Move in build system module to separate library

12 files changed, 62 insertions, 877 deletions

diff --git a/build2/b.cxx b/build2/b.cxx
index a76a8e4..907784b 100644
--- a/build2/b.cxx
+++ b/build2/b.cxx
@@ -42,20 +42,18 @@
 
 #include <libbuild2/parser.hxx>
 
+#include <build2/b-options.hxx>
+
+// Build system modules.
+//
 #include <libbuild2/dist/init.hxx>
 #include <libbuild2/test/init.hxx>
 #include <libbuild2/config/init.hxx>
 #include <libbuild2/install/init.hxx>
 
-#include <build2/b-options.hxx>
-
-using namespace butl;
-using namespace std;
-
+#include <libbuild2/in/init.hxx>
 #include <build2/version/init.hxx>
 
-#include <build2/in/init.hxx>
-
 #include <build2/bin/init.hxx>
 #include <build2/c/init.hxx>
 #include <build2/cc/init.hxx>
@@ -66,6 +64,9 @@ using namespace std;
 #  include <build2/bash/init.hxx>
 #endif
 
+using namespace butl;
+using namespace std;
+
 namespace build2
 {
   static options ops;
@@ -437,46 +438,51 @@ main (int argc, char* argv[])
       using mf = module_functions;
       auto& bm (builtin_modules);
 
-      bm["config"]  = config::build2_config_load ();
-      bm["dist"]    = dist::build2_dist_load ();
-      bm["test"]    = test::build2_test_load ();
-      bm["install"] = install::build2_install_load ();
-
-      bm["version"] = mf {&version::boot, &version::init};
-
-      bm["in.base"]  = mf {nullptr, &in::base_init};
-      bm["in"]       = mf {nullptr, &in::init};
-
-      bm["bin.vars"] = mf {nullptr, &bin::vars_init};
-      bm["bin.config"] = mf {nullptr, &bin::config_init};
-      bm["bin"] = mf {nullptr, &bin::init};
-      bm["bin.ar.config"] = mf {nullptr, &bin::ar_config_init};
-      bm["bin.ar"] = mf {nullptr, &bin::ar_init};
-      bm["bin.ld.config"] = mf {nullptr, &bin::ld_config_init};
-      bm["bin.ld"] = mf {nullptr, &bin::ld_init};
-      bm["bin.rc.config"] = mf {nullptr, &bin::rc_config_init};
-      bm["bin.rc"] = mf {nullptr, &bin::rc_init};
-
-      bm["cc.core.vars"] = mf {nullptr, &cc::core_vars_init};
-      bm["cc.core.guess"] = mf {nullptr, &cc::core_guess_init};
-      bm["cc.core.config"] = mf {nullptr, &cc::core_config_init};
-      bm["cc.core"] = mf {nullptr, &cc::core_init};
-      bm["cc.config"] = mf {nullptr, &cc::config_init};
-      bm["cc"] = mf {nullptr, &cc::init};
-
-      bm["c.guess"] = mf {nullptr, &c::guess_init};
-      bm["c.config"] = mf {nullptr, &c::config_init};
-      bm["c"] = mf {nullptr, &c::init};
-
-      bm["cxx.guess"] = mf {nullptr, &cxx::guess_init};
-      bm["cxx.config"] = mf {nullptr, &cxx::config_init};
-      bm["cxx"] = mf {nullptr, &cxx::init};
+      auto reg = [] (module_load_function* lf)
+      {
+        for (const module_functions* i (lf ()); i->name != nullptr; ++i)
+          builtin_modules[i->name] = *i;
+      };
+
+      reg (&config::build2_config_load);
+      reg (&dist::build2_dist_load);
+      reg (&test::build2_test_load);
+      reg (&install::build2_install_load);
+
+      bm["version"] = mf {"version", &version::boot, &version::init};
+
+      reg (&in::build2_in_load);
+
+      bm["bin.vars"] = mf {"bin.vars", nullptr, &bin::vars_init};
+      bm["bin.config"] = mf {"bin.config", nullptr, &bin::config_init};
+      bm["bin"] = mf {"bin", nullptr, &bin::init};
+      bm["bin.ar.config"] = mf {"bin.ar.config", nullptr, &bin::ar_config_init};
+      bm["bin.ar"] = mf {"bin.ar", nullptr, &bin::ar_init};
+      bm["bin.ld.config"] = mf {"bin.ld.config", nullptr, &bin::ld_config_init};
+      bm["bin.ld"] = mf {"bin.ld", nullptr, &bin::ld_init};
+      bm["bin.rc.config"] = mf {"bin.rc.config", nullptr, &bin::rc_config_init};
+      bm["bin.rc"] = mf {"bin.rc", nullptr, &bin::rc_init};
+
+      bm["cc.core.vars"] = mf {"cc.core.vars", nullptr, &cc::core_vars_init};
+      bm["cc.core.guess"] = mf {"cc.core.guess", nullptr, &cc::core_guess_init};
+      bm["cc.core.config"] = mf {"cc.core.config", nullptr, &cc::core_config_init};
+      bm["cc.core"] = mf {"cc.core", nullptr, &cc::core_init};
+      bm["cc.config"] = mf {"cc.config", nullptr, &cc::config_init};
+      bm["cc"] = mf {"cc", nullptr, &cc::init};
+
+      bm["c.guess"] = mf {"c.guess", nullptr, &c::guess_init};
+      bm["c.config"] = mf {"c.config", nullptr, &c::config_init};
+      bm["c"] = mf {"c", nullptr, &c::init};
+
+      bm["cxx.guess"] = mf {"cxx.guess", nullptr, &cxx::guess_init};
+      bm["cxx.config"] = mf {"cxx.config", nullptr, &cxx::config_init};
+      bm["cxx"] = mf {"cxx", nullptr, &cxx::init};
 
