coredata: Use our own implementation of commonpath

os.path.commonpath was added in Python 3.5, so just write our own for
now. pathlib was added in Python 3.4, so this should be ok. We need to
use that instead of doing str.split() etc because Windows path handling
has a lot of exceptions and pathlib handles all that for us.

Also adds a unit test for this.

1 files changed, 25 insertions, 0 deletions

diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index 2ad43c8..f0b20e1 100644
--- a/mesonbuild/mesonlib.py
+++ b/mesonbuild/mesonlib.py
@@ -496,3 +496,28 @@ def Popen_safe(args, write=None, stderr=subprocess.PIPE, **kwargs):
                          stderr=stderr, **kwargs)
     o, e = p.communicate(write)
     return p, o, e
+
+def commonpath(paths):
+    '''
+    For use on Python 3.4 where os.path.commonpath is not available.
+    We currently use it everywhere so this receives enough testing.
+    '''
+    # XXX: Replace me with os.path.commonpath when we start requiring Python 3.5
+    import pathlib
+    if not paths:
+        raise ValueError('arg is an empty sequence')
+    common = pathlib.PurePath(paths[0])
+    for path in paths[1:]:
+        new = []
+        path = pathlib.PurePath(path)
+        for c, p in zip(common.parts, path.parts):
+            if c != p:
+                break
+            new.append(c)
+        # Don't convert '' into '.'
+        if not new:
+            common = ''
+            break
+        new = os.path.join(*new)
+        common = pathlib.PurePath(new)
+    return str(common)