Add js web stuff to landing page + documentation

go/jsbundler/hmr_client_test.go

@@ -0,0 +1,32 @@
+//go:build dev
+
+package jsbundler
+
+import (
+	"strings"
+	"testing"
+
+	esbuild "github.com/evanw/esbuild/pkg/api"
+)
+
+// hmrClientJS is a hand-written JS blob served to the browser; a syntax slip in it
+// silently breaks every hot update, and the headless-browser smoke test is skipped
+// off Linux/macOS. Parse it as an ES module here so a bad edit fails at test time,
+// and assert the recompile-indicator hooks are wired.
+func TestHMRClientJSValid(t *testing.T) {
+	res := esbuild.Transform(hmrClientJS, 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("HMR client JS failed to parse:\n%s", strings.Join(msgs, "\n"))
+	}
+	for _, want := range []string{"createHotContext", "hmrBusyStart", "hmrBusyEnd", "recompiling",
+		"showErrorOverlay", "clearErrorOverlay", "errorEpoch"} {
+		if !strings.Contains(hmrClientJS, want) {
+			t.Errorf("HMR client missing %q", want)
+		}
+	}
+}