 #ifndef BUILD2_BOOTSTRAP
-      bm["cli.config"] = mf {nullptr, &cli::config_init};
-      bm["cli"] = mf {nullptr, &cli::init};
+      bm["cli.config"] = mf {"cli.config", nullptr, &cli::config_init};
+      bm["cli"] = mf {"cli", nullptr, &cli::init};
 
-      bm["bash"] = mf {nullptr, &bash::init};
+      bm["bash"] = mf {"bash", nullptr, &bash::init};
 #endif
     }
 
diff --git a/build2/bash/rule.cxx b/build2/bash/rule.cxx
index 72e3219..a612d23 100644
--- a/build2/bash/rule.cxx
+++ b/build2/bash/rule.cxx
@@ -11,7 +11,7 @@
 #include <libbuild2/algorithm.hxx>
 #include <libbuild2/diagnostics.hxx>
 
-#include <build2/in/target.hxx>
+#include <libbuild2/in/target.hxx>
 
 #include <build2/bash/target.hxx>
 #include <build2/bash/utility.hxx>
diff --git a/build2/bash/rule.hxx b/build2/bash/rule.hxx
index a6ec235..c160bb7 100644
--- a/build2/bash/rule.hxx
+++ b/build2/bash/rule.hxx
@@ -10,7 +10,7 @@
 
 #include <libbuild2/install/rule.hxx>
 
-#include <build2/in/rule.hxx>
+#include <libbuild2/in/rule.hxx>
 
 namespace build2
 {
diff --git a/build2/buildfile b/build2/buildfile
index eb22266..a940793 100644
--- a/build2/buildfile
+++ b/build2/buildfile
@@ -6,12 +6,19 @@ import libs  = libbutl%lib{butl}
 import libs += libpkgconf%lib{pkgconf}
 
 include ../libbuild2/
+libs += ../libbuild2/lib{build2}
+
+for m: in
+{
+  include ../libbuild2/in/
+  libs += ../libbuild2/$m/lib{build2-$m}
+}
 
 ./: exe{b}: {hxx ixx txx cxx}{+b} libue{b}
 
 libue{b}: {hxx ixx txx cxx}{** -b -b-options -**.test...} \
           {hxx ixx cxx}{b-options}                        \
-          ../libbuild2/lib{build2} $libs
+          $libs
 
