Fix updater failing to uninstall broken symlinks

When checking whether a file exists before uninstalling it, FileUtils::fileExists()
checked whether the link target existed instead of the link itself.  Change fileExists()
to use lstat() instead of stat().

The updater uninstalls files in the order they are listed, if a file and a symlink to it
are both being uninstalled (eg. libMendeley.so.1.6.0 and the symlink libMendeley.so.1.6)
and the real file is removed first, uninstalling the symlink later failed due to the
above issue with uninstalling broken symlinks.

MD-19006

src/FileUtils.cpp

@@ -80,7 +80,7 @@ bool FileUtils::fileExists(const char* path) throw (IOException)
 {
 #ifdef PLATFORM_UNIX
 	struct stat fileInfo;
-	if (stat(path,&fileInfo) != 0)
+	if (lstat(path,&fileInfo) != 0)
 	{
 		if (errno == ENOENT)
 		{

src/FileUtils.h

@@ -67,8 +67,17 @@ class FileUtils
 		  * Unix mode_t values.
 		  */
 		static void chmod(const char* path, int permissions) throw (IOException);
+
+		/** Returns true if the file at @p path exists.  If @p path is a symlink,
+		  * returns true if the symlink itself exists, not the target.
+		  */
 		static bool fileExists(const char* path) throw (IOException);
+
+		/** Returns the Unix mode flags of @p path.  If @p path is a symlink,
+		  * returns the mode flags of the target.
+		  */
 		static int fileMode(const char* path) throw (IOException);
+
 		static void moveFile(const char* src, const char* dest) throw (IOException);
 		static void mkdir(const char* dir) throw (IOException);
 		static void rmdir(const char* dir) throw (IOException);

src/main.cpp

@@ -25,7 +25,7 @@
 
 #include <iostream>
 
-#define UPDATER_VERSION "0.13"
+#define UPDATER_VERSION "0.14"
 
 void runWithUi(int argc, char** argv, UpdateInstaller* installer);
 

src/tests/TestFileUtils.cpp

@@ -23,9 +23,21 @@ void TestFileUtils::testIsRelative()
 #endif
 }
 
+void TestFileUtils::testSymlinkFileExists()
+{
+#ifdef PLATFORM_UNIX
+	const char* linkName = "link-name";
+	FileUtils::removeFile(linkName);
+	FileUtils::createSymLink(linkName, "target-that-does-not-exist");
+	TEST_COMPARE(FileUtils::fileExists(linkName), true);
+#endif
+}
+
 int main(int,char**)
 {
 	TestList<TestFileUtils> tests;
 	tests.addTest(&TestFileUtils::testDirName);
+	tests.addTest(&TestFileUtils::testIsRelative);
+	tests.addTest(&TestFileUtils::testSymlinkFileExists);
 	return TestUtils::runTest(tests);
 }

src/tests/TestFileUtils.h

@@ -5,4 +5,5 @@ class TestFileUtils
 	public:
 		void testDirName();
 		void testIsRelative();
+		void testSymlinkFileExists();
 };

src/tests/TestUtils.h

@@ -105,3 +105,4 @@ inline std::string TestUtils::toString(const char* value, const char*)
 #define TEST_COMPARE(x,y) \
 	TestUtils::compare(x,y,#x,#y);
 
+

src/tests/file_list.xml

@@ -47,5 +47,6 @@
  <uninstall>
   <!-- TODO - List some files to uninstall here !-->
   <file>file-to-uninstall.txt</file>
+  <file>symlink-to-file-to-uninstall.txt</file>
  </uninstall>
 </update>

src/tests/test-update.rb

@@ -104,6 +104,13 @@ def compare_dirs(src_dir, dest_dir)
 	return change_map
 end
 
+def create_test_file(name, content)
+	File.open(name, 'w') do |file|
+		file.puts content
+	end
+	return name
+end
+
 force_elevation = false
 run_in_debugger = false
 
@@ -140,10 +147,8 @@ Dir.mkdir(INSTALL_DIR)
 FileUtils.cp(OLDAPP_NAME,"#{INSTALL_DIR}/#{APP_NAME}")
 
 # Create a dummy file to uninstall
-uninstall_test_file = "#{INSTALL_DIR}/file-to-uninstall.txt"
-File.open(uninstall_test_file,"w") do |file|
-	file.puts "this file should be removed after the update"
-end
+uninstall_test_file = create_test_file("#{INSTALL_DIR}/file-to-uninstall.txt", "this file should be removed after the update")
+uninstall_test_symlink = FileUtils.ln_s("#{INSTALL_DIR}/file-to-uninstall.txt", "#{INSTALL_DIR}/symlink-to-file-to-uninstall.txt")
 
 # Populate package source dir with files to install
 Dir.mkdir(PACKAGE_SRC_DIR)

src/tests/v2_file_list.xml

@@ -62,5 +62,6 @@
  <uninstall>
   <!-- TODO - List some files to uninstall here !-->
   <file>file-to-uninstall.txt</file>
+  <file>symlink-to-file-to-uninstall.txt</file>
  </uninstall>
 </update>