all: Rework page store, add a dynacache, improve partial rebuilds, and some general spring cleaningdevelop2024

There are some breaking changes in this commit, see #11455.

Closes #11455
Closes #11549

This fixes a set of bugs (see issue list) and it is also paying some technical debt accumulated over the years. We now build with Staticcheck enabled in the CI build.

The performance should be about the same as before for regular sized Hugo sites, but it should perform and scale much better to larger data sets, as objects that uses lots of memory (e.g. rendered Markdown, big JSON files read into maps with transform.Unmarshal etc.) will now get automatically garbage collected if needed. Performance on partial rebuilds when running the server in fast render mode should be the same, but the change detection should be much more accurate.

A list of the notable new features:

* A new dependency tracker that covers (almost) all of Hugo's API and is used to do fine grained partial rebuilds when running the server.
* A new and simpler tree document store which allows fast lookups and prefix-walking in all dimensions (e.g. language) concurrently.
* You can now configure an upper memory limit allowing for much larger data sets and/or running on lower specced PCs.
We have lifted the "no resources in sub folders" restriction for branch bundles (e.g. sections).
Memory Limit
* Hugos will, by default, set aside a quarter of the total system memory, but you can set this via the OS environment variable HUGO_MEMORYLIMIT (in gigabytes). This is backed by a partitioned LRU cache used throughout Hugo. A cache that gets dynamically resized in low memory situations, allowing Go's Garbage Collector to free the memory.

New Dependency Tracker: Hugo has had a rule based coarse grained approach to server rebuilds that has worked mostly pretty well, but there have been some surprises (e.g. stale content). This is now revamped with a new dependency tracker that can quickly calculate the delta given a changed resource (e.g. a content file, template, JS file etc.). This handles transitive relations, e.g. $page -> js.Build -> JS import, or $page1.Content -> render hook -> site.GetPage -> $page2.Title, or $page1.Content -> shortcode -> partial -> site.RegularPages -> $page2.Content -> shortcode ..., and should also handle changes to aggregated values (e.g. site.Lastmod) effectively.

This covers all of Hugo's API with 2 known exceptions (a list that may not be fully exhaustive):

Changes to files loaded with template func os.ReadFile may not be handled correctly. We recommend loading resources with resources.Get
Changes to Hugo objects (e.g. Page) passed in the template context to lang.Translate may not be detected correctly. We recommend having simple i18n templates without too much data context passed in other than simple types such as strings and numbers.
Note that the cachebuster configuration (when A changes then rebuild B) works well with the above, but we recommend that you revise that configuration, as it in most situations should not be needed. One example where it is still needed is with TailwindCSS and using changes to hugo_stats.json to trigger new CSS rebuilds.

Document Store: Previously, a little simplified, we split the document store (where we store pages and resources) in a tree per language. This worked pretty well, but the structure made some operations harder than they needed to be. We have now restructured it into one Radix tree for all languages. Internally the language is considered to be a dimension of that tree, and the tree can be viewed in all dimensions concurrently. This makes some operations re. language simpler (e.g. finding translations is just a slice range), but the idea is that it should also be relatively inexpensive to add more dimensions if needed (e.g. role).

Fixes #10169
Fixes #10364
Fixes #10482
Fixes #10630
Fixes #10656
Fixes #10694
Fixes #10918
Fixes #11262
Fixes #11439
Fixes #11453
Fixes #11457
Fixes #11466
Fixes #11540
Fixes #11551
Fixes #11556
Fixes #11654
Fixes #11661
Fixes #11663
Fixes #11664
Fixes #11669
Fixes #11671
Fixes #11807
Fixes #11808
Fixes #11809
Fixes #11815
Fixes #11840
Fixes #11853
Fixes #11860
Fixes #11883
Fixes #11904
Fixes #7388
Fixes #7425
Fixes #7436
Fixes #7544
Fixes #7882
Fixes #7960
Fixes #8255
Fixes #8307
Fixes #8863
Fixes #8927
Fixes #9192
Fixes #9324

1 files changed, 1256 insertions, 0 deletions

diff --git a/hugolib/rebuild_test.go b/hugolib/rebuild_test.go
new file mode 100644
index 000000000..d3ac5665d
--- /dev/null
+++ b/hugolib/rebuild_test.go
@@ -0,0 +1,1256 @@
+package hugolib
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/fortytw2/leaktest"
+	qt "github.com/frankban/quicktest"
+	"github.com/gohugoio/hugo/common/types"
+	"github.com/gohugoio/hugo/htesting"
+	"github.com/gohugoio/hugo/resources/resource_transformers/tocss/dartsass"
+	"github.com/gohugoio/hugo/resources/resource_transformers/tocss/scss"
+)
+
+const rebuildFilesSimple = `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy", "sitemap", "robotstxt", "404"]
+disableLiveReload = true
+[outputs]
+home = ["html"]
+section = ["html"]
+page = ["html"]
+-- content/mysection/_index.md --
+---
+title: "My Section"
+---
+-- content/mysection/mysectionbundle/index.md --
+---
+title: "My Section Bundle"
+---
+My Section Bundle Content.
+-- content/mysection/mysectionbundle/mysectionbundletext.txt --
+My Section Bundle Text 2 Content.
+-- content/mysection/mysectionbundle/mysectionbundlecontent.md --
+---
+title: "My Section Bundle Content"
+---
+My Section Bundle Content.
+-- content/mysection/_index.md --
+---
+title: "My Section"
+---
+-- content/mysection/mysectiontext.txt --
+-- content/_index.md --
+---
+title: "Home"
+---
+Home Content.
+-- content/hometext.txt --
+Home Text Content.
+-- layouts/_default/single.html --
+Single: {{ .Title }}|{{ .Content }}$
+Resources: {{ range $i, $e := .Resources }}{{ $i }}:{{ .RelPermalink }}|{{ .Content }}|{{ end }}$
+Len Resources: {{ len .Resources }}|
+-- layouts/_default/list.html --
+List: {{ .Title }}|{{ .Content }}$
+Len Resources: {{ len .Resources }}|
+Resources: {{ range $i, $e := .Resources }}{{ $i }}:{{ .RelPermalink }}|{{ .Content }}|{{ end }}$
+-- layouts/shortcodes/foo.html --
+Foo.
