Make project variable to be of project_name type

32 files changed, 271 insertions, 116 deletions

diff --git a/build2/algorithm.hxx b/build2/algorithm.hxx
index 22b8471..430cc9f 100644
--- a/build2/algorithm.hxx
+++ b/build2/algorithm.hxx
@@ -65,7 +65,7 @@ namespace build2
           const string& name,
           const string* ext = nullptr,  // NULL means unspecified.
           const scope* = nullptr,       // NULL means dir is absolute.
-          const optional<string>& proj = nullopt);
+          const optional<project_name>& proj = nullopt);
 
   const target*
   search_existing (const target_type& type,
@@ -74,7 +74,7 @@ namespace build2
                    const string& name,
                    const string* ext = nullptr,
                    const scope* = nullptr,
-                   const optional<string>& proj = nullopt);
+                   const optional<project_name>& proj = nullopt);
 
   // As above but specify the target type as template argument.
   //
diff --git a/build2/algorithm.ixx b/build2/algorithm.ixx
index fb77e9c..e41b87f 100644
--- a/build2/algorithm.ixx
+++ b/build2/algorithm.ixx
@@ -78,7 +78,7 @@ namespace build2
           const string& name,
           const string* ext,
           const scope* scope,
-          const optional<string>& proj)
+          const optional<project_name>& proj)
   {
     return search (
       t,
@@ -99,7 +99,7 @@ namespace build2
                    const string& name,
                    const string* ext,
                    const scope* scope,
-                   const optional<string>& proj)
+                   const optional<project_name>& proj)
   {
     return search_existing (
       prerequisite_key {
diff --git a/build2/bash/init.cxx b/build2/bash/init.cxx
index ff653c2..7bfea58 100644
--- a/build2/bash/init.cxx
+++ b/build2/bash/init.cxx
@@ -54,7 +54,7 @@ namespace build2
         // Install into bin/<project>/ by default stripping the .bash
         // extension from <project> if present.
         //
-        const string& p (cast<string> (rs.vars[var_project]));
+        const project_name& p (cast<project_name> (rs.vars[var_project]));
 
         install_path<bash> (bs, dir_path ("bin") /= project_base (p));
         install_mode<bash> (bs, "644");
diff --git a/build2/bash/utility.hxx b/build2/bash/utility.hxx
index d8d9a43..67f4552 100644
--- a/build2/bash/utility.hxx
+++ b/build2/bash/utility.hxx
@@ -14,13 +14,12 @@ namespace build2
   {
     // Strip the .bash extension from the project name.
     //
+    // Note that the result may not be a valid project name.
+    //
     inline string
-    project_base (const string& n)
+    project_base (const project_name& pn)
     {
-      size_t p (path::traits::find_extension (n));
-      return p == string::npos || casecmp (n.c_str () + p, ".bash", 5) != 0
-        ? n
-        : string (n, 0, p);
+      return pn.base ("bash");
     }
   }
 }
diff --git a/build2/cc/common.cxx b/build2/cc/common.cxx
index 3c4994e..ca73483 100644
--- a/build2/cc/common.cxx
+++ b/build2/cc/common.cxx
@@ -444,6 +444,7 @@ namespace build2
         // search (name, scope).
         //
         dir_path out;
+
         prerequisite_key pk {n.proj, {tt, &n.dir, &out, &n.value, ext}, &s};
         xt = search_library_existing (a, sysd, usrd, pk);
 
diff --git a/build2/cc/common.hxx b/build2/cc/common.hxx
index 27706f3..18824cb 100644
--- a/build2/cc/common.hxx
+++ b/build2/cc/common.hxx
@@ -288,7 +288,7 @@ namespace build2
       bool
       pkgconfig_load (action, const scope&,
                       bin::lib&, bin::liba*, bin::libs*,
-                      const optional<string>&,
+                      const optional<project_name>&,
                       const string&,
                       const dir_path&,
                       const dir_paths&,
diff --git a/build2/cc/pkgconfig.cxx b/build2/cc/pkgconfig.cxx
index 5ace6ec..55c8b35 100644
--- a/build2/cc/pkgconfig.cxx
+++ b/build2/cc/pkgconfig.cxx
@@ -456,7 +456,7 @@ namespace build2
                     lib& lt,
                     liba* at,
                     libs* st,
-                    const optional<string>& proj,
+                    const optional<project_name>& proj,
                     const string& stem,
                     const dir_path& libd,
                     const dir_paths& top_sysd,
@@ -551,7 +551,7 @@ namespace build2
         if (proj)
         {
           f = dir;
-          f /= *proj;
+          f /= proj->string ();
           f += sfx;
           f += ".pc";
           if (exists (f))
@@ -1102,7 +1102,7 @@ namespace build2
                     lib&,
                     liba*,
                     libs*,
-                    const optional<string>&,
+                    const optional<project_name>&,
                     const string&,
                     const dir_path&,
                     const dir_paths&,
@@ -1142,7 +1142,7 @@ namespace build2
         ofdstream os (p);
 
