[folks] core: Correctly resolve symlinks when loading backends

[Philip Withnall <pwithnall src gnome org>]

commit 47f872c8dd947236a96385a3ea0e372e8d97eb75
Author: Philip Withnall <philip tecnocode co uk>
Date:   Tue Jun 24 23:47:17 2014 +0100

    core: Correctly resolve symlinks when loading backends
    
    Instead of ignoring symlinks, we should resolve their targets, and
    deduplicate after that. This fixes cases where folks is run in an
    environment with software installed in loop mounted file systems — each
    backend .so file in the backend path is actually a symlink to the proper
    .so file in the loop mounted file system. This is the case on
    Tinycorelinux. folks was previously not loading any backends in such an
    environment because it ignored all symlinks.
    
    Thanks to John Frankish for help in debugging this problem.

 NEWS                     |    2 ++
 folks/backend-store.vala |   43 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 41 insertions(+), 4 deletions(-)
---
diff --git a/NEWS b/NEWS
index c5357a0..359a2d2 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,8 @@ Overview of changes from libfolks 0.9.7.1 to libfolks 0.9.8
 Dependencies:
 
 Major changes:
+ • Fix loading backends on distributions which install software in loop mounted
+   file systems, such as Tinycorelinux
 
 Bugs fixed:
 
diff --git a/folks/backend-store.vala b/folks/backend-store.vala
index e2ec287..8e20e89 100644
--- a/folks/backend-store.vala
+++ b/folks/backend-store.vala
@@ -632,6 +632,7 @@ public class Folks.BackendStore : Object {
           FileAttribute.STANDARD_NAME + "," +
           FileAttribute.STANDARD_TYPE + "," +
           FileAttribute.STANDARD_IS_SYMLINK + "," +
+          FileAttribute.STANDARD_SYMLINK_TARGET + "," +
           FileAttribute.STANDARD_CONTENT_TYPE;
 
       GLib.List<FileInfo> infos;
@@ -660,11 +661,45 @@ public class Folks.BackendStore : Object {
       foreach (var info in infos)
         {
           var file = dir.get_child (info.get_name ());
+
+          /* Handle symlinks by derefencing them. If we look at two symlinks
+           * with the same target, we don’t end up loading that backend twice
+           * due to hashing the backend’s absolute path in @modules_final.
+           *
+           * We can’t just ignore symlinks due to the way Tinycorelinux installs
+           * software: /usr/local/lib/folks/41/backends/bluez/bluez.so is a
+           * symlink to
+           * /tmp/tcloop/folks/usr/local/lib/folks/41/backends/bluez/bluez.so,
+           * a loopback squashfs mount of the folks file system. Ignoring
+           * symlinks means we would never load backends in that environment. */
+          if (info.get_is_symlink ())
+            {
+              debug ("Handling symlink ‘%s’ to ‘%s’.",
+                  file.get_path (), info.get_symlink_target ());
+
+              var old_file = file;
+              file = dir.resolve_relative_path (info.get_symlink_target ());
+
+              try
+                {
+                  info =
+                      yield file.query_info_async (attributes,
+                          FileQueryInfoFlags.NONE);
+                }
+              catch (Error error)
+                {
+                  /* Translators: the first parameter is a folder path and the second
+                   * is an error message. */
+                  warning (_("Error querying info for target ‘%s’ of symlink ‘%s’: %s"),
+                      file.get_path (), old_file.get_path (), error.message);
+
+                  continue;
+                }
+            }
+
+          /* Handle proper files. */
           var file_type = info.get_file_type ();
           unowned string content_type = info.get_content_type ();
-          /* don't load the library multiple times for its various symlink
-           * aliases */
-          var is_symlink = info.get_is_symlink ();
 
           string? mime = ContentType.get_mime_type (content_type);
 
@@ -679,7 +714,7 @@ public class Folks.BackendStore : Object {
                     }
                 }
             }
-          else if (mime == "application/x-sharedlib" && !is_symlink)
+          else if (mime == "application/x-sharedlib")
             {
               var path = file.get_path ();
               if (path != null)