fix #337: if relative_to is given as folder instead of file consider it directly

3 files changed, 24 insertions, 5 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 12bf230..c022499 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -4,6 +4,8 @@ v5.0.0
 
 Breaking changes:
 * fix #339: strict errors on missing scms when  parsing a scm dir to avoid false version lookups
+* fix #337: if relative_to is a directory instead of a file,
+            consider it as direct target instead  of the containing folder and print a warning
 
 Bugfixes:
 
diff --git a/src/setuptools_scm/config.py b/src/setuptools_scm/config.py
index f0d9243..8b8fb8e 100644
--- a/src/setuptools_scm/config.py
+++ b/src/setuptools_scm/config.py
@@ -27,13 +27,24 @@ def _check_tag_regex(value):
 
 
 def _check_absolute_root(root, relative_to):
+    trace("l", repr(locals()))
     if relative_to:
         if os.path.isabs(root) and not root.startswith(relative_to):
             warnings.warn(
                 "absolute root path '%s' overrides relative_to '%s'"
                 % (root, relative_to)
             )
-        root = os.path.join(os.path.dirname(relative_to), root)
+        if os.path.isdir(relative_to):
+            warnings.warn(
+                "relative_to is expected to be a file,"
+                " its the directory %r\n"
+                "assuming the parent directory was passed" % (relative_to,)
+            )
+            trace("dir", relative_to)
+            root = os.path.join(relative_to, root)
+        else:
+            trace("file", relative_to)
+            root = os.path.join(os.path.dirname(relative_to), root)
     return os.path.abspath(root)
 
 
@@ -94,6 +105,7 @@ class Configuration(object):
         self._absolute_root = _check_absolute_root(self._root, value)
         self._relative_to = value
         trace("root", repr(self._absolute_root))
+        trace("relative_to", repr(value))
 
     @property
     def root(self):
@@ -104,6 +116,7 @@ class Configuration(object):
         self._absolute_root = _check_absolute_root(value, self._relative_to)
         self._root = value
         trace("root", repr(self._absolute_root))
+        trace("relative_to", repr(self._relative_to))
 
     @property
     def tag_regex(self):
diff --git a/testing/test_basic_api.py b/testing/test_basic_api.py
index 5111542..5e35a9e 100644
--- a/testing/test_basic_api.py
+++ b/testing/test_basic_api.py
@@ -90,10 +90,14 @@ def test_pretended(version, monkeypatch):
     assert setuptools_scm.get_version() == version
 
 
-def test_root_relative_to(monkeypatch, tmpdir):
-    assert_root(monkeypatch, tmpdir.join("alt").strpath)
-    __file__ = tmpdir.join("module/file.py").strpath
-    setuptools_scm.get_version(root="../alt", relative_to=__file__)
+def test_root_relative_to(monkeypatch, tmp_path):
+    assert_root(monkeypatch, str(tmp_path / "alt"))
+    module = tmp_path / "module/file.py"
+    module.parent.mkdir()
+    module.touch()
+    setuptools_scm.get_version(root="../alt", relative_to=str(module))
+    with pytest.warns(UserWarning, match="relative_to is expected to be a file.*"):
+        setuptools_scm.get_version(root="../alt", relative_to=str(module.parent))
 
 
 def test_dump_version(tmpdir):