         {
-          const string& n (cast<string> (rs.vars[var_project]));
+          const project_name& n (cast<project_name> (rs.vars[var_project]));
 
           lookup vl (rs.vars[var_version]);
           if (!vl)
diff --git a/build2/context.cxx b/build2/context.cxx
index 225ff1c..a8cf042 100644
--- a/build2/context.cxx
+++ b/build2/context.cxx
@@ -718,10 +718,10 @@ namespace build2
       // Note that subprojects is not typed since the value requires
       // pre-processing (see file.cxx).
       //
-      var_project      = &vp.insert<string>   ("project",      v_p);
-      var_amalgamation = &vp.insert<dir_path> ("amalgamation", v_p);
-      var_subprojects  = &vp.insert           ("subprojects",  v_p);
-      var_version      = &vp.insert<string>   ("version",      v_p);
+      var_project      = &vp.insert<project_name> ("project",      v_p);
+      var_amalgamation = &vp.insert<dir_path>     ("amalgamation", v_p);
+      var_subprojects  = &vp.insert               ("subprojects",  v_p);
+      var_version      = &vp.insert<string>       ("version",      v_p);
 
       var_project_url     = &vp.insert<string> ("project.url",     v_p);
       var_project_summary = &vp.insert<string> ("project.summary", v_p);
diff --git a/build2/context.hxx b/build2/context.hxx
index cfe770f..cf7eee6 100644
--- a/build2/context.hxx
+++ b/build2/context.hxx
@@ -408,11 +408,11 @@ namespace build2
 
   // Return the project name or empty string if unnamed.
   //
-  inline const string&
+  inline const project_name&
   project (const scope& root)
   {
     auto l (root[var_project]);
-    return l ? cast<string> (l) : empty_string;
+    return l ? cast<project_name> (l) : empty_project_name;
   }
 
   // Return the src/out directory corresponding to the given out/src. The
diff --git a/build2/file.cxx b/build2/file.cxx
index 1367b8c..d987226 100644
--- a/build2/file.cxx
+++ b/build2/file.cxx
@@ -47,9 +47,10 @@ namespace build2
     {
       // See find_subprojects() for details.
       //
-      const string& n (path::traits::is_separator (i->first.back ())
-                       ? empty_string
-                       : i->first);
+      const project_name& n (
+        path::traits::is_separator (i->first.string ().back ())
+        ? empty_project_name
+        : i->first);
 
       os << (i != b ? " " : "") << n << '@' << i->second;
     }
@@ -464,7 +465,7 @@ namespace build2
 
   // Extract the project name from bootstrap.build.
   //
-  static string
+  static project_name
   find_project_name (const dir_path& out_root,
                      const dir_path& fallback_src_root,
                      bool* src_hint = nullptr)
@@ -480,7 +481,7 @@ namespace build2
     if (s.root_scope () == &s && s.out_path () == out_root)
     {
       if (lookup l = s.vars[var_project])
-        return cast<string> (l);
+        return cast<project_name> (l);
 
       src_root = s.src_path_;
     }
@@ -518,7 +519,7 @@ namespace build2
       }
     }
 
-    string name;
+    project_name name;
     {
       path f (*src_root / bootstrap_file);
       auto p (extract_variable (f, *var_project));
@@ -527,7 +528,7 @@ namespace build2
         fail << "variable " << var_project->name << " expected "
              << "as a first line in " << f;
 
-      name = cast<string> (move (p.first));
+      name = cast<project_name> (move (p.first));
     }
 
     l5 ([&]{trace << "extracted project name '" << name << "' for "
@@ -576,7 +577,7 @@ namespace build2
         // Load its name. Note that here we don't use fallback src_root
         // since this function is used to scan both out_root and src_root.
         //
-        string name (find_project_name (sd, dir_path (), &src));
+        project_name name (find_project_name (sd, dir_path (), &src));
 
