From 195d152785e421af50186c475e654572fd9c5453 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Tue, 28 Apr 2020 12:49:19 +0100
Subject: [PATCH] rc: add GetStructMissingOK

---
 fs/rc/params.go      | 10 ++++++++++
 fs/rc/params_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/fs/rc/params.go b/fs/rc/params.go
index 07855b16c..306786fda 100644
--- a/fs/rc/params.go
+++ b/fs/rc/params.go
@@ -202,3 +202,13 @@ func (p Params) GetStruct(key string, out interface{}) error {
 	}
 	return nil
 }
+
+// GetStructMissingOK works like GetStruct but doesn't return an error
+// if the key is missing
+func (p Params) GetStructMissingOK(key string, out interface{}) error {
+	_, ok := p[key]
+	if !ok {
+		return nil
+	}
+	return p.GetStruct(key, out)
+}
diff --git a/fs/rc/params_test.go b/fs/rc/params_test.go
index bbca1385a..4b7a25349 100644
--- a/fs/rc/params_test.go
+++ b/fs/rc/params_test.go
@@ -249,3 +249,32 @@ func TestParamsGetStruct(t *testing.T) {
 	assert.Equal(t, 4.2, out.Float)
 	assert.Equal(t, true, IsErrParamInvalid(e3), e3.Error())
 }
+
+func TestParamsGetStructMissingOK(t *testing.T) {
+	in := Params{
+		"struct": Params{
+			"String": "one",
+			"Float":  4.2,
+		},
+	}
+	var out struct {
+		String string
+		Float  float64
+	}
+	e1 := in.GetStructMissingOK("struct", &out)
+	assert.NoError(t, e1)
+	assert.Equal(t, "one", out.String)
+	assert.Equal(t, 4.2, out.Float)
+
+	e2 := in.GetStructMissingOK("notOK", &out)
+	assert.NoError(t, e2)
+	assert.Equal(t, "one", out.String)
+	assert.Equal(t, 4.2, out.Float)
+
+	in["struct"] = "string"
+	e3 := in.GetStructMissingOK("struct", &out)
+	assert.Error(t, e3)
+	assert.Equal(t, "one", out.String)
+	assert.Equal(t, 4.2, out.Float)
+	assert.Equal(t, true, IsErrParamInvalid(e3), e3.Error())
+}