Fix potential nilpointer in httpcache config

cache/httpcache/httpcache.go

@@ -122,6 +122,10 @@ type GlobMatcher struct {
 	Includes []string
 }
 
+func (gm GlobMatcher) IsZero() bool {
+	return len(gm.Includes) == 0 && len(gm.Excludes) == 0
+}
+
 type ConfigCompiled struct {
 	For         predicate.P[string]
 	PollConfigs []PollConfigCompiled
@@ -155,6 +159,9 @@ func (p PollConfigCompiled) IsZero() bool {
 }
 
 func (gm *GlobMatcher) CompilePredicate() (func(string) bool, error) {
+	if gm.IsZero() {
+		panic("no includes or excludes")
+	}
 	var p predicate.P[string]
 	for _, include := range gm.Includes {
 		g, err := glob.Compile(include, '/')
@@ -203,5 +210,9 @@ func DecodeConfig(bcfg config.BaseConfig, m map[string]any) (Config, error) {
 		return c, err
 	}
 
+	if c.Cache.For.IsZero() {
+		c.Cache.For = DefaultConfig.Cache.For
+	}
+
 	return c, nil
 }

cache/httpcache/httpcache_integration_test.go

@@ -22,6 +22,8 @@ import (
 )
 
 func TestConfigCustom(t *testing.T) {
+	t.Parallel()
+
 	files := `
 -- hugo.toml --
 [httpcache]
@@ -51,6 +53,8 @@ includes = ["**gohugo.io**"]
 }
 
 func TestConfigDefault(t *testing.T) {
+	t.Parallel()
+
 	files := `
 -- hugo.toml --
 `
@@ -62,3 +66,30 @@ func TestConfigDefault(t *testing.T) {
 	b.Assert(compiled.For("https://gohugo.io/foo.jpg"), qt.IsFalse)
 	b.Assert(compiled.PollConfigFor("https://gohugo.io/foo.jpg").Config.Disable, qt.IsTrue)
 }
+
+func TestConfigPollsOnly(t *testing.T) {
+	t.Parallel()
+	files := `
+-- hugo.toml --
+[httpcache]
+[[httpcache.polls]]
+low = "5s"
+high = "32s"
+[httpcache.polls.for]
+includes = ["**gohugo.io**"]
+		
+	
+`
+
+	b := hugolib.Test(t, files)
+
+	compiled := b.H.Configs.Base.C.HTTPCache
+
+	b.Assert(compiled.For("https://gohugo.io/posts.json"), qt.IsFalse)
+	b.Assert(compiled.For("https://gohugo.io/foo.jpg"), qt.IsFalse)
+
+	pc := compiled.PollConfigFor("https://gohugo.io/foo.jpg")
+	b.Assert(pc.Config.Low, qt.Equals, 5*time.Second)
+	b.Assert(pc.Config.High, qt.Equals, 32*time.Second)
+	b.Assert(compiled.PollConfigFor("https://example.com/foo.jpg").IsZero(), qt.IsTrue)
+}