 # Unit tests.
 #
diff --git a/build2/in/init.cxx b/build2/in/init.cxx
deleted file mode 100644
index f01fe20..0000000
--- a/build2/in/init.cxx
+++ /dev/null
@@ -1,110 +0,0 @@
-// file      : build2/in/init.cxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#include <build2/in/init.hxx>
-
-#include <libbuild2/scope.hxx>
-#include <libbuild2/context.hxx>
-#include <libbuild2/variable.hxx>
-#include <libbuild2/diagnostics.hxx>
-
-#include <build2/in/rule.hxx>
-#include <build2/in/target.hxx>
-
-using namespace std;
-
-namespace build2
-{
-  namespace in
-  {
-    static const rule rule_ ("in", "in");
-
-    bool
-    base_init (scope& rs,
-               scope&,
-               const location&,
-               unique_ptr<module_base>&,
-               bool first,
-               bool,
-               const variable_map&)
-    {
-      tracer trace ("in::base_init");
-      l5 ([&]{trace << "for " << rs;});
-
-      assert (first);
-
-      // Enter variables.
-      //
-      {
-        auto& vp (var_pool.rw (rs));
-
-        // Alternative variable substitution symbol with '$' being the
-        // default.
-        //
-        vp.insert<string> ("in.symbol");
-
-        // Substitution mode. Valid values are 'strict' (default) and 'lax'.
-        // In the strict mode every substitution symbol is expected to start a
-        // substitution with the double symbol (e.g., $$) serving as an escape
-        // sequence.
-        //
-        // In the lax mode a pair of substitution symbols is only treated as a
-        // substitution if what's between them looks like a build2 variable
-        // name (i.e., doesn't contain spaces, etc). Everything else,
-        // including unterminated substitution symbols, is copied as is. Note
-        // also that in this mode the double symbol is not treated as an
-        // escape sequence.
-        //
-        // The lax mode is mostly useful when trying to reuse existing .in
-        // files, for example, from autoconf. Note, however, that the lax mode
-        // is still stricter than the autoconf's semantics which also leaves
-        // unknown substitutions as is.
-        //
-        vp.insert<string> ("in.substitution");
-      }
-
-      // Register target types.
-      //
-      rs.target_types.insert<in> ();
-
-      return true;
-    }
-
-    bool
-    init (scope& rs,
-          scope& bs,
-          const location& loc,
-          unique_ptr<module_base>&,
-          bool,
-          bool,
-          const variable_map&)
-    {
-      tracer trace ("in::init");
-      l5 ([&]{trace << "for " << bs;});
-
-      // Load in.base.
-      //
-      if (!cast_false<bool> (rs["in.base.loaded"]))
-        load_module (rs, rs, "in.base", loc);
-
-      // Register rules.
-      //
-      {
-        auto& r (bs.rules);
-
-        // There are rules that are "derived" from this generic in rule in
-        // order to provide extended preprocessing functionality (see the
-        // version module for an example). To make sure they are tried first
-        // we register for path_target, not file, but in rule::match() we only
-        // match if the target is a file. A bit of a hack.
-        //
-        r.insert<path_target> (perform_update_id,   "in", rule_);
-        r.insert<path_target> (perform_clean_id,    "in", rule_);
-        r.insert<path_target> (configure_update_id, "in", rule_);
-      }
-
-      return true;
-    }
-  }
-}
diff --git a/build2/in/init.hxx b/build2/in/init.hxx
deleted file mode 100644
index 3cf8ebf..0000000
--- a/build2/in/init.hxx
+++ /dev/null
@@ -1,37 +0,0 @@
-// file      : build2/in/init.hxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#ifndef BUILD2_IN_INIT_HXX
-#define BUILD2_IN_INIT_HXX
-
-#include <libbuild2/types.hxx>
-#include <libbuild2/utility.hxx>
-
-#include <libbuild2/module.hxx>
-
-namespace build2
-{
-  namespace in
-  {
-    bool
-    base_init (scope&,
-               scope&,
-               const location&,
-               unique_ptr<module_base>&,
-               bool,
-               bool,
-               const variable_map&);
-
-    bool
-    init (scope&,
-          scope&,
-          const location&,
-          unique_ptr<module_base>&,
-          bool,
