// file      : build2/test/script/runner.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#include <build2/test/script/runner.hxx>

#include <set>
#include <ios> // streamsize

#include <libbutl/fdstream.hxx> // fdopen_mode, fdnull(), fddup()

#include <build2/regex.hxx>
#include <build2/variable.hxx>
#include <build2/filesystem.hxx>

#include <build2/test/common.hxx>

#include <build2/test/script/regex.hxx>
#include <build2/test/script/parser.hxx>
#include <build2/test/script/builtin.hxx>

using namespace std;
using namespace butl;

namespace build2
{
  namespace test
  {
    namespace script
    {
      // Normalize a path. Also make the relative path absolute using the
      // scope's working directory unless it is already absolute.
      //
      static path
      normalize (path p, const scope& sp, const location& l)
      {
        path r (p.absolute () ? move (p) : sp.wd_path / move (p));

        try
        {
          r.normalize ();
        }
        catch (const invalid_path& e)
        {
          fail (l) << "invalid file path " << e.path;
        }

        return r;
      }

      // Check if a path is not empty, the referenced file exists and is not
      // empty.
      //
      static bool
      non_empty (const path& p, const location& ll)
      {
        if (p.empty () || !exists (p))
          return false;

        try
        {
          ifdstream is (p);
          return is.peek () != ifdstream::traits_type::eof ();
        }
        catch (const io_error& e)
        {
          // While there can be no fault of the test command being currently
          // executed let's add the location anyway to ease the
          // troubleshooting. And let's stick to that principle down the road.
          //
          fail (ll) << "unable to read " << p << ": " << e << endf;
        }
      }

      // If the file exists, not empty and not larger than 4KB print it to the
      // diag record. The file content goes from the new line and is not
      // indented.
      //
      static void
      print_file (diag_record& d, const path& p, const location& ll)
      {
        if (exists (p))
        {
          try
          {
            ifdstream is (p, ifdstream::in, ifdstream::badbit);

            if (is.peek () != ifdstream::traits_type::eof ())
            {
              char buf[4096 + 1]; // Extra byte is for terminating '\0'.

              // Note that the string is always '\0'-terminated with a maximum
              // sizeof (buf) - 1 bytes read.
              //
              is.getline (buf, sizeof (buf), '\0');

              // Print if the file fits 4KB-size buffer. Note that if it
              // doesn't the failbit is set.
              //
              if (is.eof ())
              {
                // Suppress the trailing newline character as the diag record
                // adds it's own one when flush.
                //
                streamsize n (is.gcount ());
                assert (n > 0);

                // Note that if the file contains '\0' it will also be counted
                // by gcount(). But even in the worst case we will stay in the
                // buffer boundaries (and so not crash).
                //
                if (buf[n - 1] == '\n')
                  buf[n - 1] = '\0';

                d << '\n' << buf;
              }
            }
          }
          catch (const io_error& e)
          {
            fail (ll) << "unable to read " << p << ": " << e;
          }
        }
      }

      // Print first 10 directory sub-entries to the diag record. The directory
      // must exist.
      //
      static void
      print_dir (diag_record& d, const dir_path& p, const location& ll)
      {
        try
        {
          size_t n (0);
          for (const dir_entry& de: dir_iterator (p))
          {
            if (n++ < 10)
              d << '\n' << (de.ltype () == entry_type::directory
                            ? path_cast<dir_path> (de.path ())
                            : de.path ());
          }

          if (n > 10)
            d << "\nand " << n - 10 << " more file(s)";
        }
        catch (const system_error& e)
        {
          fail (ll) << "unable to iterate over " << p << ": " << e;
        }
      }

      // Save a string to the file. Fail if exception is thrown by underlying
      // operations.
      //
      static void
      save (const path& p, const string& s, const location& ll)
      {
        try
        {
          ofdstream os (p);
          os << s;
          os.close ();
        }
        catch (const io_error& e)
        {
          fail (ll) << "unable to write " << p << ": " << e;
        }
      }

      // Transform string according to here-* redirect modifiers from the {/}
      // set.
      //
      static string
      transform (const string& s,
                 bool regex,
                 const string& modifiers,
                 const script& scr)
      {
        if (modifiers.find ('/') == string::npos)
          return s;

        // For targets other than Windows leave the string intact.
        //
        if (cast<target_triplet> (scr.test_target["test.target"]).class_ !=
            "windows")
          return s;

        // Convert forward slashes to Windows path separators (escape for
        // regex).
        //
        string r;
        for (size_t p (0);;)
        {
          size_t sp (s.find ('/', p));

          if (sp != string::npos)
          {
            r.append (s, p, sp - p);
            r.append (regex ? "\\\\" : "\\");
            p = sp + 1;
          }
          else
          {
            r.append (s, p, sp);
            break;
          }
        }

        return r;
      }

      // Check if the test command output matches the expected result (redirect
      // value). Noop for redirect types other than none, here_*.
      //
      static bool
      check_output (const path& pr,
                    const path& op,
                    const path& ip,
                    const redirect& rd,
                    const location& ll,
                    scope& sp,
                    bool diag,
                    const char* what)
      {
        auto input_info = [&ip, &ll] (diag_record& d)
        {
          if (non_empty (ip, ll))
            d << info << "stdin: " << ip;
        };

        auto output_info = [&what, &ll] (diag_record& d,
                                         const path& p,
                                         const char* prefix = "",
                                         const char* suffix = "")
        {
          if (non_empty (p, ll))
            d << info << prefix << what << suffix << ": " << p;
          else
            d << info << prefix << what << suffix << " is empty";
        };

        if (rd.type == redirect_type::none)
        {
          // Check that there is no output produced.
          //
          assert (!op.empty ());

          if (!non_empty (op, ll))
            return true;

          if (diag)
          {
            diag_record d (error (ll));
            d << pr << " unexpectedly writes to " << what <<
              info << what << ": " << op;

            input_info (d);

