Implement defer

Closes #8086
Closes #12589

7 files changed, 195 insertions, 23 deletions

diff --git a/common/collections/stack.go b/common/collections/stack.go
index 0f1581626..96d32fe4b 100644
--- a/common/collections/stack.go
+++ b/common/collections/stack.go
@@ -65,3 +65,16 @@ func (s *Stack[T]) Drain() []T {
 	s.items = nil
 	return items
 }
+
+func (s *Stack[T]) DrainMatching(predicate func(T) bool) []T {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	var items []T
+	for i := len(s.items) - 1; i >= 0; i-- {
+		if predicate(s.items[i]) {
+			items = append(items, s.items[i])
+			s.items = append(s.items[:i], s.items[i+1:]...)
+		}
+	}
+	return items
+}
diff --git a/common/herrors/errors.go b/common/herrors/errors.go
index 7c389c1ae..e7f91462e 100644
--- a/common/herrors/errors.go
+++ b/common/herrors/errors.go
@@ -68,6 +68,20 @@ func (e *TimeoutError) Is(target error) bool {
 	return ok
 }
 
+// errMessage wraps an error with a message.
+type errMessage struct {
+	msg string
+	err error
+}
+
+func (e *errMessage) Error() string {
+	return e.msg
+}
+
+func (e *errMessage) Unwrap() error {
+	return e.err
+}
+
 // IsFeatureNotAvailableError returns true if the given error is or contains a FeatureNotAvailableError.
 func IsFeatureNotAvailableError(err error) bool {
 	return errors.Is(err, &FeatureNotAvailableError{})
@@ -121,19 +135,38 @@ func IsNotExist(err error) bool {
 
 var nilPointerErrRe = regexp.MustCompile(`at <(.*)>: error calling (.*?): runtime error: invalid memory address or nil pointer dereference`)
 
-func ImproveIfNilPointer(inErr error) (outErr error) {
+const deferredPrefix = "__hdeferred/"
+
+var deferredStringToRemove = regexp.MustCompile(`executing "__hdeferred/.*" `)
+
+// ImproveRenderErr improves the error message for rendering errors.
+func ImproveRenderErr(inErr error) (outErr error) {
 	outErr = inErr
+	msg := improveIfNilPointerMsg(inErr)
+	if msg != "" {
+		outErr = &errMessage{msg: msg, err: outErr}
+	}
 
+	if strings.Contains(inErr.Error(), deferredPrefix) {
+		msg := deferredStringToRemove.ReplaceAllString(inErr.Error(), "executing ")
+		outErr = &errMessage{msg: msg, err: outErr}
+	}
+	return
+}
+
+func improveIfNilPointerMsg(inErr error) string {
 	m := nilPointerErrRe.FindStringSubmatch(inErr.Error())
 	if len(m) == 0 {
-		return
+		return ""
 	}
 	call := m[1]
 	field := m[2]
 	parts := strings.Split(call, ".")
+	if len(parts) < 2 {
+		return ""
+	}
 	receiverName := parts[len(parts)-2]
 	receiver := strings.Join(parts[:len(parts)-1], ".")
 	s := fmt.Sprintf("– %s is nil; wrap it in if or with: {{ with %s }}{{ .%s }}{{ end }}", receiverName, receiver, field)
-	outErr = errors.New(nilPointerErrRe.ReplaceAllString(inErr.Error(), s))
-	return
+	return nilPointerErrRe.ReplaceAllString(inErr.Error(), s)
 }
diff --git a/common/hugio/hasBytesWriter.go b/common/hugio/hasBytesWriter.go
index 5148c82f9..d2bcd1bb4 100644
--- a/common/hugio/hasBytesWriter.go
+++ b/common/hugio/hasBytesWriter.go
@@ -17,24 +17,35 @@ import (
 	"bytes"
 )
 
-// HasBytesWriter is a writer that will set Match to true if the given pattern
-// is found in the stream.
+// HasBytesWriter is a writer will match against a slice of patterns.
 type HasBytesWriter struct {
-	Match   bool
-	Pattern []byte
+	Patterns []*HasBytesPattern
 
 	i    int
 	done bool
 	buff []byte
 }
 
+type HasBytesPattern struct {
+	Match   bool
+	Pattern []byte
+}
+
+func (h *HasBytesWriter) patternLen() int {
+	l := 0
+	for _, p := range h.Patterns {
+		l += len(p.Pattern)
+	}
+	return l
+}
+
 func (h *HasBytesWriter) Write(p []byte) (n int, err error) {
 	if h.done {
 		return len(p), nil
 	}
 
 	if len(h.buff) == 0 {
-		h.buff = make([]byte, len(h.Pattern)*2)
+		h.buff = make([]byte, h.patternLen()*2)
 	}
 
 	for i := range p {
@@ -46,11 +57,23 @@ func (h *HasBytesWriter) Write(p []byte) (n int, err error) {
 			h.i = len(h.buff) / 2
 		}
 
