grafana-agent: build and embed flow mode web ui

pkgs/servers/monitoring/grafana-agent/default.nix

@@ -1,11 +1,15 @@
 { lib
 , buildGoModule
 , fetchFromGitHub
+, fetchYarnDeps
+, fixup_yarn_lock
 , grafana-agent
 , nixosTests
+, nodejs
 , stdenv
 , systemd
 , testers
+, yarn
 }:
 
 buildGoModule rec {
@@ -22,6 +26,11 @@ buildGoModule rec {
   vendorHash = "sha256-MqUkGKOzx8Qo9xbD9GdUryVwKjpVUOXFo2x0/2uz8Uk=";
   proxyVendor = true; # darwin/linux hash mismatch
 
+  frontendYarnOfflineCache = fetchYarnDeps {
+    yarnLock = src + "/web/ui/yarn.lock";
+    hash = "sha256-xJEPubIDjlZQL70UGha1MHbeek6KFPaxZGb5IRgMlTA=";
+  };
+
   ldflags = let
     prefix = "github.com/grafana/agent/pkg/build";
   in [
@@ -34,7 +43,10 @@ buildGoModule rec {
     "-X ${prefix}.BuildDate=1980-01-01T00:00:00Z"
   ];
 
+  nativeBuildInputs = [ fixup_yarn_lock nodejs yarn ];
+
   tags = [
+    "builtinassets"
     "nonetwork"
     "nodocker"
     "promtail_journal_enabled"
@@ -43,8 +55,21 @@ buildGoModule rec {
   subPackages = [
     "cmd/grafana-agent"
     "cmd/grafana-agentctl"
+    "web/ui"
   ];
 
+  preBuild = ''
+    export HOME="$TMPDIR"
+
+    pushd web/ui
+    fixup_yarn_lock yarn.lock
+    yarn config --offline set yarn-offline-mirror $frontendYarnOfflineCache
+    yarn install --offline --frozen-lockfile --ignore-platform --ignore-scripts --no-progress --non-interactive
+    patchShebangs node_modules
+    yarn --offline run build
+    popd
+  '';
+
   # uses go-systemd, which uses libsystemd headers
   # https://github.com/coreos/go-systemd/issues/351
   env.NIX_CFLAGS_COMPILE = toString (lib.optionals stdenv.isLinux [ "-I${lib.getDev systemd}/include" ]);