            // Print cached output.
            //
            print_file (d, op, ll);
          }

          // Fall through (to return false).
          //
        }
        else if (rd.type == redirect_type::here_str_literal ||
                 rd.type == redirect_type::here_doc_literal ||
                 (rd.type == redirect_type::file &&
                  rd.file.mode == redirect_fmode::compare))
        {
          // The expected output is provided as a file or as a string. Save the
          // string to a file in the later case.
          //
          assert (!op.empty ());

          path eop;

          if (rd.type == redirect_type::file)
            eop = normalize (rd.file.path, sp, ll);
          else
          {
            eop = path (op + ".orig");
            save (eop, transform (rd.str, false, rd.modifiers, *sp.root), ll);
            sp.clean ({cleanup_type::always, eop}, true);
          }

          // Use diff utility for the comparison.
          //
          path dp ("diff");
          process_path pp (run_search (dp, true));

          cstrings args {pp.recall_string (), "-u"};

          // Ignore Windows newline fluff if that's what we are running on.
          //
          if (cast<target_triplet> (
                sp.root->test_target["test.target"]).class_ == "windows")
            args.push_back ("--strip-trailing-cr");

          args.push_back (eop.string ().c_str ());
          args.push_back (op.string ().c_str ());
          args.push_back (nullptr);

          if (verb >= 2)
            print_process (args);

          try
          {
            // Save diff's stdout to a file for troubleshooting and for the
            // optional (if not too large) printing (at the end of
            // diagnostics).
            //
            path ep (op + ".diff");
            auto_fd efd;

            try
            {
              efd = fdopen (ep, fdopen_mode::out | fdopen_mode::create);
              sp.clean ({cleanup_type::always, ep}, true);
            }
            catch (const io_error& e)
            {
              fail (ll) << "unable to write " << ep << ": " << e;
            }

            // Diff utility prints the differences to stdout. But for the
            // user it is a part of the test failure diagnostics so let's
            // redirect stdout to stderr.
            //
            process p (pp, args.data (), 0, 2, efd.get ());
            efd.reset ();

            if (p.wait ())
              return true;

            assert (p.exit);
            const process_exit& pe (*p.exit);

            // Note that both POSIX and GNU diff report error by exiting with
            // the code > 1.
            //
            if (!pe.normal () || pe.code () > 1)
            {
              diag_record d (fail (ll));
              print_process (d, args);

              if (!pe.normal ())
              {
                d << " terminated abnormally: " << pe.description ();

                if (pe.core ())
                  d << " (core dumped)";
              }
              else
                d << " exited with code "
                  << static_cast<uint16_t> (pe.code ());
            }

            // Output doesn't match the expected result.
            //
            if (diag)
            {
              diag_record d (error (ll));
              d << pr << " " << what << " doesn't match expected";

              output_info (d, op);
              output_info (d, eop, "expected ");
              output_info (d, ep, "", " diff");
              input_info  (d);

              print_file (d, ep, ll);
            }

            // Fall through (to return false).
            //
          }
          catch (const process_error& e)
          {
            error (ll) << "unable to execute " << pp << ": " << e;

            if (e.child)
              exit (1);

            throw failed ();
          }
        }
        else if (rd.type == redirect_type::here_str_regex ||
                 rd.type == redirect_type::here_doc_regex)
        {
          // The overall plan is:
          //
          // 1. Create regex line string. While creating it's line characters
          //    transform regex lines according to the redirect modifiers.
          //
          // 2. Create line regex using the line string. If creation fails
          //    then save the (transformed) regex redirect to a file for
          //    troubleshooting.
          //
          // 3. Parse the output into the literal line string.
          //
          // 4. Match the output line string with the line regex.
          //
          // 5. If match fails save the (transformed) regex redirect to a file
          //    for troubleshooting.
          //
          using namespace regex;

          assert (!op.empty ());

          // Create regex line string.
          //
          line_pool pool;
          line_string rls;
          const regex_lines rl (rd.regex);

          // Parse regex flags.
          //
          // When add support for new flags don't forget to update
          // parse_regex().
          //
          auto parse_flags = [] (const string& f) -> char_flags
          {
            char_flags r (char_flags::none);

            for (char c: f)
            {
              switch (c)
              {
              case 'd': r |= char_flags::idot;  break;
              case 'i': r |= char_flags::icase; break;
              default: assert (false); // Error so should have been checked.
              }
            }

            return r;
          };

          // Return original regex line with the transformation applied.
          //
          auto line = [&rl, &rd, &sp] (const regex_line& l) -> string
          {
            string r;
            if (l.regex)                  // Regex (possibly empty),
            {
              r += rl.intro;
              r += transform (l.value, true, rd.modifiers, *sp.root);
              r += rl.intro;
              r += l.flags;
            }
            else if (!l.special.empty ()) // Special literal.
              r += rl.intro;
            else                          // Textual literal.
              r += transform (l.value, false, rd.modifiers, *sp.root);

            r += l.special;
            return r;
          };

