Add ignore_dangling parameter to dir_iterator() ctor

7 files changed, 147 insertions, 44 deletions

diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index 2650c25..d1b0424 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -285,7 +285,7 @@ namespace butl
     // An nftw()-based implementation (for platforms that support it)
     // might be a faster way.
     //
-    for (const dir_entry& de: dir_iterator (p))
+    for (const dir_entry& de: dir_iterator (p, false /* ignore_dangling */))
     {
       path ep (p / de.path ()); //@@ Would be good to reuse the buffer.
 
@@ -1083,10 +1083,25 @@ namespace butl
 
       h_ = x.h_;
       x.h_ = nullptr;
+
+      ignore_dangling_ = x.ignore_dangling_;
     }
     return *this;
   }
 
+  static inline entry_type
+  type (const struct stat& s) noexcept
+  {
+    if (S_ISREG (s.st_mode))
+      return entry_type::regular;
+    else if (S_ISDIR (s.st_mode))
+      return entry_type::directory;
+    else if (S_ISLNK (s.st_mode))
+      return entry_type::symlink;
+    else
+      return entry_type::other;
+  }
+
   entry_type dir_entry::
   type (bool link) const
   {
@@ -1095,22 +1110,9 @@ namespace butl
     if ((link
          ? stat (p.string ().c_str (), &s)
          : lstat (p.string ().c_str (), &s)) != 0)
-    {
       throw_generic_error (errno);
-    }
-
-    entry_type r;
-
-    if (S_ISREG (s.st_mode))
-      r = entry_type::regular;
-    else if (S_ISDIR (s.st_mode))
-      r = entry_type::directory;
-    else if (S_ISLNK (s.st_mode))
-      r = entry_type::symlink;
-    else
-      r = entry_type::other;
 
-    return r;
+    return butl::type (s);
   }
 
   // dir_iterator
@@ -1121,7 +1123,8 @@ namespace butl
   };
 
   dir_iterator::
-  dir_iterator (const dir_path& d)
+  dir_iterator (const dir_path& d, bool ignore_dangling)
+    : ignore_dangling_ (ignore_dangling)
   {
     unique_ptr<DIR, dir_deleter> h (opendir (d.string ().c_str ()));
     h_ = h.get ();
@@ -1189,12 +1192,33 @@ namespace butl
 
         // Skip '.' and '..'.
         //
-       if (p.current () || p.parent ())
+        if (p.current () || p.parent ())
           continue;
 
         e_.p_ = move (p);
         e_.t_ = d_type<struct dirent> (de, nullptr);
         e_.lt_ = entry_type::unknown;
+
+        // If requested, we ignore dangling symlinks, skipping ones with
+        // non-existing or inaccessible targets.
+        //
+        // Note that ltype () can potentially lstat() and so throw.
+        //
+        if (ignore_dangling_ && e_.ltype () == entry_type::symlink)
+        {
+          struct stat s;
+          path p (e_.base () / e_.path ());
+
+          if (stat (p.string ().c_str (), &s) != 0)
+          {
+            if (errno == ENOENT || errno == ENOTDIR || errno == EACCES)
+              continue;
+
+            throw_generic_error (errno);
+          }
+
+          e_.lt_ = type (s); // While at it, set the target type.
+        }
       }
       else if (errno == 0)
       {
@@ -1233,6 +1257,8 @@ namespace butl
 
       h_ = x.h_;
       x.h_ = -1;
+
+      ignore_dangling_ = x.ignore_dangling_;
     }
     return *this;
   }
@@ -1283,7 +1309,8 @@ namespace butl
   };
 
   dir_iterator::
-  dir_iterator (const dir_path& d)
+  dir_iterator (const dir_path& d, bool ignore_dangling)
+    : ignore_dangling_ (ignore_dangling)
   {
     auto_dir h (h_);
     e_.b_ = d; // Used by next() to call _findfirst().
@@ -1801,7 +1828,11 @@ namespace butl
         if (!preopen || preopen_ (p))
         {
           dir_path d (start_ / p);
-          i = dir_iterator (!d.empty () ? d : dir_path ("."));
+
+          // If we follow symlinks, then we ignore the dangling ones.
+          //
+          i = dir_iterator (!d.empty () ? d : dir_path ("."),
+                            follow_symlinks_);
         }
 
