try methods(foo) to determine if foo is an object

Use a try-catch block with the methods call.  If it has methods it
must be a class.  This allows refactoring the object identification
code a bit.  Fixes a few bugs.  Fixes #199.  Fixes #200.  Fixes #211.

Related to Issue #196.

inst/private/doctest_collect.m

@@ -30,33 +30,36 @@
   elseif (exist (what) == 3)  % .oct/.mex
     [~, what, ~] = fileparts (what);  % strip extension if present
     type = 'function';                % then access like any function
-  elseif (exist(what, 'file') && ~exist(what, 'dir')) || exist(what, 'builtin')
-    if (exist(['@' what], 'dir'))
-      % special case, e.g., @logical is class, logical is builtin
-      type = 'class';
+  else
+    type = 'unknown';
+  end
+
+  %% Let's see if its a class by checking if methods returns
+  % What about classdef in oct file above?  Should we do this even if
+  % type is 'octfile'?
+  if (strcmp (type, 'unknown'))
+    if (~ isempty (what) && strcmp (what(1), '@'))
+      temp = what(2:end);
     else
-      type = 'function';
+      temp = what;
     end
-  elseif (strcmp(what(1), '@'))
-    % comes after 'file' above for "doctest @class/method"
-    type = 'class';
-  elseif (exist(what, 'dir'))
-    type = 'dir';
-  elseif exist(what) == 2 || exist(what) == 103
-    % Notes:
-    %   * exist('@class', 'dir') only works if pwd is the parent of
-    %     '@class', having it in the path is not sufficient.
-    %   * Return 2 on Octave 3.8 and 103 on Octave 4.
-    type = 'class';
-  else
-    % classdef classes are not detected by any of the above
     try
-      temp = methods(what);
+      temp = methods(temp);
       type = 'class';
     catch
       type = 'unknown';
     end
   end
+
+  if (strcmp (type, 'unknown'))
+    if (exist(what, 'dir'))
+      type = 'dir';
+    elseif (exist(what, 'file') || exist(what, 'builtin'))
+      type = 'function';
+    else
+      type = 'unknown';
+    end
+  end
 else % Matlab
   if (strcmp(what(1), '@')) && ~isempty(methods(what(2:end)))
     % covers "doctest @class", but not "doctest @class/method"

test/bist.m

@@ -15,11 +15,9 @@ function bist()
 
 %!assert (~ doctest ('there_is_no_such_file', '-quiet'))
 
-%!assert (~ doctest ({'doctest', 'there_is_no_such_file'}, '-quiet'))
+%!assert (~ doctest ('@there_is_no_such_class', '-quiet'))
 
-%!error
-%! % TODO: maybe this should be EXTRACTION_ERROR, not raise an error...
-%! doctest @there_is_no_such_class -quiet
+%!assert (~ doctest ({'doctest', 'there_is_no_such_file'}, '-quiet'))
 
 %!test
 %! [n, t] = doctest ('doctest', '-quiet');
@@ -67,8 +65,7 @@ function bist()
 %! assert (nump == 5 && numt == 5)
 %! assert (summ.num_targets == 4)
 
-%!xtest
-%! % Currently cannot even run
+%!test
 %! % https://github.com/catch22/octave-doctest/issues/199
 %! [nump, numt, summ] = doctest ('@classdef_infile/disp');
 %! assert (nump >= 0)
@@ -88,7 +85,7 @@ function bist()
 %! assert (nump == 4 && numt == 4)
 %! assert (summ.num_targets == 3)
 
-%!xtest
+%!test
 %! % monkey-patching methods to existing builtin-objects
 %! [nump, numt, summ1] = doctest ('logical');
 %! % First, there is (at least) the "logical" builtin