Fix printing progress to non-terminal STDERR

4 files changed, 151 insertions, 14 deletions

diff --git a/libbutl/diagnostics.cxx b/libbutl/diagnostics.cxx
index 4cfc291..73eb155 100644
--- a/libbutl/diagnostics.cxx
+++ b/libbutl/diagnostics.cxx
@@ -19,7 +19,8 @@
 #include <cstddef>  // size_t
 #include <iostream> // cerr
 
-#include <libbutl/fdstream.hxx> // stderr_fd()
+#include <libbutl/optional.hxx>
+#include <libbutl/fdstream.hxx> // stderr_fd(), fdterm()
 
 using namespace std;
 
@@ -33,6 +34,8 @@ namespace butl
   static string diag_progress_blank; // Being printed blanks out the line.
   static size_t diag_progress_size;  // Size of the last printed progress.
 
+  static optional<bool> diag_term;
+
   // Print the progress string to STDERR. Ignore underlying OS errors (this is
   // a progress bar after all, and throwing from dtors wouldn't be nice). Must
   // be called with the diag_mutex being aquired.
@@ -46,18 +49,31 @@ namespace butl
   static inline void
   progress_print (string& s)
   {
-    // If the new progress string is shorter than the printed one, then we will
-    // complement it with the required number of spaces (to overwrite the
-    // trailing junk) prior to printing, and restore it afterwards.
+    if (!diag_term)
+    try
+    {
+      diag_term = fdterm (stderr_fd());
+    }
+    catch (const ios::failure&)
+    {
+      diag_term = false;
+    }
+
+    // If we print to a terminal, and the new progress string is shorter than
+    // the printed one, then we will complement it with the required number of
+    // spaces (to overwrite the trailing junk) prior to printing, and restore
+    // it afterwards.
     //
     size_t n (s.size ());
 
-    if (n < diag_progress_size)
+    if (*diag_term && n < diag_progress_size)
       s.append (diag_progress_size - n, ' ');
 
     if (!s.empty ())
     {
-      s += '\r'; // Position the cursor at the beginning of the line.
+      s += *diag_term
+        ? '\r'  // Position the cursor at the beginning of the line.
+        : '\n';
 
       try
       {
diff --git a/libbutl/diagnostics.hxx b/libbutl/diagnostics.hxx
index 9544945..c1491d6 100644
--- a/libbutl/diagnostics.hxx
+++ b/libbutl/diagnostics.hxx
@@ -52,13 +52,14 @@ namespace butl
   // Progress line facility.
   //
   // The idea is to keep a progress line at the bottom of the terminal with
-  // other output scrolling above it. The printing of the progress line is
-  // integrated into diag_stream_lock and diag_progress_lock. To print or
-  // update the progress acquire diag_progress_lock and update the
-  // diag_progress string. To remove the progress line, set this string to
-  // empty. For better readability start the progress line with a space
-  // (which is where the cursor will be parked). Should only be used if
-  // diag_stream points to std::cerr.
+  // other output scrolling above it. For a non-terminal STDERR the progress
+  // line is printed as a regular one terminated with the newline character.
+  // The printing of the progress line is integrated into diag_stream_lock and
+  // diag_progress_lock. To print or update the progress acquire
+  // diag_progress_lock and update the diag_progress string. To remove the
+  // progress line, set this string to empty. For better readability start the
+  // progress line with a space (which is where the cursor will be parked).
+  // Should only be used if diag_stream points to std::cerr.
   //
   // Note that child processes writing to the same stream may not completely
   // overwrite the progress line so in this case it makes sense to keep the
diff --git a/libbutl/fdstream.cxx b/libbutl/fdstream.cxx
index 7681c88..ab78e6a 100644
--- a/libbutl/fdstream.cxx
+++ b/libbutl/fdstream.cxx
@@ -7,7 +7,7 @@
 #ifndef _WIN32
 #  include <fcntl.h>     // open(), O_*, fcntl()
 #  include <unistd.h>    // close(), read(), write(), lseek(), dup(), pipe(),
-                         // ssize_t, STD*_FILENO
+                         // isatty(), ssize_t, STD*_FILENO
 #  include <sys/uio.h>   // writev(), iovec
 #  include <sys/stat.h>  // stat(), S_I*
 #  include <sys/types.h> // stat, off_t
@@ -20,6 +20,8 @@
 #  include <stdio.h>    // _fileno(), stdin, stdout, stderr
 #  include <fcntl.h>    // _O_*
 #  include <sys/stat.h> // S_I*
+
+#  include <cwchar> // wcsncmp(), wcsstr()
 #endif
 
 #include <errno.h> // errno, E*
@@ -928,6 +930,26 @@ namespace butl
     return r;
   }
 