-          bool,
-          const variable_map&);
-  }
-}
-
-#endif // BUILD2_IN_INIT_HXX
diff --git a/build2/in/rule.cxx b/build2/in/rule.cxx
deleted file mode 100644
index 8a3244d..0000000
--- a/build2/in/rule.cxx
+++ /dev/null
@@ -1,485 +0,0 @@
-// file      : build2/in/rule.cxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#include <build2/in/rule.hxx>
-
-#include <cstdlib> // strtoull()
-
-#include <libbuild2/depdb.hxx>
-#include <libbuild2/scope.hxx>
-#include <libbuild2/target.hxx>
-#include <libbuild2/function.hxx>
-#include <libbuild2/algorithm.hxx>
-#include <libbuild2/filesystem.hxx>
-#include <libbuild2/diagnostics.hxx>
-
-#include <build2/in/target.hxx>
-
-using namespace std;
-using namespace butl;
-
-namespace build2
-{
-  namespace in
-  {
-    bool rule::
-    match (action a, target& xt, const string&) const
-    {
-      tracer trace ("in::rule::match");
-
-      if (!xt.is_a<file> ()) // See module init() for details.
-        return false;
-
-      file& t (static_cast<file&> (xt));
-
-      bool fi (false); // Found in.
-      for (prerequisite_member p: group_prerequisite_members (a, t))
-      {
-        if (include (a, t, p) != include_type::normal) // Excluded/ad hoc.
-          continue;
-
-        fi = fi || p.is_a<in> ();
-      }
-
-      // Note that while normally we print these at verbosity level 4, this
-      // one gets quite noisy since we try this rule for any file target.
-      //
-      if (!fi)
-        l5 ([&]{trace << "no in file prerequisite for target " << t;});
-
-      return fi;
-    }
-
-    recipe rule::
-    apply (action a, target& xt) const
-    {
-      file& t (static_cast<file&> (xt));
-
-      // Derive the file name.
-      //
-      t.derive_path ();
-
-      // Inject dependency on the output directory.
-      //
-      inject_fsdir (a, t);
-
-      // Match prerequisite members.
-      //
-      match_prerequisite_members (a,
-                                  t,
-                                  [this] (action a,
-                                          const target& t,
-                                          const prerequisite_member& p,
-                                          include_type i)
-                                  {
-                                    return search (a, t, p, i);
-                                  });
-
-      switch (a)
-      {
-      case perform_update_id: return [this] (action a, const target& t)
-        {
-          return perform_update (a, t);
-        };
-      case perform_clean_id: return &perform_clean_depdb; // Standard clean.
-      default:               return noop_recipe;          // Configure update.
-      }
-    }
-
-    target_state rule::
-    perform_update (action a, const target& xt) const
-    {
-      tracer trace ("in::rule::perform_update");
-
-      const file& t (xt.as<const file&> ());
-      const path& tp (t.path ());
-
-      // Substitution symbol.
-      //
-      char sym (symbol_);
-      if (const string* s = cast_null<string> (t["in.symbol"]))
-      {
-        if (s->size () == 1)
-          sym = s->front ();
-        else
-          fail << "invalid substitution symbol '" << *s << "'";
-      }
-
-      // Substitution mode.
-      //
-      bool strict (strict_);
-      if (const string* s = cast_null<string> (t["in.substitution"]))
-      {
-        if (*s == "lax")
-          strict = false;
-        else if (*s != "strict")
-          fail << "invalid substitution mode '" << *s << "'";
-      }
-
-      // Determine if anything needs to be updated.
-      //
-      timestamp mt (t.load_mtime ());
-      auto pr (execute_prerequisites<in> (a, t, mt));
-
-      bool update (!pr.first);
-      target_state ts (update ? target_state::changed : *pr.first);
-
-      const in& i (pr.second);
-      const path& ip (i.path ());
-
-      // We use depdb to track changes to the .in file name, symbol/mode, and
-      // variable values that have been substituted.
-      //
-      depdb dd (tp + ".d");
-
-      // First should come the rule name/version.
-      //
-      if (dd.expect (rule_id_ + " 1") != nullptr)
-        l4 ([&]{trace << "rule mismatch forcing update of " << t;});
-
-      // Then the substitution symbol.
