From 822b6ac461697700782513a3641502d98063d122 Mon Sep 17 00:00:00 2001
From: Ned Batchelder <ned@nedbatchelder.com>
Date: Sun, 2 Oct 2022 21:39:36 -0400
Subject: [PATCH] fix: */foo matches "foo/x.py", to help with combining
 relative file names. #991

---
 coverage/files.py   |  2 ++
 coverage/misc.py    |  2 +-
 tests/test_files.py | 30 ++++++++++++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/coverage/files.py b/coverage/files.py
index 4475f2f11..87a18bc2a 100644
--- a/coverage/files.py
+++ b/coverage/files.py
@@ -296,6 +296,8 @@ def fnmatches_to_regex(patterns, case_insensitive=False, partial=False):
 
     """
     regexes = (fnmatch.translate(pattern) for pattern in patterns)
+    # */ at the start should also match nothing.
+    regexes = (re.sub(r"^\(\?s:\.\*(\\\\|/)", r"(?s:^(.*\1)?", regex) for regex in regexes)
     # Be agnostic: / can mean backslash or slash.
     regexes = (re.sub(r"/", r"[\\\\/]", regex) for regex in regexes)
 
diff --git a/coverage/misc.py b/coverage/misc.py
index e9b1b8eba..98a5d139f 100644
--- a/coverage/misc.py
+++ b/coverage/misc.py
@@ -181,7 +181,7 @@ def bool_or_none(b):
 
 
 def join_regex(regexes):
-    """Combine a list of regexes into one that matches any of them."""
+    """Combine a series of regexes into one that matches any of them."""
     return "|".join(f"(?:{r})" for r in regexes)
 
 
diff --git a/tests/test_files.py b/tests/test_files.py
index 58084f7c7..3f3caae6b 100644
--- a/tests/test_files.py
+++ b/tests/test_files.py
@@ -144,6 +144,12 @@ def test_flat_rootname(original, flat):
             ["abc/foo/hi.py", "ABC/foo/bar/hi.py", r"ABC\foo/bar/hi.py"],
             ["abcd/foo.py", "xabc/hi.py"],
     ),
+    (
+        ["*/foo"], False, True,
+            ["abc/foo/hi.py", "foo/hi.py"],
+            ["abc/xfoo/hi.py"],
+    ),
+
 ])
 def test_fnmatches_to_regex(patterns, case_insensitive, partial, matches, nomatches):
     regex = fnmatches_to_regex(patterns, case_insensitive=case_insensitive, partial=partial)
@@ -386,6 +392,30 @@ def test_linux_on_windows(self, paths, rel_yn):
             "project\\module\\tests\\file.py",
         )
 
+    @pytest.mark.parametrize("paths", lin_win_paths)
+    def test_relative_windows_on_linux(self, paths):
+        # https://github.com/nedbat/coveragepy/issues/991
+        aliases = PathAliases(relative=True)
+        for path in paths:
+            aliases.add(path, "project/module")
+        self.assert_mapped(
+            aliases,
+            r"project\module\tests\file.py",
+            r"project/module/tests/file.py",
+        )
+
+    @pytest.mark.parametrize("paths", lin_win_paths)
+    def test_relative_linux_on_windows(self, paths):
+        # https://github.com/nedbat/coveragepy/issues/991
+        aliases = PathAliases(relative=True)
+        for path in paths:
+            aliases.add(path, r"project\module")
+        self.assert_mapped(
+            aliases,
+            r"project/module/tests/file.py",
+            r"project\module\tests\file.py",
+        )
+
     def test_multiple_wildcard(self, rel_yn):
         aliases = PathAliases(relative=rel_yn)
         aliases.add('/home/jenkins/*/a/*/b/*/django', './django')