Initial add backend stuff

bundler/hmr_error_test.go

@@ -0,0 +1,78 @@
+//go:build dev
+
+package bundler
+
+import (
+	"errors"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	esbuild "github.com/evanw/esbuild/pkg/api"
+)
+
+// errorModule must emit a valid ES module that imports the client's
+// showErrorOverlay and calls it with the error text + file, so a failed
+// transform pops the compile-error overlay instead of just logging.
+func TestErrorModuleShape(t *testing.T) {
+	src := errorModule("ui/Broken.tsx", errors.New("Unexpected \"}\" at line 3"))
+
+	for _, want := range []string{
+		`from "/@hmr/client"`,
+		"showErrorOverlay",
+		"__hmrShowError(",
+		"ui/Broken.tsx",
+		`Unexpected`,
+	} {
+		if !strings.Contains(src, want) {
+			t.Errorf("errorModule() missing %q:\n%s", want, src)
+		}
+	}
+
+	// It must parse as an ES module (the payload is embedded JSON-as-JS).
+	res := esbuild.Transform(src, esbuild.TransformOptions{
+		Loader: esbuild.LoaderJS, Format: esbuild.FormatESModule, LogLevel: esbuild.LogLevelSilent,
+	})
+	if len(res.Errors) > 0 {
+		msgs := esbuild.FormatMessages(res.Errors, esbuild.FormatMessagesOptions{})
+		t.Fatalf("errorModule() is not valid JS:\n%s\n--- source ---\n%s", strings.Join(msgs, "\n"), src)
+	}
+}
+
+// A source file that fails to compile must be served as the overlay stub (HTTP
+// 200, not a 500 that would tear the module graph), so the browser shows the
+// error and the next save can recover.
+func TestServeModuleCompileErrorServesOverlay(t *testing.T) {
+	root, err := filepath.Abs("../..")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Chdir(root)
+	frontendAbs, _ := filepath.Abs(frontendDir)
+
+	tmpSrc := evalSymlinks(t.TempDir())
+	// Deliberately broken JSX: an unclosed tag the compiler/esbuild must reject.
+	os.WriteFile(filepath.Join(tmpSrc, "Broken.tsx"),
+		[]byte("export default function Broken() {\n  return <div><span></div>;\n}\n"), 0o644)
+
+	eps, _ := loadVendorManifest(filepath.Join(frontendAbs, "vendor"))
+	d := &devServer{hub: newHub(), frontend: frontendAbs, srcRoot: tmpSrc,
+		vendor: filepath.Join(frontendAbs, "vendor"), graph: newModuleGraph(),
+		vendorCache: map[string][]byte{}, cssTrigger: make(chan struct{}, 1), vendorEntrypoints: eps}
+
+	req := httptest.NewRequest("GET", srcURLPrefix+"Broken.tsx", nil)
+	w := httptest.NewRecorder()
+	d.serveModule(w, req)
+
+	if w.Code != 200 {
+		t.Fatalf("broken module served status %d, want 200 (overlay stub)", w.Code)
+	}
+	body := w.Body.String()
+	for _, want := range []string{"showErrorOverlay", `from "/@hmr/client"`, "Broken.tsx"} {
+		if !strings.Contains(body, want) {
+			t.Errorf("overlay stub missing %q:\n%s", want, body)
+		}
+	}
+}