added ability to unset vars and derefs (#1970)

* added ability to unset vars and derefs

synapse/lib/ast.py

@@ -23,7 +23,7 @@
 import synapse.lib.provenance as s_provenance
 import synapse.lib.stormtypes as s_stormtypes
 
-from synapse.lib.stormtypes import tobool, toint, toprim, tostr
+from synapse.lib.stormtypes import tobool, toint, toprim, tostr, undef
 
 logger = logging.getLogger(__name__)
 
@@ -757,16 +757,24 @@ async def run(self, runt, genr):
             count += 1
 
             valu = await vkid.compute(runt, path)
+            if valu is undef:
+                runt.popVar(name)
+                #TODO detect which to update here
+                path.popVar(name)
 
-            runt.setVar(name, valu)
-            #TODO detect which to update here
-            path.setVar(name, valu)
+            else:
+                runt.setVar(name, valu)
+                #TODO detect which to update here
+                path.setVar(name, valu)
 
             yield node, path
 
         if count == 0 and vkid.isRuntSafe(runt):
             valu = await vkid.compute(runt, None)
-            runt.setVar(name, valu)
+            if valu is undef:
+                runt.popVar(name)
+            else:
+                runt.setVar(name, valu)
 
     def getRuntVars(self, runt):
         yield self.kids[0].value(), self.kids[1].isRuntSafe(runt)

synapse/lib/node.py

@@ -720,6 +720,9 @@ def getVar(self, name, defv=s_common.novalu):
     def setVar(self, name, valu):
         self.vars[name] = valu
 
+    def popVar(self, name):
+        return self.vars.pop(name, s_common.novalu)
+
     def meta(self, name, valu):
         '''
         Add node specific metadata to be returned with the node.

synapse/lib/storm.py

@@ -1309,6 +1309,13 @@ def setVar(self, name, valu):
         self.vars[name] = valu
         return
 
+    def popVar(self, name):
+
+        if self._isRootScope(name):
+            return self.root.popVar(name)
+
+        return self.vars.pop(name, s_common.novalu)
+
     def addInput(self, node):
         '''
         Add a Node() object as input to the query runtime.

synapse/lib/stormtypes.py

@@ -28,6 +28,9 @@
 
 logger = logging.getLogger(__name__)
 
+class Undef: pass
+undef = Undef()
+
 class StormTypesRegistry:
     def __init__(self):
         self._LIBREG = {}
@@ -495,6 +498,7 @@ def getObjLocals(self):
             'fire': self._fire,
             'list': self._list,
             'null': self._null,
+            'undef': self._undef,
             'true': self._true,
             'false': self._false,
             'text': self._text,
@@ -506,6 +510,24 @@ def getObjLocals(self):
             'import': self._libBaseImport,
         }
 
+    @property
+    def _undef(self):
+        '''
+        This constant can be used to unset variables and derefs.
+
+        Examples:
+
+            // Unset the variable $foo
+            $foo = $lib.undef
+
+            // Remove a dictionary key bar
+            $foo.bar = $lib.undef
+
+            // Remove a list index of 0
+            $foo.0 = $lib.undef
+        '''
+        return undef
+
     @property
     def _true(self):
         '''
@@ -2006,6 +2028,11 @@ async def iter(self):
         return tuple(item for item in self.valu.items())
 
     async def setitem(self, name, valu):
+
+        if valu is undef:
+            self.valu.pop(name, None)
+            return
+
         self.valu[name] = valu
 
     async def deref(self, name):
@@ -2119,6 +2146,19 @@ def __iter__(self):
         for item in self.valu:
             yield item
 
+    async def setitem(self, name, valu):
+
+        indx = await toint(name)
+
+        if valu is undef:
+            try:
+                self.valu.pop(indx)
+            except IndexError:
+                pass
+            return
+
+        self.valu[indx] = valu
+
     async def _derefGet(self, name):
         return await self._methListIndex(name)
 
@@ -2690,6 +2730,9 @@ async def deref(self, name):
         raise s_exc.StormRuntimeError(mesg=mesg)
 
     async def setitem(self, name, valu):
+        if valu is undef:
+            self.path.popVar(name)
+            return
         self.path.setVar(name, valu)
 
     def __iter__(self):

synapse/tests/test_lib_storm.py

@@ -192,6 +192,48 @@ async def test_lib_storm_basics(self):
             resp = await core.callStorm(wget, opts=opts)
             self.true(resp['ok'])
 
+    async def test_storm_undef(self):
+
+        async with self.getTestCore() as core:
+
+            # pernode variants
+            self.none(await core.callStorm('''
+                [ ps:contact = * ]
+                if $node {
+                    $foo = $lib.dict()
+                    $foo.bar = $lib.undef
+                    return($foo.bar)
+                }
+            '''))
+            with self.raises(s_exc.NoSuchVar):
+                await core.callStorm('[ps:contact=*] $foo = $node.repr() $foo = $lib.undef return($foo)')
+
+            with self.raises(s_exc.StormRuntimeError):
+                await core.callStorm('''
+                    [ps:contact=*]
+                    $path.vars.foo = lol
+                    $path.vars.foo = $lib.undef
+                    return($path.vars.foo)
+                ''')
+
+            # runtsafe variants
+            self.eq(('foo', 'baz'), await core.callStorm('$foo = (foo, bar, baz) $foo.1 = $lib.undef return($foo)'))
+            self.eq(('foo', 'bar'), await core.callStorm('$foo = (foo, bar, baz) $foo."-1" = $lib.undef return($foo)'))
+            self.none(await core.callStorm('$foo = $lib.dict() $foo.bar = 10 $foo.bar = $lib.undef return($foo.bar)'))
+            self.eq(('woot',), await core.callStorm('''
+                $foo = (foo, bar, baz)
+                $foo.0 = $lib.undef
+                $foo.0 = $lib.undef
+                $foo.0 = $lib.undef
+                // one extra to test the exc handler
+                $foo.0 = $lib.undef
+                $foo.append(hehe)
+                $foo.0 = woot
+                return($foo)
+            '''))
+            with self.raises(s_exc.NoSuchVar):
+                await core.callStorm('$foo = 10 $foo = $lib.undef return($foo)')
+
     async def test_storm_pkg_load(self):
         cont = s_common.guid()
         pkg = {