*: check that assets are up-to-date (#4731)

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

.circleci/config.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
     - checkout
     - run: make promu
-    - run: make check_license style unused staticcheck build
+    - run: make check_license style unused staticcheck build check_assets
     - store_artifacts:
         path: prometheus
         destination: /build/prometheus

.travis.yml

@@ -10,4 +10,4 @@ go:
 go_import_path: github.com/prometheus/prometheus
 
 script:
-- make check_license style unused test staticcheck
+- make check_license style unused test staticcheck check_assets

Makefile

@@ -29,3 +29,12 @@ DOCKER_IMAGE_NAME       ?= prometheus
 assets:
 	@echo ">> writing assets"
 	cd $(PREFIX)/web/ui && go generate
+	@$(GOFMT) -w ./web/ui
+
+.PHONY: check_assets
+check_assets: assets
+	@echo ">> checking that assets are up-to-date"
+	@if ! (cd $(PREFIX)/web/ui && git diff --exit-code); then \
+		echo "Run 'make assets' and commit the changes to fix the error."; \
+		exit 1; \
+	fi

pkg/modtimevfs/modtimevfs.go

@@ -0,0 +1,67 @@
+// Copyright 2018 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.
+
+// Package modtimevfs implements a virtual file system that returns a fixed
+// modification time for all files and directories.
+package modtimevfs
+
+import (
+	"net/http"
+	"os"
+	"time"
+)
+
+type timefs struct {
+	fs http.FileSystem
+	t  time.Time
+}
+
+// New returns a file system that returns constant modification time for all files.
+func New(fs http.FileSystem, t time.Time) http.FileSystem {
+	return &timefs{fs: fs, t: t}
+}
+
+type file struct {
+	http.File
+	os.FileInfo
+	t time.Time
+}
+
+func (t *timefs) Open(name string) (http.File, error) {
+	f, err := t.fs.Open(name)
+	if err != nil {
+		return f, err
+	}
+	defer func() {
+		if err != nil {
+			f.Close()
+		}
+	}()
+
+	fstat, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+
+	return &file{f, fstat, t.t}, nil
+}
+
+// Stat implements the http.File interface.
+func (f *file) Stat() (os.FileInfo, error) {
+	return f, nil
+}
+
+// ModTime implements the os.FileInfo interface.
+func (f *file) ModTime() time.Time {
+	return f.t
+}

web/ui/assets_generate.go

@@ -17,13 +17,17 @@ package main
 
 import (
 	"log"
+	"time"
 
-	"github.com/prometheus/prometheus/web/ui"
 	"github.com/shurcooL/vfsgen"
+
+	"github.com/prometheus/prometheus/pkg/modtimevfs"
+	"github.com/prometheus/prometheus/web/ui"
 )
 
 func main() {
-	err := vfsgen.Generate(ui.Assets, vfsgen.Options{
+	fs := modtimevfs.New(ui.Assets, time.Unix(1, 0))
+	err := vfsgen.Generate(fs, vfsgen.Options{
 		PackageName:  "ui",
 		BuildTags:    "!dev",
 		VariableName: "Assets",