          // Return regex line location.
          //
          // Note that we rely on the fact that the command and regex lines
          // are always belong to the same testscript file.
          //
          auto loc = [&ll] (uint64_t line, uint64_t column) -> location
          {
            location r (ll);
            r.line = line;
            r.column = column;
            return r;
          };

          // Save the regex to file for troubleshooting, return the file path
          // it have been saved to.
          //
          // Note that we save the regex on line regex creation failure or if
          // the program output doesn't match.
          //
          auto save_regex = [&op, &rl, &rd, &ll, &line] () -> path
          {
            path rp (op + ".regex");

            // Encode here-document regex global flags if present as a file
            // name suffix. For example if icase and idot flags are specified
            // the name will look like:
            //
            // test/1/stdout.regex-di
            //
            if (rd.type == redirect_type::here_doc_regex && !rl.flags.empty ())
              rp += '-' + rl.flags;

            // Note that if would be more efficient to directly write chunks
            // to file rather than to compose a string first. Hower we don't
            // bother (about performance) for the sake of the code as we
            // already failed.
            //
            string s;
            for (auto b (rl.lines.cbegin ()), i (b), e (rl.lines.cend ());
                 i != e; ++i)
            {
              if (i != b) s += '\n';
              s += line (*i);
            }

            save (rp, s, ll);
            return rp;
          };

          // Finally create regex line string.
          //
          // Note that diagnostics doesn't refer to the program path as it is
          // irrelevant to failures at this stage.
          //
          char_flags gf (parse_flags (rl.flags)); // Regex global flags.

          for (const auto& l: rl.lines)
          {
            if (l.regex) // Regex (with optional special characters).
            {
              line_char c;

              // Empty regex is a special case repesenting the blank line.
              //
              if (l.value.empty ())
                c = line_char ("", pool);
              else
              {
                try
                {
                  string s (transform (l.value, true, rd.modifiers, *sp.root));

                  c = line_char (
                    char_regex (s, gf | parse_flags (l.flags)), pool);
                }
                catch (const regex_error& e)
                {
                  // Print regex_error description if meaningful.
                  //
                  diag_record d (fail (loc (l.line, l.column)));

                  if (rd.type == redirect_type::here_str_regex)
                    d << "invalid " << what << " regex redirect" << e <<
                      info << "regex: '" << line (l) << "'";
                  else
                    d << "invalid char-regex in " << what << " regex redirect"
                      << e <<
                      info << "regex line: '" << line (l) << "'";

                  d << endf;
                }
              }

              rls += c; // Append blank literal or regex line char.
            }
            else if (!l.special.empty ()) // Special literal.
            {
              // Literal can not be followed by special characters in the same
              // line.
              //
              assert (l.value.empty ());
            }
            else // Textual literal.
            {
              // Append literal line char.
              //
              rls += line_char (
                transform (l.value, false, rd.modifiers, *sp.root), pool);
            }

            for (char c: l.special)
            {
              if (line_char::syntax (c))
                rls += line_char (c); // Append special line char.
              else
                fail (loc (l.line, l.column))
                  << "invalid syntax character '" << c << "' in " << what
                  << " regex redirect" <<
                  info << "regex line: '" << line (l) << "'";
            }
          }

          // Create line regex.
          //
          line_regex regex;

          try
          {
            regex = line_regex (move (rls), move (pool));
          }
          catch (const regex_error& e)
          {
            // Note that line regex creation can not fail for here-string
            // redirect as it doesn't have syntax line chars. That in
            // particular means that end_line and end_column are meaningful.
            //
            assert (rd.type == redirect_type::here_doc_regex);

            diag_record d (fail (loc (rd.end_line, rd.end_column)));

            // Print regex_error description if meaningful.
            //
            d << "invalid " << what << " regex redirect" << e;

            output_info (d, save_regex (), "", " regex");
          }

          // Parse the output into the literal line string.
          //
          line_string ls;

          try
          {
            // Do not throw when eofbit is set (end of stream reached), and
            // when failbit is set (getline() failed to extract any character).
            //
            // Note that newlines are treated as line-chars separators. That
            // in particular means that the trailing newline produces a blank
            // line-char (empty literal). Empty output produces the zero-length
            // line-string.
            //
            // Also note that we strip the trailing CR characters (otherwise
            // can mismatch when cross-test).
            //
            ifdstream is (op, ifdstream::in, ifdstream::badbit);
            is.peek (); // Sets eofbit for an empty stream.

            while (!is.eof ())
            {
              string s;
              getline (is, s);

              // It is safer to strip CRs in cycle, as msvcrt unexplainably
              // adds too much trailing junk to the system_error descriptions,
              // and so it can appear in programs output. For example:
              //
              // ...: Invalid data.\r\r\n
              //
              // Note that our custom operator<<(ostream&, const exception&)
              // removes this junk.
              //
              while (!s.empty () && s.back () == '\r')
                s.pop_back ();

              ls += line_char (move (s), regex.pool);
            }
          }
          catch (const io_error& e)
          {
            fail (ll) << "unable to read " << op << ": " << e;
          }

          // Match the output with the regex.
          //
          if (regex_match (ls, regex)) // Doesn't throw.
            return true;

