Implement readonly tag for primary and attr

README.md

@@ -142,23 +142,34 @@ Tag value arguments are comma separated.  The first argument must be,
 `primary`, and the second must be the name that should appear in the
 `type`\* field for all data objects that represent this type of model.
 
+If the optional argument `readonly` is present the id will not be set when
+using `Unmarshal` methods.
+
 \* According the [JSON API](http://jsonapi.org) spec, the plural record
 types are shown in the examples, but not required.
 
 #### `attr`
 
 ```
-`jsonapi:"attr,<key name in attributes hash>,<optional: omitempty>"`
+`jsonapi:"attr,<key name in attributes hash>,<optional: omitempty>,<optional: readonly>"`
 ```
 
-These fields' values will end up in the `attributes`hash for a record.
-The first argument must be, `attr`, and the second should be the name
-for the key to display in the `attributes` hash for that record. The optional
-third argument is `omitempty` - if it is present the field will not be present
-in the `"attributes"` if the field's value is equivalent to the field types
-empty value (ie if the `count` field is of type `int`, `omitempty` will omit the
-field when `count` has a value of `0`). Lastly, the spec indicates that
-`attributes` key names should be dasherized for multiple word field names.
+These fields' values will end up in the `attributes`hash for a record.  The
+first argument must be, `attr`, and the second should be the name for the key to
+display in the `attributes` hash for that record.
+
+If the optional argument `omitempty` is present the field will not be present in
+the `"attributes"` if the field's value is equivalent to the field types empty
+value (ie if the `count` field is of type `int`, `omitempty` will omit the field
+when `count` has a value of `0`).
+
+If the optional argument `readonly` is present the field will not be set when
+using `Unmarshal` methods. This is useful for performing PATCH operations when
+you unmarshal into an existing model to update the fields but don't want to
+allow server set fields to be overwritten such as `created_at`.
+
+Lastly, the spec indicates that `attributes` key names should be dasherized for
+multiple word field names.
 
 #### `relation`
 

constants.go

@@ -8,6 +8,7 @@ const (
 	annotationAttribute = "attr"
 	annotationRelation  = "relation"
 	annotationOmitEmpty = "omitempty"
+	annotationReadOnly  = "readonly"
 	annotationISO8601   = "iso8601"
 	annotationSeperator = ","
 	annotationIgnore    = "-"

request.go

@@ -261,6 +261,14 @@ func handlePrimaryUnmarshal(data *Node, args []string, fieldType reflect.StructF
 		)
 	}
 
+	if len(args) > 2 {
+		for _, arg := range args[2:] {
+			if arg == annotationReadOnly {
+				return nil
+			}
+		}
+	}
+
 	// Deal with PTRS
 	var kind reflect.Kind
 	if fieldValue.Kind() == reflect.Ptr {
@@ -428,16 +436,21 @@ func handleAttributeUnmarshal(data *Node, args []string, fieldType reflect.Struc
 		return nil
 	}
 
-	var iso8601 bool
-
+	var iso8601, readOnly bool
 	if len(args) > 2 {
 		for _, arg := range args[2:] {
 			if arg == annotationISO8601 {
 				iso8601 = true
+			} else if arg == annotationReadOnly {
+				readOnly = true
 			}
 		}
 	}
 
+	if readOnly {
+		return nil
+	}
+
 	val := attributes[args[1]]
 
 	// continue if the attribute was not included in the request

request_test.go

@@ -794,6 +794,36 @@ func TestEmbededStructs_nilStructPtr(t *testing.T) {
 	}
 }
 
+func TestUnmarshalReadOnly(t *testing.T) {
+	type PatchBlog struct {
+		ID        int       `jsonapi:"primary,blogs,readonly"`
+		CreatedAt time.Time `jsonapi:"attr,created_at,omitempty,readonly"`
+		ViewCount int       `jsonapi:"attr,view_count,readonly,omitempty"`
+		Blog
+	}
+
+	now := time.Now()
+	blog := PatchBlog{
+		ID:        1,
+		CreatedAt: now,
+		ViewCount: 123,
+	}
+
+	if err := UnmarshalPayload(samplePayloadWithID(), &blog); err != nil {
+		t.Fatal(err)
+	}
+
+	if blog.ID != 1 {
+		t.Errorf("readonly id was set")
+	}
+	if blog.CreatedAt != now {
+		t.Errorf("readonly attr created_at was set")
+	}
+	if blog.ViewCount != 123 {
+		t.Errorf("readonly attr view_count was set")
+	}
+}
+
 func samplePayloadWithoutIncluded() map[string]interface{} {
 	return map[string]interface{}{
 		"data": map[string]interface{}{
@@ -910,6 +940,7 @@ func samplePayloadWithID() io.Reader {
 			Attributes: map[string]interface{}{
 				"title":      "New blog",
 				"view_count": 1000,
+				"created_at": time.Now().Add(1 * time.Hour).Unix(),
 			},
 		},
 	}