         // If the name is empty, then is is an unnamed project. While the
         // 'project' variable stays empty, here we come up with a surrogate
@@ -585,7 +586,8 @@ namespace build2
         // sub-directory and appending a trailing directory separator to it.
         //
         if (name.empty ())
-          name = dir.posix_string () + path::traits::directory_separator;
+          name = project_name (dir.posix_string () + '/',
+                               project_name::raw_string);
 
         // @@ Can't use move() because we may need the values in diagnostics
         // below. Looks like C++17 try_emplace() is what we need.
@@ -770,7 +772,7 @@ namespace build2
           {
             // Project name.
             //
-            string n;
+            project_name n;
             if (i->pair)
             {
               if (i->pair != '@')
@@ -778,7 +780,7 @@ namespace build2
 
               try
               {
-                n = convert<string> (move (*i));
+                n = convert<project_name> (move (*i));
 
                 if (n.empty ())
                   fail << "empty project name in variable subprojects";
@@ -821,7 +823,8 @@ namespace build2
               // See find_subprojects() for details on unnamed projects.
               //
               if (n.empty ())
-                n = d.posix_string () + '/';
+                n = project_name (d.posix_string () + '/',
+                                  project_name::raw_string);
             }
 
             sps.emplace (move (n), move (d));
@@ -1082,24 +1085,6 @@ namespace build2
     return rs;
   }
 
-  // Convert project name to import variable name.
-  //
-  static inline string
-  import_name (const string& p)
-  {
-    // For simplicity let's assume project name is a package name and only
-    // sanitize characters that we don't like from what's valid there.
-    //
-    auto sanitize = [] (char c)
-    {
-      return (c == '-' || c == '+' || c == '.') ? '_' : c;
-    };
-
-    string r;
-    transform (p.begin (), p.end (), back_inserter (r), sanitize);
-    return r;
-  }
-
   names
   import (scope& ibase, name target, const location& loc)
   {
@@ -1113,13 +1098,13 @@ namespace build2
     //
     if (target.unqualified ())
     {
-      target.proj = string ();
+      target.proj = project_name ();
       return names {move (target)};
     }
 
     // Otherwise, get the project name and convert the target to unqualified.
     //
-    string proj (move (*target.proj));
+    project_name proj (move (*target.proj));
     target.proj = nullopt;
 
     scope& iroot (*ibase.root_scope ());
@@ -1137,7 +1122,7 @@ namespace build2
 
     for (;;) // Break-out loop.
     {
-      string n ("config.import." + import_name (proj));
+      string n ("config.import." + proj.variable ());
 
       // config.import.<proj>
       //
@@ -1230,7 +1215,7 @@ namespace build2
 
         // First check the amalgamation itself.
         //
-        if (r != &iroot && cast<string> (r->vars[var_project]) == proj)
+        if (r != &iroot && cast<project_name> (r->vars[var_project]) == proj)
         {
           out_root = r->out_path ();
           break;
@@ -1345,7 +1330,7 @@ namespace build2
 
       // Now we know this project's name as well as all its subprojects.
       //
-      if (cast<string> (root->vars[var_project]) == proj)
+      if (cast<project_name> (root->vars[var_project]) == proj)
         break;
 
       if (auto l = root->vars[var_subprojects])
@@ -1422,7 +1407,7 @@ namespace build2
     tracer trace ("import");
 
     assert (pk.proj);
-    const string& proj (*pk.proj);
+    const project_name& proj (*pk.proj);
 
     // Target type-specific search.
     //
@@ -1492,7 +1477,7 @@ namespace build2
       dr << info << "consider adding its installation location" <<
         info << "or explicitly specify its project name";
     else
-      dr << info << "use config.import." << import_name (proj)
+      dr << info << "use config.import." << proj.variable ()
          << " command line variable to specifying its project out_root";
 
     dr << endf;
diff --git a/build2/file.hxx b/build2/file.hxx
index bb136cf..9f93365 100644
--- a/build2/file.hxx
+++ b/build2/file.hxx
@@ -19,7 +19,7 @@ namespace build2
   class location;
   class prerequisite_key;
 
