From 0aee13c162ccfe88fa3415791bd312b0be480dbf Mon Sep 17 00:00:00 2001
From: Andrey Semashev <andrey.semashev@gmail.com>
Date: Fri, 5 Nov 2021 20:27:02 +0300
Subject: [PATCH] Append a trailing directory separator when appending an empty
 path in v4.

If the source path ends with a non-empty filename, and the appended path
is empty, C++17 std::filesystem requires to add a trailing directory
separator.
---
 doc/reference.html                |   2 +-
 include/boost/filesystem/path.hpp |  40 ++++-----
 src/path.cpp                      |   8 ++
 test/path_test.cpp                | 139 ++++++++++++++----------------
 test/path_unit_test.cpp           |   4 +
 5 files changed, 97 insertions(+), 96 deletions(-)

diff --git a/doc/reference.html b/doc/reference.html
index 57c8327..e805da2 100644
--- a/doc/reference.html
+++ b/doc/reference.html
@@ -1380,7 +1380,7 @@ path&amp; append(const path&amp; p);</pre>
     <p><b>v4:</b> If <code>p.<a href="#path-is_absolute">is_absolute</a>() || (p.<a href="#path-has_root_name">has_root_name</a>() &amp;&amp; p.<a href="#path-root_name">root_name</a>() != <a href="#path-root_name">root_name</a>())</code>, assigns <code>p</code> to <code>*this</code>. Otherwise, modifies <code>*this</code> as if by these steps:
     <ul>
       <li>If <code>p.<a href="#path-has_root_name">has_root_directory</a>()</code>, removes root directory and relative path, if any.</li>
-      <li>Let <code>x</code> be a <code>path</code> with contents of <code>p</code> without a root name. If <code>*this</code> does not end with a directory separator and <code>x</code> does not start with one, appends <code>path::preferred_separator</code>.</li>
+      <li>Let <code>x</code> be a <code>path</code> with contents of <code>p</code> without a root name. If <code><a href="#path-has_filename">has_filename</a>()</code> is <code>true</code> and <code>x</code> does not start with a directory separator, appends <code>path::preferred_separator</code>.</li>
       <li>Appends <code>x.native()</code>.</li>
     </ul>
     </p>
diff --git a/include/boost/filesystem/path.hpp b/include/boost/filesystem/path.hpp
index 94ba5d8..f37c8c9 100644
--- a/include/boost/filesystem/path.hpp
+++ b/include/boost/filesystem/path.hpp
@@ -520,10 +520,11 @@ public:
     typename boost::disable_if< path_detail::is_native_char_ptr< InputIterator >, path& >::type
     concat(InputIterator begin, InputIterator end)
     {
-        if (begin == end)
-            return *this;
-        std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
-        path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), m_pathname);
+        if (begin != end)
+        {
+            std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
+            path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), m_pathname);
+        }
         return *this;
     }
 
@@ -537,10 +538,11 @@ public:
     typename boost::disable_if< path_detail::is_native_char_ptr< InputIterator >, path& >::type
     concat(InputIterator begin, InputIterator end, codecvt_type const& cvt)
     {
-        if (begin == end)
-            return *this;
-        std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
-        path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), m_pathname, cvt);
+        if (begin != end)
+        {
+            std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
+            path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), m_pathname, cvt);
+        }
         return *this;
     }
 
@@ -582,8 +584,6 @@ public:
         path&
     >::type append(Source const& source)
     {
-        if (path_traits::empty(source))
-            return *this;
         path p;
         path_traits::dispatch(source, p.m_pathname);
         return append(p);
@@ -613,8 +613,6 @@ public:
         path&
     >::type append(Source const& source, codecvt_type const& cvt)
     {
-        if (path_traits::empty(source))
-            return *this;
         path p;
         path_traits::dispatch(source, p.m_pathname, cvt);
         return append(p);
@@ -630,11 +628,12 @@ public:
     typename boost::disable_if< path_detail::is_native_char_ptr< InputIterator >, path& >::type
     append(InputIterator begin, InputIterator end)
     {
-        if (begin == end)
-            return *this;
-        std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
         path p;
-        path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), p.m_pathname);
+        if (begin != end)
+        {
+            std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
+            path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), p.m_pathname);
+        }
         return append(p);
     }
 