-		if bytes.Contains(h.buff, h.Pattern) {
-			h.Match = true
-			h.done = true
-			return len(p), nil
+		for _, pp := range h.Patterns {
+			if bytes.Contains(h.buff, pp.Pattern) {
+				pp.Match = true
+				done := true
+				for _, ppp := range h.Patterns {
+					if !ppp.Match {
+						done = false
+						break
+					}
+				}
+				if done {
+					h.done = true
+				}
+				return len(p), nil
+			}
 		}
+
 	}
 
 	return len(p), nil
diff --git a/common/hugio/hasBytesWriter_test.go b/common/hugio/hasBytesWriter_test.go
index af53fa5dd..49487ab0b 100644
--- a/common/hugio/hasBytesWriter_test.go
+++ b/common/hugio/hasBytesWriter_test.go
@@ -34,8 +34,11 @@ func TestHasBytesWriter(t *testing.T) {
 		var b bytes.Buffer
 
 		h := &HasBytesWriter{
-			Pattern: []byte("__foo"),
+			Patterns: []*HasBytesPattern{
+				{Pattern: []byte("__foo")},
+			},
 		}
+
 		return h, io.MultiWriter(&b, h)
 	}
 
@@ -46,19 +49,19 @@ func TestHasBytesWriter(t *testing.T) {
 	for i := 0; i < 22; i++ {
 		h, w := neww()
 		fmt.Fprintf(w, rndStr()+"abc __foobar"+rndStr())
-		c.Assert(h.Match, qt.Equals, true)
+		c.Assert(h.Patterns[0].Match, qt.Equals, true)
 
 		h, w = neww()
 		fmt.Fprintf(w, rndStr()+"abc __f")
 		fmt.Fprintf(w, "oo bar"+rndStr())
-		c.Assert(h.Match, qt.Equals, true)
+		c.Assert(h.Patterns[0].Match, qt.Equals, true)
 
 		h, w = neww()
 		fmt.Fprintf(w, rndStr()+"abc __moo bar")
-		c.Assert(h.Match, qt.Equals, false)
+		c.Assert(h.Patterns[0].Match, qt.Equals, false)
 	}
 
 	h, w := neww()
 	fmt.Fprintf(w, "__foo")
-	c.Assert(h.Match, qt.Equals, true)
+	c.Assert(h.Patterns[0].Match, qt.Equals, true)
 }
diff --git a/common/maps/cache.go b/common/maps/cache.go
index 3723d318e..7cd7410c2 100644
--- a/common/maps/cache.go
+++ b/common/maps/cache.go
@@ -74,6 +74,26 @@ func (c *Cache[K, T]) ForEeach(f func(K, T)) {
 	}
 }
 
+func (c *Cache[K, T]) Drain() map[K]T {
+	c.Lock()
+	m := c.m
+	c.m = make(map[K]T)
+	c.Unlock()
+	return m
+}
+
+func (c *Cache[K, T]) Len() int {
+	c.RLock()
+	defer c.RUnlock()
+	return len(c.m)
+}
+
+func (c *Cache[K, T]) Reset() {
+	c.Lock()
+	c.m = make(map[K]T)
+	c.Unlock()
+}
+
 // SliceCache is a simple thread safe cache backed by a map.
 type SliceCache[T any] struct {
 	m map[string][]T
diff --git a/common/paths/path.go b/common/paths/path.go
index 906270cae..de91d6a2f 100644
--- a/common/paths/path.go
+++ b/common/paths/path.go
@@ -237,12 +237,17 @@ func prettifyPath(in string, b filepathPathBridge) string {
 	return b.Join(b.Dir(in), name, "index"+ext)
 }
 
-// CommonDir returns the common directory of the given paths.
-func CommonDir(path1, path2 string) string {
+// CommonDirPath returns the common directory of the given paths.
+func CommonDirPath(path1, path2 string) string {
 	if path1 == "" || path2 == "" {
 		return ""
 	}
 
+	hadLeadingSlash := strings.HasPrefix(path1, "/") || strings.HasPrefix(path2, "/")
+
+	path1 = TrimLeading(path1)
+	path2 = TrimLeading(path2)
+
 	p1 := strings.Split(path1, "/")
 	p2 := strings.Split(path2, "/")
 
@@ -256,7 +261,13 @@ func CommonDir(path1, path2 string) string {
 		}
 	}
 
-	return strings.Join(common, "/")
+	s := strings.Join(common, "/")
+
+	if hadLeadingSlash && s != "" {
+		s = "/" + s
+	}
+
+	return s
 }
 
