From 56e88805a0545e547f163b6d5740614fa0bedf61 Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Sun, 15 Sep 2024 17:15:21 +0200
Subject: [PATCH] Refusing to write files with empty string and to a path that
 is a directory - the latter would rename the directory and later try to
 remove it

---
 src/tl/tl/tlStream.cc              | 34 +++++++++++++++++++++---------
 src/tl/unit_tests/tlStreamTests.cc | 15 +++++++++++++
 2 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/src/tl/tl/tlStream.cc b/src/tl/tl/tlStream.cc
index 751c4841d..f83be7bfb 100644
--- a/src/tl/tl/tlStream.cc
+++ b/src/tl/tl/tlStream.cc
@@ -1178,20 +1178,34 @@ OutputStream::seek (size_t pos)
 OutputFileBase::OutputFileBase (const std::string &p, int keep_backups)
   : m_keep_backups (keep_backups), m_path (tl::absolute_file_path (p)), m_has_error (false)
 {
+  if (p.empty ()) {
+    throw tl::Exception (tl::to_string (tr ("Path cannot be an empty string")));
+  }
+
   if (tl::file_exists (m_path)) {
-    m_backup_path = m_path + ".~backup";
-    if (tl::file_exists (m_backup_path)) {
-      if (! tl::rm_file (m_backup_path)) {
-        tl::warn << tl::sprintf (tl::to_string (tr ("Could not create backup file: unable to remove existing file '%s'")), m_backup_path);
-        m_backup_path = std::string ();
+
+    if (tl::is_dir (m_path)) {
+
+      throw tl::Exception (tl::to_string (tr ("Path exists and is a directory: '%s'")), m_path);
+
+    } else {
+
+      m_backup_path = m_path + ".~backup";
+      if (tl::file_exists (m_backup_path)) {
+        if (! tl::rm_file (m_backup_path)) {
+          tl::warn << tl::sprintf (tl::to_string (tr ("Could not create backup file: unable to remove existing file '%s'")), m_backup_path);
+          m_backup_path = std::string ();
+        }
       }
-    }
-    if (! m_backup_path.empty ()) {
-      if (! tl::rename_file (m_path, tl::filename (m_backup_path))) {
-        tl::warn << tl::sprintf (tl::to_string (tr ("Could not create backup file: unable to rename original file '%s' to backup file")), m_path, m_backup_path);
-        m_backup_path = std::string ();
+      if (! m_backup_path.empty ()) {
+        if (! tl::rename_file (m_path, tl::filename (m_backup_path))) {
+          tl::warn << tl::sprintf (tl::to_string (tr ("Could not create backup file: unable to rename original file '%s' to backup file")), m_path, m_backup_path);
+          m_backup_path = std::string ();
+        }
       }
+
     }
+
   }
 }
 
diff --git a/src/tl/unit_tests/tlStreamTests.cc b/src/tl/unit_tests/tlStreamTests.cc
index 517d71615..156f276c2 100644
--- a/src/tl/unit_tests/tlStreamTests.cc
+++ b/src/tl/unit_tests/tlStreamTests.cc
@@ -462,5 +462,20 @@ TEST(Backups)
   }
 }
 
+TEST(RefuseToWrite)
+{
+  try {
+    tl::OutputStream os ("");
+    EXPECT_EQ (1, 0);
+  } catch (tl::Exception &ex) {
+    EXPECT_EQ (ex.msg (), "Path cannot be an empty string");
+  }
 
+  try {
+    tl::OutputStream os (".");
+    EXPECT_EQ (1, 0);
+  } catch (tl::Exception &ex) {
+    EXPECT_EQ (ex.msg ().find ("Path exists and is a directory"), size_t (0));
+  }
+}