@@ -648,11 +647,12 @@ public:
     typename boost::disable_if< path_detail::is_native_char_ptr< InputIterator >, path& >::type
     append(InputIterator begin, InputIterator end, const codecvt_type& cvt)
     {
-        if (begin == end)
-            return *this;
-        std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
         path p;
-        path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), p.m_pathname, cvt);
+        if (begin != end)
+        {
+            std::basic_string< typename std::iterator_traits< InputIterator >::value_type > seq(begin, end);
+            path_traits::convert(seq.c_str(), seq.c_str() + seq.size(), p.m_pathname, cvt);
+        }
         return append(p);
     }
 
diff --git a/src/path.cpp b/src/path.cpp
index 78f6388..b59c54d 100644
--- a/src/path.cpp
+++ b/src/path.cpp
@@ -242,6 +242,10 @@ BOOST_FILESYSTEM_DECL void path::append_v4(path const& p)
             append_v4(rhs);
         }
     }
+    else if (has_filename_v4())
+    {
+        m_pathname.push_back(preferred_separator);
+    }
 }
 
 BOOST_FILESYSTEM_DECL void path::append_v4(const value_type* begin, const value_type* end)
@@ -298,6 +302,10 @@ BOOST_FILESYSTEM_DECL void path::append_v4(const value_type* begin, const value_
             append_v4(rhs);
         }
     }
+    else if (has_filename_v4())
+    {
+        m_pathname.push_back(preferred_separator);
+    }
 }
 
 #ifdef BOOST_WINDOWS_API
diff --git a/test/path_test.cpp b/test/path_test.cpp
index e9e8986..9e610b6 100644
--- a/test/path_test.cpp
+++ b/test/path_test.cpp
@@ -590,11 +590,15 @@ void non_member_tests()
         BOOST_TEST((b / as).native() == path("b\\a").native());
         BOOST_TEST((b / acs).native() == path("b\\a").native());
         PATH_TEST_EQ(path("a") / "b", "a\\b");
-        PATH_TEST_EQ(path("..") / "", "..");
         PATH_TEST_EQ(path("foo") / path("bar"), "foo\\bar");                // path arg
         PATH_TEST_EQ(path("foo") / "bar", "foo\\bar");                      // const char* arg
         PATH_TEST_EQ(path("foo") / path("woo/bar").filename(), "foo\\bar"); // const std::string & arg
         PATH_TEST_EQ("foo" / path("bar"), "foo\\bar");
+#if BOOST_FILESYSTEM_VERSION == 3
+        PATH_TEST_EQ(path("..") / "", "..");
+#else
+        PATH_TEST_EQ(path("..") / "", "..\\");
+#endif
         PATH_TEST_EQ(path("..") / "..", "..\\..");
         PATH_TEST_EQ(path("/") / "..", "/..");
         PATH_TEST_EQ(path("/..") / "..", "/..\\..");
@@ -631,11 +635,13 @@ void non_member_tests()
 
 #if BOOST_FILESYSTEM_VERSION == 3
         PATH_TEST_EQ(path("\\\\net1\\foo") / "\\\\net2\\bar", "\\\\net1\\foo\\\\net2\\bar");
+        PATH_TEST_EQ(path("\\\\net1\\foo") / "\\bar", "\\\\net1\\foo\\bar");
         PATH_TEST_EQ(path("c:\\foo") / "d:\\bar", "c:\\foo\\d:\\bar");
         PATH_TEST_EQ(path("c:\\foo") / "\\bar", "c:\\foo\\bar");
         PATH_TEST_EQ(path("c:foo") / "\\bar", "c:foo\\bar");
 #else
         PATH_TEST_EQ(path("\\\\net1\\foo") / "\\\\net2\\bar", "\\\\net2\\bar");
+        PATH_TEST_EQ(path("\\\\net1\\foo") / "\\bar", "\\\\net1\\bar");
         PATH_TEST_EQ(path("c:\\foo") / "d:\\bar", "d:\\bar");
         PATH_TEST_EQ(path("c:\\foo") / "\\bar", "c:\\bar");
         PATH_TEST_EQ(path("c:foo") / "\\bar", "c:\\bar");
@@ -650,12 +656,16 @@ void non_member_tests()
         PATH_TEST_EQ(b / as, "b/a");
         PATH_TEST_EQ(b / acs, "b/a");
         PATH_TEST_EQ(path("a") / "b", "a/b");
-        PATH_TEST_EQ(path("..") / "", "..");
         PATH_TEST_EQ(path("") / "..", "..");
         PATH_TEST_EQ(path("foo") / path("bar"), "foo/bar");                // path arg
         PATH_TEST_EQ(path("foo") / "bar", "foo/bar");                      // const char* arg
         PATH_TEST_EQ(path("foo") / path("woo/bar").filename(), "foo/bar"); // const std::string & arg
         PATH_TEST_EQ("foo" / path("bar"), "foo/bar");
+#if BOOST_FILESYSTEM_VERSION == 3
+        PATH_TEST_EQ(path("..") / "", "..");
+#else
+        PATH_TEST_EQ(path("..") / "", "../");
+#endif
         PATH_TEST_EQ(path("..") / "..", "../..");
         PATH_TEST_EQ(path("/") / "..", "/..");
         PATH_TEST_EQ(path("/..") / "..", "/../..");
@@ -2037,15 +2047,21 @@ void construction_tests()
 