          // Output doesn't match the regex. We save the regex to file for
          // troubleshooting regardless of whether we print the diagnostics or
          // not.
          //
          path rp (save_regex ());

          if (diag)
          {
            diag_record d (error (ll));
            d << pr << " " << what << " doesn't match regex";

            output_info (d, op);
            output_info (d, rp, "", " regex");
            input_info  (d);

            // Print cached output.
            //
            print_file (d, op, ll);
          }

          // Fall through (to return false).
          //
        }
        else // Noop.
          return true;

        return false;
      }

      bool default_runner::
      test (scope& s) const
      {
        return common_.test (s.root->test_target, s.id_path);
      }

      void default_runner::
      enter (scope& sp, const location&)
      {
        // Scope working directory shall be empty (the script working
        // directory is cleaned up by the test rule prior the script
        // execution).
        //
        // @@ Shouldn't we add an optional location parameter to mkdir() and
        // alike utility functions so the failure message can contain
        // location info?
        //
        if (mkdir (sp.wd_path, 2) == mkdir_status::already_exists)
          fail << "working directory " << sp.wd_path << " already exists" <<
            info << "are tests stomping on each other's feet?";

        // We don't change the current directory here but indicate that the
        // scope test commands will be executed in that directory.
        //
        if (verb >= 2)
          text << "cd " << sp.wd_path;

        sp.clean ({cleanup_type::always, sp.wd_path}, true);
      }

      void default_runner::
      leave (scope& sp, const location& ll)
      {
        // Perform registered cleanups if requested.
        //
        if (common_.after == output_after::clean)
        {
          // Remove files and directories in the order opposite to the order of
          // cleanup registration.
          //
          // Note that we operate with normalized paths here.
          //
          for (const auto& c: reverse_iterate (sp.cleanups))
          {
            cleanup_type t (c.type);

            // Skip whenever the path exists or not.
            //
            if (t == cleanup_type::never)
              continue;

            const path& p (c.path);
            const path& l (p.leaf ());
            const string& ls (l.string ());

            // Remove the directory recursively if not current. Fail otherwise.
            // Recursive removal of non-existing directory is not an error for
            // 'maybe' cleanup type.
            //
            if (ls == "***")
            {
              // Cast to uint16_t to avoid ambiguity with libbutl::rmdir_r().
              //
              rmdir_status r (
                rmdir_r (p.directory (), true, static_cast<uint16_t> (3)));

              if (r == rmdir_status::success ||
                  (r == rmdir_status::not_exist && t == cleanup_type::maybe))
                continue;

              // The directory is unlikely to be current but let's keep for
              // completeness.
              //
              fail (ll) << "registered for cleanup wildcard " << p
                        << (r == rmdir_status::not_empty
                            ? " matches the current directory"
                            : " doesn't match a directory");
            }

            // Remove files or directories using wildcard. Removal of
            // sub-entries of non-existing directory is not an error for
            // 'maybe' cleanup type.
            //
            // Note that only the leaf part of the cleanup wildcard is a
            // pattern in terms of libbutl::path_search().
            //
            if (ls == "*" || ls == "**")
            {
              dir_path d (p.directory ());

              if (t == cleanup_type::always && !dir_exists (d))
                fail (ll) << "registered for cleanup wildcard " << p
                          << " doesn't match a directory";

              if (l.to_directory ())
              {
                auto rm =
                  [&p, &d, &ll] (path&& de, const string&, bool interm) -> bool
                {
                  if (!interm)
                  {
                    dir_path sd (path_cast<dir_path> (d / de));

                    // We can get not_exist here due to racing conditions, but
                    // that's ok if somebody did our job.
                    //
                    rmdir_status r (rmdir (sd, 3));

                    if (r != rmdir_status::not_empty)
                      return true;

                    diag_record dr (fail (ll));
                    dr << "registered for cleanup directory " << sd
                       << " is not empty";

                    print_dir (dr, sd, ll);
                    dr << info << "wildcard: '" << p << "'";
                  }

                  return true;
                };

                path_search (l, rm, d);
              }
              else
              {
                auto rm = [&d] (path&& p, const string&, bool interm) -> bool
                {
                  if (!interm)
                    rmfile (d / p, 3); // That's ok if not exists.

                  return true;
                };

                path_search (l, rm, d);
              }

              continue;
            }

            // Remove the directory if exists and empty. Fail otherwise.
            // Removal of non-existing directory is not an error for 'maybe'
            // cleanup type.
            //
            if (p.to_directory ())
            {
              dir_path d (path_cast<dir_path> (p));

              // Trace the scope working directory removal with the verbosity
              // level 2 (that was used for its creation). For other
              // directories use level 3 (as for other cleanups).
              //
              // @@ If 'd' is a file then will fail with a diagnostics having
              //    no location info. Probably need to add an optional location
              //    parameter to rmdir() function. The same problem exists for
              //    a file cleanup when try to rmfile() directory instead of
              //    file.
              //
              rmdir_status r (rmdir (d, d == sp.wd_path ? 2 : 3));

              if (r == rmdir_status::success ||
                  (r == rmdir_status::not_exist && t == cleanup_type::maybe))
                continue;

              diag_record dr (fail (ll));
              dr << "registered for cleanup directory " << d
                 << (r == rmdir_status::not_empty
                     ? " is not empty"
                     : " does not exist");

              if (r == rmdir_status::not_empty)
                print_dir (dr, d, ll);
            }