-  using subprojects = std::map<string, dir_path>;
+  using subprojects = std::map<project_name, dir_path>;
 
   ostream&
   operator<< (ostream&, const subprojects&); // Print as name@dir sequence.
diff --git a/build2/function.cxx b/build2/function.cxx
index f1e0fdd..44bda57 100644
--- a/build2/function.cxx
+++ b/build2/function.cxx
@@ -375,6 +375,7 @@ namespace build2
   void regex_functions ();          // functions-regex.cxx
   void string_functions ();         // functions-string.cxx
   void target_triplet_functions (); // functions-target-triplet.cxx
+  void project_name_functions ();   // functions-target-triplet.cxx
 
   struct functions_init
   {
@@ -389,6 +390,7 @@ namespace build2
       regex_functions ();
       string_functions ();
       target_triplet_functions ();
+      project_name_functions ();
     }
   };
 
diff --git a/build2/functions-project-name.cxx b/build2/functions-project-name.cxx
new file mode 100644
index 0000000..f77b9cd
--- /dev/null
+++ b/build2/functions-project-name.cxx
@@ -0,0 +1,63 @@
+// file      : build2/functions-project-name.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <build2/function.hxx>
+#include <build2/variable.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  void
+  project_name_functions ()
+  {
+    function_family f ("project_name");
+
+    f["string"]    = [](project_name p) {return move (p).string ();};
+
+    f["base"] = [](project_name p, optional<string> ext)
+    {
+      return ext ? p.base (ext->c_str ()) : p.base ();
+    };
+
+    f["base"] = [](project_name p, names ext)
+    {
+      return p.base (convert<string> (move (ext)).c_str ());
+    };
+
+    f["extension"] = &project_name::extension;
+    f["variable"]  = &project_name::variable;
+
+    // Project name-specific overloads from builtins.
+    //
+    function_family b ("builtin");
+
+    b[".concat"] = [](project_name n, string s)
+    {
+      string r (move (n).string ());
+      r += s;
+      return r;
+    };
+
+    b[".concat"] = [](string s, project_name n)
+    {
+      s += n.string ();
+      return s;
+    };
+
+    b[".concat"] = [](project_name n, names ns)
+    {
+      string r (move (n).string ());
+      r += convert<string> (move (ns));
+      return r;
+    };
+
+    b[".concat"] = [](names ns, project_name n)
+    {
+      string r (convert<string> (move (ns)));
+      r += n.string ();
+      return r;
+    };
+  }
+}
diff --git a/build2/install/init.cxx b/build2/install/init.cxx
index 682f6b0..5c28cfa 100644
--- a/build2/install/init.cxx
+++ b/build2/install/init.cxx
@@ -250,7 +250,7 @@ namespace build2
         if (s)
           config::save_module (rs, "install", INT32_MAX);
 
-        const string& n (project (rs));
+        const string& n (project (rs).string ());
 
         // Global config.install.* values.
         //
diff --git a/build2/name.cxx b/build2/name.cxx
index 9fc661b..d1f9ce6 100644
--- a/build2/name.cxx
+++ b/build2/name.cxx
@@ -25,7 +25,7 @@ namespace build2
 
     if (n.proj)
     {
-      r += *n.proj;
+      r += n.proj->string ();
       r += '%';
     }
 
@@ -119,7 +119,7 @@ namespace build2
 
     if (n.proj)
     {
-      write_string (*n.proj);
+      write_string (n.proj->string ());
       os << '%';
     }
 
diff --git a/build2/name.hxx b/build2/name.hxx
index 54fd130..e688aed 100644
--- a/build2/name.hxx
+++ b/build2/name.hxx
@@ -33,7 +33,7 @@ namespace build2
   //
   struct name
   {
-    optional<string> proj;
+    optional<project_name> proj;
     dir_path dir;
     string type;
     string value;
@@ -48,7 +48,7 @@ namespace build2
     name (dir_path d, string t, string v)
         : dir (move (d)), type (move (t)), value (move (v)) {}
 
