fix: handle Bazel load statements in extension-check

tools/extension-check/README.md

@@ -16,12 +16,6 @@ go run tools/extension-check/main.go \
 Envoy source code can be found at `~/Codes/istio.io/envoy`.
 Proxy source code can be found at `~/Codes/istio.io/proxy`.
 
-First you need delete the first line of proxy extensions build config file, which is `load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")`.
-
-```bash
-sed -i '1d' ~/Codes/istio.io/proxy/bazel/extension_config/extensions_build_config.bzl
-```
-
 Then you can run the following command to check all core extensions are enabled in proxy.
 
 ```bash

tools/extension-check/main.go

@@ -35,13 +35,13 @@ func main() {
 	flag.Parse()
 	envoyCoreExtensions, err := extensions(*envoyExtensionsBuildConfig, "EXTENSIONS")
 	if err != nil {
-		fmt.Printf("error: %v", err)
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
 
 	proxyExtensions, err := extensions(*proxyExtensionsBuildConfig, "ENVOY_EXTENSIONS")
 	if err != nil {
-		fmt.Printf("error: %v", err)
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
 
@@ -79,13 +79,18 @@ func main() {
 // The file is expected to be a starlark file that defines a global variable.
 // Depends on go.starlark.net/starlark.
 func extensions(filename, key string) (map[string]string, error) {
+	src, err := os.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+
 	thread := &starlark.Thread{
 		Name:  "extensions",
 		Print: func(_ *starlark.Thread, msg string) { fmt.Println(msg) },
 	}
-	globals, err := starlark.ExecFile(thread, filename, nil, nil)
+	globals, err := starlark.ExecFile(thread, filename, stripLoadStatements(string(src)), nil)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	if v, ok := globals[key]; ok {
@@ -100,3 +105,33 @@ func extensions(filename, key string) (map[string]string, error) {
 
 	return nil, errors.New("no extensions found")
 }
+
+// stripLoadStatements removes Bazel load() statements so build config files can
+// be evaluated without resolving external repositories.
+func stripLoadStatements(src string) string {
+	lines := strings.Split(src, "\n")
+	filtered := make([]string, 0, len(lines))
+	skippingLoad := false
+	parenDepth := 0
+
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if !skippingLoad && strings.HasPrefix(trimmed, "load(") {
+			skippingLoad = true
+		}
+
+		if skippingLoad {
+			parenDepth += strings.Count(line, "(")
+			parenDepth -= strings.Count(line, ")")
+			if parenDepth <= 0 {
+				skippingLoad = false
+				parenDepth = 0
+			}
+			continue
+		}
+
+		filtered = append(filtered, line)
+	}
+
+	return strings.Join(filtered, "\n")
+}

tools/extension-check/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestExtensionsIgnoresLoadStatements(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	path := filepath.Join(dir, "extensions.bzl")
+	content := `load(
+    "@bazel_skylib//lib:dicts.bzl",
+    "dicts",
+)
+
+EXTENSIONS = {"envoy.filters.http.router": "//source/extensions/filters/http/router:config"}
+`
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := extensions(path, "EXTENSIONS")
+	if err != nil {
+		t.Fatalf("extensions() error = %v", err)
+	}
+
+	if got["envoy.filters.http.router"] != "//source/extensions/filters/http/router:config" {
+		t.Fatalf("extensions() returned unexpected map: %#v", got)
+	}
+}
+
+func TestExtensionsReturnsErrorForMissingFile(t *testing.T) {
+	t.Parallel()
+
+	if _, err := extensions(filepath.Join(t.TempDir(), "missing.bzl"), "EXTENSIONS"); err == nil {
+		t.Fatal("extensions() error = nil, want missing file error")
+	}
+}