 // Sanitize sanitizes string to be used in Hugo's file paths and URLs, allowing only
@@ -384,12 +395,27 @@ func PathEscape(pth string) string {
 
 // ToSlashTrimLeading is just a filepath.ToSlash with an added / prefix trimmer.
 func ToSlashTrimLeading(s string) string {
-	return strings.TrimPrefix(filepath.ToSlash(s), "/")
+	return TrimLeading(filepath.ToSlash(s))
+}
+
+// TrimLeading trims the leading slash from the given string.
+func TrimLeading(s string) string {
+	return strings.TrimPrefix(s, "/")
 }
 
 // ToSlashTrimTrailing is just a filepath.ToSlash with an added / suffix trimmer.
 func ToSlashTrimTrailing(s string) string {
-	return strings.TrimSuffix(filepath.ToSlash(s), "/")
+	return TrimTrailing(filepath.ToSlash(s))
+}
+
+// TrimTrailing trims the trailing slash from the given string.
+func TrimTrailing(s string) string {
+	return strings.TrimSuffix(s, "/")
+}
+
+// ToSlashTrim trims any leading and trailing slashes from the given string and converts it to a forward slash separated path.
+func ToSlashTrim(s string) string {
+	return strings.Trim(filepath.ToSlash(s), "/")
 }
 
 // ToSlashPreserveLeading converts the path given to a forward slash separated path
@@ -397,3 +423,8 @@ func ToSlashTrimTrailing(s string) string {
 func ToSlashPreserveLeading(s string) string {
 	return "/" + strings.Trim(filepath.ToSlash(s), "/")
 }
+
+// IsSameFilePath checks if s1 and s2 are the same file path.
+func IsSameFilePath(s1, s2 string) bool {
+	return path.Clean(ToSlashTrim(s1)) == path.Clean(ToSlashTrim(s2))
+}
diff --git a/common/paths/path_test.go b/common/paths/path_test.go
index 3605bfc43..bc27df6c6 100644
--- a/common/paths/path_test.go
+++ b/common/paths/path_test.go
@@ -262,3 +262,52 @@ func TestFieldsSlash(t *testing.T) {
 	c.Assert(FieldsSlash("/"), qt.DeepEquals, []string{})
 	c.Assert(FieldsSlash(""), qt.DeepEquals, []string{})
 }
+
+func TestCommonDirPath(t *testing.T) {
+	c := qt.New(t)
+
+	for _, this := range []struct {
+		a, b, expected string
+	}{
+		{"/a/b/c", "/a/b/d", "/a/b"},
+		{"/a/b/c", "a/b/d", "/a/b"},
+		{"a/b/c", "/a/b/d", "/a/b"},
+		{"a/b/c", "a/b/d", "a/b"},
+		{"/a/b/c", "/a/b/c", "/a/b/c"},
+		{"/a/b/c", "/a/b/c/d", "/a/b/c"},
+		{"/a/b/c", "/a/b", "/a/b"},
+		{"/a/b/c", "/a", "/a"},
+		{"/a/b/c", "/d/e/f", ""},
+	} {
+		c.Assert(CommonDirPath(this.a, this.b), qt.Equals, this.expected, qt.Commentf("a: %s b: %s", this.a, this.b))
+	}
+}
+
+func TestIsSameFilePath(t *testing.T) {
+	c := qt.New(t)
+
+	for _, this := range []struct {
+		a, b     string
+		expected bool
+	}{
+		{"/a/b/c", "/a/b/c", true},
+		{"/a/b/c", "/a/b/c/", true},
+		{"/a/b/c", "/a/b/d", false},
+		{"/a/b/c", "/a/b", false},
+		{"/a/b/c", "/a/b/c/d", false},
+		{"/a/b/c", "/a/b/cd", false},
+		{"/a/b/c", "/a/b/cc", false},
+		{"/a/b/c", "/a/b/c/", true},
+		{"/a/b/c", "/a/b/c//", true},
+		{"/a/b/c", "/a/b/c/.", true},
+		{"/a/b/c", "/a/b/c/./", true},
+		{"/a/b/c", "/a/b/c/./.", true},
+		{"/a/b/c", "/a/b/c/././", true},
+		{"/a/b/c", "/a/b/c/././.", true},
+		{"/a/b/c", "/a/b/c/./././", true},
+		{"/a/b/c", "/a/b/c/./././.", true},
+		{"/a/b/c", "/a/b/c/././././", true},
+	} {
+		c.Assert(IsSameFilePath(filepath.FromSlash(this.a), filepath.FromSlash(this.b)), qt.Equals, this.expected, qt.Commentf("a: %s b: %s", this.a, this.b))
+	}
+}