Fixed nil pointer exception on some rare case with multiple libs selection

arduino/libraries/librarieslist.go

@@ -61,6 +61,14 @@ func (list *List) SortByArchitecturePriority(arch string) {
 	})
 }
 
+// SortByName sorts the libraries by name
+func (list *List) SortByName() {
+	sort.Slice(*list, func(i, j int) bool {
+		a, b := (*list)[i], (*list)[j]
+		return a.Name < b.Name
+	})
+}
+
 /*
 // HasHigherPriority returns true if library x has higher priority compared to library
 // y for the given header and architecture.

arduino/libraries/librariesresolver/cpp.go

@@ -105,11 +105,14 @@ func (resolver *Cpp) ResolveFor(header, architecture string) *libraries.Library
 
 	// If more than one library qualifies use the "closestmatch" algorithm to
 	// find the best matching one (instead of choosing it randomly)
-	winner := findLibraryWithNameBestDistance(header, found)
-	if winner != nil {
-		logrus.WithField("lib", winner.Name).Info("  library with the best mathing name")
+	if best := findLibraryWithNameBestDistance(header, found); best != nil {
+		logrus.WithField("lib", best.Name).Info("  library with the best matching name")
+		return best
 	}
-	return winner
+
+	found.SortByName()
+	logrus.WithField("lib", found[0].Name).Info("  first library in alphabetic order")
+	return found[0]
 }
 
 func simplify(name string) string {

arduino/libraries/librariesresolver/cpp_test.go

@@ -32,6 +32,18 @@ var l5 = &libraries.Library{Name: "Yet Another Calculus Lib Improved", Location:
 var l6 = &libraries.Library{Name: "Calculus Unified Lib", Location: libraries.Sketchbook}
 var l7 = &libraries.Library{Name: "AnotherLib", Location: libraries.Sketchbook}
 
+func TestClosestMatchWithTotallyDifferentNames(t *testing.T) {
+	libraryList := libraries.List{}
+	libraryList.Add(l5)
+	libraryList.Add(l6)
+	libraryList.Add(l7)
+	resolver := NewCppResolver()
+	resolver.headers["XYZ.h"] = libraryList
+	res := resolver.ResolveFor("XYZ.h", "xyz")
+	require.NotNil(t, res)
+	require.Equal(t, l7, res, "selected library")
+}
+
 func TestCppHeaderPriority(t *testing.T) {
 	r1 := computePriority(l1, "calculus_lib.h", "avr")
 	r2 := computePriority(l2, "calculus_lib.h", "avr")

go.mod

@@ -43,7 +43,6 @@ require (
 	go.bug.st/serial.v1 v0.0.0-20180827123349-5f7892a7bb45
 	golang.org/x/net v0.0.0-20190311183353-d8887717615a
 	golang.org/x/text v0.3.0
-	google.golang.org/appengine v1.4.0 // indirect
 	google.golang.org/genproto v0.0.0-20190327125643-d831d65fe17d // indirect
 	google.golang.org/grpc v1.21.1
 	gopkg.in/mgo.v2 v2.0.0-20180705113604-9856a29383ce // indirect