[tracker] libtracker-extract: Add builtin dummy extractor

[Carlos Garnacho <carlosg src gnome org>]

commit 51e2021fa150e4f4d463ed4baf16051fc54e4fda
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Aug 4 18:57:33 2015 +0200

    libtracker-extract: Add builtin dummy extractor
    
    For rules with no ModulePath key (i.e. those we only want to set
    rdf:types for) we relied on the lack of generic extractors that
    might handle the mimetype.
    
    If there was one such generic extractor, the TrackerMimetypeInfo
    iterator would skip the empty rule and directly attempt the generic
    extractor.
    
    Because it is conceivable that no-op is desired for some files,
    we shouldn't attempt to skip it, nor run further modules after the
    dummy rules, so just give this dummy fastpath a presence that
    tracker-extract will make sense of.

 src/libtracker-extract/tracker-module-manager.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-extract/tracker-module-manager.c b/src/libtracker-extract/tracker-module-manager.c
index a7a8ef9..b28ad56 100644
--- a/src/libtracker-extract/tracker-module-manager.c
+++ b/src/libtracker-extract/tracker-module-manager.c
@@ -42,6 +42,13 @@ typedef struct {
        guint initialized : 1;
 } ModuleInfo;
 
+static gboolean dummy_extract_func (TrackerExtractInfo *info);
+
+static ModuleInfo dummy_module = {
+       NULL, TRACKER_MODULE_MAIN_THREAD,
+       dummy_extract_func, NULL, TRUE
+};
+
 static GHashTable *modules = NULL;
 static GHashTable *mimetype_map = NULL;
 static gboolean initialized = FALSE;
@@ -55,6 +62,12 @@ struct _TrackerMimetypeInfo {
 };
 
 static gboolean
+dummy_extract_func (TrackerExtractInfo *info)
+{
+       return TRUE;
+}
+
+static gboolean
 load_extractor_rule (GKeyFile  *key_file,
                      GError   **error)
 {
@@ -307,7 +320,7 @@ load_module (RuleInfo *info,
        ModuleInfo *module_info = NULL;
 
        if (!info->module_path) {
-               return NULL;
+               return &dummy_module;
        }
 
        if (modules) {