resources/images: Refactor golden image tests to locate them closer to the implementation

resources/images/imagetesting/testing.go

@@ -0,0 +1,215 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// 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 imagetesting
+
+import (
+	"image"
+	"image/gif"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"github.com/google/go-cmp/cmp"
+
+	"github.com/disintegration/gift"
+	"github.com/gohugoio/hugo/common/hashing"
+	"github.com/gohugoio/hugo/common/hugio"
+	"github.com/gohugoio/hugo/htesting"
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+var eq = qt.CmpEquals(
+	cmp.Comparer(func(p1, p2 os.FileInfo) bool {
+		return p1.Name() == p2.Name() && p1.Size() == p2.Size() && p1.IsDir() == p2.IsDir()
+	}),
+	cmp.Comparer(func(d1, d2 fs.DirEntry) bool {
+		p1, err1 := d1.Info()
+		p2, err2 := d2.Info()
+		if err1 != nil || err2 != nil {
+			return false
+		}
+		return p1.Name() == p2.Name() && p1.Size() == p2.Size() && p1.IsDir() == p2.IsDir()
+	}),
+)
+
+// GoldenImageTestOpts provides options for a golden image test.
+type GoldenImageTestOpts struct {
+	// The test.
+	T testing.TB
+
+	// Name of the test. Will be used as the base folder for generated images.
+	// Slashes allowed and encouraged.
+	Name string
+
+	// The test site's files in txttar format.
+	Files string
+
+	// Set to true to write golden files to disk.
+	WriteFiles bool
+
+	// Set to true to skip any assertions. Useful when adding new golden variants to a test.
+	DevMode bool
+}
+
+// To rebuild all Golden image tests, toggle WriteFiles=true and run:
+// GOARCH=amd64 go test -count 1 -timeout 30s -run "^TestImagesGolden" ./...
+// TODO(bep) see if we can do this via flags.
+var DefaultGoldenOpts = GoldenImageTestOpts{
+	WriteFiles: false,
+	DevMode:    false,
+}
+
+func RunGolden(opts GoldenImageTestOpts) *hugolib.IntegrationTestBuilder {
+	opts.T.Helper()
+
+	c := hugolib.Test(opts.T, opts.Files, hugolib.TestOptWithOSFs()) // hugolib.TestOptWithPrintAndKeepTempDir(true))
+	c.AssertFileContent("public/index.html", "Home.")
+
+	outputDir := filepath.Join(c.H.Conf.WorkingDir(), "public", "images")
+	goldenBaseDir := filepath.Join("testdata", "images_golden")
+	goldenDir := filepath.Join(goldenBaseDir, filepath.FromSlash(opts.Name))
+	if opts.WriteFiles {
+		c.Assert(htesting.IsRealCI(), qt.IsFalse)
+		c.Assert(os.MkdirAll(goldenBaseDir, 0o777), qt.IsNil)
+		c.Assert(os.RemoveAll(goldenDir), qt.IsNil)
+		c.Assert(hugio.CopyDir(hugofs.Os, outputDir, goldenDir, nil), qt.IsNil)
+		return c
+	}
+
+	if opts.DevMode {
+		c.Assert(htesting.IsRealCI(), qt.IsFalse)
+		return c
+	}
+
+	decodeAll := func(f *os.File) []image.Image {
+		c.Helper()
+
+		var images []image.Image
+
+		if strings.HasSuffix(f.Name(), ".gif") {
+			gif, err := gif.DecodeAll(f)
+			c.Assert(err, qt.IsNil, qt.Commentf(f.Name()))
+			images = make([]image.Image, len(gif.Image))
+			for i, img := range gif.Image {
+				images[i] = img
+			}
+		} else {
+			img, _, err := image.Decode(f)
+			c.Assert(err, qt.IsNil, qt.Commentf(f.Name()))
+			images = append(images, img)
+		}
+		return images
+	}
+