 //  append_tests  --------------------------------------------------------------------//
 
-void append_test_aux(const path& p, const std::string& s, const std::string& expect)
-{
-    PATH_TEST_EQ((p / path(s)).string(), expect);
-    PATH_TEST_EQ((p / s.c_str()).string(), expect);
-    PATH_TEST_EQ((p / s).string(), expect);
-    path x(p);
-    x.append(s.begin(), s.end());
-    PATH_TEST_EQ(x.string(), expect);
-}
+#define APPEND_TEST(pth, appnd, expected)\
+    {\
+        const path p(pth);\
+        const std::string s(appnd);\
+        PATH_TEST_EQ(p / appnd, expected);\
+        PATH_TEST_EQ((p / path(s)).string(), expected);\
+        PATH_TEST_EQ((p / s.c_str()).string(), expected);\
+        PATH_TEST_EQ((p / s).string(), expected);\
+        path p1(p);\
+        p1 /= appnd;\
+        PATH_TEST_EQ(p1, expected);\
+        path p2(p);\
+        p2.append(s.begin(), s.end());\
+        PATH_TEST_EQ(p2.string(), expected);\
+    }
 
 void append_tests()
 {
@@ -2068,100 +2084,73 @@ void append_tests()
     //for (int i = 0; i < sizeof(x)/sizeof(char*); ++i)
     //  for (int j = 0; j < sizeof(y)/sizeof(char*); ++j)
     //  {
-    //    std::cout << "\n    PATH_TEST_EQ(path(\"" << x[i] << "\") / \"" << y[j] << "\", \""
-    //              << path(x[i]) / y[j] << "\");\n";
-    //    std::cout << "    append_test_aux(\"" << x[i] << "\", \"" << y[j] << "\", \""
+    //    std::cout << "    APPEND_TEST(\"" << x[i] << "\", \"" << y[j] << "\", \""
     //              << path(x[i]) / y[j] << "\");\n";
     //  }
 
-    PATH_TEST_EQ(path("") / "", "");
-    append_test_aux("", "", "");
-
-    PATH_TEST_EQ(path("") / "/", "/");
-    append_test_aux("", "/", "/");
-
-    PATH_TEST_EQ(path("") / "bar", "bar");
-    append_test_aux("", "bar", "bar");
-
-    PATH_TEST_EQ(path("") / "/bar", "/bar");
-    append_test_aux("", "/bar", "/bar");
-
-    PATH_TEST_EQ(path("/") / "", "/");
-    append_test_aux("/", "", "/");
+    APPEND_TEST("", "", "");
+    APPEND_TEST("", "/", "/");
+    APPEND_TEST("", "bar", "bar");
+    APPEND_TEST("", "/bar", "/bar");
 
+    APPEND_TEST("/", "", "/");
 #if BOOST_FILESYSTEM_VERSION == 3
-    PATH_TEST_EQ(path("/") / "/", "//");
-    append_test_aux("/", "/", "//");
+    APPEND_TEST("/", "/", "//");
 #else
-    PATH_TEST_EQ(path("/") / "/", "/");
-    append_test_aux("/", "/", "/");
+    APPEND_TEST("/", "/", "/");
 #endif
-
-    PATH_TEST_EQ(path("/") / "bar", "/bar");
-    append_test_aux("/", "bar", "/bar");
-
+    APPEND_TEST("/", "bar", "/bar");
 #if BOOST_FILESYSTEM_VERSION == 3
-    PATH_TEST_EQ(path("/") / "/bar", "//bar");
-    append_test_aux("/", "/bar", "//bar");
+    APPEND_TEST("/", "/bar", "//bar");
 #else
-    PATH_TEST_EQ(path("/") / "/bar", "/bar");
-    append_test_aux("/", "/bar", "/bar");
-#endif
-
-    PATH_TEST_EQ(path("foo") / "", "foo");
-    append_test_aux("foo", "", "foo");
-
-#if BOOST_FILESYSTEM_VERSION == 3
-    PATH_TEST_EQ(path("foo") / "/", "foo/");
-    append_test_aux("foo", "/", "foo/");
-#else
-    PATH_TEST_EQ(path("foo") / "/", "/");
-    append_test_aux("foo", "/", "/");
+    APPEND_TEST("/", "/bar", "/bar");
 #endif
 
