is_exe: more robust, esp. on Windows

Use PATHEXT to confirm .exe status

Author: scivision

+stdlib/is_exe.m

@@ -19,17 +19,26 @@
   p = p(:);
   i = isfile(p);
   ok(size(p)) = false;
+
+  if ispc()
+    pe = split(string(getenv("PATHEXT")), pathsep);
+    i = i & endsWith(stdlib.suffix(p(i)), pe, 'IgnoreCase', true);
+  end
+
   if ~any(i), return, end
 
   t(i, :) = getPermissions(filePermissions(p(i)), props);
 
   ok(i) = isfile(p(i)) & any(t{i,:}, 2);
 
 catch e
+  ok = false;
+  if ~isfile(p), return, end
+
   switch e.identifier
     case {'MATLAB:UndefinedFunction', 'Octave:undefined-function'}
       a = file_attributes_legacy(p);
-      ok = isfile(p) && (a.UserExecute || a.GroupExecute || a.OtherExecute);
+      ok = a.UserExecute || a.GroupExecute || a.OtherExecute;
     otherwise, rethrow(e)
   end
 end

test/TestIsExe.m

@@ -1,22 +1,31 @@
 classdef TestIsExe < matlab.unittest.TestCase
 
 properties (TestParameter)
-p = {{".", false}}
+p = {{fileparts(mfilename('fullpath')) + "/../Readme.md", false}}
 end
 
 methods(Test, TestTags="impure")
+
 function test_is_exe(tc, p)
+tc.assumeThat(p{1}, matlab.unittest.constraints.IsFile)
+
 tc.verifyEqual(stdlib.is_exe(p{1}), p{2})
 end
 
+
+function test_is_exe_dir(tc)
+tc.verifyFalse(stdlib.is_exe('.'))
+end
+
+
 function test_matlab_exe(tc)
 
 f = fullfile(matlabroot, "bin/matlab");
 if ispc()
   f = f + ".exe";
 end
 
-tc.verifyEqual(stdlib.is_exe(f), true)
+tc.verifyTrue(stdlib.is_exe(f))
 end
 
 end