Fix refreshing (and give a warning if refreshing gives the same result)

go.mod

@@ -3,7 +3,7 @@ module gdrive-filereplacer
 go 1.16
 
 require (
-	golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4 // indirect
-	golang.org/x/oauth2 v0.0.0-20210402161424-2e8d93401602 // indirect
-	google.golang.org/api v0.43.0 // indirect
+	golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4
+	golang.org/x/oauth2 v0.0.0-20210402161424-2e8d93401602
+	google.golang.org/api v0.43.0
 )

go.sum

@@ -97,6 +97,7 @@ github.com/google/go-cmp v0.5.1/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
 github.com/google/martian/v3 v3.0.0/go.mod h1:y5Zk1BBys9G+gd6Jrk0W3cC1+ELVxBWuIGO+w/tUAp0=
@@ -339,6 +340,7 @@ golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
 google.golang.org/api v0.7.0/go.mod h1:WtwebWUNSVBH/HAw79HIFXZNqEvBhG+Ra+ax0hx3E3M=

main.go

@@ -50,7 +50,7 @@ func (c *TokenCache) Token() (*oauth2.Token, error) {
 		log.Printf("Could not get token from cache: %v", err)
 	} else if !tok.Valid() {
 		log.Print("Cached token is invalid, refreshing...")
-		tok, err = c.CachedToken()
+		tok, err = c.RefreshToken(tok)
 		if err != nil {
 			log.Printf("Cached token failed to refresh: %v", err)
 		}
@@ -102,6 +102,9 @@ func (c *TokenCache) RefreshToken(token *oauth2.Token) (*oauth2.Token, error) {
 	if err != nil {
 		return nil, err
 	}
+	if token.AccessToken == newToken.AccessToken {
+		return nil, fmt.Errorf("refreshed token is the same as the original token")
+	}
 	return newToken, nil
 }