+
+`
+
+func TestRebuildEditTextFileInLeafBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/mysection/mysectionbundle/index.html",
+		"Resources: 0:/mysection/mysectionbundle/mysectionbundletext.txt|My Section Bundle Text 2 Content.|1:|<p>My Section Bundle Content.</p>\n|$")
+
+	b.EditFileReplaceAll("content/mysection/mysectionbundle/mysectionbundletext.txt", "Content.", "Content Edited.").Build()
+	b.AssertFileContent("public/mysection/mysectionbundle/index.html",
+		"Text 2 Content Edited")
+	b.AssertRenderCountPage(1)
+	b.AssertRenderCountContent(1)
+}
+
+func TestRebuildEditTextFileInHomeBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/index.html", "Home Content.")
+	b.AssertFileContent("public/index.html", "Home Text Content.")
+
+	b.EditFileReplaceAll("content/hometext.txt", "Content.", "Content Edited.").Build()
+	b.AssertFileContent("public/index.html", "Home Content.")
+	b.AssertFileContent("public/index.html", "Home Text Content Edited.")
+	b.AssertRenderCountPage(1)
+	b.AssertRenderCountContent(1)
+}
+
+func TestRebuildEditTextFileInBranchBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/mysection/index.html", "My Section")
+
+	b.EditFileReplaceAll("content/mysection/mysectiontext.txt", "Content.", "Content Edited.").Build()
+	b.AssertFileContent("public/mysection/index.html", "My Section")
+	b.AssertRenderCountPage(1)
+	b.AssertRenderCountContent(1)
+}
+
+func TestRebuildRenameTextFileInLeafBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/mysection/mysectionbundle/index.html", "My Section Bundle Text 2 Content.")
+
+	b.RenameFile("content/mysection/mysectionbundle/mysectionbundletext.txt", "content/mysection/mysectionbundle/mysectionbundletext2.txt").Build()
+	b.AssertFileContent("public/mysection/mysectionbundle/index.html", "mysectionbundletext2", "My Section Bundle Text 2 Content.")
+	b.AssertRenderCountPage(3)
+	b.AssertRenderCountContent(3)
+}
+
+func TestRebuildRenameTextFileInBranchBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/mysection/index.html", "My Section")
+
+	b.RenameFile("content/mysection/mysectiontext.txt", "content/mysection/mysectiontext2.txt").Build()
+	b.AssertFileContent("public/mysection/index.html", "mysectiontext2", "My Section")
+	b.AssertRenderCountPage(2)
+	b.AssertRenderCountContent(2)
+}
+
+func TestRebuildRenameTextFileInHomeBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.AssertFileContent("public/index.html", "Home Text Content.")
+
+	b.RenameFile("content/hometext.txt", "content/hometext2.txt").Build()
+	b.AssertFileContent("public/index.html", "hometext2", "Home Text Content.")
+	b.AssertRenderCountPage(2)
+}
+
+func TestRebuildRenameDirectoryWithLeafBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.RenameDir("content/mysection/mysectionbundle", "content/mysection/mysectionbundlerenamed").Build()
+	b.AssertFileContent("public/mysection/mysectionbundlerenamed/index.html", "My Section Bundle")
+	b.AssertRenderCountPage(1)
+}
+
+func TestRebuildRenameDirectoryWithBranchBundle(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	b.RenameDir("content/mysection", "content/mysectionrenamed").Build()
+	b.AssertFileContent("public/mysectionrenamed/index.html", "My Section")
+	b.AssertFileContent("public/mysectionrenamed/mysectionbundle/index.html", "My Section Bundle")
+	b.AssertFileContent("public/mysectionrenamed/mysectionbundle/mysectionbundletext.txt", "My Section Bundle Text 2 Content.")
+	b.AssertRenderCountPage(2)
+}
+
+func TestRebuildRenameDirectoryWithRegularPageUsedInHome(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableLiveReload = true
+-- content/foo/p1.md --
+---
+title: "P1"
+---
+-- layouts/index.html --
+Pages: {{ range .Site.RegularPages }}{{ .RelPermalink }}|{{ end }}$
+`
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "Pages: /foo/p1/|$")
+
+	b.RenameDir("content/foo", "content/bar").Build()
+
+	b.AssertFileContent("public/index.html", "Pages: /bar/p1/|$")
+}
+
+func TestRebuildAddRegularFileRegularPageUsedInHomeMultilingual(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableLiveReload = true
+[languages]
+[languages.en]
+weight = 1
+[languages.nn]
+weight = 2
+[languages.fr]
+weight = 3
+[languages.a]
+weight = 4
+[languages.b]
+weight = 5
+[languages.c]
+weight = 6
+[languages.d]
+weight = 7
+[languages.e]
+weight = 8
+[languages.f]
+weight = 9
+[languages.g]
+weight = 10
+[languages.h]
+weight = 11
+[languages.i]
+weight = 12
+[languages.j]
+weight = 13
+-- content/foo/_index.md --
+-- content/foo/data.txt --
+-- content/foo/p1.md --
+-- content/foo/p1.nn.md --
+-- content/foo/p1.fr.md --
+-- content/foo/p1.a.md --
+-- content/foo/p1.b.md --
+-- content/foo/p1.c.md --
+-- content/foo/p1.d.md --
+-- content/foo/p1.e.md --
+-- content/foo/p1.f.md --
+-- content/foo/p1.g.md --
+-- content/foo/p1.h.md --
+-- content/foo/p1.i.md --
+-- content/foo/p1.j.md --
+-- layouts/index.html --
+RegularPages: {{ range .Site.RegularPages }}{{ .RelPermalink }}|{{ end }}$
+`
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "RegularPages: /foo/p1/|$")
+	b.AssertFileContent("public/nn/index.html", "RegularPages: /nn/foo/p1/|$")
+	b.AssertFileContent("public/i/index.html", "RegularPages: /i/foo/p1/|$")
+
+	b.AddFiles("content/foo/p2.md", ``).Build()
+
+	b.AssertFileContent("public/index.html", "RegularPages: /foo/p1/|/foo/p2/|$")
+	b.AssertFileContent("public/fr/index.html", "RegularPages: /fr/foo/p1/|$")
+
+	b.AddFiles("content/foo/p2.fr.md", ``).Build()
+	b.AssertFileContent("public/fr/index.html", "RegularPages: /fr/foo/p1/|/fr/foo/p2/|$")
+
+	b.AddFiles("content/foo/p2.i.md", ``).Build()
+	b.AssertFileContent("public/i/index.html", "RegularPages: /i/foo/p1/|/i/foo/p2/|$")
+}
+
+func TestRebuildRenameDirectoryWithBranchBundleFastRender(t *testing.T) {
+	recentlyVisited := types.NewEvictingStringQueue(10).Add("/a/b/c/")
+	b := TestRunning(t, rebuildFilesSimple, func(cfg *IntegrationTestConfig) { cfg.BuildCfg = BuildCfg{RecentlyVisited: recentlyVisited} })
+	b.RenameDir("content/mysection", "content/mysectionrenamed").Build()
+	b.AssertFileContent("public/mysectionrenamed/index.html", "My Section")
+	b.AssertFileContent("public/mysectionrenamed/mysectionbundle/index.html", "My Section Bundle")
+	b.AssertFileContent("public/mysectionrenamed/mysectionbundle/mysectionbundletext.txt", "My Section Bundle Text 2 Content.")
