helper/schema: don't ask for input if provider default would not be nil

helper/schema/schema.go

@@ -72,6 +72,9 @@ type Schema struct {
 	// If Required is true above, then Default cannot be set. DefaultFunc
 	// can be set with Required. If the DefaultFunc returns nil, then there
 	// will no default and the user will be asked to fill it in.
+	//
+	// If either of these is set, then the user won't be asked for input
+	// for this key if the default is not nil.
 	Default     interface{}
 	DefaultFunc SchemaDefaultFunc
 
@@ -81,6 +84,8 @@ type Schema struct {
 	Description string
 
 	// InputDefault is the default value to use for when inputs are requested.
+	// This differs from Default in that if Default is set, no input is
+	// asked for. If Input is asked, this will be the default value offered.
 	InputDefault string
 
 	// The fields below relate to diffs.
@@ -308,6 +313,21 @@ func (m schemaMap) Input(
 			continue
 		}
 
+		// Skip if it has a default
+		if v.Default != nil {
+			continue
+		}
+		if f := v.DefaultFunc; f != nil {
+			value, err := f()
+			if err != nil {
+				return nil, fmt.Errorf(
+					"%s: error loading default: %s", k, err)
+			}
+			if value != nil {
+				continue
+			}
+		}
+
 		var value interface{}
 		var err error
 		switch v.Type {

helper/schema/schema_test.go

@@ -1419,6 +1419,66 @@ func TestSchemaMap_Input(t *testing.T) {
 
 			Err: false,
 		},
+
+		{
+			Schema: map[string]*Schema{
+				"availability_zone": &Schema{
+					Type:     TypeString,
+					Default:  "foo",
+					Optional: true,
+				},
+			},
+
+			Input: map[string]string{
+				"availability_zone": "bar",
+			},
+
+			Result: map[string]interface{}{},
+
+			Err: false,
+		},
+
+		{
+			Schema: map[string]*Schema{
+				"availability_zone": &Schema{
+					Type: TypeString,
+					DefaultFunc: func() (interface{}, error) {
+						return "foo", nil
+					},
+					Optional: true,
+				},
+			},
+
+			Input: map[string]string{
+				"availability_zone": "bar",
+			},
+
+			Result: map[string]interface{}{},
+
+			Err: false,
+		},
+
+		{
+			Schema: map[string]*Schema{
+				"availability_zone": &Schema{
+					Type: TypeString,
+					DefaultFunc: func() (interface{}, error) {
+						return nil, nil
+					},
+					Optional: true,
+				},
+			},
+
+			Input: map[string]string{
+				"availability_zone": "bar",
+			},
+
+			Result: map[string]interface{}{
+				"availability_zone": "bar",
+			},
+
+			Err: false,
+		},
 	}
 
 	for i, tc := range cases {