ui/compress: Do not change git worktree (#10467)

This change makes sure that the git worktree is not changed while
compressing assets, making it better for local development.

To achieve this, the compression script keeps the un-compressed assets
and generates the go:embed directory when compressing the files.

A .gitignore file has been added to ignore generated files.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

Makefile

@@ -57,11 +57,6 @@ assets-compress:
 	@echo '>> compressing assets'
 	scripts/compress_assets.sh
 
-.PHONY: assets-decompress
-assets-decompress:
-	@echo '>> decompressing assets'
-	scripts/compress_assets.sh -d
-
 .PHONY: test
 # If we only want to only test go code we have to change the test target
 # which is called by all.
@@ -84,7 +79,7 @@ tarball: npm_licenses common-tarball
 docker: npm_licenses common-docker
 
 .PHONY: build
-build: assets assets-compress common-build assets-decompress
+build: assets assets-compress common-build
 
 .PHONY: bench_tsdb
 bench_tsdb: $(PROMU)
@@ -97,6 +92,3 @@ bench_tsdb: $(PROMU)
 	@$(GO) tool pprof --alloc_space -svg $(PROMTOOL) $(TSDB_BENCHMARK_OUTPUT_DIR)/mem.prof > $(TSDB_BENCHMARK_OUTPUT_DIR)/memprof.alloc.svg
 	@$(GO) tool pprof -svg $(PROMTOOL) $(TSDB_BENCHMARK_OUTPUT_DIR)/block.prof > $(TSDB_BENCHMARK_OUTPUT_DIR)/blockprof.svg
 	@$(GO) tool pprof -svg $(PROMTOOL) $(TSDB_BENCHMARK_OUTPUT_DIR)/mutex.prof > $(TSDB_BENCHMARK_OUTPUT_DIR)/mutexprof.svg
-
-.PHONY: clean
-clean: assets-decompress

scripts/compress_assets.sh

@@ -1,5 +1,11 @@
 #!/usr/bin/env bash
 #
-# [de]compress static assets
+# compress static assets
 
-find web/ui/static -type f -exec gzip "$@" {} \;
+set -euo pipefail
+
+cd web/ui
+cp embed.go.tmpl embed.go
+find static -type f -name '*.gz' -delete
+find static -type f -exec gzip -fk '{}' \; -print0 | xargs -0 -I % echo %.gz | xargs echo //go:embed >> embed.go
+echo var EmbedFS embed.FS >> embed.go

web/ui/.gitignore

@@ -0,0 +1,2 @@
+*.gz
+embed.go

web/ui/assets_embed.go

@@ -17,12 +17,9 @@
 package ui
 
 import (
-	"embed"
-	"github.com/prometheus/common/assets"
 	"net/http"
+
+	"github.com/prometheus/common/assets"
 )
 
-//go:embed static
-var EmbedFS embed.FS
-
 var Assets = http.FS(assets.New(EmbedFS))

web/ui/embed.go.tmpl

@@ -0,0 +1,20 @@
+// Copyright 2022 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build builtinassets
+// +build builtinassets
+
+package ui
+
+import "embed"
+