+	b.AssertRenderCountPage(2)
+}
+
+func TestRebuilErrorRecovery(t *testing.T) {
+	b := TestRunning(t, rebuildFilesSimple)
+	_, err := b.EditFileReplaceAll("content/mysection/mysectionbundle/index.md", "My Section Bundle Content.", "My Section Bundle Content\n\n\n\n{{< foo }}.").BuildE()
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, filepath.FromSlash(`"/content/mysection/mysectionbundle/index.md:8:9": unrecognized character`))
+
+	// Fix the error
+	b.EditFileReplaceAll("content/mysection/mysectionbundle/index.md", "{{< foo }}", "{{< foo >}}").Build()
+}
+
+func TestRebuildScopedToOutputFormat(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy", "sitemap", "robotstxt", "404"]
+disableLiveReload = true
+-- content/p1.md --
+---
+title: "P1"
+outputs: ["html", "json"]
+---
+P1 Content.
+
+{{< myshort >}}
+-- layouts/_default/single.html --
+Single HTML: {{ .Title }}|{{ .Content }}|
+-- layouts/_default/single.json --
+Single JSON: {{ .Title }}|{{ .Content }}|
+-- layouts/shortcodes/myshort.html --
+My short.
+`
+	b := Test(t, files, TestOptRunning())
+	b.AssertRenderCountPage(3)
+	b.AssertRenderCountContent(1)
+	b.AssertFileContent("public/p1/index.html", "Single HTML: P1|<p>P1 Content.</p>\n")
+	b.AssertFileContent("public/p1/index.json", "Single JSON: P1|<p>P1 Content.</p>\n")
+	b.EditFileReplaceAll("layouts/_default/single.html", "Single HTML", "Single HTML Edited").Build()
+	b.AssertFileContent("public/p1/index.html", "Single HTML Edited: P1|<p>P1 Content.</p>\n")
+	b.AssertRenderCountPage(1)
+
+	// Edit shortcode. Note that this is reused across all output formats.
+	b.EditFileReplaceAll("layouts/shortcodes/myshort.html", "My short", "My short edited").Build()
+	b.AssertFileContent("public/p1/index.html", "My short edited")
+	b.AssertFileContent("public/p1/index.json", "My short edited")
+	b.AssertRenderCountPage(3) // rss (uses .Content) + 2 single pages.
+}
+
+func TestRebuildBaseof(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+title = "Hugo Site"
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+-- layouts/_default/baseof.html --
+Baseof: {{ .Title }}|
+{{ block "main" . }}default{{ end }}
+-- layouts/index.html --
+{{ define "main" }}
+Home: {{ .Title }}|{{ .Content }}|
+{{ end }}
+`
+	b := Test(t, files, TestOptRunning())
+	b.AssertFileContent("public/index.html", "Baseof: Hugo Site|", "Home: Hugo Site||")
+	b.EditFileReplaceFunc("layouts/_default/baseof.html", func(s string) string {
+		return strings.Replace(s, "Baseof", "Baseof Edited", 1)
+	}).Build()
+	b.AssertFileContent("public/index.html", "Baseof Edited: Hugo Site|", "Home: Hugo Site||")
+}
+
+func TestRebuildSingleWithBaseof(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+title = "Hugo Site"
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+-- content/p1.md --
+---
+title: "P1"
+---
+P1 Content.
+-- layouts/_default/baseof.html --
+Baseof: {{ .Title }}|
+{{ block "main" . }}default{{ end }}
+-- layouts/index.html --
+Home.
+-- layouts/_default/single.html --
+{{ define "main" }}
+Single: {{ .Title }}|{{ .Content }}|
+{{ end }}
+`
+	b := Test(t, files, TestOptRunning())
+	b.AssertFileContent("public/p1/index.html", "Baseof: P1|\n\nSingle: P1|<p>P1 Content.</p>\n|")
+	b.EditFileReplaceFunc("layouts/_default/single.html", func(s string) string {
+		return strings.Replace(s, "Single", "Single Edited", 1)
+	}).Build()
+	b.AssertFileContent("public/p1/index.html", "Baseof: P1|\n\nSingle Edited: P1|<p>P1 Content.</p>\n|")
+}
+
+func TestRebuildFromString(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy", "sitemap", "robotstxt", "404"]
+disableLiveReload = true
+-- content/p1.md --
+---
+title: "P1"
+layout: "l1"
+---
+P1 Content.
+-- content/p2.md --
+---
+title: "P2"
+layout: "l2"
+---
+P2 Content.