-    name (optional<string> p, dir_path d, string t, string v)
+    name (optional<project_name> p, dir_path d, string t, string v)
         : proj (move (p)), dir (move (d)), type (move (t)), value (move (v)) {}
 
     bool
diff --git a/build2/operation.cxx b/build2/operation.cxx
index 37e7c91..c42f92a 100644
--- a/build2/operation.cxx
+++ b/build2/operation.cxx
@@ -493,7 +493,7 @@ namespace build2
       // This could be a simple project that doesn't set project name.
       //
       cout
-        << "project: "      << cast_empty<string> (s[var_project]) << endl
+        << "project: "      << cast_empty<project_name> (s[var_project]) << endl
         << "version: "      << cast_empty<string> (s[var_version]) << endl
         << "summary: "      << cast_empty<string> (s[var_project_summary]) << endl
         << "url: "          << cast_empty<string> (s[var_project_url]) << endl
diff --git a/build2/parser.cxx b/build2/parser.cxx
index 4fe30e9..57c7fc9 100644
--- a/build2/parser.cxx
+++ b/build2/parser.cxx
@@ -2150,6 +2150,7 @@ namespace build2
       n == "name"           ? ptr (value_traits<name>::value_type)           :
       n == "name_pair"      ? ptr (value_traits<name_pair>::value_type)      :
       n == "target_triplet" ? ptr (value_traits<target_triplet>::value_type) :
+      n == "project_name"   ? ptr (value_traits<project_name>::value_type)   :
 
       n == "uint64s"        ? ptr (value_traits<uint64s>::value_type)        :
       n == "strings"        ? ptr (value_traits<strings>::value_type)        :
@@ -2799,7 +2800,7 @@ namespace build2
                 names& ns,
                 const char* what,
                 size_t pairn,
-                const optional<string>& pp,
+                const optional<project_name>& pp,
                 const dir_path* dp,
                 const string* tp)
   {
@@ -2827,7 +2828,7 @@ namespace build2
 
       // Project.
       //
-      optional<string> p;
+      optional<project_name> p;
       if (cn.proj)
       {
         if (pp)
@@ -3186,7 +3187,7 @@ namespace build2
                        const char* what,
                        const string* separators,
                        size_t pairn,
-                       const optional<string>& pp,
+                       const optional<project_name>& pp,
                        const dir_path* dp,
                        const string* tp,
                        bool cross)
@@ -3209,7 +3210,7 @@ namespace build2
     // Parse names until closing '}' expanding patterns.
     //
     auto parse = [&r, &t, &tt, pmode, what, separators, this] (
-      const optional<string>& pp,
+      const optional<project_name>& pp,
       const dir_path* dp,
       const string* tp)
     {
@@ -3350,7 +3351,7 @@ namespace build2
                const char* what,
                const string* separators,
                size_t pairn,
-               const optional<string>& pp,
+               const optional<project_name>& pp,
                const dir_path* dp,
                const string* tp,
                bool cross) -> parse_names_result
@@ -3708,8 +3709,8 @@ namespace build2
         // First take care of project. A project-qualified name is not very
         // common, so we can afford some copying for the sake of simplicity.
         //
-        optional<string> p1;
-        const optional<string>* pp1 (&pp);
+        optional<project_name> p1;
+        const optional<project_name>* pp1 (&pp);
 
         if (p != string::npos)
         {
@@ -3733,7 +3734,17 @@ namespace build2
             if (pp)
               fail (t) << "nested project name " << proj;
 
-            p1 = move (proj);
+            try
+            {
+              p1 = !proj.empty ()
+                ? project_name (move (proj))
+                : project_name ();
+            }
+            catch (const invalid_argument& e)
+            {
+              fail (t) << "invalid project name '" << proj << "': " << e;
+            }
+
             pp1 = &p1;
           }
         }
diff --git a/build2/parser.hxx b/build2/parser.hxx
index edb2f84..acd0845 100644
--- a/build2/parser.hxx
+++ b/build2/parser.hxx
@@ -307,7 +307,7 @@ namespace build2
                  const char* what = "name",
                  const string* separators = &name_separators,
                  size_t pairn = 0,
-                 const optional<string>& prj = nullopt,
+                 const optional<project_name>& prj = nullopt,
                  const dir_path* dir = nullptr,
                  const string* type = nullptr,
                  bool cross = true);
@@ -319,7 +319,7 @@ namespace build2
                          const char* what,
                          const string* separators,
                          size_t pairn,
-                         const optional<string>& prj,
+                         const optional<project_name>& prj,
                          const dir_path* dir,
                          const string* type,
                          bool cross);
@@ -341,7 +341,7 @@ namespace build2
                   names&,
                   const char* what,
                   size_t pairn,
-                  const optional<string>& prj,
+                  const optional<project_name>& prj,
                   const dir_path* dir,
                   const string* type);
 
