu4web/maildir.py
@@ -6,6 +6,8 @@ from .util import find
 
 from urllib.parse import urlencode
 
+from pathlib import Path
+
 from typing import (
     Union
 )
@@ -47,7 +49,7 @@ def _build_tree(items: list[list[str]]) -> MaildirGroup:
     return node
 
 
-def find_maildirs(basedir) -> MaildirGroup:
+def find_maildirs(basedir: str) -> MaildirGroup:
     """
     Find all maildirs located under basedir.
 
@@ -59,7 +61,7 @@ def find_maildirs(basedir) -> MaildirGroup:
     and a group of maildirs then it will have two separate entries.
     """
     basedir = basedir.rstrip('/')
-    files = find(basedir, type='d', name='cur')
+    files = find(Path(basedir), type='d', name='cur')
     # + 1 removes leading slash
     # - 4 removes '/cur'
     dirs = [entry[len(basedir) + 1:-4].decode('UTF-8').split(os.path.sep)
@@ -72,6 +74,7 @@ def serialize_maildir(maildir: MaildirGroup, path: list[str] = []) -> HTML:
     """Build a (recursive) list from a maildir node."""
     entries: list[HTML] = []
     for node in natsorted(maildir.children, key=lambda n: n.name):
+        entry: HTML
         if isinstance(node, MaildirEntry):
             parts = '/'.join(path + [node.name])
             url = 'search?' + urlencode({'q': f'maildir:"/{parts}"'})
diff --git a/mu4web/main.py b/mu4web/main.py
index c147ab7..5d2d975 100644
--- a/mu4web/main.py
+++ b/mu4web/main.py
@@ -149,7 +149,7 @@ def page_base(title: Optional[str] = None,
              ('meta', {'name': 'viewport',
                        'content': 'width=device-width, initial-scale=0.5'}),
              ('title', title, ' — Mu4Web'),
-             include_stylesheet(url_for('static', 'style.css')),
+             include_stylesheet(url_for('static', filename='style.css')),
              ),
             ('body',
              ('nav',
@@ -420,7 +420,7 @@ def attachement_response(attachement: EmailMessage):
     Gets content type and encoding from the attachements headers.
     """
     response = flask.Response()
-    response.charset = attachement.get_content_charset()
+    response.charset = attachement.get_content_charset() or 'application/binary'
     response.mimetype = attachement.get_content_type()
     # does get_content do stuff depending on content-type?
     # Check how to explicitly get the raw bytes.
@@ -500,7 +500,7 @@ class IMGParser(HTMLParser):
                         self.result += f' {key}="{data}"'
 
                         key = 'src'
-                        data = url_for('static', 'content-blocked.svg')
+                        data = url_for('static', filename='content-blocked.svg')
                         self.result += f' {key}="{data}"'
                 else:
                     key = html.escape(key)
@@ -571,7 +571,7 @@ def attachement_part_page():
         # above, which unblocks it.
         # TODO this "fails" for images wrapped in anchor tags, since
         # the anchor tag has priority.
-        url = url_for('static', 'enable_images.js')
+        url = url_for('static', filename='enable_images.js')
         result += f"\n<script src='{url}'></script>"
 
         return str(result)
diff --git a/mu4web/mu.py b/mu4web/mu.py
index d75d7a9..8efbd38 100644
--- a/mu4web/mu.py
+++ b/mu4web/mu.py
@@ -11,17 +11,20 @@ import xml.dom.minidom
 import xml.dom
 from xdg.BaseDirectory import xdg_cache_home
 import os.path
-import xapian
+from . import xapian
 from datetime import datetime
+from os import PathLike
+from pathlib import Path
 
 from typing import (
     Optional,
+    TypedDict,
 )
 
 parser = BytesParser(policy=email.policy.default)
 
 
-def find_file(id: str) -> Optional[str]:
+def find_file(id: str) -> Optional[PathLike]:
     cmd = subprocess.run(['mu', 'find', '-u', f'i:{id}',
                           '--fields', 'l'],
                          stdout=PIPE)
@@ -31,7 +34,7 @@ def find_file(id: str) -> Optional[str]:
         return None
     if cmd.returncode != 0:
         raise MuError(cmd.returncode)
-    return filename
+    return Path(filename)
 
 
 def get_mail(id: str) -> email.message.Message:
@@ -41,7 +44,11 @@ def get_mail(id: str) -> email.message.Message:
     [Raises]
         MuError
     """
-    with open(find_file(id), "rb") as f:
+    filename = find_file(id)
+    if not filename:
+        # TODO better error here
+        raise MuError(1)
+    with open(filename, "rb") as f:
         mail = parser.parse(f)
     return mail
 
@@ -57,10 +64,10 @@ class MuError(Exception):
         self.returncode: int = returncode
         self.msg: str = MuError.codes.get(returncode, 'Unknown Error')
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f'MuError({self.returncode}, "{self.msg}")'
 
-    def __str__(self):
+    def __str__(self) -> str:
         return repr(self)
 
 
@@ -118,7 +125,7 @@ def search(query: str,
     return message_list
 
 
-def base_directory():
+def base_directory() -> PathLike:
     """
     Returns where where mu stores its files.
 