+-- assets/mytext.txt --
+My Text
+-- layouts/_default/l1.html --
+{{ $r := partial "get-resource.html" . }}
+L1: {{ .Title }}|{{ .Content }}|R: {{ $r.Content }}|
+-- layouts/_default/l2.html --
+L2.
+-- layouts/partials/get-resource.html --
+{{ $mytext := resources.Get "mytext.txt" }}
+{{ $txt := printf "Text: %s" $mytext.Content }}
+{{ $r := resources.FromString "r.txt"  $txt }}
+{{ return $r }}
+
+`
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/p1/index.html", "L1: P1|<p>P1 Content.</p>\n|R: Text: My Text|")
+
+	b.EditFileReplaceAll("assets/mytext.txt", "My Text", "My Text Edited").Build()
+
+	b.AssertFileContent("public/p1/index.html", "L1: P1|<p>P1 Content.</p>\n|R: Text: My Text Edited|")
+
+	b.AssertRenderCountPage(1)
+}
+
+func TestRebuildDeeplyNestedLink(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com/"
+disableKinds = ["term", "taxonomy", "sitemap", "robotstxt", "404"]
+disableLiveReload = true
+-- content/s/p1.md --
+---
+title: "P1"
+---
+-- content/s/p2.md --
+---
+title: "P2"
+---
+-- content/s/p3.md --
+---
+title: "P3"
+---
+-- content/s/p4.md --
+---
+title: "P4"
+---
+-- content/s/p5.md --
+---
+title: "P5"
+---
+-- content/s/p6.md --
+---
+title: "P6"
+---
+-- content/s/p7.md --
+---
+title: "P7"
+---
+-- layouts/_default/list.html --
+List.
+-- layouts/_default/single.html --
+Single.
+-- layouts/_default/single.html --
+Next: {{ with  .PrevInSection }}{{ .Title }}{{ end }}|
+Prev: {{ with  .NextInSection }}{{ .Title }}{{ end }}|
+
+
+`
+
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/s/p1/index.html", "Next: P2|")
+	b.EditFileReplaceAll("content/s/p7.md", "P7", "P7 Edited").Build()
+	b.AssertFileContent("public/s/p6/index.html", "Next: P7 Edited|")
+}
+
+func TestRebuildVariations(t *testing.T) {
+	// t.Parallel() not supported, see https://github.com/fortytw2/leaktest/issues/4
+	// This leaktest seems to be a little bit shaky on Travis.
+	if !htesting.IsCI() {
+		defer leaktest.CheckTimeout(t, 10*time.Second)()
+	}
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disdableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+defaultContentLanguage = "nn"
+paginate = 20
+[security]
+enableInlineShortcodes = true
+[languages]
+[languages.en]
+weight = 1
+[languages.nn]
+weight = 2
+-- content/mysect/p1/index.md --
+---
+title: "P1"
+---
+P1 Content.
+{{< include "mysect/p2" >}}
+§§§go { page="mysect/p3" }
+hello
+§§§
+
+{{< foo.inline >}}Foo{{< /foo.inline >}}
+-- content/mysect/p2/index.md --
+---
+title: "P2"
+---
+P2 Content.
+-- content/mysect/p3/index.md --
+---
+title: "P3"
+---
+P3 Content.
+-- content/mysect/sub/_index.md --
+-- content/mysect/sub/p4/index.md --
+---
+title: "P4"
+---
+P4 Content.
+-- content/mysect/sub/p5/index.md --
+---
+title: "P5"
+lastMod: 2019-03-02
+---
+P5 Content.
+-- content/myothersect/_index.md --
+---
+cascade:
+- _target:
+  cascadeparam: "cascadevalue"
+---
+-- content/myothersect/sub/_index.md --
+-- content/myothersect/sub/p6/index.md --
+---
+title: "P6"
+---
+P6 Content.
+-- content/translations/p7.en.md --
+---
+title: "P7 EN"
+---
+P7 EN Content.
+-- content/translations/p7.nn.md --
+---
+title: "P7 NN"
+---
+P7 NN Content.
+-- layouts/index.html --
+Home: {{ .Title }}|{{ .Content }}|
+RegularPages: {{ range .RegularPages }}{{ .RelPermalink }}|{{ end }}$
+Len RegularPagesRecursive: {{ len .RegularPagesRecursive }}
+Site.Lastmod: {{ .Site.Lastmod.Format "2006-01-02" }}|
+Paginate: {{ range (.Paginate .Site.RegularPages).Pages }}{{ .RelPermalink }}|{{ .Title }}|{{ end }}$
+-- layouts/_default/single.html --
+Single: {{ .Title }}|{{ .Content }}|
+Single Partial Cached: {{ partialCached "pcached" . }}|
+Page.Lastmod: {{ .Lastmod.Format "2006-01-02" }}|
+Cascade param: {{ .Params.cascadeparam }}|
+-- layouts/_default/list.html --
+List: {{ .Title }}|{{ .Content }}|
+RegularPages: {{ range .RegularPages }}{{ .Title }}|{{ end }}$
+Len RegularPagesRecursive: {{ len .RegularPagesRecursive }}
+RegularPagesRecursive: {{ range .RegularPagesRecursive }}{{ .RelPermalink }}|{{ end }}$
+List Partial P1: {{ partial "p1" . }}|
+Page.Lastmod: {{ .Lastmod.Format "2006-01-02" }}|
+Cascade param: {{ .Params.cascadeparam }}|
+-- layouts/partials/p1.html --
+Partial P1.
+-- layouts/partials/pcached.html --
+Partial Pcached.
+-- layouts/shortcodes/include.html --
+{{ $p := site.GetPage (.Get 0)}}
+{{ with $p }}
+Shortcode Include: {{ .Title }}|
+{{ end }}
+Shortcode .Page.Title: {{ .Page.Title }}|
+Shortcode Partial P1: {{ partial "p1" . }}|
+-- layouts/_default/_markup/render-codeblock.html --
+{{ $p := site.GetPage (.Attributes.page)}}
+{{ with $p }}
+Codeblock Include: {{ .Title }}|
+{{ end }}
+
+
+
+`
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			Running:     true,
+			BuildCfg: BuildCfg{
+				testCounters: &buildCounters{},
+			},
+			// Verbose:     true,
+			// LogLevel: logg.LevelTrace,
+		},
+	).Build()
+
+	// When running the server, this is done on shutdown.