diff --git a/build2/prerequisite.cxx b/build2/prerequisite.cxx
index 5900589..5837328 100644
--- a/build2/prerequisite.cxx
+++ b/build2/prerequisite.cxx
@@ -15,8 +15,6 @@ namespace build2
 {
   // prerequisite_key
   //
-  const optional<string> prerequisite_key::nullproj = nullopt;
-
   ostream&
   operator<< (ostream& os, const prerequisite_key& pk)
   {
diff --git a/build2/prerequisite.hxx b/build2/prerequisite.hxx
index b8707ce..3d8121a 100644
--- a/build2/prerequisite.hxx
+++ b/build2/prerequisite.hxx
@@ -31,12 +31,10 @@ namespace build2
   public:
     typedef build2::scope scope_type;
 
-    const optional<string>& proj;
+    const optional<project_name>& proj;
     target_key tk;                // The .dir and .out members can be relative.
     const scope_type* scope;      // Can be NULL if tk.dir is absolute.
 
-    static const optional<string> nullproj;
-
     template <typename T>
     bool is_a () const {return tk.is_a<T> ();}
     bool is_a (const target_type& tt) const {return tk.is_a (tt);}
@@ -65,7 +63,7 @@ namespace build2
     // bar/ here is relative to the scope, not to foo/. Plus, bar/ can resolve
     // to either src or out.
     //
-    const optional<string>  proj;
+    const optional<project_name> proj;
     const target_type_type& type;
     const dir_path dir;         // Normalized absolute or relative (to scope).
     const dir_path out;         // Empty, normalized absolute, or relative.
@@ -102,7 +100,7 @@ namespace build2
     append (const variable&, const target_type&);
 
   public:
-    prerequisite (optional<string> p,
+    prerequisite (optional<project_name> p,
                   const target_type_type& t,
                   dir_path d,
                   dir_path o,
diff --git a/build2/target.hxx b/build2/target.hxx
index 0f8c8ea..db5de67 100644
--- a/build2/target.hxx
+++ b/build2/target.hxx
@@ -882,14 +882,12 @@ namespace build2
       return member != nullptr ? member->dir : prerequisite.dir;
     }
 
-    const optional<string>&
+    const optional<project_name>&
     proj () const
     {
       // Member cannot be project-qualified.
       //
-      return member != nullptr
-        ? prerequisite_key::nullproj
-        : prerequisite.proj;
+      return member != nullptr ? nullopt_project_name : prerequisite.proj;
     }
 
     const scope_type&
diff --git a/build2/types.hxx b/build2/types.hxx
index 8764c35..94604e0 100644
--- a/build2/types.hxx
+++ b/build2/types.hxx
@@ -42,6 +42,7 @@
 #include <libbutl/timestamp.mxx>
 #include <libbutl/vector-view.mxx>
 #include <libbutl/small-vector.mxx>
+#include <libbutl/project-name.mxx>
 #include <libbutl/target-triplet.mxx>
 #include <libbutl/standard-version.mxx>
 
@@ -273,6 +274,10 @@ namespace build2
   using butl::standard_version;
   using butl::standard_version_constraint;
 
+  // <libbutl/project-name.mxx>
+  //
+  using butl::project_name;
+
   // Diagnostics location.
   //
   class location
diff --git a/build2/utility.cxx b/build2/utility.cxx
index 07cf88e..2d8e59b 100644
--- a/build2/utility.cxx
+++ b/build2/utility.cxx
@@ -254,13 +254,15 @@ namespace build2
     fail (loc) << "unable to execute " << args[0] << ": " << e << endf;
   }
 
-  const string   empty_string;
-  const path     empty_path;
-  const dir_path empty_dir_path;
-
-  const optional<string>   nullopt_string;
-  const optional<path>     nullopt_path;
-  const optional<dir_path> nullopt_dir_path;
+  const string       empty_string;
+  const path         empty_path;
+  const dir_path     empty_dir_path;
+  const project_name empty_project_name;
+
+  const optional<string>       nullopt_string;
+  const optional<path>         nullopt_path;
+  const optional<dir_path>     nullopt_dir_path;
+  const optional<project_name> nullopt_project_name;
 
   void
   append_options (cstrings& args, const lookup& l, const char* e)
diff --git a/build2/utility.hxx b/build2/utility.hxx
index 6e76f05..0beec2e 100644
--- a/build2/utility.hxx
+++ b/build2/utility.hxx
@@ -388,15 +388,17 @@ namespace build2
       verbosity, pp, args, forward<F> (f), error, ignore_exit, checksum);
   }
 
