get_permissions: simplify, robust

Author: scivision

+stdlib/get_permissions.m

@@ -9,14 +9,15 @@
 
 p = '';
 
-if ~stdlib.isoctave() && ~stdlib.too_old('R2025a')
+try
   perms = filePermissions(f);
   p = perm2char(perms);
-% elseif ~ispc && ~isMATLABReleaseOlderThan('R2024b')
-% % undocumented internals in Matlab R2024b, does not work on Windows
-%   perms = matlab.io.UnixPermissions(f);
-%   p = perm2str(perms);
-else
+catch e
+  if ~strcmp(e.identifier, "MATLAB:UndefinedFunction") && ...
+      ~strcmp(e.identifier, "Octave:undefined-function")
+    rethrow(e)
+  end
+
   [status, v] = fileattrib(f);
   if status == 0
     return
@@ -31,28 +32,36 @@
 
 p = '---------';
 
-groupRead = ~isnan(v.GroupRead) && logical(v.GroupRead);
-groupWrite = ~isnan(v.GroupWrite) && logical(v.GroupWrite);
-groupExecute = ~isnan(v.GroupExecute) && logical(v.GroupExecute);
-otherRead = ~isnan(v.OtherRead) && logical(v.OtherRead);
-otherWrite = ~isnan(v.OtherWrite) && logical(v.OtherWrite);
-otherExecute = ~isnan(v.OtherExecute) && logical(v.OtherExecute);
+try
+  % filePermissions object
+  if v.Readable,  p(1) = 'r'; end
+  if v.Writable,  p(2) = 'w'; end
+catch e
+  if ~strcmp(e.identifier, "MATLAB:nonExistentField") && ...
+      ~strcmp(e.identifier, "Octave:invalid-indexing")
+    rethrow(e)
+  end
 
-if isstruct(v) % from fileattrib
   if v.UserRead,  p(1) = 'r'; end
   if v.UserWrite, p(2) = 'w'; end
-else % filePermissions object
-  if v.Readable,  p(1) = 'r'; end
-  if v.Writable,  p(2) = 'w'; end
 end
 
 if v.UserExecute, p(3) = 'x'; end
-if groupRead,     p(4) = 'r'; end
-if groupWrite,    p(5) = 'w'; end
-if groupExecute,  p(6) = 'x'; end
-if otherRead,     p(7) = 'r'; end
-if otherWrite,    p(8) = 'w'; end
-if otherExecute,  p(9) = 'x'; end
+
+try
+  if v.GroupRead,     p(4) = 'r'; end
+  if v.GroupWrite,    p(5) = 'w'; end
+  if v.GroupExecute,  p(6) = 'x'; end
+  if v.OtherRead,     p(7) = 'r'; end
+  if v.OtherWrite,    p(8) = 'w'; end
+  if v.OtherExecute,  p(9) = 'x'; end
+catch e
+  if ~strcmp(e.identifier, "MATLAB:nologicalnan") && ...
+     ~strcmp(e.identifier, "MATLAB:nonExistentField") && ...
+      ~strcmp(e.message, "invalid conversion from NaN to logical")
+    rethrow(e)
+  end
+end
 
 end
 

example/Filesystem.java

@@ -112,7 +112,7 @@ public static Boolean is_absolute(String path) {
 
     public static Boolean is_exe(String path) {
         File f = new File(path);
-        return f.isFile() && f.canExecute();
+        return f.canExecute();
     }
 
     public static Boolean is_readable(String path) {