+	// Do this here to satisfy the leak detector above.
+	defer func() {
+		b.Assert(b.H.Close(), qt.IsNil)
+	}()
+
+	contentRenderCount := b.counters.contentRenderCounter.Load()
+	pageRenderCount := b.counters.pageRenderCounter.Load()
+
+	b.Assert(contentRenderCount > 0, qt.IsTrue)
+	b.Assert(pageRenderCount > 0, qt.IsTrue)
+
+	// Test cases:
+	// - Edit content file direct
+	// - Edit content file transitive shortcode
+	// - Edit content file transitive render hook
+	// - Rename one languge version of a content file
+	// - Delete content file, check site.RegularPages and section.RegularPagesRecursive (length)
+	// - Add content file (see above).
+	// - Edit shortcode
+	// - Edit inline shortcode
+	// - Edit render hook
+	// - Edit partial used in template
+	// - Edit partial used in shortcode
+	// - Edit partial cached.
+	// - Edit lastMod date in content file, check site.Lastmod.
+	editFile := func(filename string, replacementFunc func(s string) string) {
+		b.EditFileReplaceFunc(filename, replacementFunc).Build()
+		b.Assert(b.counters.contentRenderCounter.Load() < contentRenderCount, qt.IsTrue, qt.Commentf("count %d < %d", b.counters.contentRenderCounter.Load(), contentRenderCount))
+		b.Assert(b.counters.pageRenderCounter.Load() < pageRenderCount, qt.IsTrue, qt.Commentf("count %d < %d", b.counters.pageRenderCounter.Load(), pageRenderCount))
+	}
+
+	b.AssertFileContent("public/index.html", "RegularPages: $", "Len RegularPagesRecursive: 7", "Site.Lastmod: 2019-03-02")
+
+	b.AssertFileContent("public/mysect/p1/index.html",
+		"Single: P1|<p>P1 Content.",
+		"Shortcode Include: P2|",
+		"Codeblock Include: P3|")
+
+	editFile("content/mysect/p1/index.md", func(s string) string {
+		return strings.ReplaceAll(s, "P1", "P1 Edited")
+	})
+
+	b.AssertFileContent("public/mysect/p1/index.html", "Single: P1 Edited|<p>P1 Edited Content.")
+	b.AssertFileContent("public/index.html", "RegularPages: $", "Len RegularPagesRecursive: 7", "Paginate: /mysect/sub/p5/|P5|/mysect/p1/|P1 Edited")
+	b.AssertFileContent("public/mysect/index.html", "RegularPages: P1 Edited|P2|P3|$", "Len RegularPagesRecursive: 5")
+
+	// p2 is included in p1 via shortcode.
+	editFile("content/mysect/p2/index.md", func(s string) string {
+		return strings.ReplaceAll(s, "P2", "P2 Edited")
+	})
+
+	b.AssertFileContent("public/mysect/p1/index.html", "Shortcode Include: P2 Edited|")
+
+	// p3 is included in p1 via codeblock hook.
+	editFile("content/mysect/p3/index.md", func(s string) string {
+		return strings.ReplaceAll(s, "P3", "P3 Edited")
+	})
+
+	b.AssertFileContent("public/mysect/p1/index.html", "Codeblock Include: P3 Edited|")
+
+	// Remove a content file in a nested section.
+	b.RemoveFiles("content/mysect/sub/p4/index.md").Build()
+	b.AssertFileContent("public/mysect/index.html", "RegularPages: P1 Edited|P2 Edited|P3 Edited", "Len RegularPagesRecursive: 4")
+	b.AssertFileContent("public/mysect/sub/index.html", "RegularPages: P5|$", "RegularPagesRecursive: 1")
+
+	// Rename one of the translations.
+	b.AssertFileContent("public/translations/index.html", "RegularPagesRecursive: /translations/p7/")
+	b.AssertFileContent("public/en/translations/index.html", "RegularPagesRecursive: /en/translations/p7/")
+	b.RenameFile("content/translations/p7.nn.md", "content/translations/p7rename.nn.md").Build()
+	b.AssertFileContent("public/translations/index.html", "RegularPagesRecursive: /translations/p7rename/")
+	b.AssertFileContent("public/en/translations/index.html", "RegularPagesRecursive: /en/translations/p7/")
+
+	// Edit shortcode
+	editFile("layouts/shortcodes/include.html", func(s string) string {
+		return s + "\nShortcode Include Edited."
+	})
+	b.AssertFileContent("public/mysect/p1/index.html", "Shortcode Include Edited.")
+
+	// Edit render hook
+	editFile("layouts/_default/_markup/render-codeblock.html", func(s string) string {
+		return s + "\nCodeblock Include Edited."
+	})
+	b.AssertFileContent("public/mysect/p1/index.html", "Codeblock Include Edited.")
+
+	// Edit partial p1
+	editFile("layouts/partials/p1.html", func(s string) string {
+		return strings.Replace(s, "Partial P1", "Partial P1 Edited", 1)
+	})
+	b.AssertFileContent("public/mysect/index.html", "List Partial P1: Partial P1 Edited.")
+	b.AssertFileContent("public/mysect/p1/index.html", "Shortcode Partial P1: Partial P1 Edited.")
+
+	// Edit partial cached.
+	editFile("layouts/partials/pcached.html", func(s string) string {
+		return strings.Replace(s, "Partial Pcached", "Partial Pcached Edited", 1)
+	})
+	b.AssertFileContent("public/mysect/p1/index.html", "Pcached Edited.")
+
+	// Edit lastMod date in content file, check site.Lastmod.
+	editFile("content/mysect/sub/p5/index.md", func(s string) string {
+		return strings.Replace(s, "2019-03-02", "2020-03-10", 1)
+	})
+	b.AssertFileContent("public/index.html", "Site.Lastmod: 2020-03-10|")
+	b.AssertFileContent("public/mysect/index.html", "Page.Lastmod: 2020-03-10|")
+
+	// Adjust the date back a few days.