         iters_.emplace_back (move (i), move (p));
diff --git a/libbutl/filesystem.ixx b/libbutl/filesystem.ixx
index 170c108..e5c1298 100644
--- a/libbutl/filesystem.ixx
+++ b/libbutl/filesystem.ixx
@@ -9,7 +9,7 @@ namespace butl
   {
     // @@ Could 0 size be a valid and faster way?
     //
-    return dir_iterator (d) == dir_iterator ();
+    return dir_iterator (d, false /* ignore_dangling */) == dir_iterator ();
   }
 
   inline bool
@@ -126,7 +126,7 @@ namespace butl
   //
   inline dir_iterator::
   dir_iterator (dir_iterator&& x) noexcept
-      : e_ (std::move (x.e_)), h_ (x.h_)
+    : e_ (std::move (x.e_)), h_ (x.h_), ignore_dangling_ (x.ignore_dangling_)
   {
 #ifndef _WIN32
     x.h_ = nullptr;
diff --git a/libbutl/filesystem.mxx b/libbutl/filesystem.mxx
index ff9a4a6..da5ab59 100644
--- a/libbutl/filesystem.mxx
+++ b/libbutl/filesystem.mxx
@@ -251,9 +251,17 @@ LIBBUTL_MODEXPORT namespace butl
   //    deleted at a later stage, then the filesystem API functions may fail
   //    when encounter such a symlink. This includes rmsymlink().
   //
-  //  - Symlinks are not visible when iterating over a directory with
-  //    dir_iterator. As a result, a directory that contains symlinks can not
-  //    be recursively deleted.
+  //  - Dangling symlinks are not visible when iterating over a directory with
+  //    dir_iterator. As a result, a directory that contains such symlinks can
+  //    not be recursively deleted.
+  //
+  //  @@ Note that the above restrictions seems to be Wine-specific (as of
+  //     2.20). It is probably make sense to properly support directory
+  //     symlinks when run natively.
+  //
+  //  - Symlinks that refer to existing targets are recognized as ordinary
+  //    directories by dir_iterator. As a result rmdir_r() function removes the
+  //    target directories content, rather then symlinks entries.
   //
   LIBBUTL_SYMEXPORT void
   mksymlink (const path& target, const path& link, bool dir = false);
@@ -629,8 +637,15 @@ LIBBUTL_MODEXPORT namespace butl
     ~dir_iterator ();
     dir_iterator () = default;
 
+    // If it is requested to ignore dangling symlinks, then the increment
+    // operator will skip symlinks that refer to non-existing or inaccessible
+    // targets. That implies that it will always try to stat() symlinks.
+    //
+    // Note that we currently do not fully support symlinks on Windows, so the
+    // ignore_dangling argument is noop there (see mksymlink() for details).
+    //
     explicit
-    dir_iterator (const dir_path&);
+    dir_iterator (const dir_path&, bool ignore_dangling);
 
     dir_iterator (const dir_iterator&) = delete;
     dir_iterator& operator= (const dir_iterator&) = delete;
@@ -658,6 +673,8 @@ LIBBUTL_MODEXPORT namespace butl
 #else
     intptr_t h_ = -1;
 #endif
+
+    bool ignore_dangling_;
   };
 
   // Range-based for loop support.
diff --git a/tests/dir-iterator/driver.cxx b/tests/dir-iterator/driver.cxx
index 1adef6f..bad9e58 100644
--- a/tests/dir-iterator/driver.cxx
+++ b/tests/dir-iterator/driver.cxx
@@ -41,45 +41,71 @@ operator<< (ostream& os, entry_type e)
   return os << entry_type_string[static_cast<size_t> (e)];
 }
 
