[tracker/wip/carlosg/sparql-parser-ng: 297/306] libtracker-data: Add back 'NULL' literal handling for INSERT OR REPLACE

[Carlos Garnacho <carlosg src gnome org>]

commit 535e91faab525193ab66ee993002461ebe98e740
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Sep 23 12:39:07 2018 +0200

    libtracker-data: Add back 'NULL' literal handling for INSERT OR REPLACE
    
    This is a tracker extension that allows INSERT OR REPLACE to also delete
    values.

 src/libtracker-data/tracker-sparql-grammar.h | 8 +++++++-
 src/libtracker-data/tracker-sparql.c         | 8 ++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
---
diff --git a/src/libtracker-data/tracker-sparql-grammar.h b/src/libtracker-data/tracker-sparql-grammar.h
index d6baf45f9..fc03a0d1e 100644
--- a/src/libtracker-data/tracker-sparql-grammar.h
+++ b/src/libtracker-data/tracker-sparql-grammar.h
@@ -243,6 +243,7 @@ typedef enum {
        LITERAL_NAMED,
        LITERAL_NOT,
        LITERAL_NOW,
+       LITERAL_NULL, /* TRACKER EXTENSION */
        LITERAL_OFFSET,
        LITERAL_OP_AND,
        LITERAL_OP_EQ,
@@ -392,6 +393,7 @@ static const gchar literals[][N_LITERALS] = {
        "named", /* LITERAL_NAMED */
        "not", /* LITERAL_NOT */
        "now", /* LITERAL_NOW */
+       "null", /* LITERAL_NULL (TRACKER EXTENSION) */
        "offset", /* LITERAL_OFFSET */
        "&&", /* LITERAL_OP_AND */
        "=", /* LITERAL_OP_EQ */
@@ -891,8 +893,12 @@ static const TrackerGrammarRule helper_GraphNodePath_or[] = { R(VarOrTerm), R(Tr
 static const TrackerGrammarRule rule_GraphNodePath[] = { OR(helper_GraphNodePath_or), NIL };
 
 /* GraphNode ::= VarOrTerm | TriplesNode
+ *
+ * TRACKER EXTENSION:
+ * Literal 'NULL' is also accepted, rule is effectively:
+ *   VarOrTerm | TriplesNode | 'NULL'
  */
-static const TrackerGrammarRule helper_GraphNode_or[] = { R(VarOrTerm), R(TriplesNode), NIL };
+static const TrackerGrammarRule helper_GraphNode_or[] = { R(VarOrTerm), R(TriplesNode), L(NULL), NIL };
 static const TrackerGrammarRule rule_GraphNode[] = { OR(helper_GraphNode_or), NIL };
 
 /* CollectionPath ::= '(' GraphNodePath+ ')'
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index a962bb439..011b5ab5e 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -4204,6 +4204,10 @@ translate_GraphNode (TrackerSparql  *sparql,
        GError *inner_error = NULL;
 
        /* GraphNode ::= VarOrTerm | TriplesNode
+        *
+        * TRACKER EXTENSION:
+        * Literal 'NULL' is also accepted, rule is effectively:
+        *   VarOrTerm | TriplesNode | 'NULL'
         */
        if (_check_in_rule (sparql, NAMED_RULE_VarOrTerm)) {
                sparql->current_state.token = &sparql->current_state.object;
@@ -4213,6 +4217,10 @@ translate_GraphNode (TrackerSparql  *sparql,
                sparql->current_state.token = &sparql->current_state.object;
                _call_rule (sparql, NAMED_RULE_TriplesNode, error);
                g_assert (!tracker_token_is_empty (&sparql->current_state.object));
+       } else if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_NULL)) {
+               if (sparql->current_state.type != TRACKER_SPARQL_TYPE_UPDATE)
+                       _raise (PARSE, "«NULL» literal is not allowed in this mode", "NULL");
+               /* Object token is left unset on purpose */
        } else {
                g_assert_not_reached ();
        }