+	editFile("content/mysect/sub/p5/index.md", func(s string) string {
+		return strings.Replace(s, "2020-03-10", "2019-03-08", 1)
+	})
+	b.AssertFileContent("public/mysect/index.html", "Page.Lastmod: 2019-03-08|")
+	b.AssertFileContent("public/index.html", "Site.Lastmod: 2019-03-08|")
+
+	// Check cascade mods.
+	b.AssertFileContent("public/myothersect/index.html", "Cascade param: cascadevalue|")
+	b.AssertFileContent("public/myothersect/sub/index.html", "Cascade param: cascadevalue|")
+	b.AssertFileContent("public/myothersect/sub/p6/index.html", "Cascade param: cascadevalue|")
+
+	editFile("content/myothersect/_index.md", func(s string) string {
+		return strings.Replace(s, "cascadevalue", "cascadevalue edited", 1)
+	})
+	b.AssertFileContent("public/myothersect/index.html", "Cascade param: cascadevalue edited|")
+	b.AssertFileContent("public/myothersect/sub/p6/index.html", "Cascade param: cascadevalue edited|")
+
+	// Repurpose the cascadeparam to set the title.
+	editFile("content/myothersect/_index.md", func(s string) string {
+		return strings.Replace(s, "cascadeparam:", "title:", 1)
+	})
+	b.AssertFileContent("public/myothersect/sub/index.html", "Cascade param: |", "List: cascadevalue edited|")
+
+	// Revert it.
+	editFile("content/myothersect/_index.md", func(s string) string {
+		return strings.Replace(s, "title:", "cascadeparam:", 1)
+	})
+	b.AssertFileContent("public/myothersect/sub/index.html", "Cascade param: cascadevalue edited|", "List: |")
+}
+
+func TestRebuildVariationsJSNoneFingerprinted(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com/"
+disableKinds = ["term", "taxonomy", "sitemap", "robotsTXT", "404", "rss"]
+disableLiveReload = true
+-- content/p1/index.md --
+---
+title: "P1"
+---
+P1.
+-- content/p2/index.md --
+---
+title: "P2"
+---
+P2.
+-- content/p3/index.md --
+---
+title: "P3"
+---
+P3.
+-- content/p4/index.md --
+---
+title: "P4"
+---
+P4.
+-- assets/main.css --
+body {
+	background: red;
+}
+-- layouts/default/list.html --
+List.
+-- layouts/_default/single.html --
+Single.
+{{ $css := resources.Get "main.css" | minify }}
+RelPermalink: {{ $css.RelPermalink }}|
+
+`
+
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/p1/index.html", "RelPermalink: /main.min.css|")
+	b.AssertFileContent("public/main.min.css", "body{background:red}")
+
+	b.EditFileReplaceAll("assets/main.css", "red", "blue")
+	b.RemoveFiles("content/p2/index.md")
+	b.RemoveFiles("content/p3/index.md")
+	b.Build()
+
+	b.AssertFileContent("public/main.min.css", "body{background:blue}")
+}
+
+func TestRebuildVariationsJSInNestedCachedPartialFingerprinted(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com/"
+disableKinds = ["term", "taxonomy", "sitemap", "robotsTXT", "404", "rss"]
+disableLiveReload = true
+-- content/p1/index.md --
+---
+title: "P1"
+---
+P1.
+-- content/p2/index.md --
+---
+title: "P2"
+---
+P2.
+-- content/p3/index.md --
+---
+title: "P3"
+---
+P3.
+-- content/p4/index.md --
+---
+title: "P4"
+---
+P4.
+-- assets/js/main.js --
+console.log("Hello");
+-- layouts/_default/list.html --
+List. {{ partial "head.html" . }}$
+-- layouts/_default/single.html --
+Single. {{ partial "head.html" . }}$
+-- layouts/partials/head.html --
+{{ partialCached "js.html" . }}$
+-- layouts/partials/js.html --
+{{ $js := resources.Get "js/main.js" | js.Build | fingerprint }}
+RelPermalink: {{ $js.RelPermalink }}|
+`
+
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/p1/index.html", "/js/main.712a50b59d0f0dedb4e3606eaa3860b1f1a5305f6c42da30a2985e473ba314eb.js")
+	b.AssertFileContent("public/index.html", "/js/main.712a50b59d0f0dedb4e3606eaa3860b1f1a5305f6c42da30a2985e473ba314eb.js")
+
+	b.EditFileReplaceAll("assets/js/main.js", "Hello", "Hello is Edited").Build()
+
+	for i := 1; i < 5; i++ {
+		b.AssertFileContent(fmt.Sprintf("public/p%d/index.html", i), "/js/main.6535698cec9a21875f40ae03e96f30c4bee41a01e979224761e270b9034b2424.js")
+	}
+
+	b.AssertFileContent("public/index.html", "/js/main.6535698cec9a21875f40ae03e96f30c4bee41a01e979224761e270b9034b2424.js")
+}
+
+func TestRebuildVariationsJSInNestedPartialFingerprintedInBase(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com/"
+disableKinds = ["term", "taxonomy", "sitemap", "robotsTXT", "404", "rss"]
+disableLiveReload = true
+-- assets/js/main.js --
+console.log("Hello");
+-- layouts/_default/baseof.html --
+Base. {{ partial "common/head.html" . }}$
+{{ block "main" . }}default{{ end }}
+-- layouts/_default/list.html --
+{{ define "main" }}main{{ end }}
+-- layouts/partials/common/head.html --
+{{ partial "myfiles/js.html" . }}$
+-- layouts/partials/myfiles/js.html --
+{{ $js := resources.Get "js/main.js" | js.Build | fingerprint }}
+RelPermalink: {{ $js.RelPermalink }}|
+`
+
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "/js/main.712a50b59d0f0dedb4e3606eaa3860b1f1a5305f6c42da30a2985e473ba314eb.js")
+
+	b.EditFileReplaceAll("assets/js/main.js", "Hello", "Hello is Edited").Build()
+
+	b.AssertFileContent("public/index.html", "/js/main.6535698cec9a21875f40ae03e96f30c4bee41a01e979224761e270b9034b2424.js")
+}
+
+func TestRebuildVariationsJSBundled(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy", "sitemap", "robotsTXT", "404", "rss"]
+disableLiveReload = true
+-- content/_index.md --
+---
+title: "Home"
+---
+-- content/p1.md --
+---
+title: "P1"
+layout: "main"
+---
+-- content/p2.md --
+---
+title: "P2"
+---
+{{< jsfingerprinted >}}
+-- content/p3.md --
+---
+title: "P3"
+layout: "plain"
+---
+{{< jsfingerprinted >}}
+-- content/main.js --
+console.log("Hello");
+-- content/foo.js --
+console.log("Foo");
+-- layouts/index.html --
+Home.
