From 19932b77ccf3707f76733dc16fad715a03db7663 Mon Sep 17 00:00:00 2001
From: Denys Smirnov <denis.smirnov.91@gmail.com>
Date: Sat, 14 Apr 2018 18:06:00 +0200
Subject: [PATCH] gizmo: expose SaveOptional; resolves #702

---
 docs/GizmoAPI.md          | 10 ++++++++++
 query/gizmo/gizmo_test.go |  8 ++++++++
 query/gizmo/traversals.go | 30 ++++++++++++++++++++++++------
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/docs/GizmoAPI.md b/docs/GizmoAPI.md
index 3fe878804..70c95cf24 100644
--- a/docs/GizmoAPI.md
+++ b/docs/GizmoAPI.md
@@ -513,6 +513,16 @@ g.V("<bob>").SaveInPredicates("pred").All()
 ```
 
 
+### `path.SaveOpt(*)`
+
+SaveOpt is the same as Save, but returns empty tags if predicate does not exists.
+
+
+### `path.SaveOptR(*)`
+
+SaveOptR is the same as SaveOpt, but tags values via reverse predicate.
+
+
 ### `path.SaveOutPredicates(tag)`
 
 SaveOutPredicates tags the list of predicates that are pointing out from a node.
diff --git a/query/gizmo/gizmo_test.go b/query/gizmo/gizmo_test.go
index b087e592b..d60041cba 100644
--- a/query/gizmo/gizmo_test.go
+++ b/query/gizmo/gizmo_test.go
@@ -381,6 +381,14 @@ var testQueries = []struct {
 		tag:    "somecool",
 		expect: []string{"cool_person", "cool_person", "cool_person", "smart_person", "smart_person"},
 	},
+	{
+		message: "show a simple save optional",
+		query: `
+			g.V("<bob>","<charlie>").Out("<follows>").SaveOpt("<status>", "somecool").All()
+		`,
+		tag:    "somecool",
+		expect: []string{"cool_person", "cool_person"},
+	},
 	{
 		message: "show a simple saveR",
 		query: `
diff --git a/query/gizmo/traversals.go b/query/gizmo/traversals.go
index 4fe96352a..b487d870a 100644
--- a/query/gizmo/traversals.go
+++ b/query/gizmo/traversals.go
@@ -437,7 +437,7 @@ func (p *pathObject) has(call goja.FunctionCall, rev bool) goja.Value {
 	}
 	return p.newVal(np)
 }
-func (p *pathObject) save(call goja.FunctionCall, rev bool) goja.Value {
+func (p *pathObject) save(call goja.FunctionCall, rev, opt bool) goja.Value {
 	args := exportArgs(call.Arguments)
 	if len(args) > 2 || len(args) == 0 {
 		return throwErr(p.s.vm, errArgCount{Got: len(args)})
@@ -461,10 +461,18 @@ func (p *pathObject) save(call goja.FunctionCall, rev bool) goja.Value {
 		}
 	}
 	np := p.clonePath()
-	if rev {
-		np = np.SaveReverse(via, tag)
+	if opt {
+		if rev {
+			np = np.SaveOptionalReverse(via, tag)
+		} else {
+			np = np.SaveOptional(via, tag)
+		}
 	} else {
-		np = np.Save(via, tag)
+		if rev {
+			np = np.SaveReverse(via, tag)
+		} else {
+			np = np.Save(via, tag)
+		}
 	}
 	return p.newVal(np)
 }
@@ -486,12 +494,22 @@ func (p *pathObject) save(call goja.FunctionCall, rev bool) goja.Value {
 //	//   {"id" : "<dani>", "target": "<greg>" }
 //	g.V("<dani>", "<bob>").Save("<follows>", "target").All()
 func (p *pathObject) Save(call goja.FunctionCall) goja.Value {
-	return p.save(call, false)
+	return p.save(call, false, false)
 }
 
 // SaveR is the same as Save, but tags values via reverse predicate.
 func (p *pathObject) SaveR(call goja.FunctionCall) goja.Value {
-	return p.save(call, true)
+	return p.save(call, true, false)
+}
+
+// SaveOpt is the same as Save, but returns empty tags if predicate does not exists.
+func (p *pathObject) SaveOpt(call goja.FunctionCall) goja.Value {
+	return p.save(call, false, true)
+}
+
+// SaveOptR is the same as SaveOpt, but tags values via reverse predicate.
+func (p *pathObject) SaveOptR(call goja.FunctionCall) goja.Value {
+	return p.save(call, true, true)
 }
 
 // Except removes all paths which match query from current path.