+  bool
+  fdterm (int fd)
+  {
+    int r (isatty (fd));
+
+    if (r == 1)
+      return true;
+
+    // POSIX specifies ENOTTY errno code for an indication that the descriptor
+    // doesn't refer to a terminal. However, both Linux and FreeBSD man pages
+    // also mention EINVAL for this case.
+    //
+    assert (r == 0);
+
+    if (errno == ENOTTY || errno == EINVAL)
+      return false;
+
+    throw_ios_failure (errno);
+  }
+
 #else
 
   auto_fd
@@ -1108,5 +1130,97 @@ namespace butl
 
     return {auto_fd (pd[0]), auto_fd (pd[1])};
   }
+
+  bool
+  fdterm (int fd)
+  {
+    // Resolve file descriptor to HANDLE. Note that the handle is closed either
+    // when CloseHandle() is called for it or when _close() is called for the
+    // associated file descriptor. So we don't need to close it.
+    //
+    HANDLE h (reinterpret_cast<HANDLE> (_get_osfhandle (fd)));
+    if (h == INVALID_HANDLE_VALUE)
+      throw_ios_failure (errno);
+
+    // Obtain the descriptor type.
+    //
+    DWORD t (GetFileType (h));
+    DWORD e;
+
+    if (t == FILE_TYPE_UNKNOWN && (e = GetLastError ()) != 0)
+      throw_ios_system_failure (e);
+
+    if (t == FILE_TYPE_CHAR) // Terminal.
+      return true;
+
+    if (t != FILE_TYPE_PIPE) // Pipe still can be a terminal (see below).
+      return false;
+
+    // MSYS2 terminal file descriptor has the pipe type. To distinguish it
+    // from other pipes we will try to obtain the associated file name and
+    // heuristically decide if it is a terminal or not. If we fail to obtain
+    // the name (for any reason), then we consider the descriptor as not
+    // referring to a terminal.
+    //
+    // Note that the API we need to use is only available starting with
+    // Windows Vista/Server 2008. To allow programs linked to libbutl to run
+    // on earlier Windows versions we will link the API in run-time and will
+    // fallback to the non-terminal descriptor type on failure. We also need
+    // to partially reproduce the original API types.
+    //
+    HMODULE kh (GetModuleHandle ("kernel32.dll"));
+    if (kh == nullptr)
+      return false;
+
+    // The original type is FILE_INFO_BY_HANDLE_CLASS enum.
+    //
+    enum file_info
+    {
+      file_name = 2
+    };
+
+    using func = BOOL (*) (HANDLE, file_info, LPVOID, DWORD);
+
+    func f (reinterpret_cast<func> (
+      GetProcAddress (kh, "GetFileInformationByHandleEx")));
+
+    if (f == nullptr)
+      return false;
+
+    // The original type is FILE_NAME_INFO structure.
+    //
+    struct
+    {
+      DWORD length;
+      wchar_t name[_MAX_PATH + 1];
+    } fn;
+
+    // Reserve space for the trailing NULL character.
+    //
+    if (!f (h, file_name, &fn, sizeof (fn) - sizeof (wchar_t)))
+      return false;
+
+    // Add the trailing NULL character. Sounds strange, but the name length is
+    // expressed in bytes.
+    //
+    fn.name[fn.length / sizeof (wchar_t)] = L'\0';
+
+    // The MSYS2 terminal descriptor file name looks like this:
+    //
+    // \msys-dd50a72ab4668b33-pty0-to-master
+    //
+    // We will recognize it by the '\msys-' prefix and the presence of the
+    // '-ptyN' entry.
+    //
+    if (wcsncmp (fn.name, L"\\msys-", 6) == 0)
+    {
+      const wchar_t* e (wcsstr (fn.name, L"-pty"));
+
+      return e != nullptr && e[4] >= L'0' && e[4] <= L'9' &&
+        (e[5] == L'-' || e[5] == L'\0');
+    }
+
+    return false;
+  }
 #endif
 }
diff --git a/libbutl/fdstream.hxx b/libbutl/fdstream.hxx
index fa62ff4..3bd8e8b 100644
--- a/libbutl/fdstream.hxx
+++ b/libbutl/fdstream.hxx
@@ -686,6 +686,12 @@ namespace butl
   //
   LIBBUTL_SYMEXPORT fdpipe
   fdopen_pipe (fdopen_mode = fdopen_mode::none);
+
+  // Test whether a file descriptor refers to a terminal. Throw ios::failure on
+  // the underlying OS error.
+  //
+  LIBBUTL_SYMEXPORT bool
+  fdterm (int);
 }
 
 #include <libbutl/fdstream.ixx>