            // Remove the file if exists. Fail otherwise. Removal of
            // non-existing file is not an error for 'maybe' cleanup type.
            //
            if (rmfile (p, 3) == rmfile_status::not_exist &&
                t == cleanup_type::always)
              fail (ll) << "registered for cleanup file " << p
                        << " does not exist";
          }
        }

        // Return to the parent scope directory or to the out_base one for the
        // script scope.
        //
        if (verb >= 2)
          text << "cd " << (sp.parent != nullptr
                            ? sp.parent->wd_path
                            : sp.wd_path.directory ());
      }

      // The set pseudo-builtin: set variable from the stdin input.
      //
      // set [-e|--exact] [(-n|--newline)|(-w|--whitespace)] [<attr>] <var>
      //
      static void
      set_builtin (scope& sp,
                   const strings& args,
                   auto_fd in,
                   const location& ll)
      {
        try
        {
          // Do not throw when eofbit is set (end of stream reached), and
          // when failbit is set (read operation failed to extract any
          // character).
          //
          ifdstream cin  (move (in), ifdstream::badbit);

          auto i (args.begin ());
          auto e (args.end ());

          // Process options.
          //
          bool exact (false);
          bool newline (false);
          bool whitespace (false);

          for (; i != e; ++i)
          {
            const string& o (*i);

            if (o == "-e" || o == "--exact")
              exact = true;
            else if (o == "-n" || o == "--newline")
              newline = true;
            else if (o == "-w" || o == "--whitespace")
              whitespace = true;
            else
            {
              if (*i == "--")
                ++i;

              break;
            }
          }

          // Process arguments.
          //
          if (i == e)
            fail (ll) << "missing variable name";

          const string& a (*i++); // Either attributes or variable name.
          const string* ats (i == e ? nullptr : &a);
          const string& vname (i == e ? a : *i++);

          if (i != e)
	    fail (ll) << "unexpected argument";

          if (ats != nullptr && ats->empty ())
	    fail (ll) << "empty variable attributes";

          if (vname.empty ())
	    fail (ll) << "empty variable name";

          // Read the input.
          //
          cin.peek (); // Sets eofbit for an empty stream.

          names ns;
          while (!cin.eof ())
          {
            // Read next element that depends on the whitespace mode being
            // enabled or not. For the later case it also make sense to strip
            // the trailing CRs that can appear while cross-testing Windows
            // target or as a part of msvcrt junk production (see above).
            //
            string s;
            if (whitespace)
              cin >> s;
            else
            {
              getline (cin, s);

              while (!s.empty () && s.back () == '\r')
                s.pop_back ();
            }

            // If failbit is set then we read nothing into the string as eof is
            // reached. That in particular means that the stream has trailing
            // whitespaces (possibly including newlines) if the whitespace mode
            // is enabled, or the trailing newline otherwise. If so then
            // we append the "blank" to the variable value in the exact mode
            // prior to bailing out.
            //
            if (cin.fail ())
            {
              if (exact)
              {
                if (whitespace || newline)
                  ns.emplace_back (move (s)); // Reuse empty string.
                else if (ns.empty ())
                  ns.emplace_back ("\n");
                else
                  ns[0].value += '\n';
              }

              break;
            }

            if (whitespace || newline || ns.empty ())
              ns.emplace_back (move (s));
            else
            {
              ns[0].value += '\n';
              ns[0].value += s;
            }
          }

          cin.close ();

          // Set the variable value and attributes. Note that we need to aquire
          // unique lock before potentially changing the script's variable
          // pool. The obtained variable reference can safelly be used with no
          // locking as the variable pool is an associative container
          // (underneath) and we are only adding new variables into it.
          //
          ulock ul (sp.root->var_pool_mutex);
          const variable& var (sp.root->var_pool.insert (move (vname)));
          ul.unlock ();

          value& lhs (sp.assign (var));

          // If there are no attributes specified then the variable assignment
          // is straightforward. Otherwise we will use the build2 parser helper
          // function.
          //
          if (ats == nullptr)
            lhs.assign (move (ns), &var);
          else
          {
            // Come up with a "path" that contains both the expression line
            // location as well as the attributes string. The resulting
            // diagnostics will look like this:
            //
            // testscript:10:1: ([x]):1:1: error: unknown value attribute x
            //
            path name;
            {
              string n (ll.file->string ());
              n += ':';

              if (!ops.no_line ())
              {
                n += to_string (ll.line);
                n += ':';

                if (!ops.no_column ())
                {
                  n += to_string (ll.column);
                  n += ':';
                }
              }

              n += " (";
              n += *ats;
              n += ')';
              name = path (move (n));
            }

            parser p;
            p.apply_value_attributes(
              &var, lhs, value (move (ns)), *ats, token_type::assign, name);
          }
        }
        catch (const io_error& e)
        {
          fail (ll) << "set: " << e;
        }
      }

      static bool
      run_pipe (scope& sp,
                command_pipe::const_iterator bc,
                command_pipe::const_iterator ec,
                auto_fd ifd,
                size_t ci, size_t li, const location& ll,
                bool diag)
      {
        if (bc == ec) // End of the pipeline.
          return true;

