chore: Refactor site to improve testing (#2014)

It was difficult to develop this package due to the
embed build tag being mandatory on the tests. The logic
to test doesn't require any embedded files.

coderd/coderd.go

@@ -334,7 +334,7 @@ func New(options *Options) *API {
 			r.Get("/state", api.workspaceBuildState)
 		})
 	})
-	r.NotFound(site.DefaultHandler().ServeHTTP)
+	r.NotFound(site.Handler(site.FS()).ServeHTTP)
 
 	return api
 }

site/embed_slim.go

@@ -1,12 +0,0 @@
-//go:build !embed
-// +build !embed
-
-package site
-
-import (
-	"net/http"
-)
-
-func DefaultHandler() http.Handler {
-	return http.NotFoundHandler()
-}

site/site.go

@@ -1,11 +1,7 @@
-//go:build embed
-// +build embed
-
 package site
 
 import (
 	"bytes"
-	"embed"
 	"fmt"
 	"io"
 	"io/fs"
@@ -21,26 +17,6 @@ import (
 	"golang.org/x/xerrors"
 )
 
-// The `embed` package ignores recursively including directories
-// that prefix with `_`. Wildcarding nested is janky, but seems to
-// work quite well for edge-cases.
-//go:embed out
-//go:embed out/bin/*
-var site embed.FS
-
-func DefaultHandler() http.Handler {
-	// the out directory is where webpack builds are created. It is in the same
-	// directory as this file (package site).
-	siteFS, err := fs.Sub(site, "out")
-
-	if err != nil {
-		// This can't happen... Go would throw a compilation error.
-		panic(err)
-	}
-
-	return Handler(siteFS)
-}
-
 // Handler returns an HTTP handler for serving the static site.
 func Handler(fileSystem fs.FS) http.Handler {
 	// html files are handled by a text/template. Non-html files

site/site_embed.go

@@ -0,0 +1,24 @@
+//go:build embed
+// +build embed
+
+package site
+
+import (
+	"embed"
+	"io/fs"
+)
+
+//go:embed out
+//go:embed out/bin/*
+var site embed.FS
+
+func FS() fs.FS {
+	// the out directory is where webpack builds are created. It is in the same
+	// directory as this file (package site).
+	out, err := fs.Sub(site, "out")
+	if err != nil {
+		// This can't happen... Go would throw a compilation error.
+		panic(err)
+	}
+	return out
+}

site/site_slim.go

@@ -0,0 +1,15 @@
+//go:build !embed
+// +build !embed
+
+package site
+
+import (
+	"embed"
+	"io/fs"
+)
+
+var slim embed.FS
+
+func FS() fs.FS {
+	return slim
+}

site/site_test.go

@@ -1,6 +1,3 @@
-//go:build embed
-// +build embed
-
 package site_test
 
 import (