From f017a829d999f2237a83b25221446a7d9de0cb90 Mon Sep 17 00:00:00 2001
From: Gunnar Aastrand Grimnes <gromgull@gmail.com>
Date: Thu, 19 Jan 2017 20:25:28 +0100
Subject: [PATCH] Fix initBindings in SPARQL

initBindings are now special fixed bindings, they are always in scope
in all parts of the query.

Fixes #294 (once and for all)
---
 rdflib/plugins/sparql/evaluate.py | 36 ++++---------------------------
 rdflib/plugins/sparql/sparql.py   | 13 +++++------
 rdflib/plugins/sparql/update.py   | 12 ++++-------
 test/test_initbindings.py         |  3 +++
 4 files changed, 18 insertions(+), 46 deletions(-)

diff --git a/rdflib/plugins/sparql/evaluate.py b/rdflib/plugins/sparql/evaluate.py
index e79e51493..8d22c2d92 100644
--- a/rdflib/plugins/sparql/evaluate.py
+++ b/rdflib/plugins/sparql/evaluate.py
@@ -446,41 +446,13 @@ def evalConstructQuery(ctx, query):
 
 
 def evalQuery(graph, query, initBindings, base=None):
-    ctx = QueryContext(graph)
 
-    ctx.prologue = query.prologue
+    initBindings = dict( ( Variable(k),v ) for k,v in initBindings.iteritems() )
 
-    main = query.algebra
+    ctx = QueryContext(graph, initBindings=initBindings)
 
-    if initBindings:
-        # add initBindings as a values clause
-
-        values = {} # no dict comprehension in 2.6 :(
-        for k,v in initBindings.iteritems():
-            if not isinstance(k, Variable):
-                k = Variable(k)
-            values[k] = v
-
-        main = main.clone() # clone to not change prepared q
-        main['p'] = main.p.clone()
-        # Find the right place to insert MultiSet join
-        repl = main.p
-        if repl.name == 'Slice':
-            repl['p'] = repl.p.clone()
-            repl = repl.p
-        if repl.name == 'Distinct':
-            repl['p'] = repl.p.clone()
-            repl = repl.p
-        if repl.p.name == 'OrderBy':
-            repl['p'] = repl.p.clone()
-            repl = repl.p
-        if repl.p.name == 'Extend':
-            repl['p'] = repl.p.clone()
-            repl = repl.p
-
-        repl['p'] = Join(repl.p, ToMultiSet(Values([values])))
-
-        # TODO: Vars?
+    ctx.prologue = query.prologue
+    main = query.algebra
 
     if main.datasetClause:
         if ctx.dataset is None:
diff --git a/rdflib/plugins/sparql/sparql.py b/rdflib/plugins/sparql/sparql.py
index 695055618..c012a8fc7 100644
--- a/rdflib/plugins/sparql/sparql.py
+++ b/rdflib/plugins/sparql/sparql.py
@@ -197,8 +197,8 @@ def forget(self, before, _except=None):
         since before
         """
         if not _except : _except = []
-
-        return FrozenBindings(self.ctx, (x for x in self.iteritems() if x[0] in _except or before[x[0]] is None))
+        # bindings from initBindings are newer forgotten
+        return FrozenBindings(self.ctx, (x for x in self.iteritems() if x[0] in _except or x[0] in self.ctx.initBindings or before[x[0]] is None))
 
     def remember(self, these):
         """
@@ -213,8 +213,10 @@ class QueryContext(object):
     Query context - passed along when evaluating the query
     """
 
-    def __init__(self, graph=None, bindings=None):
-        self.bindings = bindings or Bindings()
+    def __init__(self, graph=None, bindings=None, initBindings=None):
+        self.initBindings = initBindings
+        self.bindings = Bindings(d=bindings or [])
+        if initBindings: self.bindings.update(initBindings)
 
         if isinstance(graph, ConjunctiveGraph):
             self._dataset = graph
@@ -233,9 +235,8 @@ def __init__(self, graph=None, bindings=None):
 
     def clone(self, bindings=None):
         r = QueryContext(
-            self._dataset if self._dataset is not None else self.graph)
+            self._dataset if self._dataset is not None else self.graph, bindings or self.bindings, initBindings=self.initBindings)
         r.prologue = self.prologue
-        r.bindings.update(bindings or self.bindings)
         r.graph = self.graph
         r.bnodes = self.bnodes
         return r
diff --git a/rdflib/plugins/sparql/update.py b/rdflib/plugins/sparql/update.py
index 57c5bf461..f5a5f2eb1 100644
--- a/rdflib/plugins/sparql/update.py
+++ b/rdflib/plugins/sparql/update.py
@@ -252,7 +252,7 @@ def evalCopy(ctx, u):
     dstg += srcg
 
 
-def evalUpdate(graph, update, initBindings=None):
+def evalUpdate(graph, update, initBindings={}):
     """
 
     http://www.w3.org/TR/sparql11-update/#updateLanguage
@@ -274,15 +274,11 @@ def evalUpdate(graph, update, initBindings=None):
 
     for u in update:
 
-        ctx = QueryContext(graph)
+        initBindings = dict( ( Variable(k),v ) for k,v in initBindings.iteritems() )
+
+        ctx = QueryContext(graph, initBindings=initBindings)
         ctx.prologue = u.prologue
 
-        if initBindings:
-            for k, v in initBindings.iteritems():
-                if not isinstance(k, Variable):
-                    k = Variable(k)
-                ctx[k] = v
-            # ctx.push()  # nescessary?
 
         try:
             if u.name == 'Load':
diff --git a/test/test_initbindings.py b/test/test_initbindings.py
index ad94db4f2..e44f9fff5 100644
--- a/test/test_initbindings.py
+++ b/test/test_initbindings.py
@@ -150,6 +150,9 @@ def testVariableKeyWithQuestionMark():
     results = list(g2.query("SELECT ?o WHERE { ?s :p ?o }", initBindings={Variable("?s"): EX['s1']}))
     assert len(results) == 1, results
 
+def testFilter():
+    results = list(g2.query("SELECT ?o WHERE { ?s :p ?o FILTER (?s = ?x)}", initBindings={Variable("?x"): EX['s1']}))
+    assert len(results) == 1, results
 
 if __name__ == "__main__":