        // The overall plan is to run the first command in the pipe, reading
        // its input from the file descriptor passed (or, for the first
        // command, according to stdin redirect specification) and redirecting
        // its output to the right-hand part of the pipe recursively. Fail if
        // the right-hand part fails. Otherwise check the process exit code,
        // match stderr (and stdout for the last command in the pipe) according
        // to redirect specification(s) and fail if any of the above fails.
        //
        const command& c (*bc);

        // Register the command explicit cleanups. Verify that the path being
        // cleaned up is a sub-path of the testscript working directory. Fail
        // if this is not the case.
        //
        for (const auto& cl: c.cleanups)
        {
          const path& p (cl.path);
          path np (normalize (p, sp, ll));

          const string& ls (np.leaf ().string ());
          bool wc (ls == "*" || ls == "**" || ls == "***");
          const path& cp (wc ? np.directory () : np);
          const dir_path& wd (sp.root->wd_path);

          if (!cp.sub (wd))
            fail (ll) << (wc
                          ? "wildcard"
                          : p.to_directory ()
                            ? "directory"
                            : "file")
                      << " cleanup " << p << " is out of working directory "
                      << wd;

          sp.clean ({cl.type, move (np)}, false);
        }

        // Create a unique path for a command standard stream cache file.
        //
        auto std_path = [&sp, &ci, &li, &ll] (const char* n) -> path
        {
          path p (n);

          // 0 if belongs to a single-line test scope, otherwise is the
          // command line number (start from one) in the test scope.
          //
          if (li > 0)
            p += "-" + to_string (li);

          // 0 if belongs to a single-command expression, otherwise is the
          // command number (start from one) in the expression.
          //
          // Note that the name like stdin-N can relate to N-th command of a
          // single-line test or to N-th single-command line of multi-line
          // test. These cases are mutually exclusive and so are unambiguous.
          //
          if (ci > 0)
            p += "-" + to_string (ci);

          return normalize (move (p), sp, ll);
        };

        const redirect& in  (c.in.effective ());
        const redirect& out (c.out.effective ());
        const redirect& err (c.err.effective ());

        // If stdin file descriptor is not open then this is the first pipeline
        // command. Open stdin descriptor according to the redirect specified.
        //
        path isp;

        if (ifd.get () != -1)
          assert (in.type == redirect_type::none); // No redirect expected.
        else
        {
          // Open a file for passing to the command stdin.
          //
          auto open_stdin = [&isp, &ifd, &ll] ()
          {
            assert (!isp.empty ());

            try
            {
              ifd = fdopen (isp, fdopen_mode::in);
            }
            catch (const io_error& e)
            {
              fail (ll) << "unable to read " << isp << ": " << e;
            }
          };

          switch (in.type)
          {
          case redirect_type::pass:
            {
              try
              {
                ifd = fddup (0);
              }
              catch (const io_error& e)
              {
                fail (ll) << "unable to duplicate stdin: " << e;
              }

              break;
            }

          case redirect_type::none:
            // Somehow need to make sure that the child process doesn't read
            // from stdin. That is tricky to do in a portable way. Here we
            // suppose that the program which (erroneously) tries to read some
            // data from stdin being redirected to /dev/null fails not being
            // able to read the expected data, and so the test doesn't pass
            // through.
            //
            // @@ Obviously doesn't cover the case when the process reads
            //    whatever available.
            // @@ Another approach could be not to redirect stdin and let the
            //    process to hang which can be interpreted as a test failure.
            // @@ Both ways are quite ugly. Is there some better way to do
            //    this?
            //
            // Fall through.
            //
          case redirect_type::null:
            {
              try
              {
                ifd = fdnull ();
              }
              catch (const io_error& e)
              {
                fail (ll) << "unable to write to null device: " << e;
              }

              break;
            }

          case redirect_type::file:
            {
              isp = normalize (in.file.path, sp, ll);

              open_stdin ();
              break;
            }

          case redirect_type::here_str_literal:
          case redirect_type::here_doc_literal:
            {
              // We could write to the command stdin directly but instead will
              // cache the data for potential troubleshooting.
              //
              isp = std_path ("stdin");

              save (
                isp, transform (in.str, false, in.modifiers, *sp.root), ll);

              sp.clean ({cleanup_type::always, isp}, true);

              open_stdin ();
              break;
            }

          case redirect_type::trace:
          case redirect_type::merge:
          case redirect_type::here_str_regex:
          case redirect_type::here_doc_regex:
          case redirect_type::here_doc_ref:   assert (false); break;
          }
        }

        assert (ifd.get () != -1);

        command_pipe::const_iterator nc (bc + 1);
        bool last (nc == ec);

        // Prior to follow up with opening file descriptors for command
        // outputs redirects let's check if the command is the set builtin.
        // Being a builtin syntactically it differs from the regular ones in a
        // number of ways. It either succeeds or terminates abnormally, so
        // redirecting stderr is meaningless. It also never produces any output
        // and may appear only as a terminal command in a pipeline. That means
        // we can short-circuit here calling the builtin and returning right
        // after that. Checking that the user didn't specify any meaningless
        // redirects or exit code check sounds as a right thing to do.
        //
        if (c.program.string () == "set")
        {
          if (!last)
            fail (ll) << "set builtin must be the last pipe command";

          if (out.type != redirect_type::none)
            fail (ll) << "set builtin stdout cannot be redirected";

          if (err.type != redirect_type::none)
            fail (ll) << "set builtin stderr cannot be redirected";

          if ((c.exit.comparison == exit_comparison::eq) != (c.exit.code == 0))
            fail (ll) << "set builtin exit code cannot be non-zero";

