check docs/checks.md is up-to-date in CI

Author: rhysd

.github/workflows/ci.yaml

@@ -91,14 +91,21 @@ jobs:
       - uses: actions/setup-go@v5
         with:
           go-version: '1.23'
-      - run: sudo apt-get install -y shellcheck
+      - name: Install dependencies
+        run: |
+          sudo apt-get install -y shellcheck
+          pip install pyflakes
+          shellcheck --version
+          pyflakes --version
       - name: Check Go sources are formatted
         run: |
           diffs="$(gofmt -d ./*.go ./cmd/actionlint/*.go ./scripts/*/*.go ./playground/*.go)"
           if [[ "$diffs" != "" ]]; then
             echo "$diffs" >&2
             exit 1
           fi
+      - name: Check `docs/checks.md` is up-to-date
+        run: go run ./scripts/update-checks-doc -check ./docs/checks.md
       - name: Install staticcheck
         run: |
           go install honnef.co/go/tools/cmd/staticcheck@latest

scripts/update-checks-doc/main.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/rhysd/actionlint"
 )
 
@@ -180,28 +181,43 @@ func update(in []byte) ([]byte, error) {
 }
 
 func Main(args []string) error {
-	if len(os.Args) < 2 {
-		return errors.New("usage: update-checks-doc FILE")
+	var path string
+	var check bool
+	switch len(args) {
+	case 2:
+		path = args[1]
+	case 3:
+		if args[1] != "-check" && args[1] != "--check" {
+			return errors.New("usage: update-checks-doc [-check] FILE")
+		}
+		path = args[2]
+		check = true
+	default:
+		return errors.New("usage: update-checks-doc [-check] FILE")
 	}
-	p := os.Args[1]
-	in, err := os.ReadFile(p)
+
+	in, err := os.ReadFile(path)
 	if err != nil {
 		return err
 	}
-	log.Printf("Read %d bytes from %q", len(in), p)
+	log.Printf("Read %d bytes from %q", len(in), path)
 
 	out, err := update(in)
 	if err != nil {
 		return err
 	}
 
 	if bytes.Equal(in, out) {
-		log.Printf("Do nothing because there is no update in %q", p)
+		log.Printf("Do nothing because there is no update in %q", path)
 		return nil
 	}
 
-	log.Printf("Generate the updated content (%d bytes) for %q", len(out), p)
-	if err := os.WriteFile(p, out, 0666); err != nil {
+	if check {
+		return errors.New("checks document has some update. run `go run ./scripts/update-checks-doc ./docs/checks.md` and commit the changes. the diff:\n\n" + cmp.Diff(in, out))
+	}
+
+	log.Printf("Generate the updated content (%d bytes) for %q", len(out), path)
+	if err := os.WriteFile(path, out, 0666); err != nil {
 		return err
 	}