-// @@ Should we make the test silent unless -v arg passed. In silen mode could
-// compare the output with a set of predefined dir entries.
+// Usage: argv[0] [-v] [-i] <dir>
+//
+// Iterates over a directory filesystem sub-entries, obtains their types and
+// target types for symlinks.
+//
+// -v
+//    Print the filesystem entries types and names to STDOUT.
+//
+// -i
+//    Ignore dangling symlinks, rather than fail trying to obtain the target
+//    type.
 //
 int
 main (int argc, const char* argv[])
 {
-  if (!(argc == 2 || (argc == 3 && argv[1] == string ("-v"))))
+  assert (argc > 0);
+
+  bool verbose (false);
+  bool ignore_dangling (false);
+
+  int i (1);
+  for (; i != argc; ++i)
+  {
+    string v (argv[i]);
+
+    if (v == "-v")
+      verbose = true;
+    else if (v == "-i")
+      ignore_dangling = true;
+    else
+      break;
+  }
+
+  if (i != argc - 1)
   {
-    cerr << "usage: " << argv[0] << " [-v] <dir>" << endl;
+    cerr << "usage: " << argv[0] << " [-v] [-i] <dir>" << endl;
     return 1;
   }
 
-  bool v (argc == 3);
-  const char* d (argv[argc - 1]);
+  const char* d (argv[i]);
 
   try
   {
-    for (const dir_entry& de: dir_iterator (dir_path (d)))
+    for (const dir_entry& de: dir_iterator (dir_path (d), ignore_dangling))
     {
       entry_type lt (de.ltype ());
-      entry_type t (lt == entry_type::symlink ? de.ltype () : lt);
+      entry_type t (lt == entry_type::symlink ? de.type () : lt);
       const path& p (de.path ());
 
-      if (v)
+      if (verbose)
       {
-        cerr << lt << " ";
+        cout << lt << " ";
 
         if (lt == entry_type::symlink)
-          cerr << t;
+          cout << t;
         else
-          cerr << "   ";
+          cout << "   ";
 
-        cerr << " " << p << endl;
+        cout << " " << p << endl;
       }
     }
   }
   catch (const exception& e)
   {
-    cerr << argv[1] << ": " << e << endl;
+    cerr << e << endl;
     return 1;
   }
 }
diff --git a/tests/dir-iterator/testscript b/tests/dir-iterator/testscript
index 75a1ca6..f592c78 100644
--- a/tests/dir-iterator/testscript
+++ b/tests/dir-iterator/testscript
@@ -8,9 +8,24 @@ test.options = -v
 :
 mkdir a;
 touch a/b;
-$* a 2>"reg     b"
+$* a >"reg     b"
 
 : dir
 :
 mkdir -p a/b;
-$* a 2>"dir     b"
+$* a >"dir     b"
+
+: dangling-link
+:
+if ($cxx.target.class != 'windows')
+{
+  +mkdir a
+  +touch --no-cleanup a/b
+  +ln -s a/b a/l
+  +rm a/b
+
+  +touch a/c
+
+  $* ../a     >! 2>!       != 0 : keep
+  $* -i ../a  >'reg     c'      : skip
+}
diff --git a/tests/link/driver.cxx b/tests/link/driver.cxx
index 463ad23..7ee8c3b 100644
--- a/tests/link/driver.cxx
+++ b/tests/link/driver.cxx
@@ -96,11 +96,11 @@ link_dir (const dir_path& target,
   dir_path tp (target.absolute () ? target : link.directory () / target);
 
   set<pair<entry_type, path>> te;
-  for (const dir_entry& de: dir_iterator (tp))
+  for (const dir_entry& de: dir_iterator (tp, false /* ignore_dangling */))
     te.emplace (de.ltype (), de.path ());
 
   set<pair<entry_type, path>> le;
-  for (const dir_entry& de: dir_iterator (link))
+  for (const dir_entry& de: dir_iterator (link, false /* ignore_dangling */))
     le.emplace (de.ltype (), de.path ());
 
   return te == le;
diff --git a/tests/wildcard/testscript b/tests/wildcard/testscript
index 489f724..85f5a33 100644
--- a/tests/wildcard/testscript
+++ b/tests/wildcard/testscript
@@ -113,7 +113,7 @@
 
     : absolute
     :
-    : When cross-testing we can't guarantee that host absolute paths are
+    : When cross-testing we cannot guarantee that host absolute paths are
     : recognized by the target process.
     :
     if ($test.target == $build.host)
@@ -566,6 +566,20 @@
       }
     }
   }
+
+  : dangling-link
+  :
+  if ($cxx.target.class != 'windows')
+  {
+    mkdir a;
+    touch --no-cleanup a/b;
+    ln -s a/b a/l;
+    rm a/b;
+
+    touch a/c;
+
+    $* a/* >/'a/c'
+  }
 }
 
 : path-entry-search