-  // Empty/nullopt string and path.
+  // Empty/nullopt string, path, and project name.
   //
-  extern const string   empty_string;
-  extern const path     empty_path;
-  extern const dir_path empty_dir_path;
+  extern const string       empty_string;
+  extern const path         empty_path;
+  extern const dir_path     empty_dir_path;
+  extern const project_name empty_project_name;
 
-  extern const optional<string>   nullopt_string;
-  extern const optional<path>     nullopt_path;
-  extern const optional<dir_path> nullopt_dir_path;
+  extern const optional<string>       nullopt_string;
+  extern const optional<path>         nullopt_path;
+  extern const optional<dir_path>     nullopt_dir_path;
+  extern const optional<project_name> nullopt_project_name;
 
   // Hash a path potentially without the specific directory prefix.
   //
diff --git a/build2/variable.cxx b/build2/variable.cxx
index 406123d..c304d0c 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -549,7 +549,7 @@ namespace build2
     //
     if (n.qualified ())
     {
-      string p (*n.proj);
+      string p (move (*n.proj).string ());
       p += '%';
       p += s;
       p.swap (s);
@@ -563,7 +563,7 @@ namespace build2
 
       if (r->qualified ())
       {
-        s += *r->proj;
+        s += r->proj->string ();
         s += '%';
       }
 
@@ -1080,6 +1080,55 @@ namespace build2
     &default_empty<target_triplet>
   };
 
+  // project_name value
+  //
+  project_name value_traits<project_name>::
+  convert (name&& n, name* r)
+  {
+    if (r == nullptr)
+    {
+      if (n.simple ())
+      {
+        try
+        {
+          return n.empty () ? project_name () : project_name (move (n.value));
+        }
+        catch (const invalid_argument& e)
+        {
+          throw invalid_argument (
+            string ("invalid project_name value: ") + e.what ());
+        }
+      }
+
+      // Fall through.
+    }
+
+    throw_invalid_argument (n, r, "project_name");
+  }
+
+  const project_name&
+  value_traits<project_name>::empty_instance = empty_project_name;
+
+  const char* const value_traits<project_name>::type_name = "project_name";
+
+  const value_type value_traits<project_name>::value_type
+  {
+    type_name,
+    sizeof (project_name),
+    nullptr,                         // No base.
+    nullptr,                         // No element.
+    &default_dtor<project_name>,
+    &default_copy_ctor<project_name>,
+    &default_copy_assign<project_name>,
+    &simple_assign<project_name>,
+    nullptr,                         // Append not supported.
+    nullptr,                         // Prepend not supported.
+    &simple_reverse<project_name>,
+    nullptr,                         // No cast (cast data_ directly).
+    &simple_compare<project_name>,
+    &default_empty<project_name>
+  };
+
   // variable_pool
   //
   void variable_pool::
diff --git a/build2/variable.hxx b/build2/variable.hxx
index f9b8b3c..401cc77 100644
--- a/build2/variable.hxx
+++ b/build2/variable.hxx
@@ -820,7 +820,6 @@ namespace build2
     static const build2::value_type value_type;
   };
 
-
   // target_triplet
   //
   template <>
@@ -841,6 +840,27 @@ namespace build2
     static const build2::value_type value_type;
   };
 
+  // project_name
+  //
+  template <>
+  struct value_traits<project_name>
+  {
+    static_assert (sizeof (project_name) <= value::size_,
+                   "insufficient space");
+
+    static project_name convert (name&&, name*);
+    static void assign (value&, project_name&&);
+    static name reverse (const project_name& x) {return name (x.string ());}
+    static int compare (const project_name& x, const project_name& y) {
+      return x.compare (y);}
+    static bool empty (const project_name& x) {return x.empty ();}
+
+    static const bool empty_value = true;
+    static const project_name& empty_instance;
+    static const char* const type_name;
+    static const build2::value_type value_type;
+  };
+
   // vector<T>
   //
   template <typename T>
diff --git a/build2/variable.ixx b/build2/variable.ixx
index 991556a..8c16559 100644
--- a/build2/variable.ixx
+++ b/build2/variable.ixx
@@ -611,6 +611,17 @@ namespace build2
       new (&v.data_) target_triplet (move (x));
   }
 
