Add remote version check

cmd/version.go

@@ -1,9 +1,13 @@
 package cmd
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"log"
 
+	"github.com/google/go-github/v35/github"
+	"github.com/hashicorp/go-version"
 	"github.com/spf13/afero"
 	"github.com/terraform-linters/tflint/plugin"
 	"github.com/terraform-linters/tflint/tflint"
@@ -12,6 +16,8 @@ import (
 func (cli *CLI) printVersion(opts Options) int {
 	fmt.Fprintf(cli.outStream, "TFLint version %s\n", tflint.Version)
 
+	cli.printLatestReleaseVersion()
+
 	workingDirs, err := findWorkingDirs(opts)
 	if err != nil {
 		cli.formatter.Print(tflint.Issues{}, fmt.Errorf("Failed to find workspaces; %w", err), map[string][]byte{})
@@ -81,3 +87,35 @@ func getPluginVersions(opts Options) []string {
 
 	return versions
 }
+
+// Checks GitHub releases and prints new version, if current version is outdated.
+// requires GitHub releases to follow semver.
+func (cli *CLI) printLatestReleaseVersion() {
+	latest, err := getLatestVersion()
+	if err != nil {
+		cli.formatter.Print(tflint.Issues{}, fmt.Errorf("Failed to check updates; %w", err), map[string][]byte{})
+	}
+	latestVersion, err := version.NewSemver(*latest.Name)
+	compare := tflint.Version.Compare(latestVersion)
+	if compare < 0 {
+		fmt.Fprintf(cli.outStream, "New version available: %s\n", *latest.HTMLURL)
+	}
+}
+
+func getLatestVersion() (*github.RepositoryRelease, error) {
+	ghClient := github.NewClient(nil)
+	releases, _, err := ghClient.Repositories.ListReleases(context.Background(),
+		"terraform-linters", "tflint", &github.ListOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	// GitHub sorts releases results. Select first non-prerelease version and return it.
+	for i := range releases {
+		release := releases[i]
+		if !*release.Prerelease {
+			return release, nil
+		}
+	}
+	return nil, errors.New("not found")
+}

go.mod

@@ -49,7 +49,7 @@ require (
 	github.com/bgentry/go-netrc v0.0.0-20140422174119-9fd32a8b3d3d // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
-	github.com/google/go-querystring v1.0.0 // indirect
+	github.com/google/go-querystring v1.1.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.2.0 // indirect
 	github.com/googleapis/gax-go/v2 v2.7.0 // indirect
 	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect

go.sum

@@ -304,8 +304,9 @@ github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-github/v35 v35.3.0 h1:fU+WBzuukn0VssbayTT+Zo3/ESKX9JYWjbZTLOTEyho=
 github.com/google/go-github/v35 v35.3.0/go.mod h1:yWB7uCcVWaUbUP74Aq3whuMySRMatyRmq5U9FTNlbio=
-github.com/google/go-querystring v1.0.0 h1:Xkwi/a1rcvNg1PPYe5vI8GbeBY/jrVuDX5ASuANWTrk=
 github.com/google/go-querystring v1.0.0/go.mod h1:odCYkC5MyYFN7vkCjXpyrEuKhc/BUO6wN/zVPAxq5ck=
+github.com/google/go-querystring v1.1.0 h1:AnCroh3fv4ZBgVIf1Iwtovgjaw/GiKJo8M8yD/fhyJ8=
+github.com/google/go-querystring v1.1.0/go.mod h1:Kcdr2DB4koayq7X8pmAG4sNG59So17icRSOU623lUBU=
 github.com/google/martian v2.1.0+incompatible h1:/CP5g8u/VJHijgedC/Legn3BAbAaWPgecwXBIDzw5no=
 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=