Fix URLMatcher eating leading host chars (unescaped dots in prefix regex) (#2808)

URLMatcher._HTTP_URL_RE_STR was "^https?://(www.|m.)?(.+)$". The dots in
the optional (www.|m.)? subdomain-prefix group were unescaped, so each `.`
matched ANY character. For a host that simply starts with `m` or `www`
(not the literal `m.`/`www.` prefix), the group greedily ate the first
characters:

    extract_main_part('https://medium.com/alice')  -> 'dium.com/alice'
    extract_main_part('https://myspace.com/bob')   -> 'space.com/bob'

extract_main_part feeds make_profile_url_regexp / get_url_template, so the
generated site-detection regexp was corrupted too (medium.com -> dium.com),
and the loose prefix could match bogus hosts like `xmedium.com`. 170+ hosts
in resources/data.json start with `m`.

Fix: escape the dots with a raw string, r"^https?://(www\.|m\.)?(.+)$".
Genuine `m.`/`www.` prefixes are still stripped
(m.wikipedia.org -> wikipedia.org). The two existing tests that pinned the
unescaped pattern string are updated to the corrected form, and a
regression test covers hosts beginning with m/www.

maigret/utils.py

@@ -48,7 +48,7 @@ def enrich_link_str(link: str) -> str:
 
 
 class URLMatcher:
-    _HTTP_URL_RE_STR = "^https?://(www.|m.)?(.+)$"
+    _HTTP_URL_RE_STR = r"^https?://(www\.|m\.)?(.+)$"
     HTTP_URL_RE = re.compile(_HTTP_URL_RE_STR)
     UNSAFE_SYMBOLS = ".?"
 

tests/test_sites.py

@@ -160,7 +160,7 @@ def test_site_url_detector():
 
     assert (
         db.sites[0].url_regexp.pattern
-        == r'^https?://(www.|m.)?forum\.amperka\.ru/members/\?username=(.+?)$'
+        == r'^https?://(www\.|m\.)?forum\.amperka\.ru/members/\?username=(.+?)$'
     )
     assert (
         db.sites[0].detect_username('http://forum.amperka.ru/members/?username=test')

tests/test_utils.py

@@ -123,6 +123,17 @@ def test_url_extract_main_part():
         assert not url_regexp.match(url) is None
 
 
+def test_url_extract_main_part_keeps_host_starting_with_prefix_letters():
+    # The optional (www.|m.)? group must only strip the literal 'www.'/'m.'
+    # subdomain prefixes. With unescaped dots it instead ate the first
+    # character(s) of any host starting with 'm'/'www' (e.g. medium.com).
+    assert URLMatcher.extract_main_part('https://medium.com/alice') == 'medium.com/alice'
+    assert URLMatcher.extract_main_part('https://myspace.com/bob') == 'myspace.com/bob'
+    # genuine mobile/web subdomain prefixes are still stripped
+    assert URLMatcher.extract_main_part('https://m.wikipedia.org/wiki/Foo') == 'wikipedia.org/wiki/Foo'
+    assert URLMatcher.extract_main_part('https://www.flickr.com/photos/x') == 'flickr.com/photos/x'
+
+
 def test_url_make_profile_url_regexp():
     url_main_part = 'flickr.com/photos/{username}'
 
@@ -139,7 +150,7 @@ def test_url_make_profile_url_regexp():
         # ensure all combinations match pattern
         assert (
             URLMatcher.make_profile_url_regexp(url).pattern
-            == r'^https?://(www.|m.)?flickr\.com/photos/(.+?)$'
+            == r'^https?://(www\.|m\.)?flickr\.com/photos/(.+?)$'
         )