read_symlink: always string class

Author: scivision

+stdlib/read_symlink.m

@@ -1,6 +1,7 @@
 %% READ_SYMLINK read symbolic link
 %
 % empty string if path is not a symlink
+% always of string class in Matlab
 
 function r = read_symlink(p)
 arguments
@@ -10,7 +11,7 @@
 
 try
   [ok, r] = isSymbolicLink(p);
-  if ~ok, r = ''; end
+  if ~ok, r = string.empty; end
 catch e
   switch e.identifier
     case "Octave:undefined-function", r = readlink(p);
@@ -23,16 +24,12 @@
         % https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/file/Files.html#readSymbolicLink(java.nio.file.Path)
         r = java.nio.file.Files.readSymbolicLink(javaPathObject(r)).string;
       else
-        r = '';
+        r = string.empty;
       end
     otherwise, rethrow(e)
   end
 end
 
-if isstring(p)
-  r = string(r);
-end
-
 end
 
 %!test

src/read_symlink.cpp

@@ -17,6 +17,12 @@ class MexFunction : public matlab::mex::Function {
 
     matlab::data::ArrayFactory factory;
 
-    outputs[0] = factory.createScalar(fs_read_symlink(matlab_1string_input(inputs)));
+    std::string p = fs_read_symlink(matlab_1string_input(inputs));
+
+    if (p.empty()) {
+      outputs[0] = factory.createArray<matlab::data::MATLABString>({0, 0});
+    } else {
+      outputs[0] = factory.createScalar(p);
+    }
   }
 };

src/symlink_fs.cpp

@@ -77,6 +77,7 @@ std::string fs_read_symlink(std::string_view path)
   std::error_code ec;
   if(auto p = std::filesystem::read_symlink(path, ec); !ec)
     return p.string();
+  // need .string() explict for MSVC
 #endif
 
   return {};

test/TestSymlink.m

@@ -16,9 +16,9 @@ function setup_symlink(tc)
 
 tc.tempDir = tc.createTemporaryFolder();
 
-tc.link = fullfile(tc.tempDir, "my.lnk");
+tc.link = fullfile(tc.tempDir, 'my.lnk');
 
-tc.target = mfilename("fullpath") + ".m";
+tc.target = strcat(mfilename("fullpath"), '.m');
 
 tc.assumeTrue(stdlib.create_symlink(tc.target, tc.link), ...
     "failed to create test link " + tc.link)
@@ -29,27 +29,32 @@ function setup_symlink(tc)
 methods (Test)
 
 function test_is_symlink(tc, p)
+fprintf("is_symlink  mex: %d\n", stdlib.is_mex_fun("stdlib.is_symlink"))
 tc.verifyTrue(stdlib.is_symlink(tc.link), "failed to detect own link")
 tc.verifyEqual(stdlib.is_symlink(p{1}), p{2}, p{1})
 end
 
 
 function test_read_symlink(tc)
+fprintf("read_symlink  mex: %d\n", stdlib.is_mex_fun("stdlib.read_symlink"))
+tc.verifyEmpty(stdlib.read_symlink(""))
+tc.verifyEmpty(stdlib.read_symlink(''))
+tc.verifyEmpty(stdlib.read_symlink(tempname))
+tc.verifyEmpty(stdlib.read_symlink(tc.target))
 
-tc.verifyEqual(stdlib.read_symlink(""), "")
-tc.verifyEqual(stdlib.read_symlink(''), '')
-tc.verifyEqual(stdlib.read_symlink(tempname), '')
-tc.verifyEqual(stdlib.read_symlink(tc.target), "")
 
 t = stdlib.read_symlink(tc.link);
-tc.verifyNotEmpty(t)
-tc.verifyClass(t, 'string')
-tc.verifyEqual(tc.target, t)
+
+targ = string(tc.target);
+
+tc.verifyEqual(targ, t)
 
 end
 
 
 function test_create_symlink(tc)
+fprintf("create_symlink  mex: %d\n", stdlib.is_mex_fun("stdlib.create_symlink"))
+
 tc.applyFixture(matlab.unittest.fixtures.SuppressedWarningsFixture(["MATLAB:io:filesystem:symlink:TargetNotFound","MATLAB:io:filesystem:symlink:FileExists"]))
 
 tc.verifyFalse(stdlib.create_symlink('', tempname()))