-      //
-      if (dd.expect (string (1, sym)) != nullptr)
-        l4 ([&]{trace << "substitution symbol mismatch forcing update of"
-                      << t;});
-
-      // Then the substitution mode.
-      //
-      if (dd.expect (strict ? "strict" : "lax") != nullptr)
-        l4 ([&]{trace << "substitution mode mismatch forcing update of"
-                      << t;});
-
-      // Then the .in file.
-      //
-      if (dd.expect (i.path ()) != nullptr)
-        l4 ([&]{trace << "in file mismatch forcing update of " << t;});
-
-      // Update if any mismatch or depdb is newer that the output.
-      //
-      if (dd.writing () || dd.mtime > mt)
-        update = true;
-
-      // Substituted variable values.
-      //
-      // The plan is to save each substituted variable name and the hash of
-      // its value one entry per line. Plus the line location of its expansion
-      // for diagnostics.
-      //
-      // If update is true (i.e., the .in file has changes), then we simply
-      // overwrite the whole list.
-      //
-      // If update is false, then we need to read each name/hash, query and
-      // hash its current value, and compare. If hashes differ, then we need
-      // to start overwriting from this variable (the prefix of variables
-      // couldn't have changed since the .in file hasn't changed).
-      //
-      // Note that if the .in file substitutes the same variable multiple
-      // times, then we will end up with multiple entries for such a variable.
-      // For now we assume this is ok since this is probably not very common
-      // and it makes the overall logic simpler.
-      //
-      // Note also that because updating the depdb essentially requires
-      // performing the substitutions, this rule ignored the dry-run mode.
-      //
-      size_t dd_skip (0); // Number of "good" variable lines.
-
-      if (update)
-      {
-        // If we are still reading, mark the next line for overwriting.
-        //
-        if (dd.reading ())
-        {
-          dd.read ();  // Read the first variable line, if any.
-          dd.write (); // Mark it for overwriting.
-        }
-      }
-      else
-      {
-        while (dd.more ())
-        {
-          if (string* s = dd.read ())
-          {
-            // The line format is:
-            //
-            // <ln> <name> <hash>
-            //
-            // Note that <name> can contain spaces (see the constraint check
-            // expressions in the version module).
-            //
-            char* e (nullptr);
-            uint64_t ln (strtoull (s->c_str (), &e, 10));
-
-            size_t p1 (*e == ' ' ? e - s->c_str () : string::npos);
-            size_t p2 (s->rfind (' '));
-
-            if (p1 != string::npos && p2 != string::npos && p2 - p1 > 1)
-            {
-              string n (*s, p1 + 1, p2 - p1 - 1);
-
-              // Note that we have to call substitute(), not lookup() since it
-              // can be overriden with custom substitution semantics.
-              //
-              optional<string> v (
-                substitute (location (&ip, ln), a, t, n, strict));
-
-              assert (v); // Rule semantics change without version increment?
-
-              if (s->compare (p2 + 1,
-                              string::npos,
-                              sha256 (*v).string ()) == 0)
-              {
-                dd_skip++;
-                continue;
-              }
-              else
-                l4 ([&]{trace << n << " variable value mismatch forcing "
-                              << "update of " << t;});
-              // Fall through.
-            }
-
-            dd.write (); // Mark this line for overwriting.
-
-            // Fall through.
-          }
-
-          break;
-        }
-      }
-
-      if (dd.writing ()) // Recheck.
-        update = true;
-
-      // If nothing changed, then we are done.
-      //
-      if (!update)
-      {
-        dd.close ();
-        return ts;
-      }
-
-      if (verb >= 2)
-        text << program_ << ' ' << ip << " >" << tp;
-      else if (verb)
-        text << program_ << ' ' << ip;
-
-      // Read and process the file, one line at a time, while updating depdb.