+  // project_name value
+  //
+  inline void value_traits<project_name>::
+  assign (value& v, project_name&& x)
+  {
+    if (v)
+      v.as<project_name> () = move (x);
+    else
+      new (&v.data_) project_name (move (x));
+  }
+
   // vector<T> value
   //
   template <typename T>
diff --git a/build2/version/init.cxx b/build2/version/init.cxx
index 397d7da..4234451 100644
--- a/build2/version/init.cxx
+++ b/build2/version/init.cxx
@@ -138,10 +138,18 @@ namespace build2
                 catch (const invalid_argument& e)
                 {
                   fail (l) << "invalid version constraint for dependency "
-                           << b << ": " << e;
+                           << d << ": " << e;
                 }
 
-                ds.emplace (move (n), move (c));
+                try
+                {
+                  ds.emplace (project_name (move (n)).variable (), move (c));
+                }
+                catch (const invalid_argument& e)
+                {
+                  fail (l) << "invalid package name for dependency "
+                           << d << ": " << e;
+                }
               }
             }
           }
@@ -232,7 +240,7 @@ namespace build2
 
       // Create the module.
       //
-      mod.reset (new module (cast<string> (rs.vars[var_project]),
+      mod.reset (new module (cast<project_name> (rs.vars[var_project]),
                              move (v),
                              committed,
                              rewritten,
@@ -284,7 +292,7 @@ namespace build2
 
         if (!val)
         {
-          string p (cast<string> (rs.vars[var_project]));
+          string p (cast<project_name> (rs.vars[var_project]).string ());
           p += '-';
           p += v.string ();
           val = move (p);
diff --git a/build2/version/module.hxx b/build2/version/module.hxx
index 56536c3..36dd735 100644
--- a/build2/version/module.hxx
+++ b/build2/version/module.hxx
@@ -16,7 +16,8 @@ namespace build2
 {
   namespace version
   {
-    // The 'depends' values from manifest.
+    // The 'depends' values from manifest. Note that the package names are
+    // sanitized for use in variable names.
     //
     using dependency_constraints = std::map<string, string>;
 
@@ -24,7 +25,9 @@ namespace build2
     {
       static const string name;
 
-      const string& project; // The project variable value.
+      // The project variable value sanitized for use in variable names.
+      //
+      const string project;
 
       butl::standard_version version;
       bool committed; // Whether this is a committed snapshot.
@@ -34,12 +37,12 @@ namespace build2
 
       bool dist_uncommitted = false;
 
-      module (const string& p,
+      module (const project_name& p,
               butl::standard_version v,
               bool c,
               bool r,
               dependency_constraints d)
-          : project (p),
+          : project (p.variable ()),
             version (move (v)),
             committed (c),
             rewritten (r),
diff --git a/tests/name/pattern.test b/tests/name/pattern.test
index 792a7c3..fad8478 100644
--- a/tests/name/pattern.test
+++ b/tests/name/pattern.test
@@ -9,8 +9,8 @@ define txt: file
 txt{*}: extension = txt
 EOI
 
-$* <'print p%*.txt'       >'p%*.txt'       : project-simple
-$* <'print p%{*.txt -x*}' >'p%*.txt p%-x*' : project-group
+$* <'print pp%*.txt'       >'pp%*.txt'        : project-simple
+$* <'print pp%{*.txt -x*}' >'pp%*.txt pp%-x*' : project-group
 
 $* <"print '*.txt'" >'*.txt' : quoted-single
 $* <'print "*.txt"' >'*.txt' : quoted-double
diff --git a/tests/value/reverse.test b/tests/value/reverse.test
index 5208536..9ea9d09 100644
--- a/tests/value/reverse.test
+++ b/tests/value/reverse.test
@@ -42,9 +42,9 @@
   : combined
   :
   $* <<EOI >>EOO
-  print ([strings] x%foo@y%bar x%foo/@y%bar/)
+  print ([strings] xx%foo@yy%bar xx%foo/@yy%bar/)
   EOI
-  x%foo@y%bar x%foo/@y%bar/
+  xx%foo@yy%bar xx%foo/@yy%bar/
   EOO
 }