build: fix check_generate not printing changed files (#33299)

Fixes an issue where HashFolder skipped the root directory upon hitting
the first file in the excludes list. This happened because the walk function
returned SkipDir even for regular files.

Author: wit765

build/ci.go

@@ -343,7 +343,7 @@ func buildFlags(env build.Environment, staticLinking bool, buildTags []string) (
 		}
 		ld = append(ld, "-extldflags", "'"+strings.Join(extld, " ")+"'")
 	}
-    // TODO(gballet): revisit after the input api has been defined
+	// TODO(gballet): revisit after the input api has been defined
 	if runtime.GOARCH == "wasm" {
 		ld = append(ld, "-gcflags=all=-d=softfloat")
 	}
@@ -462,9 +462,14 @@ func doCheckGenerate() {
 	)
 	pathList := []string{filepath.Join(protocPath, "bin"), protocGenGoPath, os.Getenv("PATH")}
 
+	excludes := []string{"tests/testdata", "build/cache", ".git"}
+	for i := range excludes {
+		excludes[i] = filepath.FromSlash(excludes[i])
+	}
+
 	for _, mod := range goModules {
 		// Compute the origin hashes of all the files
-		hashes, err := build.HashFolder(mod, []string{"tests/testdata", "build/cache", ".git"})
+		hashes, err := build.HashFolder(mod, excludes)
 		if err != nil {
 			log.Fatal("Error computing hashes", "err", err)
 		}
@@ -474,7 +479,7 @@ func doCheckGenerate() {
 		c.Dir = mod
 		build.MustRun(c)
 		// Check if generate file hashes have changed
-		generated, err := build.HashFolder(mod, []string{"tests/testdata", "build/cache", ".git"})
+		generated, err := build.HashFolder(mod, excludes)
 		if err != nil {
 			log.Fatalf("Error re-computing hashes: %v", err)
 		}

internal/build/file.go

@@ -21,20 +21,21 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"sort"
-	"strings"
+	"slices"
 )
 
 // HashFolder iterates all files under the given directory, computing the hash
 // of each.
-func HashFolder(folder string, exlude []string) (map[string][32]byte, error) {
+func HashFolder(folder string, excludes []string) (map[string][32]byte, error) {
 	res := make(map[string][32]byte)
 	err := filepath.WalkDir(folder, func(path string, d os.DirEntry, _ error) error {
 		// Skip anything that's exluded or not a regular file
-		for _, skip := range exlude {
-			if strings.HasPrefix(path, filepath.FromSlash(skip)) {
+		// Skip anything that's excluded or not a regular file
+		if slices.Contains(excludes, path) {
+			if d.IsDir() {
 				return filepath.SkipDir
 			}
+			return nil
 		}
 		if !d.Type().IsRegular() {
 			return nil
@@ -71,6 +72,6 @@ func DiffHashes(a map[string][32]byte, b map[string][32]byte) []string {
 			updates = append(updates, file)
 		}
 	}
-	sort.Strings(updates)
+	slices.Sort(updates)
 	return updates
 }