-      //
-      const char* what;
-      const path* whom;
-      try
-      {
-        what = "open"; whom = &ip;
-        ifdstream ifs (ip, fdopen_mode::in, ifdstream::badbit);
-
-        // See fdopen() for details (umask, etc).
-        //
-        permissions prm (permissions::ru | permissions::wu |
-                         permissions::rg | permissions::wg |
-                         permissions::ro | permissions::wo);
-
-        if (t.is_a<exe> ())
-          prm |= permissions::xu | permissions::xg | permissions::xo;
-
-        // Remove the existing file to make sure permissions take effect. If
-        // this fails then presumable writing to it will fail as well and we
-        // will complain there.
-        //
-        try_rmfile (tp, true /* ignore_error */);
-
-        what = "open"; whom = &tp;
-        ofdstream ofs (fdopen (tp,
-                               fdopen_mode::out | fdopen_mode::create,
-                               prm));
-        auto_rmfile arm (tp);
-
-        string s; // Reuse the buffer.
-        for (size_t ln (1);; ++ln)
-        {
-          what = "read"; whom = &ip;
-          if (!getline (ifs, s))
-            break; // Could not read anything, not even newline.
-
-          // Not tracking column for now (see also depdb above).
-          //
-          const location l (&ip, ln);
-
-          // Scan the line looking for substiutions in the $<name>$ form. In
-          // the strict mode treat $$ as an escape sequence.
-          //
-          for (size_t b (0), n, d; b != (n = s.size ()); b += d)
-          {
-            d = 1;
-
-            if (s[b] != sym)
-              continue;
-
-            // Note that in the lax mode these should still be substitutions:
-            //
-            // @project@@
-            // @@project@
-
-            // Find the other end.
-            //
-            size_t e (b + 1);
-            for (; e != (n = s.size ()); ++e)
-            {
-              if (s[e] == sym)
-              {
-                if (strict && e + 1 != n && s[e + 1] == sym) // Escape.
-                  s.erase (e, 1); // Keep one, erase the other.
-                else
-                  break;
-              }
-            }
-
-            if (e == n)
-            {
-              if (strict)
-                fail (l) << "unterminated '" << sym << "'" << endf;
-
-              break;
-            }
-
-            if (e - b == 1) // Escape (or just double symbol in the lax mode).
-            {
-              if (strict)
-                s.erase (b, 1); // Keep one, erase the other.
-
-              continue;
-            }
-
-            // We have a (potential, in the lax mode) substition with b
-            // pointing to the opening symbol and e -- to the closing.
-            //
-            string name (s, b + 1, e - b -1);
-            if (optional<string> val = substitute (l, a, t, name, strict))
-            {
-              // Save in depdb.
-              //
-              if (dd_skip == 0)
-              {
-                // The line format is:
-                //
-                // <ln> <name> <hash>
-                //
-                string s (to_string (ln));
-                s += ' ';
-                s += name;
-                s += ' ';
-                s += sha256 (*val).string ();
-                dd.write (s);
-              }
-              else
-                --dd_skip;
-
-              // Patch the result in and adjust the delta.
-              //
-              s.replace (b, e - b + 1, *val);
-              d = val->size ();
-            }
-            else
-              d = e - b + 1; // Ignore this substitution.
-          }
-
-          what = "write"; whom = &tp;
-          if (ln != 1)
-            ofs << '\n'; // See below.
-          ofs << s;
-        }
-
-        // Close depdb before closing the output file so its mtime is not
-        // newer than of the output.
-        //
-        dd.close ();
-
-        what = "close"; whom = &tp;
-        ofs << '\n'; // Last write to make sure our mtime is older than dd.
-        ofs.close ();
-        arm.cancel ();
-
-        what = "close"; whom = &ip;
-        ifs.close ();
-      }
