Embedded the frontend in the binary, and built it in the build script

`npm run sync` in web/ copies the build output (web/dist, from npm run build)
to internal/frontend/dist, which the binary embeds. Go can't embed from
outside the package's directory (web/ is also outside the Go module), hence
the copy. Only dist/.gitkeep is committed, so a fresh clone still compiles,
and a binary built without syncing first serves no frontend.

job-search serve serves server.frontend.dir if it is set, or else the
embedded build, or warns that there is no frontend. scripts/build.sh builds
and syncs the frontend before building, running npm ci first for a release
or when web/node_modules is missing.

internal/cli/serve/command.go

@@ -31,7 +31,9 @@ func NewCommand(opts *cli.Options) *cobra.Command {
 		Use:   "serve",
 		Short: "Serve the REST API, WebSocket and frontend, and fetch from sources",
 		Long: `Serve the REST API under /api, the WebSocket endpoint under /ws, and the
-frontend's files from server.frontend.dir under / if it is set.
+frontend under /: the files in server.frontend.dir if it is set, or else the
+build embedded in the binary (copied there by npm run sync in web/ before
+building), if there is one.
 
 It also runs a worker for every enabled source, as fetcher service does,
 saving what they fetch to database.file if it is set, and pushing an
@@ -196,9 +198,10 @@ set, the API serves the stored opportunities under /api/opportunities.`,
 }
 
 // serverOptions returns the server's options for conf: the access log, if
-// server.access_log is set, and the frontend's files, if server.frontend.dir
-// is (checked first). closeAccessLog closes the access log; call it once the
-// server has stopped.
+// server.access_log is set, and the frontend's files: those in
+// server.frontend.dir if it is set (checked first), or else the build
+// embedded in the binary, if there is one. closeAccessLog closes the access
+// log; call it once the server has stopped.
 func serverOptions(
 	conf *config.JSCServer,
 ) ([]server.Option, func() error, error) {
@@ -225,7 +228,15 @@ func serverOptions(
 			)
 		}
 		options = append(options, server.WithFrontend(files))
+		return options, closeAccessLog, nil
 	}
 
+	files := frontend.Embedded()
+	if files == nil {
+		slog.Warn("no frontend embedded and server.frontend.dir not set")
+		return options, closeAccessLog, nil
+	}
+	options = append(options, server.WithFrontend(files))
+
 	return options, closeAccessLog, nil
 }

internal/config/README.md

@@ -179,7 +179,7 @@ The `server` section is split into a number of sub-sections:
 
 | Key | Type | Default | Notes |
 |---|---|---|---|
-| `server.frontend.dir` | string | | Directory of the frontend's build output, holding `index.html`; empty: no frontend is served (there is no embedded build yet) |
+| `server.frontend.dir` | string | | Directory of the frontend's build output, holding `index.html`; empty: the build embedded in the binary (see `npm run sync` in `web/`), or no frontend if it has none |
 | `server.frontend.immutable_prefix` | string | | Where Vite emits content-hashed files, cached for a year; empty: `/assets/` |
 | `server.frontend.index_cache_control` | string | | `Cache-Control` of HTML and other files without a hash; empty: `no-cache` |
 

internal/config/conf_server_frontend.go

@@ -9,7 +9,7 @@ const JSCKServerFrontend string = "frontend"
 
 // JSCServerFrontend configures how the server serves the frontend. Dir is
 // the directory of the frontend's build output (holding index.html); empty
-// means no frontend is served, as there is no embedded build yet.
+// means the build embedded in the binary, or no frontend if it has none.
 // ImmutablePrefix is where Vite emits content-hashed files, cached for a
 // year; empty means "/assets/". IndexCacheControl is the Cache-Control of
 // HTML and other files without a hash; empty means "no-cache".

internal/frontend/embed.go

@@ -0,0 +1,24 @@
+package frontend
+
+import (
+	"embed"
+	"io/fs"
+)
+
+// dist holds the frontend's build output, copied from web/dist by `npm run
+// sync` in web/. Only dist/.gitkeep is committed (Go can't embed a missing
+// directory), so a binary built without syncing first has no frontend.
+//
+//go:embed all:dist
+var dist embed.FS
+
+// Embedded returns the frontend's build output embedded in the binary, or
+// nil if none was synced before it was built (there is no index.html).
+func Embedded() fs.FS {
+	files, err := fs.Sub(dist, "dist")
+	if err != nil || CheckFS(files) != nil {
+		return nil
+	}
+
+	return files
+}