+{{ $js := site.Home.Resources.Get "main.js"  }}
+{{ with $js }}
+<script src="{{ .RelPermalink }}"></script>
+{{ end }}
+-- layouts/_default/single.html --
+Single. Deliberately no .Content in here.
+-- layouts/_default/plain.html --
+Content: {{ .Content }}|
+-- layouts/_default/main.html --
+{{ $js := site.Home.Resources.Get "main.js"  }}
+{{ with $js }}
+<script>
+{{ .Content }}
+</script>
+{{ end }}
+-- layouts/shortcodes/jsfingerprinted.html --
+{{ $js := site.Home.Resources.Get "foo.js" | fingerprint  }}
+<script src="{{ $js.RelPermalink }}"></script>
+`
+
+	testCounters := &buildCounters{}
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			Running:     true,
+			// LogLevel:    logg.LevelTrace,
+			// Verbose:     true,
+			BuildCfg: BuildCfg{
+				testCounters: testCounters,
+			},
+		},
+	).Build()
+
+	b.AssertFileContent("public/index.html", `<script src="/main.js"></script>`)
+	b.AssertFileContent("public/p1/index.html", "<script>\n\"console.log(\\\"Hello\\\");\"\n</script>")
+	b.AssertFileContent("public/p2/index.html", "Single. Deliberately no .Content in here.")
+	b.AssertFileContent("public/p3/index.html", "foo.57b4465b908531b43d4e4680ab1063d856b475cb1ae81ad43e0064ecf607bec1.js")
+	b.AssertRenderCountPage(4)
+
+	// Edit JS file.
+	b.EditFileReplaceFunc("content/main.js", func(s string) string {
+		return strings.Replace(s, "Hello", "Hello is Edited", 1)
+	}).Build()
+
+	b.AssertFileContent("public/p1/index.html", "<script>\n\"console.log(\\\"Hello is Edited\\\");\"\n</script>")
+	// The p1 (the one inlining the JS) should be rebuilt.
+	b.AssertRenderCountPage(2)
+	// But not the content file.
+	b.AssertRenderCountContent(0)
+
+	// This is included with RelPermalink in a shortcode used in p3, but it's fingerprinted
+	// so we need to rebuild on change.
+	b.EditFileReplaceFunc("content/foo.js", func(s string) string {
+		return strings.Replace(s, "Foo", "Foo Edited", 1)
+	}).Build()
+
+	// Verify that the hash has changed.
+	b.AssertFileContent("public/p3/index.html", "foo.3a332a088521231e5fc9bd22f15e0ccf507faa7b373fbff22959005b9a80481c.js")
+
+	b.AssertRenderCountPage(1)
+	b.AssertRenderCountContent(1)
+}
+
+func TestRebuildEditData(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableLiveReload = true
+[security]
+enableInlineShortcodes=true
+-- data/mydata.yaml --
+foo: bar
+-- content/_index.md --
+---
+title: "Home"
+---
+{{< data "mydata.foo" >}}}
+-- content/p1.md --
+---
+title: "P1"
+---
+
+Foo inline: {{< foo.inline >}}{{ site.Data.mydata.foo }}|{{< /foo.inline >}}
+-- layouts/shortcodes/data.html --
+{{ $path := split (.Get 0) "." }}
+{{ $data := index site.Data $path }}
+Foo: {{ $data }}|
+-- layouts/index.html --
+Content: {{ .Content }}|
+-- layouts/_default/single.html --
+Single: {{ .Content }}|
+`
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "Foo: bar|")
+	b.AssertFileContent("public/p1/index.html", "Foo inline: bar|")
+	b.EditFileReplaceFunc("data/mydata.yaml", func(s string) string {
+		return strings.Replace(s, "bar", "bar edited", 1)
+	}).Build()
+	b.AssertFileContent("public/index.html", "Foo: bar edited|")
+	b.AssertFileContent("public/p1/index.html", "Foo inline: bar edited|")
+}
+
+func TestRebuildEditHomeContent(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableLiveReload = true
+-- content/_index.md --
+---
+title: "Home"
+---
+Home.
+-- layouts/index.html --
+Content: {{ .Content }}
+`
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "Content: <p>Home.</p>")
+	b.EditFileReplaceAll("content/_index.md", "Home.", "Home").Build()
+	b.AssertFileContent("public/index.html", "Content: <p>Home</p>")
+}
+
+func TestRebuildVariationsAssetsJSImport(t *testing.T) {
+	t.Parallel()
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+-- layouts/index.html --
+Home. {{ now }}
+{{ with (resources.Get "js/main.js" | js.Build | fingerprint) }}
+<script>{{ .Content | safeJS }}</script>
+{{ end }}
+-- assets/js/lib/foo.js --
+export function foo() {
+	console.log("Foo");
+}
+-- assets/js/main.js --
+import { foo } from "./lib/foo.js";
+console.log("Hello");
+foo();
+`
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			Running:     true,
+			// LogLevel:    logg.LevelTrace,
+			NeedsOsFS: true,
+		},
+	).Build()
+
+	b.AssertFileContent("public/index.html", "Home.", "Hello", "Foo")
+	// Edit the imported file.