-      catch (const io_error& e)
-      {
-        fail << "unable to " << what << ' ' << *whom << ": " << e;
-      }
-
-      dd.check_mtime (tp);
-
-      t.mtime (system_clock::now ());
-      return target_state::changed;
-    }
-
-    prerequisite_target rule::
-    search (action,
-            const target& t,
-            const prerequisite_member& p,
-            include_type i) const
-    {
-      return prerequisite_target (&build2::search (t, p), i);
-    }
-
-    string rule::
-    lookup (const location& l, action, const target& t, const string& n) const
-    {
-      if (auto x = t[n])
-      {
-        value v (*x);
-
-        // For typed values call string() for conversion.
-        //
-        try
-        {
-          return convert<string> (
-            v.type == nullptr
-            ? move (v)
-            : functions.call (&t.base_scope (),
-                              "string",
-                              vector_view<value> (&v, 1),
-                              l));
-        }
-        catch (const invalid_argument& e)
-        {
-          fail (l) << e <<
-            info << "while substituting '" << n << "'" << endf;
-        }
-      }
-      else
-        fail (l) << "undefined variable '" << n << "'" << endf;
-    }
-
-    optional<string> rule::
-    substitute (const location& l,
-                action a,
-                const target& t,
-                const string& n,
-                bool strict) const
-    {
-      // In the lax mode scan the fragment to make sure it is a variable name
-      // (that is, it can be expanded in a buildfile as just $<name>; see
-      // lexer's variable mode for details).
-      //
-      if (!strict)
-      {
-        for (size_t i (0), e (n.size ()); i != e; )
-        {
-          bool f (i == 0); // First.
-          char c (n[i++]);
-          bool l (i == e); // Last.
-
-          if (c == '_' || (f ? alpha (c) : alnum (c)))
-            continue;
-
-          if (c == '.' && !l)
-            continue;
-
-          return nullopt; // Ignore this substitution.
-        }
-      }
-
-      return lookup (l, a, t, n);
-    }
-  }
-}
diff --git a/build2/in/rule.hxx b/build2/in/rule.hxx
deleted file mode 100644
index 71dc032..0000000
--- a/build2/in/rule.hxx
+++ /dev/null
@@ -1,88 +0,0 @@
-// file      : build2/in/rule.hxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#ifndef BUILD2_IN_RULE_HXX
-#define BUILD2_IN_RULE_HXX
-
-#include <libbuild2/types.hxx>
-#include <libbuild2/utility.hxx>
-
-#include <libbuild2/rule.hxx>
-
-namespace build2
-{
-  namespace in
-  {
-    // Preprocess an .in file.
-    //
-    // Note that a derived rule can use the target data pad to cache data
-    // (e.g., in match()) to be used in substitute/lookup() calls.
-    //
-    // Note also that currently this rule ignores the dry-run mode (see
-    // perform_update() for the rationale).
-    //
-    class rule: public build2::rule
-    {
-    public:
-      // The rule id is used to form the rule name/version entry in depdb. The
-      // program argument is the pseudo-program name to use in the command
-      // line diagnostics.
-      //
-      rule (string rule_id,
-            string program,
-            char symbol = '$',
-            bool strict = true)
-          : rule_id_ (move (rule_id)),
-            program_ (move (program)),
-            symbol_ (symbol),
-            strict_ (strict) {}
-
-      virtual bool
-      match (action, target&, const string&) const override;
-
-      virtual recipe
-      apply (action, target&) const override;
-
-      virtual target_state
-      perform_update (action, const target&) const;
-
-      // Customization hooks.
-      //
-
-      // Perform prerequisite search.
-      //
-      virtual prerequisite_target
-      search (action,
-              const target&,
-              const prerequisite_member&,
-              include_type) const;
-
-      // Perform variable lookup.
-      //
-      virtual string
-      lookup (const location&,
-              action,
-              const target&,
-              const string& name) const;
-
-      // Perform variable substitution. Return nullopt if it should be
-      // ignored.
-      //
