relative,proximate: can use python

Author: scivision

+stdlib/relative_to.m

@@ -8,6 +8,7 @@
 % * rel {mustBeTextScalar}
 %
 % Note: Java Path.relativize has an algorithm so different that we choose not to use it.
+% javaPathObject(base).relativize(javaPathObject(other))
 % https://docs.oracle.com/javase/8/docs/api/java/nio/file/Path.html#relativize-java.nio.file.Path-
 
 function rel = relative_to(base, other)
@@ -38,6 +39,20 @@
     % https://learn.microsoft.com/en-us/dotnet/api/system.io.path.getrelativepath
     rel = string(System.IO.Path.GetRelativePath(base, other));
   end
+elseif stdlib.has_python()
+  try
+    bp = py.pathlib.Path(other);
+    if stdlib.python_version() >= "3.12"
+      r = bp.relative_to(base, pyargs(walk_up=true));
+    else
+      r = bp.relative_to(base);
+    end
+    rel = string(py.str(r));
+  catch e
+    if e.identifier == "MATLAB:Python:PyException" && startsWith(e.message, 'Python Error: ValueError')
+      rel = "";
+    end
+  end
 else
   error('no supported relative path method found, please install .NET or "buildtool mex"')
 end

test/TestRelative.m

@@ -32,27 +32,39 @@ function test_proximate_to(tc, pp)
 {"Hello", "Hello/", "."}, ...
 {"a/./b", "a/b", "."}, ...
 {"a/b", "a/./b", "."}, ...
-{"./a/b", "./a/c", fullfile("..", "c")}, ...
 {"/", "/", "."}, ...
+{"a/b", "a/b", "."} ...
+};
+% NOTE: ".." in relative_to(base) is ambiguous including for python.pathlib, C++ <filesystem>, etc.
+
+if stdlib.has_dotnet() || stdlib.python_version() >= "3.12"
+p = [p, {
+{"/a/b", "/a/c", fullfile("..", "c")}, ...
 {"a/b/c/d", "a/b", fullfile("..", "..")}, ...
 {"a/b", "a/c", fullfile("..", "c")}, ...
 {"a/b", "c", fullfile("..", "..", "c")}, ...
 {"c", "a/b", fullfile("..", "a", "b")}, ...
-{"a/b", "a/b", "."}, ...
-{"a/b", "a", ".."}
-};
-% NOTE: ".." in relative_to(base) is ambiguous including for python.pathlib, C++ <filesystem>, etc.
+{"a/b", "a", ".."}, ...
+  }];
+end
 
 if ispc
-p = [p, ...
-{{"C:/a/b", "C:/", fullfile("..", "..")}, ...
-{"C:/", "C:/a/b", fullfile("a", "b")}, ...
-{"c:/a/b", "c:/a/b", "."}, ...
+
+if stdlib.has_dotnet() || stdlib.python_version() >= "3.12"
+p = [p, { ...
+{"C:/a/b", "C:/", fullfile("..", "..")}, ...
 {"c:/a/b", "c:/a", ".."}, ...
 {"c:\a/b\c/d", "c:/a\b", fullfile("..", "..")}, ...
+  }];
+end
+
+p = [p, {
+{"C:/", "C:/a/b", fullfile("a", "b")}, ...
+{"c:/a/b", "c:/a/b", "."}, ...
 {"C:/path", "D:/path", ""}, ...
 {"D:/a/b", "c", ""}}];
 % note: on Windows the drive letter should be uppercase!
+
 else
   p = [p, ...
 {{"", "a", "a"}, ...