+	b.EditFileReplaceAll("assets/js/lib/foo.js", "Foo", "Foo Edited").Build()
+	b.AssertFileContent("public/index.html", "Home.", "Hello", "Foo Edited")
+}
+
+func TestRebuildVariationsAssetsPostCSSImport(t *testing.T) {
+	if !htesting.IsCI() {
+		t.Skip("skip CI only")
+	}
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy", "sitemap", "rss"]
+disableLiveReload = true
+-- assets/css/lib/foo.css --
+body {
+	background: red;
+}
+-- assets/css/main.css --
+@import "lib/foo.css";
+-- package.json --
+{
+	"devDependencies": {
+		"postcss-cli": "^9.0.1"
+	}
+}
+-- content/p1.md --
+---
+title: "P1"
+---
+-- content/p2.md --
+---
+title: "P2"
+layout: "foo"
+---
+{{< fingerprinted >}}
+-- content/p3.md --
+---
+title: "P3"
+layout: "foo"
+---
+{{< notfingerprinted >}}
+-- layouts/shortcodes/fingerprinted.html --
+Fingerprinted.
+{{ $opts := dict "inlineImports" true "noMap" true }}
+{{ with (resources.Get "css/main.css" | postCSS $opts | fingerprint) }}
+<style src="{{ .RelPermalink }}"></style>
+{{ end }}
+-- layouts/shortcodes/notfingerprinted.html --
+Fingerprinted.
+{{ $opts := dict "inlineImports" true "noMap" true }}
+{{ with (resources.Get "css/main.css" | postCSS $opts) }}
+<style src="{{ .RelPermalink }}"></style>
+{{ end }}
+-- layouts/index.html --
+Home.
+{{ $opts := dict "inlineImports" true "noMap" true }}
+{{ with (resources.Get "css/main.css" | postCSS $opts) }}
+<style>{{ .Content | safeCSS }}</style>
+{{ end }}
+-- layouts/_default/foo.html --
+Foo.
+{{ .Title }}|{{ .Content }}|
+-- layouts/_default/single.html --
+Single.
+{{ $opts := dict "inlineImports" true "noMap" true }}
+{{ with (resources.Get "css/main.css" | postCSS $opts) }}
+<style src="{{ .RelPermalink }}"></style>
+{{ end }}
+`
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:               t,
+			TxtarString:     files,
+			Running:         true,
+			NeedsOsFS:       true,
+			NeedsNpmInstall: true,
+			// LogLevel:        logg.LevelTrace,
+		},
+	).Build()
+
+	b.AssertFileContent("public/index.html", "Home.", "<style>body {\n\tbackground: red;\n}</style>")
+	b.AssertFileContent("public/p1/index.html", "Single.", "/css/main.css")
+	b.AssertRenderCountPage(4)
+
+	// Edit the imported file.
+	b.EditFileReplaceFunc("assets/css/lib/foo.css", func(s string) string {
+		return strings.Replace(s, "red", "blue", 1)
+	}).Build()
+
+	b.AssertRenderCountPage(3)
+
+	b.AssertFileContent("public/index.html", "Home.", "<style>body {\n\tbackground: blue;\n}</style>")
+}
+
+func TestRebuildVariationsAssetsSassImport(t *testing.T) {
+	if !htesting.IsCI() {
+		t.Skip("skip CI only")
+	}
+
+	filesTemplate := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+-- assets/css/lib/foo.scss --
+body {
+	background: red;
+}
+-- assets/css/main.scss --
+@import "lib/foo";
+-- layouts/index.html --
+Home.
+{{ $opts := dict "transpiler" "TRANSPILER" }}
+{{ with (resources.Get "css/main.scss" | toCSS $opts) }}
+<style>{{ .Content | safeCSS }}</style>
+{{ end }}
+`
+
+	runTest := func(transpiler string) {
+		t.Run(transpiler, func(t *testing.T) {
+			files := strings.Replace(filesTemplate, "TRANSPILER", transpiler, 1)
+			b := NewIntegrationTestBuilder(
+				IntegrationTestConfig{
+					T:           t,
+					TxtarString: files,
+					Running:     true,
+					NeedsOsFS:   true,
+				},
+			).Build()
+
+			b.AssertFileContent("public/index.html", "Home.", "background: red")
+
+			// Edit the imported file.
+			b.EditFileReplaceFunc("assets/css/lib/foo.scss", func(s string) string {
+				return strings.Replace(s, "red", "blue", 1)
+			}).Build()
+
+			b.AssertFileContent("public/index.html", "Home.", "background: blue")
+		})
+	}
+
+	if scss.Supports() {
+		runTest("libsass")
+	}
+
+	if dartsass.Supports() {
+		runTest("dartsass")
+	}
+}
+
+func benchmarkFilesEdit(count int) string {
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disdableKinds = ["term", "taxonomy"]
+disableLiveReload = true
+-- layouts/_default/single.html --
+Single: {{ .Title }}|{{ .Content }}|
+-- layouts/_default/list.html --
+List: {{ .Title }}|{{ .Content }}|
+-- content/mysect/_index.md --
+---
+title: "My Sect"
+---
+	`
+
+	contentTemplate := `
+---
+title: "P%d"
+---
+P%d Content.	
+`
+
+	for i := 0; i < count; i++ {
+		files += fmt.Sprintf("-- content/mysect/p%d/index.md --\n%s", i, fmt.Sprintf(contentTemplate, i, i))
+	}
+
+	return files
+}
+
+func BenchmarkRebuildContentFileChange(b *testing.B) {
+	files := benchmarkFilesEdit(500)
+
+	cfg := IntegrationTestConfig{
+		T:           b,
+		TxtarString: files,
+		Running:     true,
+		// Verbose:     true,
+		// LogLevel: logg.LevelInfo,
+	}
+	builders := make([]*IntegrationTestBuilder, b.N)
+
+	for i := range builders {
+		builders[i] = NewIntegrationTestBuilder(cfg)
+		builders[i].Build()
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bb := builders[i]
+		bb.EditFileReplaceFunc("content/mysect/p123/index.md", func(s string) string {
+			return s + "... Edited"
+		}).Build()
+		// fmt.Println(bb.LogString())
+	}
+}