-      virtual optional<string>
-      substitute (const location&,
-                  action,
-                  const target&,
-                  const string& name,
-                  bool strict) const;
-
-    protected:
-      const string rule_id_;
-      const string program_;
-      char symbol_;
-      bool strict_;
-    };
-  }
-}
-
-#endif // BUILD2_IN_RULE_HXX
diff --git a/build2/in/target.cxx b/build2/in/target.cxx
deleted file mode 100644
index 8dc520b..0000000
--- a/build2/in/target.cxx
+++ /dev/null
@@ -1,62 +0,0 @@
-// file      : build2/in/target.cxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#include <build2/in/target.hxx>
-
-using namespace std;
-
-namespace build2
-{
-  namespace in
-  {
-    static const target*
-    in_search (const target& xt, const prerequisite_key& cpk)
-    {
-      // If we have no extension then derive it from our target. Then delegate
-      // to file_search().
-      //
-      prerequisite_key pk (cpk);
-      optional<string>& e (pk.tk.ext);
-
-      if (!e)
-      {
-        if (const file* t = xt.is_a<file> ())
-        {
-          const string& te (t->derive_extension ());
-          e = te + (te.empty () ? "" : ".") + "in";
-        }
-        else
-          fail << "prerequisite " << pk << " for a non-file target " << xt;
-      }
-
-      return file_search (xt, pk);
-    }
-
-    static bool
-    in_pattern (const target_type&,
-                const scope&,
-                string&,
-                optional<string>&,
-                const location& l,
-                bool)
-    {
-      fail (l) << "pattern in in{} prerequisite" << endf;
-    }
-
-    extern const char in_ext_def[] = ""; // No extension by default.
-
-    const target_type in::static_type
-    {
-      "in",
-      &file::static_type,
-      &target_factory<in>,
-      &target_extension_fix<in_ext_def>,
-      nullptr, /* default_extension */   // Taken care of by search.
-      &in_pattern,
-      &target_print_1_ext_verb,          // Same as file.
-      &in_search,
-      false
-    };
-  }
-}
diff --git a/build2/in/target.hxx b/build2/in/target.hxx
deleted file mode 100644
index 47b0eed..0000000
--- a/build2/in/target.hxx
+++ /dev/null
@@ -1,46 +0,0 @@
-// file      : build2/in/target.hxx -*- C++ -*-
-// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
-// license   : MIT; see accompanying LICENSE file
-
-#ifndef BUILD2_IN_TARGET_HXX
-#define BUILD2_IN_TARGET_HXX
-
-#include <libbuild2/types.hxx>
-#include <libbuild2/utility.hxx>
-
-#include <libbuild2/target.hxx>
-
-namespace build2
-{
-  namespace in
-  {
-    // This is the venerable .in ("input") file that needs some kind of
-    // preprocessing.
-    //
-    // One interesting aspect of this target type is that the prerequisite
-    // search is target-dependent. Consider:
-    //
-    // hxx{version}: in{version.hxx} // version.hxx.in -> version.hxx
-    //
-    // Having to specify the header extension explicitly is inelegant. Instead
-    // what we really want to write is this:
-    //
-    // hxx{version}: in{version}
-    //
-    // But how do we know that in{version} means version.hxx.in? That's where
-    // the target-dependent search comes in: we take into account the target
-    // we are a prerequisite of.
-    //
-    class in: public file
-    {
-    public:
-      using file::file;
-
-    public:
-      static const target_type static_type;
-      virtual const target_type& dynamic_type () const {return static_type;}
-    };
-  }
-}
-
-#endif // BUILD2_IN_TARGET_HXX
diff --git a/build2/version/rule.cxx b/build2/version/rule.cxx
index 912efe3..f110e3e 100644
--- a/build2/version/rule.cxx
+++ b/build2/version/rule.cxx
@@ -8,7 +8,7 @@
 #include <libbuild2/target.hxx>
 #include <libbuild2/diagnostics.hxx>
 
-#include <build2/in/target.hxx>
+#include <libbuild2/in/target.hxx>
 
 #include <build2/version/module.hxx>
 #include <build2/version/utility.hxx>
diff --git a/build2/version/rule.hxx b/build2/version/rule.hxx
index 6d841df..7bfb783 100644
--- a/build2/version/rule.hxx
+++ b/build2/version/rule.hxx
@@ -10,7 +10,7 @@
 
 #include <libbuild2/install/rule.hxx>
 
-#include <build2/in/rule.hxx>
+#include <libbuild2/in/rule.hxx>
 
 namespace build2
 {