@@ -127,28 +134,47 @@ def base_directory():
 
     TODO make this configurable.
     """
-    return os.getenv('MUHOME') or os.path.join(xdg_cache_home, 'mu')
+    return Path(os.getenv('MUHOME') or os.path.join(xdg_cache_home, 'mu'))
 
 
-def info():
+class MuInfo(TypedDict):
+    database_path: str
+    changed: datetime
+    created: datetime
+    indexed: datetime
+    maildir: str
+    schema_version: str
+    messages_in_store: int
+
+
+def info() -> MuInfo:
 
     db = os.path.join(base_directory(), "xapian")
 
-    info = {
-        'database-path': db,
-    }
+    def f(key: str) -> datetime:
+        return datetime.fromtimestamp(int(xapian.metadata_get(db, key), 16))
 
-    for key in ['changed', 'created', 'indexed']:
-        info[key] = datetime.fromtimestamp(int(xapian.metadata_get(db, key), 16))
+    changed = f('changed')
+    created = f('created')
+    indexed = f('indexed')
 
-    for key in ['maildir', 'schema-version']:
-        info[key] = xapian.metadata_get(db, key)
+    maildir = xapian.metadata_get(db, 'maildir')
+    schema_version = xapian.metadata_get(db, 'schema-version')
 
-    cmd = subprocess.Popen(['xapian-delve', '-V3', '-1', db], stdout=subprocess.PIPE)
+    cmd = subprocess.Popen(['xapian-delve', '-V3', '-1', db],
+                           stdout=subprocess.PIPE)
     # Start at minus one to ignore header
     count = -1
-    for line in cmd.stdout:
-        count += 1
-    info['messages-in-store'] = count
-
-    return info
+    if cmd.stdout:
+        for line in cmd.stdout:
+            count += 1
+
+    return {
+        'database_path': db,
+        'messages_in_store': count,
+        'changed': changed,
+        'created': created,
+        'indexed': indexed,
+        'maildir': maildir,
+        'schema_version': schema_version,
+    }
diff --git a/mu4web/password.py b/mu4web/password.py
index af33cb6..26bc712 100755
--- a/mu4web/password.py
+++ b/mu4web/password.py
@@ -89,7 +89,7 @@ class Passwords:
         return data['hash'] == digest
 
 
-def main():
+def main() -> None:
     import argparse
     parser = argparse.ArgumentParser()
 
diff --git a/mu4web/user/__init__.py b/mu4web/user/__init__.py
index 1ecc49f..bb14f67 100644
--- a/mu4web/user/__init__.py
+++ b/mu4web/user/__init__.py
@@ -3,16 +3,16 @@ class User:
         self._username = username
         self._authenticated = False
 
-    def is_authenticated(self):
+    def is_authenticated(self) -> bool:
         return self._authenticated
 
-    def is_active(self):
+    def is_active(self) -> bool:
         return True
 
-    def is_anonymous(self):
+    def is_anonymous(self) -> bool:
         return False
 
-    def get_id(self):
+    def get_id(self) -> str:
         return self._username
 
     def validate(self, _: str) -> bool:
diff --git a/mu4web/util.py b/mu4web/util.py
index c8ccc7d..41601c5 100644
--- a/mu4web/util.py
+++ b/mu4web/util.py
@@ -1,8 +1,13 @@
 import subprocess
+from os import PathLike
+from typing import (
+    Union,
+)
 
 
-def find(basedir, **flags) -> list[bytes]:
-    cmdline = ['find', basedir]
+def find(basedir: PathLike,
+         **flags: str | bytes) -> list[bytes]:
+    cmdline: list[Union[str, bytes, PathLike]] = ['find', basedir]
     for key, value in flags.items():
         cmdline += [f'-{key}', value]
     cmdline.append('-print0')
diff --git a/mu4web/xapian.py b/mu4web/xapian.py
index 8aebf72..d23b2d1 100644
--- a/mu4web/xapian.py
+++ b/mu4web/xapian.py
@@ -1,7 +1,8 @@
 import subprocess
 from typing import Optional
 
-def metadata_list(db, prefix: Optional[str] = None) -> list[str]:
+
+def metadata_list(db: str, prefix: Optional[str] = None) -> list[str]:
     cmdline = ['xapian-metadata', 'list', db]
     if prefix:
         cmdline.append(prefix)
@@ -9,8 +10,7 @@ def metadata_list(db, prefix: Optional[str] = None) -> list[str]:
     return cmd.stdout.split('\n')
 
 
-def metadata_get(db, key: str) -> str:
+def metadata_get(db: str, key: str) -> str:
     cmd = subprocess.run(['xapian-metadata', 'get', db, key],
                          capture_output=True, text=True)
     return cmd.stdout.strip()
-
diff --git a/setup.cfg b/setup.cfg
index 688b4fa..b6ab484 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -29,6 +29,16 @@ include_package_data = True
 
 [options.packages.find]
 
+[mypy]
+ignore_missing_imports = True
+disallow_untyped_defs = True
+
+[mypy-mu4web.main]
+# NOTE Flask endpoints aren't typed.
+# Prefer to move everything except flask endpoints
+# to proper modules
+disallow_untyped_defs = False
+
 [flake8]
 ignore = E731
 max-line-length = 100