 #if BOOST_FILESYSTEM_VERSION == 3
-    PATH_TEST_EQ(path("foo") / "/bar", "foo/bar");
-    append_test_aux("foo", "/bar", "foo/bar");
+    APPEND_TEST("foo", "/", "foo/");
 #else
-    PATH_TEST_EQ(path("foo") / "/bar", "/bar");
-    append_test_aux("foo", "/bar", "/bar");
+    APPEND_TEST("foo", "/", "/");
 #endif
-
-    PATH_TEST_EQ(path("foo/") / "", "foo/");
-    append_test_aux("foo/", "", "foo/");
-
 #if BOOST_FILESYSTEM_VERSION == 3
-    PATH_TEST_EQ(path("foo/") / "/", "foo//");
-    append_test_aux("foo/", "/", "foo//");
+    APPEND_TEST("foo", "/bar", "foo/bar");
 #else
-    PATH_TEST_EQ(path("foo/") / "/", "/");
-    append_test_aux("foo/", "/", "/");
+    APPEND_TEST("foo", "/bar", "/bar");
 #endif
 
-    PATH_TEST_EQ(path("foo/") / "bar", "foo/bar");
-    append_test_aux("foo/", "bar", "foo/bar");
+    APPEND_TEST("foo/", "", "foo/");
+#if BOOST_FILESYSTEM_VERSION == 3
+    APPEND_TEST("foo/", "/", "foo//");
+#else
+    APPEND_TEST("foo/", "/", "/");
+#endif
+    APPEND_TEST("foo/", "bar", "foo/bar");
 
     if (platform == "Windows")
     {
-        PATH_TEST_EQ(path("foo") / "bar", "foo\\bar");
-        append_test_aux("foo", "bar", "foo\\bar");
+#if BOOST_FILESYSTEM_VERSION == 3
+        APPEND_TEST("foo", "", "foo");
+#else
+        APPEND_TEST("foo", "", "foo\\");
+#endif
+        APPEND_TEST("foo", "bar", "foo\\bar");
 
 #if BOOST_FILESYSTEM_VERSION == 3
-        PATH_TEST_EQ(path("foo\\") / "\\bar", "foo\\\\bar");
-        append_test_aux("foo\\", "\\bar", "foo\\\\bar");
+        APPEND_TEST("foo\\", "\\bar", "foo\\\\bar");
 #else
-        PATH_TEST_EQ(path("foo\\") / "\\bar", "\\bar");
-        append_test_aux("foo\\", "\\bar", "\\bar");
+        APPEND_TEST("foo\\", "\\bar", "\\bar");
 #endif
 
         // hand created test case specific to Windows
-        PATH_TEST_EQ(path("c:") / "bar", "c:bar");
-        append_test_aux("c:", "bar", "c:bar");
+        APPEND_TEST("c:", "bar", "c:bar");
     }
     else
     {
-        PATH_TEST_EQ(path("foo") / "bar", "foo/bar");
-        append_test_aux("foo", "bar", "foo/bar");
+#if BOOST_FILESYSTEM_VERSION == 3
+        APPEND_TEST("foo", "", "foo");
+#else
+        APPEND_TEST("foo", "", "foo/");
+#endif
+        APPEND_TEST("foo", "bar", "foo/bar");
     }
 
     // ticket #6819
diff --git a/test/path_unit_test.cpp b/test/path_unit_test.cpp
index e31d207..09d69da 100644
--- a/test/path_unit_test.cpp
+++ b/test/path_unit_test.cpp
@@ -321,7 +321,11 @@ void test_appends()
 
     x = "/foo";
     x /= path(""); // empty path
+#if BOOST_FILESYSTEM_VERSION == 3
     PATH_IS(x, L"/foo");
+#else
+    PATH_IS(x, L"/foo/");
+#endif
 
     x = "/foo";
     x /= path("/"); // slash path