engine: resources, lang: Set resource fields more accurately

There were some bugs about setting resource fields that were structs
with various fields. This makes things more strict and correct. Now we
check for duplicate field names earlier (duplicates due to identical
aliases) and we also don't try and set private fields, or incorrectly
set partial structs.

Most interestingly, this also cleans up all of the resources and ensures
that each one has nicer docs and a clear struct tag for fields that we
want to use in mcl. These are mandatory now, and if you're missing the
tag, then we will ignore the field.

engine/resources/test.go

@@ -55,7 +55,7 @@ type TestRes struct {
 	Uint32 uint32 `lang:"uint32" yaml:"uint32"`
 	Uint64 uint64 `lang:"uint64" yaml:"uint64"`
 
-	//Uintptr uintptr `yaml:"uintptr"`
+	//Uintptr uintptr `lang:"uintptr" yaml:"uintptr"`
 	Byte byte `lang:"byte" yaml:"byte"` // alias for uint8
 	Rune rune `lang:"rune" yaml:"rune"` // alias for int32, represents a Unicode code point
 
@@ -76,10 +76,11 @@ type TestRes struct {
 	SliceString []string          `lang:"slicestring" yaml:"slicestring"`
 	MapIntFloat map[int64]float64 `lang:"mapintfloat" yaml:"mapintfloat"`
 	MixedStruct struct {
-		somebool  bool
-		somestr   string
-		someint   int64
-		somefloat float64
+		SomeBool         bool    `lang:"somebool" yaml:"somebool"`
+		SomeStr          string  `lang:"somestr" yaml:"somestr"`
+		SomeInt          int64   `lang:"someint" yaml:"someint"`
+		SomeFloat        float64 `lang:"somefloat" yaml:"somefloat"`
+		somePrivatefield string
 	} `lang:"mixedstruct" yaml:"mixedstruct"`
 	Interface interface{} `lang:"interface" yaml:"interface"`
 
@@ -394,8 +395,8 @@ func (obj *TestRes) GroupCmp(r engine.GroupableRes) error {
 // TestSends is the struct of data which is sent after a successful Apply.
 type TestSends struct {
 	// Hello is some value being sent.
-	Hello  *string `lang:"hello"`
-	Answer int     `lang:"answer"` // some other value being sent
+	Hello  *string `lang:"hello" yaml:"hello"`
+	Answer int     `lang:"answer" yaml:"answer"` // some other value being sent
 }
 
 // Sends represents the default struct of values we can send using Send/Recv.