          set_builtin (sp, c.arguments, move (ifd), ll);
          return true;
        }

        // Open a file for command output redirect if requested explicitly
        // (file overwrite/append redirects) or for the purpose of the output
        // validation (none, here_*, file comparison redirects), register the
        // file for cleanup, return the file descriptor. Interpret trace
        // redirect according to the verbosity level (as null if below 2, as
        // pass otherwise). Return nullfd, standard stream descriptor duplicate
        // or null-device descriptor for merge, pass or null redirects
        // respectively (not opening any file).
        //
        auto open = [&sp, &ll, &std_path] (const redirect& r,
                                           int dfd,
                                           path& p) -> auto_fd
        {
          assert (dfd == 1 || dfd == 2);
          const char* what (dfd == 1 ? "stdout" : "stderr");

          fdopen_mode m (fdopen_mode::out | fdopen_mode::create);

          auto_fd fd;
          redirect_type rt (r.type != redirect_type::trace
                            ? r.type
                            : verb < 2
                              ? redirect_type::null
                              : redirect_type::pass);
          switch (rt)
          {
          case redirect_type::pass:
            {
              try
              {
                fd = fddup (dfd);
              }
              catch (const io_error& e)
              {
                fail (ll) << "unable to duplicate " << what << ": " << e;
              }

              return fd;
            }

          case redirect_type::null:
            {
              try
              {
                fd = fdnull ();
              }
              catch (const io_error& e)
              {
                fail (ll) << "unable to write to null device: " << e;
              }

              return fd;
            }

          case redirect_type::merge:
            {
              // Duplicate the paired file descriptor later.
              //
              return fd; // nullfd
            }

          case redirect_type::file:
            {
              // For the cmp mode the user-provided path refers a content to
              // match against, rather than a content to be produced (as for
              // overwrite and append modes). And so for cmp mode we redirect
              // the process output to a temporary file.
              //
              p = r.file.mode == redirect_fmode::compare
                ? std_path (what)
                : normalize (r.file.path, sp, ll);

              m |= r.file.mode == redirect_fmode::append
                ? fdopen_mode::at_end
                : fdopen_mode::truncate;

              break;
            }

          case redirect_type::none:
          case redirect_type::here_str_literal:
          case redirect_type::here_doc_literal:
          case redirect_type::here_str_regex:
          case redirect_type::here_doc_regex:
            {
              p = std_path (what);
              m |= fdopen_mode::truncate;
              break;
            }

          case redirect_type::trace:
          case redirect_type::here_doc_ref: assert (false); break;
          }

          try
          {
            fd = fdopen (p, m);

            if ((m & fdopen_mode::at_end) != fdopen_mode::at_end)
              sp.clean ({cleanup_type::always, p}, true);
          }
          catch (const io_error& e)
          {
            fail (ll) << "unable to write " << p << ": " << e;
          }

          return fd;
        };

        path osp;
        auto_fd ofd;

        // If this is the last command in the pipeline than redirect the
        // command process stdout to a file. Otherwise create a pipe and
        // redirect the stdout to the write-end of the pipe. The read-end will
        // be passed as stdin for the next command in the pipeline.
        //
        // @@ Shouldn't we allow the here-* and file output redirects for a
        //    command with pipelined output? Say if such redirect is present
        //    then the process output is redirected to a file first (as it is
        //    when no output pipelined), and only after the process exit code
        //    and the output are validated the next command in the pipeline is
        //    executed taking the file as an input. This could be usefull for
        //    test failures investigation and for tests "tightening".
        //
        fdpipe p;
        if (last)
          ofd = open (out, 1, osp);
        else
        {
          assert (out.type == redirect_type::none); // No redirect expected.

          try
          {
            p = fdopen_pipe ();
          }
          catch (const io_error& e)
          {
            fail (ll) << "unable to open pipe: " << e;
          }

          ofd = move (p.out);
        }

        path esp;
        auto_fd efd (open (err, 2, esp));

        // Merge standard streams.
        //
        bool mo (out.type == redirect_type::merge);
        if (mo || err.type == redirect_type::merge)
        {
          auto_fd& self  (mo ? ofd : efd);
          auto_fd& other (mo ? efd : ofd);

          try
          {
            assert (self.get () == -1 && other.get () != -1);
            self = fddup (other.get ());
          }
          catch (const io_error& e)
          {
            fail (ll) << "unable to duplicate " << (mo ? "stderr" : "stdout")
                      << ": " << e;
          }
        }

        // All descriptors should be open to the date.
        //
        assert (ofd.get () != -1 && efd.get () != -1);

        optional<process_exit> exit;
        builtin_func* bf (builtins.find (c.program.string ()));

        bool success;

        auto process_args = [&c] () -> cstrings
        {
          cstrings args {c.program.string ().c_str ()};

          for (const auto& a: c.arguments)
            args.push_back (a.c_str ());

          args.push_back (nullptr);
          return args;
        };

        if (bf != nullptr)
        {
          // Execute the builtin.
          //
          if (verb >= 2)
            print_process (process_args ());

          try
          {
            uint8_t r; // Storage.
            builtin b (
              bf (sp, r, c.arguments, move (ifd), move (ofd), move (efd)));

            success = run_pipe (sp, nc, ec, move (p.in), ci + 1, li, ll, diag);

