chore: add Go template dependency sync command (#4)

Add a command for keeping the embedded Go template dependency files
in sync with the generated Go example.

The command copies examples/simple-go/go.mod and go.sum back to the
corresponding template files and supports --check for CI drift detection.

Refs hatchet-dev/hatchet#4107.

Author: BloggerBust

.github/workflows/validate.yml

@@ -16,6 +16,9 @@ jobs:
         with:
           go-version-file: go.mod
 
+      - name: Go template dependencies are in sync
+        run: go run ./cmd/sync-go-template-deps --check
+
       - name: Generated examples are up to date
         run: go run ./cmd/generate-examples --check
 

cmd/sync-go-template-deps/main.go

@@ -0,0 +1,96 @@
+// Command sync-go-template-deps keeps the embedded Go template dependency files
+// in sync with the generated Go example.
+//
+// The Go template cannot hold a real go.mod, since it sits under the embedded
+// template tree, so it uses go.mod.embed and go.sum. This command keeps those
+// identical to examples/simple-go/go.mod and go.sum. It does not parse versions
+// and does not run go commands.
+//
+// Usage:
+//
+//	go run ./cmd/sync-go-template-deps
+//	go run ./cmd/sync-go-template-deps --check
+//
+// Run it from the repository root. Paths are relative to the working directory.
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+)
+
+type syncPair struct {
+	src string
+	dst string
+}
+
+var pairs = []syncPair{
+	{src: "examples/simple-go/go.mod", dst: "templates/go/go.mod.embed"},
+	{src: "examples/simple-go/go.sum", dst: "templates/go/go.sum"},
+}
+
+func main() {
+	check := flag.Bool("check", false, "verify the template files match the generated Go example instead of writing them")
+	flag.Parse()
+
+	if err := run(*check); err != nil {
+		fmt.Fprintln(os.Stderr, "sync-go-template-deps:", err)
+		os.Exit(1)
+	}
+}
+
+func run(check bool) error {
+	if check {
+		return runCheck()
+	}
+	return runSync()
+}
+
+// runSync writes each example file onto its template counterpart, preserving
+// the destination's existing file mode.
+func runSync() error {
+	for _, p := range pairs {
+		content, err := os.ReadFile(p.src)
+		if err != nil {
+			return fmt.Errorf("reading %s: %w", p.src, err)
+		}
+
+		mode := os.FileMode(0644)
+		if info, err := os.Stat(p.dst); err == nil {
+			mode = info.Mode().Perm()
+		}
+
+		if err := os.WriteFile(p.dst, content, mode); err != nil {
+			return fmt.Errorf("writing %s: %w", p.dst, err)
+		}
+	}
+	return nil
+}
+
+// runCheck reports any template file that does not match its example
+// counterpart byte-for-byte, leaving the working tree untouched.
+func runCheck() error {
+	var stale []string
+	for _, p := range pairs {
+		srcContent, err := os.ReadFile(p.src)
+		if err != nil {
+			return fmt.Errorf("reading %s: %w", p.src, err)
+		}
+		dstContent, err := os.ReadFile(p.dst)
+		if err != nil {
+			return fmt.Errorf("reading %s: %w", p.dst, err)
+		}
+		if !bytes.Equal(srcContent, dstContent) {
+			stale = append(stale, fmt.Sprintf("%s is out of sync with %s", p.dst, p.src))
+		}
+	}
+
+	if len(stale) > 0 {
+		return fmt.Errorf("Go template dependency files are out of sync:\n  %s\nrun `go run ./cmd/sync-go-template-deps` to update",
+			strings.Join(stale, "\n  "))
+	}
+	return nil
+}