feat: show templ CLI and go.mod version mismatch warning (#338)

cmd/templ/generatecmd/main.go

@@ -31,6 +31,8 @@ import (
 	"github.com/cenkalti/backoff/v4"
 	"github.com/cli/browser"
 	"github.com/fatih/color"
+	"golang.org/x/mod/modfile"
+	"golang.org/x/mod/semver"
 )
 
 type Arguments struct {
@@ -92,7 +94,7 @@ func runCmd(ctx context.Context, w io.Writer, args Arguments) (err error) {
 	}
 	var opts []generator.GenerateOpt
 	if args.IncludeVersion {
-		opts = append(opts, generator.WithVersion(templ.Version))
+		opts = append(opts, generator.WithVersion(templ.Version()))
 	}
 	if args.IncludeTimestamp {
 		opts = append(opts, generator.WithTimestamp(time.Now()))
@@ -176,6 +178,10 @@ func runCmd(ctx context.Context, w io.Writer, args Arguments) (err error) {
 				}()
 			}
 		}
+		if err = checkTemplVersion(args.Path); err != nil {
+			logWarning(w, "templ version check failed: %v\n", err)
+			err = nil
+		}
 		if firstRunComplete {
 			if changesFound > 0 {
 				bo.Reset()
@@ -400,3 +406,54 @@ func logWithDecoration(w io.Writer, decoration string, col color.Attribute, form
 	color.New(col).Fprintf(w, "(%s) ", decoration)
 	fmt.Fprintf(w, format, a...)
 }
+
+func checkTemplVersion(dir string) error {
+	// Walk up the directory tree, starting at dir, until we find a go.mod file.
+	// If it contains a go.mod file, parse it and find the templ version.
+	dir, err := filepath.Abs(dir)
+	if err != nil {
+		return fmt.Errorf("failed to get absolute path: %w", err)
+	}
+	for {
+		current := filepath.Join(dir, "go.mod")
+		_, err := os.Stat(current)
+		if err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("failed to stat go.mod file: %w", err)
+		}
+		if os.IsNotExist(err) {
+			// Move up.
+			prev := dir
+			dir = filepath.Dir(dir)
+			if dir == prev {
+				return fmt.Errorf("could not find go.mod file")
+			}
+			continue
+		}
+		// Found a go.mod file.
+		// Read it and find the templ version.
+		m, err := os.ReadFile(current)
+		if err != nil {
+			return fmt.Errorf("failed to read go.mod file: %w", err)
+		}
+		mf, err := modfile.Parse(current, m, nil)
+		if err != nil {
+			return fmt.Errorf("failed to parse go.mod file: %w", err)
+		}
+		if mf.Module.Mod.Path == "github.com/a-h/templ" {
+			// The go.mod file is for templ itself.
+			return nil
+		}
+		for _, r := range mf.Require {
+			if r.Mod.Path == "github.com/a-h/templ" {
+				cmp := semver.Compare(r.Mod.Version, templ.Version())
+				if cmp < 0 {
+					return fmt.Errorf("generator %v is newer than templ version %v found in go.mod file, consider running `go get github.com/a-h/templ`", templ.Version(), r.Mod.Version)
+				}
+				if cmp > 0 {
+					return fmt.Errorf("generator %v is older than templ version %v found in go.mod file, consider upgrading templ CLI", templ.Version(), r.Mod.Version)
+				}
+				return nil
+			}
+		}
+	}
+}

cmd/templ/main.go

@@ -51,10 +51,10 @@ func run(w io.Writer, args []string) (code int) {
 	case "lsp":
 		return lspCmd(w, args[2:])
 	case "version":
-		fmt.Fprintln(w, templ.Version)
+		fmt.Fprintln(w, templ.Version())
 		return 0
 	case "--version":
-		fmt.Fprintln(w, templ.Version)
+		fmt.Fprintln(w, templ.Version())
 		return 0
 	}
 	fmt.Fprint(w, usageText)

cmd/templ/main_test.go

@@ -36,13 +36,13 @@ func TestMain(t *testing.T) {
 		{
 			name:         `"templ version" prints version`,
 			args:         []string{"templ", "version"},
-			expected:     templ.Version + "\n",
+			expected:     templ.Version() + "\n",
 			expectedCode: 0,
 		},
 		{
 			name:         `"templ --version" prints version`,
 			args:         []string{"templ", "--version"},
-			expected:     templ.Version + "\n",
+			expected:     templ.Version() + "\n",
 			expectedCode: 0,
 		},
 		{

flake.nix

@@ -34,7 +34,7 @@
           name = "templ";
           src = gitignore.lib.gitignoreSource ./.;
           subPackages = [ "cmd/templ" ];
-          vendorHash = "sha256-skftApJDp52ZMFf4+jG0sNWK2jIXi3rDQP199suRgNw=";
+          vendorHash = "sha256-buJArvaaKGRg3yS7BdcVY0ydyi4zah57ABeo+CHkZQU=";
           CGO_ENABLED = 0;
           flags = [
             "-trimpath"
@@ -82,4 +82,5 @@
         templ-docs = self.packages.${final.stdenv.system}.templ-docs;
       };
     };
-}
+}
+

version.go

@@ -3,4 +3,8 @@ package templ
 import _ "embed"
 
 //go:embed .version
-var Version string
+var version string
+
+func Version() string {
+	return "v" + version
+}