+	entries1, err := os.ReadDir(outputDir)
+	c.Assert(err, qt.IsNil)
+	entries2, err := os.ReadDir(goldenDir)
+	c.Assert(err, qt.IsNil)
+	c.Assert(len(entries1), qt.Equals, len(entries2))
+	for i, e1 := range entries1 {
+		c.Assert(filepath.Ext(e1.Name()), qt.Not(qt.Equals), "")
+		func() {
+			e2 := entries2[i]
+
+			f1, err := os.Open(filepath.Join(outputDir, e1.Name()))
+			c.Assert(err, qt.IsNil)
+			defer f1.Close()
+
+			f2, err := os.Open(filepath.Join(goldenDir, e2.Name()))
+			c.Assert(err, qt.IsNil)
+			defer f2.Close()
+
+			imgs2 := decodeAll(f2)
+			imgs1 := decodeAll(f1)
+			c.Assert(len(imgs1), qt.Equals, len(imgs2))
+
+			if !UsesFMA {
+				c.Assert(e1, eq, e2)
+				_, err = f1.Seek(0, 0)
+				c.Assert(err, qt.IsNil)
+				_, err = f2.Seek(0, 0)
+				c.Assert(err, qt.IsNil)
+
+				hash1, _, err := hashing.XXHashFromReader(f1)
+				c.Assert(err, qt.IsNil)
+				hash2, _, err := hashing.XXHashFromReader(f2)
+				c.Assert(err, qt.IsNil)
+
+				c.Assert(hash1, qt.Equals, hash2)
+			}
+
+			for i, img1 := range imgs1 {
+				img2 := imgs2[i]
+				nrgba1 := image.NewNRGBA(img1.Bounds())
+				gift.New().Draw(nrgba1, img1)
+				nrgba2 := image.NewNRGBA(img2.Bounds())
+				gift.New().Draw(nrgba2, img2)
+				c.Assert(goldenEqual(nrgba1, nrgba2), qt.Equals, true, qt.Commentf(e1.Name()))
+			}
+		}()
+	}
+	return c
+}
+
+// goldenEqual compares two NRGBA images.  It is used in golden tests only.
+// A small tolerance is allowed on architectures using "fused multiply and add"
+// (FMA) instruction to accommodate for floating-point rounding differences
+// with control golden images that were generated on amd64 architecture.
+// See https://golang.org/ref/spec#Floating_point_operators
+// and https://github.com/gohugoio/hugo/issues/6387 for more information.
+//
+// Based on https://github.com/disintegration/gift/blob/a999ff8d5226e5ab14b64a94fca07c4ac3f357cf/gift_test.go#L598-L625
+// Copyright (c) 2014-2019 Grigory Dryapak
+// Licensed under the MIT License.
+func goldenEqual(img1, img2 *image.NRGBA) bool {
+	maxDiff := 0
+	if runtime.GOARCH != "amd64" {
+		// The golden files are created using the AMD64 architecture.
+		// Be lenient on other platforms due to floaging point and dithering differences.
+		maxDiff = 15
+	}
+	if !img1.Rect.Eq(img2.Rect) {
+		return false
+	}
+	if len(img1.Pix) != len(img2.Pix) {
+		return false
+	}
+	for i := 0; i < len(img1.Pix); i++ {
+		diff := int(img1.Pix[i]) - int(img2.Pix[i])
+		if diff < 0 {
+			diff = -diff
+		}
+		if diff > maxDiff {
+			return false
+		}
+	}
+	return true
+}
+
+// We don't have a CI test environment for these, and there are known dithering issues that makes these time consuming to maintain.
+var SkipGoldenTests = runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "s390x"
+
+// UsesFMA indicates whether "fused multiply and add" (FMA) instruction is
+// used.  The command "grep FMADD go/test/codegen/floats.go" can help keep
+// the FMA-using architecture list updated.
+var UsesFMA = runtime.GOARCH == "s390x" ||
+	runtime.GOARCH == "ppc64" ||
+	runtime.GOARCH == "ppc64le" ||
+	runtime.GOARCH == "arm64" ||
+	runtime.GOARCH == "riscv64"