Merge Development (globalsign#111)

* Brings in a patch on having flusher not suppress errors. (globalsign#81)

go-mgo#360

* Fallback to JSON tags when BSON tag isn't present (globalsign#91)

* Fallback to JSON tags when BSON tag isn't present


Cleanup.

* Add test to demonstrate tagging fallback.

- Test coverage for tagging test.

* socket: only send client metadata once per socket

Periodic cluster synchronisation calls isMaster() which currently resends the
"client" metadata every call - the spec specifies:

	isMaster commands issued after the initial connection handshake MUST NOT
	contain handshake arguments

	https://github.com/mongodb/specifications/blob/master/source/mongodb-handshake/handshake.rst#connection-handshake

This hotfix prevents subsequent isMaster calls from sending the client metadata
again - fixes globalsign#101 and fixes globalsign#103.

Thanks to @changwoo-nam @qhenkart @canthefason @jyoon17 for spotting the initial
issue, opening tickets, and having the problem debugged with a PoC fix before I
even woke up.

* Cluster abended test 254 (globalsign#100)

* Add a test that mongo Server gets their abended reset as necessary.

See https://github.com/go-mgo/mgo/issues/254 and
https://github.com/go-mgo/mgo/pull/255/files

* Include the patch from Issue 255.

This brings in a test which fails without the patch, and passes with the
patch. Still to be tested, manual tcpkill of a socket.

* changeStream support (globalsign#97)

Add $changeStream support

* readme: credit @peterdeka and @steve-gray (globalsign#110)

.gitignore

@@ -0,0 +1,2 @@
+_harness
+

README.md

@@ -34,6 +34,8 @@ Further PR's (with tests) are welcome, but please maintain backwards compatibili
 * Minimise socket connection timeouts due to excessive locking ([details](https://github.com/globalsign/mgo/pull/52))
 * Natively support X509 client authentication ([details](https://github.com/globalsign/mgo/pull/55))
 * Gracefully recover from a temporarily unreachable server ([details](https://github.com/globalsign/mgo/pull/69))
+* Use JSON tags when no explicit BSON are tags set ([details](https://github.com/globalsign/mgo/pull/91))
+* Support [$changeStream](https://docs.mongodb.com/manual/changeStreams/) tailing on 3.6+ ([details](https://github.com/globalsign/mgo/pull/97))
 
 ---
 
@@ -51,6 +53,8 @@ Further PR's (with tests) are welcome, but please maintain backwards compatibili
 * @jameinel
 * @gazoon
 * @mapete94
+* @peterdeka
 * @Reenjii
 * @smoya
+* @steve-gray
 * @wgallagher

bson/bson.go

@@ -698,9 +698,21 @@ func getStructInfo(st reflect.Type) (*structInfo, error) {
 		info := fieldInfo{Num: i}
 
 		tag := field.Tag.Get("bson")
-		if tag == "" && strings.Index(string(field.Tag), ":") < 0 {
-			tag = string(field.Tag)
+
+		// Fall-back to JSON struct tag, if feature flag is set.
+		if tag == "" && useJSONTagFallback {
+			tag = field.Tag.Get("json")
 		}
+
+		// If there's no bson/json tag available.
+		if tag == "" {
+			// If there's no tag, and also no tag: value splits (i.e. no colon)
+			// then assume the entire tag is the value
+			if strings.Index(string(field.Tag), ":") < 0 {
+				tag = string(field.Tag)
+			}
+		}
+
 		if tag == "-" {
 			continue
 		}

bson/compatability_test.go

@@ -0,0 +1,54 @@
+package bson_test
+
+import (
+	"github.com/globalsign/mgo/bson"
+	. "gopkg.in/check.v1"
+)
+
+type mixedTagging struct {
+	First  string
+	Second string `bson:"second_field"`
+	Third  string `json:"third_field"`
+	Fourth string `bson:"fourth_field" json:"alternate"`
+}
+
+// TestTaggingFallback checks that tagging fallback can be used/works as expected.
+func (s *S) TestTaggingFallback(c *C) {
+	initial := &mixedTagging{
+		First:  "One",
+		Second: "Two",
+		Third:  "Three",
+		Fourth: "Four",
+	}
+
+	// Take only testing.T, leave only footprints.
+	initialState := bson.JSONTagFallbackState()
+	defer bson.SetJSONTagFallback(initialState)
+
+	// Marshal with the new mode applied.
+	bson.SetJSONTagFallback(true)
+	bsonState, errBSON := bson.Marshal(initial)
+	c.Assert(errBSON, IsNil)
+
+	// Unmarshal into a generic map so that we can pick up the actual field names
+	// selected.
+	target := make(map[string]string)
+	errUnmarshal := bson.Unmarshal(bsonState, target)
+	c.Assert(errUnmarshal, IsNil)
+
+	// No tag, so standard naming
+	_, firstExists := target["first"]
+	c.Assert(firstExists, Equals, true)
+
+	// Just a BSON tag
+	_, secondExists := target["second_field"]
+	c.Assert(secondExists, Equals, true)
+
+	// Just a JSON tag
+	_, thirdExists := target["third_field"]
+	c.Assert(thirdExists, Equals, true)
+
+	// Should marshal 4th as fourth_field (since we have both tags)
+	_, fourthExists := target["fourth_field"]
+	c.Assert(fourthExists, Equals, true)
+}

bson/compatibility.go

@@ -0,0 +1,16 @@
+package bson
+
+// Current state of the JSON tag fallback option. 
+var useJSONTagFallback = false
+
+// SetJSONTagFallback enables or disables the JSON-tag fallback for structure tagging. When this is enabled, structures
+// without BSON tags on a field will fall-back to using the JSON tag (if present).
+func SetJSONTagFallback(state bool) {
+	useJSONTagFallback = state
+}
+
+// JSONTagFallbackState returns the current status of the JSON tag fallback compatability option. See SetJSONTagFallback
+// for more information.
+func JSONTagFallbackState() bool {
+	return useJSONTagFallback
+}