            exit = process_exit (b.wait ());
          }
          catch (const system_error& e)
          {
            fail (ll) << "unable to execute " << c.program << " builtin: "
                      << e << endf;
          }
        }
        else
        {
          // Execute the process.
          //
          cstrings args (process_args ());

          try
          {
            process_path pp (process::path_search (args[0]));

            if (verb >= 2)
              print_process (args);

            process pr (sp.wd_path.string ().c_str (),
                        pp,
                        args.data (),
                        ifd.get (), ofd.get (), efd.get ());

            ifd.reset ();
            ofd.reset ();
            efd.reset ();

            success = run_pipe (sp, nc, ec, move (p.in), ci + 1, li, ll, diag);

            pr.wait ();

            exit = move (pr.exit);
          }
          catch (const process_error& e)
          {
            error (ll) << "unable to execute " << args[0] << ": " << e;

            if (e.child)
              std::exit (1);

            throw failed ();
          }
        }

        assert (exit);

        // If the righ-hand side pipeline failed than the whole pipeline fails,
        // and no further checks are required.
        //
        if (!success)
          return false;

        const path& pr (c.program);

        // If there is no valid exit code available by whatever reason then we
        // print the proper diagnostics, dump stderr (if cached and not too
        // large) and fail the whole test. Otherwise if the exit code is not
        // correct then we print diagnostics if requested and fail the
        // pipeline.
        //
        bool valid (exit->normal ());

        // On Windows the exit code can be out of the valid codes range being
        // defined as uint16_t.
        //
#ifdef _WIN32
        if (valid)
          valid = exit->code () < 256;
#endif

        bool eq (c.exit.comparison == exit_comparison::eq);
        success = valid && eq == (exit->code () == c.exit.code);

        if (!valid || (!success && diag))
        {
          // In the presense of a valid exit code we print the diagnostics and
          // return false rather than throw.
          //
          diag_record d (valid ? error (ll) : fail (ll));

          if (!exit->normal ())
          {
            d << pr << " terminated abnormally: " << exit->description ();

            if (exit->core ())
              d << " (core dumped)";
          }
          else
          {
            uint16_t ec (exit->code ()); // Make sure is printed as integer.

            if (!valid)
              d << pr << " exit code " << ec << " out of 0-255 range";
            else if (!success)
            {
              if (diag)
                d << pr << " exit code " << ec << (eq ? " != " : " == ")
                  << static_cast<uint16_t> (c.exit.code);
            }
            else
              assert (false);
          }

          if (non_empty (esp, ll))
            d << info << "stderr: " << esp;

          if (non_empty (osp, ll))
            d << info << "stdout: " << osp;

          if (non_empty (isp, ll))
            d << info << "stdin: " << isp;

          // Print cached stderr.
          //
          print_file (d, esp, ll);
        }

        // If exit code is correct then check if the standard outputs match the
        // expectations. Note that stdout is only redirected to file for the
        // last command in the pipeline.
        //
        if (success)
          success =
            (!last ||
             check_output (pr, osp, isp, out, ll, sp, diag, "stdout")) &&
            check_output (pr, esp, isp, err, ll, sp, diag, "stderr");

        return success;
      }

      static bool
      run_expr (scope& sp,
                const command_expr& expr,
                size_t li, const location& ll,
                bool diag)
      {
        bool r (false);

        // Commands are numbered sequentially throughout the expression
        // starting with 1. Number 0 means the command is a single one.
        //
        size_t ci (expr.size () == 1 && expr.back ().pipe.size () == 1
                   ? 0
                   : 1);

        // If there is no ORs to the right of a pipe then the pipe failure is
        // fatal for the whole expression. In particular, the pipe must print
        // the diagnostics on failure (if generally allowed). So we find the
        // pipe that "switches on" the diagnostics potential printing.
        //
        command_expr::const_iterator trailing_ands; // Undefined if diag is
                                                    // disallowed.
        if (diag)
        {
          auto i (expr.crbegin ());
          for (; i != expr.crend () && i->op == expr_operator::log_and; ++i) ;
          trailing_ands = i.base ();
        }

        bool print (false);
        for (auto b (expr.cbegin ()), i (b), e (expr.cend ()); i != e; ++i)
        {
          if (diag && i + 1 == trailing_ands)
            print = true;

          const command_pipe& p (i->pipe);
          bool or_op (i->op == expr_operator::log_or);

          // Short-circuit if the pipe result must be OR-ed with true or AND-ed
          // with false.
          //
          if (!((or_op && r) || (!or_op && !r)))
            r = run_pipe (
              sp, p.begin (), p.end (), auto_fd (), ci, li, ll, print);

          ci += p.size ();
        }

        return r;
      }

      void default_runner::
      run (scope& sp,
           const command_expr& expr, command_type ct,
           size_t li,
           const location& ll)
      {
        // Noop for teardown commands if keeping tests output is requested.
        //
        if (ct == command_type::teardown &&
            common_.after == output_after::keep)
          return;

        if (verb >= 3)
          text << ct << expr;

        if (!run_expr (sp, expr, li, ll, true))
          throw failed (); // Assume diagnostics is already printed.
      }

      bool default_runner::
      run_if (scope& sp,
              const command_expr& expr,
              size_t li, const location& ll)
      {
        if (verb >= 3)
          text << "? " << expr;

        return run_expr (sp, expr, li, ll, false);
      }
    }
  }
}