Fix server rebuilds when adding a content file on Linux

Fixes #12362

4 files changed, 91 insertions, 33 deletions

diff --git a/hugolib/hugo_sites_build.go b/hugolib/hugo_sites_build.go
index a77900e27..411f90734 100644
--- a/hugolib/hugo_sites_build.go
+++ b/hugolib/hugo_sites_build.go
@@ -610,7 +610,7 @@ func (h *HugoSites) processPartial(ctx context.Context, l logg.LevelLogger, conf
 
 	// For a list of events for the different OSes, see the test output in https://github.com/bep/fsnotifyeventlister/.
 	events = h.fileEventsFilter(events)
-	events = h.fileEventsTranslate(events)
+	events = h.fileEventsTrim(events)
 	eventInfos := h.fileEventsApplyInfo(events)
 
 	logger := h.Log
diff --git a/hugolib/integrationtest_builder.go b/hugolib/integrationtest_builder.go
index be11c18d6..8daf7b1ca 100644
--- a/hugolib/integrationtest_builder.go
+++ b/hugolib/integrationtest_builder.go
@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"sort"
 	"strings"
 	"sync"
@@ -685,8 +686,17 @@ func (s *IntegrationTestBuilder) build(cfg BuildCfg) error {
 	return nil
 }
 
+// We simulate the fsnotify events.
+// See the test output in https://github.com/bep/fsnotifyeventlister for what events gets produced
+// by the different OSes.
 func (s *IntegrationTestBuilder) changeEvents() []fsnotify.Event {
-	var events []fsnotify.Event
+	var (
+		events    []fsnotify.Event
+		isLinux   = runtime.GOOS == "linux"
+		isMacOs   = runtime.GOOS == "darwin"
+		isWindows = runtime.GOOS == "windows"
+	)
+
 	for _, v := range s.removedFiles {
 		events = append(events, fsnotify.Event{
 			Name: v,
@@ -713,12 +723,32 @@ func (s *IntegrationTestBuilder) changeEvents() []fsnotify.Event {
 			Name: v,
 			Op:   fsnotify.Write,
 		})
+		if isLinux || isWindows {
+			// Duplicate write events, for some reason.
+			events = append(events, fsnotify.Event{
+				Name: v,
+				Op:   fsnotify.Write,
+			})
+		}
+		if isMacOs {
+			events = append(events, fsnotify.Event{
+				Name: v,
+				Op:   fsnotify.Chmod,
+			})
+		}
 	}
 	for _, v := range s.createdFiles {
 		events = append(events, fsnotify.Event{
 			Name: v,
 			Op:   fsnotify.Create,
 		})
+		if isLinux || isWindows {
+			events = append(events, fsnotify.Event{
+				Name: v,
+				Op:   fsnotify.Write,
+			})
+		}
+
 	}
 
 	// Shuffle events.
diff --git a/hugolib/rebuild_test.go b/hugolib/rebuild_test.go
index 23e3e0532..ea7efcb6f 100644
--- a/hugolib/rebuild_test.go
+++ b/hugolib/rebuild_test.go
@@ -1553,3 +1553,27 @@ Single: {{ .Title }}|{{ .Content }}|
 	b.AssertRenderCountPage(1)
 	b.AssertRenderCountContent(1)
 }
+
+func TestRebuildEditSingleListChangeUbuntuIssue12362(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['rss','section','sitemap','taxonomy','term']
+disableLiveReload = true
+-- layouts/_default/list.html --
+{{ range .Pages }}{{ .Title }}|{{ end }}
+-- layouts/_default/single.html --
+{{ .Title }}
+-- content/p1.md --
+---
+title: p1
+---
+`
+
+	b := TestRunning(t, files)
+	b.AssertFileContent("public/index.html", "p1|")
+
+	b.AddFiles("content/p2.md", "---\ntitle: p2\n---").Build()
+	b.AssertFileContent("public/index.html", "p1|p2|") // this test passes, which doesn't match reality
+}
diff --git a/hugolib/site.go b/hugolib/site.go
index 9ab361722..b66a1284b 100644
--- a/hugolib/site.go
+++ b/hugolib/site.go
@@ -424,7 +424,35 @@ func (h *HugoSites) fileEventsFilter(events []fsnotify.Event) []fsnotify.Event {
 		events[n] = ev
 		n++
 	}
-	return events[:n]
+	events = events[:n]
+
+	eventOrdinal := func(e fsnotify.Event) int {
+		// Pull the structural changes to the top.
+		if e.Op.Has(fsnotify.Create) {
+			return 1
+		}
+		if e.Op.Has(fsnotify.Remove) {
+			return 2
+		}
+		if e.Op.Has(fsnotify.Rename) {
+			return 3
+		}
+		if e.Op.Has(fsnotify.Write) {
+			return 4
+		}
+		return 5
+	}
+
+	sort.Slice(events, func(i, j int) bool {
+		// First sort by event type.
+		if eventOrdinal(events[i]) != eventOrdinal(events[j]) {
+			return eventOrdinal(events[i]) < eventOrdinal(events[j])
+		}
+		// Then sort by name.
+		return events[i].Name < events[j].Name
+	})
+
+	return events
 }
 
 type fileEventInfo struct {
@@ -494,41 +522,17 @@ func (h *HugoSites) fileEventsApplyInfo(events []fsnotify.Event) []fileEventInfo
 	return infos
 }
 
-func (h *HugoSites) fileEventsTranslate(events []fsnotify.Event) []fsnotify.Event {
-	eventMap := make(map[string][]fsnotify.Event)
-
-	// We often get a Remove etc. followed by a Create, a Create followed by a Write.
-	// Remove the superfluous events to make the update logic simpler.
-	for _, ev := range events {
-		eventMap[ev.Name] = append(eventMap[ev.Name], ev)
-	}
-
+func (h *HugoSites) fileEventsTrim(events []fsnotify.Event) []fsnotify.Event {
+	seen := make(map[string]bool)
 	n := 0
 	for _, ev := range events {
-		mapped := eventMap[ev.Name]
-
-		// Keep one
-		found := false
-		var kept fsnotify.Event
-		for i, ev2 := range mapped {
-			if i == 0 {
-				kept = ev2
-			}
-
-			if ev2.Op&fsnotify.Write == fsnotify.Write {
-				kept = ev2
-				found = true
-			}
-
-			if !found && ev2.Op&fsnotify.Create == fsnotify.Create {
-				kept = ev2
-			}
+		if seen[ev.Name] {
+			continue
 		}
-
-		events[n] = kept
+		seen[ev.Name] = true
+		events[n] = ev
 		n++
 	}
-
 	return events
 }