From 5a072fbd100970e3f3a797b025113be1ad83e5f9 Mon Sep 17 00:00:00 2001
From: Deluan <deluan@deluan.com>
Date: Thu, 23 Apr 2020 20:12:32 -0400
Subject: [PATCH] Follow symlinks to directories when scanning

---
 scanner/change_detector.go      | 27 ++++++++++++++++++++++++++-
 scanner/change_detector_test.go | 19 +++++++++++++++++++
 tests/fixtures/symlink          |  1 +
 tests/fixtures/symlink2dir      |  1 +
 tests/fixtures/synlink_invalid  |  1 +
 5 files changed, 48 insertions(+), 1 deletion(-)
 create mode 120000 tests/fixtures/symlink
 create mode 120000 tests/fixtures/symlink2dir
 create mode 120000 tests/fixtures/synlink_invalid

diff --git a/scanner/change_detector.go b/scanner/change_detector.go
index 5b51d4b84..459975d0d 100644
--- a/scanner/change_detector.go
+++ b/scanner/change_detector.go
@@ -61,7 +61,12 @@ func (s *ChangeDetector) loadDir(dirPath string) (children []string, lastUpdated
 		return
 	}
 	for _, f := range files {
-		if f.IsDir() {
+		isDir, err := IsDirOrSymlinkToDir(dirPath, f)
+		// Skip invalid symlinks
+		if err != nil {
+			continue
+		}
+		if isDir {
 			children = append(children, filepath.Join(dirPath, f.Name()))
 		} else {
 			if f.ModTime().After(lastUpdated) {
@@ -72,6 +77,26 @@ func (s *ChangeDetector) loadDir(dirPath string) (children []string, lastUpdated
 	return
 }
 
+// IsDirOrSymlinkToDir returns true if and only if the Dirent represents a file
+// system directory, or a symbolic link to a directory. Note that if the Dirent
+// is not a directory but is a symbolic link, this method will resolve by
+// sending a request to the operating system to follow the symbolic link.
+// Copied from github.com/karrick/godirwalk
+func IsDirOrSymlinkToDir(baseDir string, info os.FileInfo) (bool, error) {
+	if info.IsDir() {
+		return true, nil
+	}
+	if info.Mode()&os.ModeSymlink == 0 {
+		return false, nil
+	}
+	// Does this symlink point to a directory?
+	info, err := os.Stat(filepath.Join(baseDir, info.Name()))
+	if err != nil {
+		return false, err
+	}
+	return info.IsDir(), nil
+}
+
 func (s *ChangeDetector) loadMap(dirMap dirInfoMap, path string, since time.Time, maybe bool) error {
 	children, lastUpdated, err := s.loadDir(path)
 	if err != nil {
diff --git a/scanner/change_detector_test.go b/scanner/change_detector_test.go
index 12b02a3c0..a3f3d9b2b 100644
--- a/scanner/change_detector_test.go
+++ b/scanner/change_detector_test.go
@@ -110,6 +110,25 @@ var _ = Describe("ChangeDetector", func() {
 		Expect(deleted).To(BeEmpty())
 		Expect(changed).To(ConsistOf(P("a/b")))
 	})
+
+	Describe("IsDirOrSymlinkToDir", func() {
+		It("returns true for normal dirs", func() {
+			dir, _ := os.Stat("tests/fixtures")
+			Expect(IsDirOrSymlinkToDir("tests", dir)).To(BeTrue())
+		})
+		It("returns true for symlinks to dirs", func() {
+			dir, _ := os.Stat("tests/fixtures/symlink2dir")
+			Expect(IsDirOrSymlinkToDir("tests/fixtures", dir)).To(BeTrue())
+		})
+		It("returns false for files", func() {
+			dir, _ := os.Stat("tests/fixtures/test.mp3")
+			Expect(IsDirOrSymlinkToDir("tests/fixtures", dir)).To(BeFalse())
+		})
+		It("returns false for symlinks to files", func() {
+			dir, _ := os.Stat("tests/fixtures/symlink")
+			Expect(IsDirOrSymlinkToDir("tests/fixtures", dir)).To(BeFalse())
+		})
+	})
 })
 
 // I hate time-based tests....
diff --git a/tests/fixtures/symlink b/tests/fixtures/symlink
new file mode 120000
index 000000000..64233a9e9
--- /dev/null
+++ b/tests/fixtures/symlink
@@ -0,0 +1 @@
+index.html
\ No newline at end of file
diff --git a/tests/fixtures/symlink2dir b/tests/fixtures/symlink2dir
new file mode 120000
index 000000000..b870225aa
--- /dev/null
+++ b/tests/fixtures/symlink2dir
@@ -0,0 +1 @@
+../
\ No newline at end of file
diff --git a/tests/fixtures/synlink_invalid b/tests/fixtures/synlink_invalid
new file mode 120000
index 000000000..d30fa5577
--- /dev/null
+++ b/tests/fixtures/synlink_invalid
@@ -0,0 +1 @@
+INVALID
\ No newline at end of file