Fix golint warnings in the gql package. (#3639)

gql/math.go

@@ -54,6 +54,7 @@ func (s *mathTreeStack) peek() *MathTree {
 	return s.a[len(s.a)-1]
 }
 
+// MathTree represents math operations in tree form for evaluation.
 type MathTree struct {
 	Fn    string
 	Var   string

gql/mutation.go

@@ -28,7 +28,7 @@ import (
 )
 
 var (
-	ErrInvalidUID = errors.New("UID has to be greater than one")
+	errInvalidUID = errors.New("UID has to be greater than one")
 )
 
 // Mutation stores the strings corresponding to set and delete operations.
@@ -37,19 +37,21 @@ type Mutation struct {
 	Del []*api.NQuad
 }
 
-// Gets the uid corresponding
+// ParseUid parses the given string into an UID. This method returns with an error
+// if the string cannot be parsed or the parsed UID is zero.
 func ParseUid(xid string) (uint64, error) {
 	// If string represents a UID, convert to uint64 and return.
 	uid, err := strconv.ParseUint(xid, 0, 64)
 	if err != nil {
 		return 0, err
 	}
 	if uid == 0 {
-		return 0, ErrInvalidUID
+		return 0, errInvalidUID
 	}
 	return uid, nil
 }
 
+// NQuad is an alias for the NQuad type in the API protobuf library.
 type NQuad struct {
 	*api.NQuad
 }
@@ -97,7 +99,7 @@ func byteVal(nq NQuad) ([]byte, types.TypeID, error) {
 }
 
 func toUid(subject string, newToUid map[string]uint64) (uid uint64, err error) {
-	if id, err := ParseUid(subject); err == nil || err == ErrInvalidUID {
+	if id, err := ParseUid(subject); err == nil || err == errInvalidUID {
 		return id, err
 	}
 	// It's an xid
@@ -119,13 +121,16 @@ func (nq NQuad) createEdgePrototype(subjectUid uint64) *pb.DirectedEdge {
 	}
 }
 
+// CreateUidEdge returns a Directed edge connecting the given subject and object UIDs.
 func (nq NQuad) CreateUidEdge(subjectUid uint64, objectUid uint64) *pb.DirectedEdge {
 	out := nq.createEdgePrototype(subjectUid)
 	out.ValueId = objectUid
 	out.ValueType = pb.Posting_UID
 	return out
 }
 
+// CreateValueEdge returns a DirectedEdge with the given subject. The predicate, label,
+// language, and facet values are derived from the NQuad.
 func (nq NQuad) CreateValueEdge(subjectUid uint64) (*pb.DirectedEdge, error) {
 	var err error
 
@@ -136,6 +141,8 @@ func (nq NQuad) CreateValueEdge(subjectUid uint64) (*pb.DirectedEdge, error) {
 	return out, nil
 }
 
+// ToDeletePredEdge takes an NQuad of the form '* p *' and returns the equivalent
+// directed edge. Returns an error if the NQuad does not have the expected form.
 func (nq NQuad) ToDeletePredEdge() (*pb.DirectedEdge, error) {
 	if nq.Subject != x.Star && nq.ObjectValue.String() != x.Star {
 		return &emptyEdge, errors.Errorf("Subject and object both should be *. Got: %+v", nq)

gql/parser.go

@@ -84,11 +84,13 @@ type GraphQuery struct {
 	IsEmpty bool
 }
 
+// RecurseArgs stores the arguments needed to process the @recurse directive.
 type RecurseArgs struct {
 	Depth     uint64
 	AllowLoop bool
 }
 
+// GroupByAttr stores the arguments needed to process the @groupby directive.
 type GroupByAttr struct {
 	Attr  string
 	Alias string
@@ -101,15 +103,15 @@ type pair struct {
 	Val string
 }
 
-// Internal structure for doing dfs on fragments.
+// fragmentNode is an internal structure for doing dfs on fragments.
 type fragmentNode struct {
 	Name    string
 	Gq      *GraphQuery
 	Entered bool // Entered in dfs.
 	Exited  bool // Exited in dfs.
 }
 
-// Key is fragment names.
+// fragmentMap is used to associate fragment names to their corresponding fragmentNode.
 type fragmentMap map[string]*fragmentNode
 
 const (
@@ -119,6 +121,7 @@ const (
 	ListVar  = 3
 )
 
+// VarContext stores information about the vars needed to complete a query.
 type VarContext struct {
 	Name string
 	Typ  int //  1 for UID vars, 2 for value vars
@@ -142,6 +145,7 @@ type FilterTree struct {
 	Func  *Function
 }
 
+// Arg stores an argument to a function.
 type Arg struct {
 	Value        string
 	IsValueVar   bool // If argument is val(a)
@@ -194,10 +198,12 @@ var mathOpPrecedence = map[string]int{
 	"!=": 5,
 }
 
+// IsAggregator returns true if the function name is an aggregation function.
 func (f *Function) IsAggregator() bool {
 	return isAggregator(f.Name)
 }
 
+// IsPasswordVerifier returns true if the function name is "checkpwd".
 func (f *Function) IsPasswordVerifier() bool {
 	return f.Name == "checkpwd"
 }
@@ -267,6 +273,7 @@ func convertToVarMap(variables map[string]string) (vm varMap) {
 	return vm
 }
 
+// Request stores the query text and the variable mapping.
 type Request struct {
 	Str       string
 	Variables map[string]string
@@ -2496,12 +2503,12 @@ func isSortkey(k string) bool {
 	return k == "orderasc" || k == "orderdesc"
 }
 
-type Count int
+type countType int
 
 const (
-	notSeen      Count = iota // default value
-	seen                      // when we see count keyword
-	seenWithPred              // when we see a predicate within count.
+	notSeen      countType = iota // default value
+	seen                          // when we see count keyword
+	seenWithPred                  // when we see a predicate within count.
 )
 
 func validateEmptyBlockItem(it *lex.ItemIterator, val string) error {
@@ -2533,7 +2540,7 @@ func godeep(it *lex.ItemIterator, gq *GraphQuery) error {
 	if gq == nil {
 		return it.Errorf("Bad nesting of predicates or functions")
 	}
-	var count Count
+	var count countType
 	var alias, varName string
 	curp := gq // Used to track current node, for nesting.
 	for it.Next() {